eHam

eHam Forums => Boat Anchors => Topic started by: KB1WSY on September 12, 2017, 12:10:46 PM



Title: All-American Five
Post by: KB1WSY on September 12, 2017, 12:10:46 PM
I picked up this little "All-American Five" at a neighbor's yard sale. It is an Admiral Model 7T10E-N with the 5K1 chassis.

(http://tinyurl.com/y7uguyxr)

(http://tinyurl.com/y7anpfr4)

This is the classic design used in millions of postwar radios regardless of manufacturer. This one is the "octal tube" version and probably dates from the late 1940s or early 1950s. To save money, there is no power transformer. The B+ is rectified directly from the AC power supply. The filaments are connected in series across the AC supply, which explains the strange heater voltages of the last two tubes (as denoted in the first two digits of the tube name): 12SA7 pentagrid RF/oscillator/mixer, 12SK7 pentode IF amplifier, 12SQ7 double diode/triode detector and first AF amplifier, 50L6 tetrode final AF amplifier, 35Z5 rectifier.

I changed the power cord, making sure that the wider "neutral" pin went to the chassis side. I replaced all the "waxy capacitors" and the filter caps. A 1K resistor had gone high (reading slightly more than 2K) so I replaced that, too.

(http://tinyurl.com/yb36e5y7)

(http://tinyurl.com/y9d2gfg8)

Powered up the radio: zilch. The tubes lit up (so at least all the filaments are good) but no sound. Touching the wiper lug of the volume control with a screwdriver did not produce any sound. Feeding an audio signal to the grids of the AF stages using an AF frequency generator had no result either.

First possible culprit: the speaker. Feeding a brief 1.5V pulse to the speaker with a small battery produced a crackling sound. So the speaker is OK. Next: measure the resistances of the AF output transformer. Aha.... the primary is open-circuit. Next: connected a pair of high-impedance headphones across the primary and turned the radio on. After about 30 seconds, there is a reassuring "woosh" in the headphones.

Turned off the set and unplugged from AC, then temporarily replaced the dead output transformer with a tiny spare transformer with a rating of 150mW (which is under-powered for this radio and earmarked for another project, but good enough for a brief test). Powered up the radio and it works! I am only running it for a few minutes at a time, to avoid blowing the tiny transformer and have ordered a proper replacement. There is also a missing power/volume knob so I need to find a replacement.

First impressions: surprisingly good, in particular the sensitivity (better than most of the other BC AM radios in the house, whether tube or solid-state), and this is just with the wire-loop antenna that is built into the back of the set. Pleasing sound quality, within the limitations of a small set with a narrow AF bandwidth. Am amazed that such a bare-bones radio, clearly produced to the lowest possible cost and of fairly dubious build quality, works so well. No wonder they built them by the millions, well into the 1960s.

Those reading this post probably know this already: these radios are also "death traps" (another term was "widow makers"). Even when they are switched off, the chassis can be live. Fortunately this little Admiral set is about as well insulated as these things ever were. There are only a couple of metal screws that can be touched from the outside of the cabinet, and the bracket that they screw into is insulated from the chassis with a thin strip of bakelite. Still, the idea that people had things like this in their kitchens (and who knows, maybe even in their bathrooms) makes me shudder. Similar circuits were used by European manufacturers with 220-240VAC supplies. Yeech.

So far, this has nothing to do with ham radio, but maybe I'll built a small converter to put in front of the set to see if I can pull in 40m. (I guess I could also build a small BFO to feed to the IF stage, but it would have to be loosely coupled rather than directly connected.)

73 de Martin, KB1WSY


Title: RE: All-American Five
Post by: KB2WVO on September 12, 2017, 12:41:15 PM
pix no show....


Title: RE: All-American Five
Post by: KB1WSY on September 12, 2017, 12:49:43 PM
Sorry about that. I posted the photos to Google Photos then posted them to this forum. When I then "shared" them so everyone could see them, the links changed so the original links no longer worked. Silly me. Here they are (too late to edit the original post):

(https://lh3.googleusercontent.com/uAvmT75cT6biayytFkYcsSYt5mDnGVFoorZAbxa6-k4-GDR-DssxcCSZ1mLjh0PHRbhfMkAIW_e-oZOMNzQ3oQYh0XLMJkDHrzJoK25IGMMyOHIG8DjMyvzzUyehTglu4MIlXg79_pNV-zOTTJnJtZG1ELWxdmulKvzgKGqRYP7P-TyXCl2B3cNYbOoAWgeBlmqOiQTEU-XGsgy7rFPoFSQegG0BWNNESthC4Uq3egfYTWgH5NoDKuCUBKfHaXc5KLl0EpLa91MSBsbD1pHJPrxXB2WfPaYS1vX-pVqVjStm6oTFaYGJW4m2w7z7762EKzb1noS0H63nz6lc_sM2MHppUT52OQfLt9KU5rMFAVWFyprvgVp_FwSEhC8mOeL9xilMjz8BkIocXHerjf_B_nS3h6pMTpbB1cmRKhUOTjti5jkZgijcMAb-oI9CAI-ZCVfeoLFcpHJ3Edzt8QvOg2EbTbS3wzwiH7b4zCdD1uK2T4E3aykmHHiGQG3uhxxt2fp7juhBdEgKOoo_Vf15DTB_GjC1nN10B3QpbEg1PIfg5E5UXko_4JMckJX3mTUwIZe0fPBvdKGkKb0NK3ktWKpq4oDwlymuIKyyIwrk_PgADSYUGH_zPDN8wXEzfAimkRdzIp2SQQak34kK3jtZuIqqKqTdfbfGIhw=w368-h248-no)

(https://lh3.googleusercontent.com/ItKyRJMlsN8XP2xBVPkK4FJBzoj40SqkthB_lNDhkP5tmGuK2rm4t8uqVIaQZLBl8ihhxGANKz2KvYvus2j4qBd228_5wuxOi8yQm1JFrKCxwUCBdM4Ianj7hNfcFgDGjYlZDLAgnlZ9d1de_pQkP2-wQbRL_Oh3D8NQAw9SHE2g2sjj0rnaMrwEuDbx7RlOoha0vYlvRyU7BC9RqiUyC_Q98i2AI8v3hTlbA2FyI_0Kky30sqWQW0MRlcsOwRsUeb_L6PDJYpbn-s-_fmLkgNOEpiouOu1r9SNPdQcvoUOl9-iTcwH3Vh_nfEmiRptGm2C4Vc05A15vqcBw7eAs3Ty3e4XEWzARN1txREpMnOB1oWqCmQmPDx08Wc2nEKWF_rzfGMDkdkCdtasopr7_tedrbIfcaR3tFsxlkSgtBfBIbqp0boopy_Nxca2Bf2IMB9JSkTQ7SVFKFrfaFN14u6XhjKDSl1LvHqxTppQs0dAqGcWBRMlkY4sRj1ROxzBmJFxWZpOKDscMmVi-Yn2RfE6iRGSzqeF0rEpq13LT9jeAQbARrtH1Q_gKyM7H5sHFkzmi5pcerdr6KMmjtI15VFYzAfdWJRNsVGCS9cYWtA2JSi2CtoF9qYzHkmouHd39iCD3PisW1x3QQjig3y8WQgxOij87gvNrRL4=w374-h207-no)

(https://lh3.googleusercontent.com/v6R7cyNIcjbyx2RLRXGPYHPHyKz8cB0mlWhJ6nPV4BQupdRO9-QgW3Bo3eYSxDuOvrit5lgtob9dVNsj6CjB5eHa3fKPWkOv3NevOuPwsy8x4pTZJnIdfbnMqTV4eVNMQEYp-r7nhcFLVPX_jZau6UxbcnCjtdLh7yZ3bGG8aDy_GxXPk5IkJg59U9_v-WBOsLgAB3V3gH7xLezGJSnL-tZPD9-3j5j59ZestqZQEdasAfnA35JMY4B_b7CXp4RZZUtT9aok5jycTHE65hTkoD3THt3vHasUSvNazdBKAFmIf5f9IrNlTbfMxozPeEY1tM8UunuKkQWnFWb1R_cpzLEa-nYlhAkVux6eR3gttdfeJD5bmFBzt9hbie6XZjsw9g7Er7T9tr_M1gTxn23ufDZh_e8hrb4e1v5U5Q6bB-gbwgQksZFK3fmVbJ16_UCINGrea7IcmUu-gMJzoKupdFGXmqKo60TV9ymlCMEgrwqDkAaX2V2Wu4wVAcp-K-m0U9NBoJvEb5UwnIy0_32nYdskAe0tLglciHX0ixIVsQBG3JWkLlmqXc2Ugd33Nm-nNMWCkY1D3aN6hgE6xGoc8oI9LdgbkcGVLQcxMS1k9kCvgXMNTlfd1QR_pC1jWEWK9HX4dSKY9XbEFSQ9bLD5oIHGikJDM0uedZw=w397-h276-no)

(https://lh3.googleusercontent.com/aVqHf23use8ICusu5Yoxb0BMZ-lc64C0YpYlYBdNFwa28zDAQpGVHT_Rq4V3u8J3251Tg498lxIcZCk0etW7wit7zDh_6S_XB3uomKicqwVWm7peh9cvRn5hVUpCMByY5hRMRGEFq879b4_K3vY8TWIr5tI2UxcSaUQe06tRTm-hTlvLreFuXFHt4gtkcw28hcEQm2kRmCqvsEfspHGoQ9vJPJwr9uJF6VD8vVR8TVSj10b1-DbKmvBEkn3tXiq4js5R-L_FP38PKfTkwxnSpY-wCoiUs9FWJsJEiZGiL5RutJ6vDkO58_OfKAqyKgowuxImwxbfUm2gnNQNJg1rlmFryQSRmh4yMp7w2T3ZFmX-TfR32TwjAKCjosMUsTwJ51gNjAXS76PbSR3qk5LOWmfvV-1IQuB5_k6mv-aEt8sa3iwupkYJe_ZyTmcS4IriyHuHHdrY0ESR5d-j3uWs_E19anOxrR8BmReI7Kw8mvWo5ER6tN_4VUUel3DDKVOdhO7r_V_ZkSGt7cMf-ROJYeONX_HsuowHR9LT3RfQZ3ATHSpY3YcK9woCS9AmLe040ux743gzuZ4lqHGfEO4J7_nuk-kTXZmHJxOl2kpz-1cgi5D6BqrcpOTEsN65HzJJT1bfuCNeuoCGYrWmBWwFu6649MDJuTmO6TY=w395-h192-no)

73 de Martin, KB1WSY



Title: RE: All-American Five
Post by: KB2WVO on September 12, 2017, 01:40:44 PM
cool radio.. love the sound of old stuff


Title: RE: All-American Five
Post by: AC5UP on September 12, 2017, 04:28:54 PM
If you have a small-ish 6.3 vac filament transformer in the junque box you can use it to sub the AF output transformer.

Won't be a perfect match and certainly not Hi-Fi, but neither was the original.  The radio was designed for 20% tolerance parts so don't sweat the details........


Title: RE: All-American Five
Post by: KC4ZGP on September 12, 2017, 06:25:35 PM

Just one picture. Looks like capacitors and one resistor.

Kraus


Title: RE: All-American Five
Post by: K0OD on September 12, 2017, 07:00:33 PM
Is this it?

(https://thumbs.worthpoint.com/zoom/images1/1/0511/01/vintage-admiral-model-7t10e-5k1-tube_1_072a6b0c7563cc4476c3999021e75a94.jpg)


Title: RE: All-American Five
Post by: KB1WSY on September 12, 2017, 07:11:11 PM
OK let's have another go at sharing these photos. Several years ago I used Picasa and it always worked fine on eham. Then, Picasa was bought up by Google (and renamed as Google Photos). The interface changed completely and ever since, I have had a lot of trouble sharing my pics. All my fault no doubt.

(https://lh3.googleusercontent.com/x1Ak8Rp75JGSXEyNpedoRrACnqAkLHBVJQ9MZ2h6tVW2CDqhvjD2nqkeJ9ZzNRIRoEeZPohJ6PbI6hBODeLAfUHwcBmtox_Bc8LBCHQxF7OHdB6UpVi8ZuBaEXZgrDAvSnWLHLT-ImoUjcN_-FMCkjuz2Uz_n56DgV7PbO5Wg9H-GYiedN3T6D4QtlPMRk5tFzaZL1TNPvjavF_qT0gmGLCThdCIadwccQb_JCjxBlmjSWIPnZ0lW5kPmKf8nU63kAk8VNlKf0kYkXuhd9rM4teg_h9lhqsHA7vvUuHufWJAQtMMvG9SVTOHS6Ug1VUN6oG2KavMFAeiJo_UbzqiyNNgWFNcwsW0UhQOQReLd5FwAwCCqXpxJGtHU_B8v8GBzypYWVTJVOhefb_aSVmi9Y_LfH9ISMEYzqri_SnNnWX8IlhEms2jdEvnMPTkUV8V3TARXYvEnyDZmJzVssxrscDCmDLOul6smFe1OKJ_f2GBFD6muoIufw_pOk5hYkfQInnNtf5gz0u7rFsU2ChnSAm2qngjfK5MHXl_k1QxeVah8DVW5qWpE4GCSqmYPjXsVrQYiufrPGcuBJUskKoHm6yRD_f4guhEDSDRDdD553niHpdtOnGYt4nJmzWY-nvUuyFumB0FnaoHdCO8I1V16oiLp98t8jlhWuccGrFKISbLtA=w368-h248-no)

(https://lh3.googleusercontent.com/CT7tgFf1aKcbLs0dwA2VJ2OCOu0N1PLZRB81m8VBamfRXPxAahj_I7hGVOELO9p4DHoBWSCCxftoi1Y9MJZkgkyybl9LBrBkVvvvejGtVmtZQuYO6e-cyKw7z2Hfarp3jg-xtgRDnKH_KctdYA5VM_ngTwPyqoug30XTvt7MSeQ0yjtfrlbMmyhct5vRWB3RmKQjhhxSIhZVIA1BeVYKsnhsGrhal_ivOL5YZ0hZwbTmydnBFOwJfTozq_tROXlGwg1sFaweIVA0N48wHBKxVv8op5Dv2hCnUM47vIOmxaddUfmfJpSEcyfIdMMtI6ffvuy-rY68QKrQhBcAo3oIBXuL300m6t2CWxIx-zXt5SklXacbopjEURG0YxcoYVFrNn6cN5tyjXtrjKBhrQOq6CwjpacwqaM8ZZ6djkzyTfNMlJEoxreJvbl6NeKXAUhIcYdXJaepSs-nNw2GjqkEszvpZ8kH6zZal3KgVv0QA691Q1rMEkyD_Swp9KxINsiXR0vPmRZJ8G8bKdKD_wXBT3M2N0I-RHIlnrwXoqwBUd9EUaCNDQiLCMrTbGnFCtKGi0zjpk9mBFTetYNX6lgWwtOzgnE53gE0MIBnKOrngoIzmF3E4y3qs9-5WmTaL_Vv8CkmFRuk2wBVlBE-oSzfT_QYNNoreYM7wOyvdn717uxdYg=w374-h207-no)

(https://lh3.googleusercontent.com/N6gswCDgOVW957QrjFBM6KOdiKMC2_XyQ9Zq_fRbcJ6MbZ21JigvSWTsV4KNiGEVwmRku3tjCFl2NenffKNlO0xMazw0v-OMbTFLq1MotccoCFfrWuVGRV-tDQKzvJsv2IJiVRB3Z15yOhkAVCXxvVQnfMaVCb3kcmWHHTcDwAs2ii9LUlWN3lnO2ltzPLUJho6ozYspBsdmmXCQH0RgiqrZiBg2oQa7ZjlRYqyxAut8vMjOFb8yrwTYmPEUIgFKwKGYpH_iQp34A-jBtxVThkyn9ENNMBF7oZ22u2g9IYtjR3E4iBedcv70LMNXdw027Y2Am6ndN5b_M9N74JAiEaPzRNxsCVEyahcw6txjBqBMlGq75rWRP1Zk7ThjGG_jw7f1ereLHYZwB_Odsr-9mdLO2u3isX14f4d78w6bCxd8m_3BFobQuF0TFPZONlTwBNi89KbBdL5JotG9ih7wkYxST6yJHw97-AJk8aJQtPgWsetHrqq_ZuWpwtRBjUGjt6oSSFR-X80ewmjYWIyEqLO_GIpO_nQjqr00X80Q42OYOCMmEAnYbaXPTQqMmCfWOD49zHPaDNsco8L7UuQmgh9MLEYbEOePf59_6K-rnnJIjpiBFUXfJeH4CxF_XbbPbigZkU5RCTENVk3Kubu4LO70kVHqq9nPiVrn9ZHa3OkyIQ=w397-h276-no)

(https://lh3.googleusercontent.com/_2hVCkJzRXUZfls9XrsCISYcnvtYscrXVym5IyIxCx-VwPljEuW2xAJNeC0PjzmDcGY2sc_Z2JD9AqCOsZRPpIpweiyjx8LJnmGhnUXciFBDOoOzb3FCMeSJQkAWngAGi_NX07PYyUcx-2q5HZ_x5EObt0F1BIQ1VBvr6ZEmrlBMsq2EdY488k20yuA6zVIG7Ur323aCMmDexF73tlC0lOcHIzKj0lk2dqH1buXD9lhH30t_cW6JUE0ZNitoOpMWL8UxCDl1aMbTJJ_-CZLu8GXmLNr0t-lOx612N0EjQfKwWyxvjO-IvTQAbERxBIk51WdhPm1NUAeO99n6a-1HAuFQxXZonr2eP_TShqH19grq0AIrSs-cPfJaX7dKW65rZMy50VLZH0xexQUnIuGoavoVAzNq6euiKZZPYSJoGD-5yjD5obfOunkB0tf1sYR7OioC2QX_D0fNxw0rWD-nn-aRPGdV6Z4bF7Cn-9Qj903KDRV7ZcxitFJQ2Cf_lLID2tkgJ1orpkUKm7z3Q9Eye2YX2tFtt2fs9g29c3nHmBlZR4IE2d5NJBkRXIISdcSBjpcvdC154AR6joeK3cYDE2tjV9EEFVeghM0v0eH4S2NtRWnmY60c7GNge_w7Uk7JCyM82iiZ0xAvkEfvtYqRAE34n8NbB1axXB4MRi5acr1H4Q=w395-h192-no)

Did that work? (I have no problem seeing these photos on eham but that is because I'm the one who posted them in the first place. The issue is with the sharing permissions.)

73 de Martin, KB1WSY


Title: RE: All-American Five
Post by: KB1WSY on September 13, 2017, 01:52:53 PM
The new audio output transformer has been installed. Everything working fine now.

(https://lh3.googleusercontent.com/OTPUI7vCjr4ixjb_p7ABBjUHrbIy0uI644Pj9uG4YfNgig8L90977Ad3MDxjiXgJ0QvDV5kEUBD2VvYAh7oICsdFMdpQZ_X9Oe0PyI7vSQwYknGIaRNZSKjPSpOmOUgwOPncAE9jDYxADhYiMVjVgJrfQ8EBhey23Anyz8EIUVoSvZVLRdiQpfWZY3a6odlZNTjqDasQ7qpQdAaTI0NF1_KBcGM2RNPdVjA2OdbeK0IaYX_8vprwGMlQ1aVA7KcuqD2Z_XOKr66CCLH9cOqFiJiE2AwmjeHpj5SeuSIftyUu2I2stfMRpkYzYlnGm0ClOW2XdkWCr5gdPCQrBd5ZTyY9_Jqb6t4sUZJWaP0YvYuslSNNSkhXtO-z31C8YM2JPWwVFJzbiMCn_JaYXsxE5CbOIa66QP2PryTVx__SqVhhngm-YV5xN_53U67QVvYD9bw2w7aqXIOcoDZZZCeHTS6dUAUAldNwnc57UVC9l_CT_c7g1T_l6kb7xvUvYZY1bvaJh8lT3LH4h60mcR7sftovSF0W2NU7NTDoaa0wsiD1zMdekYqpp5YyV4_MqTC_FaPgWOfJ1sJXw5iYYbv01AN_EHbtNB14s_SI3zJ0TsxghR2I5IiX4SxG6xLyImGkIvtIYyaTJ0fKrEJtLyY7mr_3k2A99IB6Hoo=w397-h298-no)

73 de Martin, KB1WSY


Title: RE: All-American Five
Post by: AC2EU on September 13, 2017, 06:56:31 PM
Wow that was almost a total "re manufacture" of the radio !   :o
BTW, The pictures worked this time.


Title: RE: All-American Five
Post by: N8FVJ on September 14, 2017, 09:19:33 AM
These old tube radios have a voice clarity missing from transistor radios. My GF (soon to be wife) listened to a cheap cube shaped transistor AM-FM radio. It sounded terrible. I replaced it with an early 1960s AM-FM tube type table radio. Even with a small 4 inch speaker the audio sound from the tube radio was far superior & enjoyable vs that terrible sounding transistor radio.


Title: RE: All-American Five
Post by: KB1WSY on September 14, 2017, 06:53:06 PM
Wow that was almost a total "re manufacture" of the radio !   :o

Re-capping the radio was optional, but I had the parts in the junk box so why not. The one resistor that I changed was way out of range. The AC cord on the original set was rotted down to bare wires, so no choice there, it had to be replaced. The open-circuit output transformer obviously had to be replaced (or rewound, but I don't have that expertise) -- unfortunately the new $20 transformer cost more than what I paid for the entire radio at the yard sale. Even with all of that, most of the parts are still original!

Even with a small 4 inch speaker the audio sound from the tube radio was far superior & enjoyable vs that terrible sounding transistor radio.

I know what you mean but, at that (very crude) quality level I don't think it's a tube-vs-transistor issue per se. I have several transistor radios built in the 1950s with point-to-point wiring and two-transistor push-pull output stages with an output transformer, relatively large speakers and sturdy cabinets. They sound very similar to the contemporaneous tube radios. Even when the solid-state radios transitioned to "transformerless" AF output stages, miniaturized PC designs and smaller speakers, they didn't necessarily sound any worse, or better, than tube radios. When I was at school in the UK in the 1960s and 70s many people had sturdy "Roberts" solid-state AM/FM radios (almost as large and heavy as my AA5) that sounded great (but, for that matter, so did the earlier Roberts tube radios).

At a much higher level (hi-fi) it gets much more controversial. I personally like the "tube" sound, but there is quite a lot of evidence that this effect can be attributed to "pleasing" harmonic distortion, that "warm tube sound." Likewise, I often prefer the sound of an LP to the "antiseptic" CD/digital sound but am totally prepared to admit that the CD sound is probably closer to the original.

Anyway, getting back to ham radio, I am still rather impressed by the economy/efficiency of the AA5 design and looking at it is giving me some ideas for receiver design. Perhaps I will use a pentagrid tube in the front end of my first homebrew superhet, when I get around to it!

73 de Martin, KB1WSY



Title: RE: All-American Five
Post by: VE3WGO on September 14, 2017, 06:56:29 PM
looks like a nice restoration!  I like the sound of those radios.

And the hum your can hear in the few brief moments while it is warming up and the tube audio sound bring back fond old memories of childhood listening to the Hit Parade on the AM radio in the living room.

I guess those replacement electrolytics you used make it no longer completely "All American" anymore   ;)



Title: RE: All-American Five
Post by: N2DTS on September 15, 2017, 12:05:02 PM
Simple is sometimes better then complex.
I have built my own ham receivers and used the AA5 detector/agc setup, as well as the single conversion and low plate voltage ideas.
Its very quiet and high fidelity.
For ham use I added a more stable seperate LO tube, a good filter, an S meter circuit, and a bfo.
I also used a freq counter with an offset to show the exact frequency.
Works great.
(https://photos.smugmug.com/Ham-radio/i-MNgG3tR/0/7916126d/L/100_2703-L.jpg)


Title: RE: All-American Five
Post by: KD8IIC on September 15, 2017, 11:24:12 PM
 Anymore I'm leaving working wax caps intact.
 The one's I have replaced gave very little, if any, improvement in performance.


Title: RE: All-American Five
Post by: KM1H on September 16, 2017, 05:17:23 PM
Quote
Re-capping the radio was optional, but I had the parts in the junk box so why not. The one resistor that I changed was way out of range.

Nope, it is mandatory if you intend to use it regularly. All the caps will have high leakage simply due to the technology used and the AA5 throwaways used the cheapest parts available. Sometimes a way out of tolerance resistor appears to have no effect but one common result is the AVC is shot; the converter and/or the IF amp gain is down and eventually the volume control needs to be full on. One real fun cap isolates the chassis from the AC line since the line cord can be plugged in either way; many have been introduced to their first electrical shock that way.
As leakage increases so does current and eventually the 35Z5 will let go as well as the audio transformer. In AC sets the power transformers are added to the trash.

The more complicated radios have their own ways of reacting from defective components.

The various tube radios here run from 4 to 20+ tubes. Some I have fully restored and use, others are display shelf queens.

Carl


Title: RE: All-American Five
Post by: N8FVJ on September 17, 2017, 07:02:15 AM

Even with a small 4 inch speaker the audio sound from the tube radio was far superior & enjoyable vs that terrible sounding transistor radio.

I know what you mean but, at that (very crude) quality level I don't think it's a tube-vs-transistor issue per se. I have several transistor radios built in the 1950s with point-to-point wiring and two-transistor push-pull output stages with an output transformer, relatively large speakers and sturdy cabinets. They sound very similar to the contemporaneous tube radios. Even when the solid-state radios transitioned to "transformerless" AF output stages, miniaturized PC designs and smaller speakers, they didn't necessarily sound any worse, or better, than tube radios. When I was at school in the UK in the 1960s and 70s many people had sturdy "Roberts" solid-state AM/FM radios (almost as large and heavy as my AA5) that sounded great (but, for that matter, so did the earlier Roberts tube radios).

At a much higher level (hi-fi) it gets much more controversial. I personally like the "tube" sound, but there is quite a lot of evidence that this effect can be attributed to "pleasing" harmonic distortion, that "warm tube sound." Likewise, I often prefer the sound of an LP to the "antiseptic" CD/digital sound but am totally prepared to admit that the CD sound is probably closer to the original.

I hear a distinct difference of tube vs SS even if SS uses discrete components vs the modern OP-Amps. I can hear a cheap tube radio in another room and always correctly identify it. And, when moving into high-end tube audio the difference is more apparent. I ship custom high-end tube electronics around the planet.


Title: RE: All-American Five
Post by: W3RSW on September 17, 2017, 08:09:15 AM
As you may know, "Working" is relative.   The approx. .01 cap from the plate of the first triode AF amp, (12SQ7) to the grid of the AF output tube (50L6 or equivalent. ) may be working but have just enough DC leakage to upset the grid bias in the 50L6.  If you have a bit of audio distortion, replacing that cap may cure it.  Also the cathode bias resistor on the 50L6 is notorious for being underrated and baking to different value over time.  This resistor is usually around 220 ohms, possibly 1 watt. Should be 2 watts to help heat aging.

Also be sure to replace the dial lamp if installed.  It is needed to keep the filament string in current balance.  The 35z5 rectifier tube filament is tapped for best current distribution using the lamp bulb for balance.


Title: RE: All-American Five
Post by: VE3WGO on September 17, 2017, 10:26:42 AM
I suppose the "tube sound" of those older AA5 (1940s - 1960s) AM table radios was due mainly to the fact that their cabinets were fairly large, perhaps 1/2 the size of a cinder block, for heat management and tube height as much as anything.  They usually had fairly common 4-inch paper cone speakers, and most of them had almost identical circuits.  With their steel chassis, output transformers, and either solid bakelite/plastic or even wood cabinets, they were on the solid weighty side too.  So the sound was pretty good.

I'm what you'd probably call an audiophile, ... however... while the AA5 radios I have collected and semi-restored almost all sound similar with that kind of recognizable "woody-sounding" 250 to 2500 Hz audio response, I don't mind it at all.  Not much high frequency response to speak of, just enough low-end (with some kind of bump due to the cabinet in the 300-400 Hz range) to not sound too crappy, the distortion is acceptable (most probably because of the high frequency rolloff), and tuning is easy.  At 110 VDC on the plate, a 50C5 is capable of putting out almost 2 watts, so that's a pretty healthy audio level.  50L6 is over 2 Watts, but interestingly the 35L6 in some radios is a little less capable, spec'd at only 1.5 watts. I do like the sound, but these days most AM stations are just talk shows so the music station pickings are getting slimmer.

I have a couple of mono AM-FM wood cabinet table tube radios, equipped with a couple more tubes for the FM path so they have unusual series string heater voltages and solid state rectifiers, but the sound is better on FM..... still kind of "woody" but with brighter treble.  Of course these are not AA5, more like "AA7" if such a label exists.

The solid state table radios seem to have only had solid wood cabinets for a while, and I guess the designers soon took advantage of their lower heat and smaller size with smaller and plastic cabinets that usually called for smaller speakers too.  So the sound changed.  I have a couple of those, but I'm not too fond of them.

73, Ed VE3WGO


Title: RE: All-American Five
Post by: VE3CUI on September 17, 2017, 02:14:32 PM
Hi Guys,

For what it's worth --- in case nobody mentioned here (I didn't see any reference to it, anyway), the "Beginner & Novice" section of QST in the early 70's, I believe, featured a piece entitled, "New Life For The All-American 5."

It was a nice little treatise on converting one of these little classics into a working Ham bands receiver…

~73!~ de Eddy VE3CUI - VE3XZ


Title: RE: All-American Five
Post by: KC4ZGP on September 18, 2017, 11:09:17 AM


I am turned on.

Kraus


Title: RE: All-American Five
Post by: KA4LFP on September 18, 2017, 11:53:02 AM
Anymore I'm leaving working wax caps intact.
 The one's I have replaced gave very little, if any, improvement in performance.

Replacing the caps isn't about performance increase, usually. Sometimes hum goes away, sometimes not.

It's ALWAYS about avoiding that old was cap from shorting through and taking the unobtainium main transformer or an unobtainium IF can with it.

I've seen half a dozen "grandpa's old radio from the basement storage " turned on proudly at the yard sale only to turn the transformer into slag and the radio into a parts donor.

I'm not a huge believer in the value of "re-forming" old caps at the price of new ones either....
although, starting up a newly obtained radio with a dim-bulb tester or variac is always good.



Title: RE: All-American Five
Post by: KB1WSY on September 18, 2017, 01:50:59 PM
It's ALWAYS about avoiding that old was cap from shorting through and taking the unobtainium main transformer or an unobtainium IF can with it.

At this point I have done a lot of restorations of 1950s-era tube equipment. In most cases, I replaced all of the paper tubular caps (whether "waxy" or similar) with modern tubular film types, often with somewhat higher voltage ratings. Sometimes I replaced the power-supply filter caps, sometimes not. In a couple of cases, I later regretted not replacing the filter caps because the old ones failed a few hours after power-up and ended up having to be replaced anyway.

It seems there are several philosophies, all of them valid I guess. (a) Change as little as possible, just fix what needs to be fixed to get the set working. (b) My system, which is described above. (c) Change all the caps (apart from the micas) and a lot of other stuff, in some cases stripping the chassis down, deep-cleaning/replating it, and rebuilding the whole set from scratch.

To each, his/her way. They each have their own advantages and drawbacks. For sure, (a) is the *cheapest* route but only if it does not cause something expensive or unobtainium to fail later!

I had a lot of fun restoring this rack of test gear, and it's been become a great set of tools in further restoration work:

(https://lh3.googleusercontent.com/dgfffgEZ7a0FmjXt48X6yReOC74kgF17uFJ74weUY79V5dEds8IFzdsvXASvNPt-XhrL1NGO2Fm6TTGZuWHNRPkcz06-3wlkMSo0WCjJovC8MbE3qMBSssYoEYNoz79AAaBRcHCuBoKrWiqiln2Ba1DEx8ApFxjZNyXhCCdQXGNTUtS3FpxyMYrgo2dENtBtl9mWP1vM6eODvPXnAVpvTrWd_tYBiz5YPRein5S9WBdmGqLue4VGO70t0dR_T-vLVCx_uhWj8t9yiFzcPYNprmGNAnQtk4UJy9D1mTH7QLis_8t_tHXnmzSM5EmB0RVzNYm7xaQyr_XU24HS9Q5bdCX1X23sWEH4xCIKQ6fioaSVJ1VEJgjF3AzDgb4vtzlds8ffvL_kMWOjrZeoAoz801-AscqB6jJ1xwMqpM5VWlQU4eJRRUmyvim8u_BnH0dvQ-iKMhyhSDOF3HkSJdc28BFqLJAbepQjndOYheEfQq8lnPhOK6Tm7pWWIhy7jzNnxZbF-C4NPmMBPI64UbFwC60M6PzVAuQdALfANCEW8y-k-xgmDjL4BbsVQsVwo22WEg9N9IBmCLTCX8oN393o8O51JnN1LYVm12nFoupE6DuKvMi6IoKNzJRCBO6IwK6S7IzLtwlXhxOM_6dJW-XUY27Kn_KdpBBRDZE=w245-h730-no)

The 'scope has not been restored yet. That will be quite a challenge because it looks like a previous owner has messed with the EHT section.

Missing from the photo: an Eico grid-dip meter and several other items of restored equipment.

73 de Martin, KB1WSY


Title: RE: All-American Five
Post by: AC5UP on September 18, 2017, 03:33:09 PM
The 'scope has not been restored yet. That will be quite a challenge because it looks like a previous owner has messed with the EHT section.

It's possible what you're seeing is a flat line zero signal trace with a buttload of AC power supply hum.  The thickness of the trace might be a clue-by-four something is superimposed on the vertical amplifier and 60 or 120 cps ripple would be my first suspect.  This is easily confirmed with your DMM........  Measure the B+ as DC volts and AC volts. 

If DC volts are near the schematic value and AC volts are near zero you're golden.  Otherwise, it's time to swap out the electrolytic(s).


Title: RE: All-American Five
Post by: KB1WSY on September 18, 2017, 07:12:12 PM
It's possible what you're seeing is a flat line zero signal trace with a buttload of AC power supply hum.

The horizontal sweep control is set to 60 Hz. On that setting there is no problem getting a clean sine wave, (presumably the vertical signal is just noise, given that I have not even input an external signal). The bluriness is fixable with the focus control. So overall I think there isn't too much wrong with this 'scope (but see below).

This is easily confirmed with your DMM........  Measure the B+ as DC volts and AC volts.  

If DC volts are near the schematic value and AC volts are near zero you're golden.  Otherwise, it's time to swap out the electrolytic(s).

The problem, from what I remember (and it has been a year or two since I looked at it) is that the EHT circuit has been considerably altered from what is in the schematic. Perhaps there was a good reason, perhaps not. This kinda stopped me in my tracks because of the high voltages involved -- I am rather interested in stayin' alive. I will get round to it eventually.

There is also a large capacitor close to (or in) the EHT circuit that has dripped molten wax over the bottom of the cabinet. So definitely something to work on! When I get around to it I will start a new Boat Anchor thread about this 'scope.

It is an Eico 460, really crude by comparison to everything that followed, but this would have presumably have been a prized possession for a 1950s ham. I also have an Eico dual-trace "electronic switch" which is shown on the shelf above the 'scope in the photo I posted.

Edited to add: I also have a second Eico 460, in less good order, to cannibalize for parts, if needed. I also have the Heathkit EF-2 educational "How to Understand and Use Your Oscilloscope" kit and its textbook, to learn more about my 'scope once it is fixed.

73 de Martin, KB1WSY


Title: RE: All-American Five
Post by: AC5UP on September 18, 2017, 07:45:23 PM
The horizontal sweep control is set to 60 Hz. On that setting there is no problem getting a clean sine wave, (presumably the vertical signal is just noise, given that I have not even input an external signal). The bluriness is fixable with the focus control. So overall I think there isn't too much wrong with this 'scope (but see below).

Me Thinks it's time to review how an oscilloscope operates.........

When you select 60 cps horizontal line sweep it should do exactly that, sweep the beam horizontally at the rate of 60 passes per second.  If there is no vertical input signal to encourage vertical deflection there will be no sine wave or anything other than a horizontal line.  Maybe a little noise from the vertical amplifier, but aside from that, a flat horizontal line swept at the AC line frequency.  'Cuz that's the only signal the 'scope has to work with............  On a typical recurrent sweep 'scope like the EICO the Q&D vertical amplifier test is to touch a finger to the vertical input.  The flat line should become a distorted vertical pattern much like an audio amplifier will buzz when the input jack is touched.

What I suspect you have is a vertical amplifier being modulated by ripple on the B+ power supply.  With no vertical input there should be no vertical deflection.


Title: RE: All-American Five
Post by: N2EY on September 19, 2017, 05:59:35 AM
As you may know, "Working" is relative.   The approx. .01 cap from the plate of the first triode AF amp, (12SQ7) to the grid of the AF output tube (50L6 or equivalent. ) may be working but have just enough DC leakage to upset the grid bias in the 50L6.  If you have a bit of audio distortion, replacing that cap may cure it. 

And there's more!

As you say, if that coupling cap between the 12SQ7 plate and 50L6 grid is even slightly leaky - tens of megohms - it will upset the bias and cause the 50L6 to draw excessive plate current. The set will still work - but, over time, the high plate current can/will fry various components, such as the 50L6 cathode resistor, the 35Z5 rectifier, the 50L6 itself, etc. Worst of all, the most likely candidate for destruction is the audio output transformer.

A shorted 50L6 cathode bypass electrolytic can have similar results.

73 de Jim, N2EY


Title: RE: All-American Five
Post by: KB1WSY on September 19, 2017, 08:34:02 AM
As you say, if that coupling cap between the 12SQ7 plate and 50L6 grid is even slightly leaky - tens of megohms - it will upset the bias and cause the 50L6 to draw excessive plate current. The set will still work - but, over time, the high plate current can/will fry various components, such as the 50L6 cathode resistor, the 35Z5 rectifier, the 50L6 itself, etc. Worst of all, the most likely candidate for destruction is the audio output transformer.

I replaced two .01uF paper "waxies" during the restoration. I still have the removed caps, but of course have no way to tell which was the AF coupling cap since they look identical. On my VTVM, one of them is more than 60 megs, but the other one zooms down to 7 megs before drifting back higher as it charges.

So Jim-san and W3RSW seem to have found the most likely culprit in the destruction of the original output transformer. Changing the cap prior to installing the new transformer made sense!


... the Q&D vertical amplifier test is to touch a finger to the vertical input.  The flat line should become a distorted vertical pattern much like an audio amplifier will buzz when the input jack is touched.

What I suspect you have is a vertical amplifier being modulated by ripple on the B+ power supply.  With no vertical input there should be no vertical deflection.

Thanks, that advice will be very useful when I start on the restoration!

73 de Martin, KB1WSY


Title: RE: All-American Five
Post by: KC2QYM on September 19, 2017, 09:26:24 AM
We have to admire the ingenuity of previous generations of radio engineers and technicians that led the way in the last century to the proliferation of radio products.  Every time I see an old radio I can certainly relate to them because of my age and being lucky to have owned them and still be part of the radio hobbyist community. 


Title: RE: All-American Five
Post by: N2EY on September 19, 2017, 12:36:54 PM
Couple of things:

 1) It is a common meme today to point out unsafe practices of the past and then say "so why are we all here?" or "we survived!" or similar.....implying that the modern push for safety is overblown.

 BUT....those who didn't survive aren't around to speak up and remind us of what happened to them, because they're dead. Often they are forgotten. This distorts the perception of the actual danger. (Just look at motor vehicle deaths and rates before and after seatbelts):

https://en.wikipedia.org/wiki/List_of_motor_vehicle_deaths_in_U.S._by_year

 And all it takes to become a statistic is ONE mistake. Just ONE.

 2) AC/DC "transformerless" radios were usually housed in cabinets made of wood or plastic, with plastic knobs having no setscrews, with back panels of nonconductive material and with no exposed conductive hardware. No shock hazard as long as you didn't poke around inside, and the cabinet, knobs, etc. are intact. But if you are restoring/repairing/aligning such a set, you probably have the cabinet off.....

 3) In many - but by no means all, or even most - AC/DC "transformerless" designs, the chassis is NOT, repeat NOT, tied to one side of the power line. The chassis is isolated for power by a capacitor, so that if you touch the chassis or a control shaft, you won't get full line voltage if the plug is in the socket "the wrong way". In most of these designs, the short-circuit current through the capacitor is very low - IF the capacitor is in good condition.

 For example, suppose the coupling capacitor is 0.05 uF. Such a capacitor has a reactance of about 53,000 ohms at 60 Hz, and at 120 volts, only about 2.2 mA will flow. If you were in series with such a capacitor and the AC line, you'd get even less unless you were well grounded and soaking wet. 2.2 mA of shock current is no joke but it's not the same as getting yourself directly across the 120 volt line.

 HOWEVER - in old radios, the capacitor(s) mentioned above may be leaky or even shorted. In every "isolated" design I have seen, the capacitors mentioned above can fail and the set will still work perfectly - but the isolation the capacitor provided is GONE.

 So the risk of decades ago, when a set was relatively new, is very different from today. And the "isolation" of the design can actually be a trap, because the set can work perfectly with the isolation failed.

 4) Transformerless radios were made for three reasons:

 First, they cost less - even a small power transformer cost several dollars back then, which was a sizable part of the cost of the radio. So the parts used were often not top-of-the-line.

 Second, not having a power transformer made the set smaller and lighter.

 Third, such sets could be used in 60 Hz, 50 Hz, 25 Hz and DC territories with no changes at all. (Fun fact: There were parts of Boston that had DC power at least into the 1960s, and parts of Buffalo NY that had 25 Hz at least into the 1980s)

 All big concerns in the past....not so much today.

 5) (The big one) - No matter what the original design was and no matter what the schematic says, you must NEVER assume ANYTHING about a transformerless AC/DC set until you personally check it out. Bypass capacitors fail shorted or leaky. Insulating hardware dries out, cracks, and fails. Schematics contain mistakes. Most of all, there may be undocumented repairs, modifications, substitutions and other hazards which can only be found by actual test and examination.

 Be safe - it only takes ONE mistake.

 73 de Jim, N2EY


Title: RE: All-American Five
Post by: KB1WSY on September 19, 2017, 01:13:02 PM
3) In many - but by no means all, or even most - AC/DC "transformerless" designs, the chassis is NOT, repeat NOT, tied to one side of the power line.

This particular Admiral set came in two versions. The older version *does* have the chassis tied to one side of the power line, and that is the version I have. There is a later version whose model number has the suffix "UL" (Underwriters Lab version) in which the ground is "floating," isolated from the AC with a capacitor.

What I did when restoring the set is that I made absolutely sure that the power cord was fully unplugged from the AC power strip whenever I was working on the chassis. But I know exactly what you mean! If you are tired or have had a beer or two, it would be too easy to forget to do this!

73 de Martin, KB1WSY


Title: RE: All-American Five
Post by: AA4PB on September 19, 2017, 01:49:24 PM
Back in the late 1950's at the tv/radio shop we used to get a fair number of these AC/DC sets in for repair. We had an isolation transformer that was ALWAYS used to power a radio that we were working on. If you connected the ground clip of a signal tracer or other test equipment to the chassis that was plugged directly into an out let the wrong way, you were in for a fireworks display!


Title: RE: All-American Five
Post by: KD0REQ on September 19, 2017, 02:05:04 PM
we also had DC power in downtown Fargo into the 60s.

what seems a lifetime ago, when Sylvania owned the ECG parts line, they had a note in one of their counter handouts about flyback transistors blowing on or shortly after installation. turns out a snubber capacitor, a "safety part," was hosed also and needed to be replaced.

don't be shy about shotgunning wax/paper caps, it's the same thing... you could probably use anything close in an AA5 and never know the difference, but if it's acting like a different part and not a capacitor, squirrelly things are sure to happen. it isn't worth the labor and equipment to test them, when you can swap them out for a buck on today's market.


Title: RE: All-American Five
Post by: KM1H on September 20, 2017, 03:34:21 PM
Quote
This particular Admiral set came in two versions. The older version *does* have the chassis tied to one side of the power line, and that is the version I have. There is a later version whose model number has the suffix "UL" (Underwriters Lab version) in which the ground is "floating," isolated from the AC with a capacitor.

Im glad you corrected that misconception Martin. An experienced tech with those radios would not have made that mistake.
Earlier AC-DC sets before the RCA 1939 intro of the AA-5 tube set also suffered but it was not an across the board thing. Ive rewired my own collectibles and do it for customers.

Quote
And there's more!

As you say, if that coupling cap between the 12SQ7 plate and 50L6 grid is even slightly leaky - tens of megohms - it will upset the bias and cause the 50L6 to draw excessive plate current. The set will still work - but, over time, the high plate current can/will fry various components, such as the 50L6 cathode resistor, the 35Z5 rectifier, the 50L6 itself, etc. Worst of all, the most likely candidate for destruction is the audio output transformer.


Before all that happens the less negative bias due to paper cap leakage will eventually start with audio distortion plus AVC problems and eventually lead to G-K leakage and a resultant gas to further poison the tube leading to runaway element dissipation This is particularly common with the pentode IF/RF and audio output tubes and requires a good quality tube tester to find it. I use a Hickok 752A formally used by National Radio in the Service Dept where I worked in the 1963-69 time frame and have culled out many 6/7 and 12/14/25/28/35/45/50/117V heater versions that would be totally missed by all the entry level emission testers and a good many of the Radio/TV shop grade. Many if not all military testers do a good job of this, I also have a TV-7B/U and an I-177 and have compared all three over a wide range of tubes.

Carl


Title: RE: All-American Five
Post by: KB1WSY on September 23, 2017, 08:34:47 AM
Back in the late 1950's at the tv/radio shop we used to get a fair number of these AC/DC sets in for repair. We had an isolation transformer that was ALWAYS used to power a radio that we were working on. If you connected the ground clip of a signal tracer or other test equipment to the chassis that was plugged directly into an out let the wrong way, you were in for a fireworks display!

Since I have the service sheets for this set, I am thinking of checking the voltages. Given that the chassis is connected to the AC neutral line (or could be connected to the live line if there is a polarity mistake), I assume it would be a bad idea to use my VTVM even though that meter has only a two-wire AC cord (the meter's case is not connected to a third-pin AC ground). The risk of damaging the VTVM, not to mention shock risk from connecting its case (which is at the same potential as the floating  "ground" probe) to AC when measuring the radio voltages, is just too great. So I suppose the "safe" thing to do (well, the least-dangerous) is to use a VOM or DMM and be extra careful not to touch anything with my hands.... (Well, I am always careful when measuring voltages but in this case I need to be even more careful!).

Part of the reason I want to check the voltages is to make sure that the voltage being fed to the grid of the output tube is within normal range, i.e. that it not overdriving the tube. After all, when I restored the set I found that the old output transformer had an open-circuit primary so presumably it was overdriven in the past. I have changed the coupling capacitor, but it would be good to check that all is well.

73 de Martin, KB1WSY



Title: RE: All-American Five
Post by: AC2EU on September 23, 2017, 09:05:41 AM
Yes a VTVM WOULD BE a BAD idea. However there SHOULD NOT be a connection between either leg of the AC to the metal chassis. That was "isolated", though in a very dangerous way with a paper foil cap which could leak or short.

the radio ground should be floating which does connect to an AC leg.
You can test the voltage more safely with a battery DMM , be be aware that that is exposed wall
AC in there.
We  use a current limited or fused isolation transformer  to work on hot chassis sets, which is still needed if you wanted to use a scope or generator on it.

BE SAFE!


Title: RE: All-American Five
Post by: KB1WSY on September 23, 2017, 09:35:33 AM
However there SHOULD NOT be a connection between either leg of the AC to the metal chassis. That was "isolated", though in a very dangerous way with a paper foil cap which could leak or short. ...the radio ground should be floating which does connect to an AC leg.

My set is an early AA5 that does *not* have the "floating ground." One side of the AC is indeed connected to the chassis. My model has the "plain" 5K1 chassis. There was a later version, UL5K1, which did have the floating ground. This is well explained on the schematic (see the text at the bottom).

Arguably, I should be modifying the set so that it *does* have a floating ground, i.e. I should convert it to match the "UL" (Underwriter Labs) version. Of course that is only slightly safer....

(https://lh3.googleusercontent.com/1y0ASfyNCuBFdr2ovl7V_VvZpjkQb9Lvfp9l5nw0QLAruUf85jFHwjGHsdnAsw4EAZ7aDZBlxUJwKae6hNDyYAweu6X6fosWA76JetiN4PCTybwnbhI7CDwdXzwVkVorK1JH4wh7IXQt_xpcmkZybi0Isws1O2yrOS3RBnup0lHcSzxw-5NLzlxK9t8cRqo3495frZuJarht_5mbZ_gyXojB4IfDnHSvkTMbeyBLtKtZf6JADxTu20wEtlx8BCNGVGGNotYEuubei8nvp0MI1vZF64NO45txzKi7FQ2Zj5PgL4c48jclfMpwj4KmPK2wbqMs2wvLe8Nr3xl7G2Nx2DeM2ykui0APxmfgSTbdwpcsIAVp7Kom6AHtwpyXkLzHJUTsG4YrDLJC8-EZ8QJA8LaAn6smqFIXhgU2fss_HPZD_f3UDzRWbeMunK2pE2Yw-szNQf9TLcAh5cfeQZ1nbRo2Ay2liDTgtru0E6CoIhlKz86NtFsUxMFaNHCXmob8CRurMYtuLkRoTFCITieJwe0WNAT6T-3GbUJ3sMjXxuGAd72DTwtqiw6NY-4Cazsb5ZnQ2xPmR9OMsOs8q8JHxm0AWK6oSC7-K2-Kdr8GLZEH37b_H40BrWLgALOWS02Ca4WLBsNVyBkafwC2YDm96oe1Sn5VdFqtN1s=w694-h523-no)

73 de Martin, KB1WSY


Title: RE: All-American Five
Post by: AC2EU on September 23, 2017, 11:13:24 AM
Wow that's REALLY dangerous.
Well, at least put a polarized cord on it and/or use it with a small isolation transformer.
It's amazing that they made stuff like that!


Title: RE: All-American Five
Post by: KB1WSY on September 23, 2017, 11:30:34 AM
Wow that's REALLY dangerous.

Yup, that's what I've been trying to say. I knew these sets were lethal but had never owned one, and was amazed at just how dangerous this one is. What makes it even worse is that the power switch is on the chassis side of the line, so that even if you connect that side of the power cord to Neutral, the Live side is permanently switched on (since it is a single-pole switch, mounted on the back of the volume pot). According to one source, such switches were typically wired in the chassis side of the circuit "to save money and avoid having a terminal strip."

With that configuration, you could get zapped if you touched just about any part of the heater chain, even when the set is switched off (and because the heater resistance is low when cold, it could be lethal). So I have made sure to unplug the AC cord from the power socket whenever working on this set!!!!

Well, at least put a polarized cord on it and/or use it with a small isolation transformer.

I have fitted a polarized cord. But of course that will not protect me if the house wiring is wrong. I live in a 90-year-old house with some very old wiring in some rooms (plenty of two-prong sockets still there). Fortunately, the shack/workshop has modern sockets that seem to be wired the right way round.

I don't own an isolation transformer but obviously should get one. Although, thinking about it, even that cannot eliminate all of the risk -- surely you can still get a shock if you make a path to ground?

On one site dedicated to fixing these radios, I found an intriguing safety tip. Find a cheap electric hair dryer (or a broken/used one in a junk shop). In recent years these have been fitted with a GFCI safety cutoff that is part of the power cord. Chop off the cord and fit it to the AA5.

(You can also buy a pre-made GFCI cord but those seem to be quite expensive.)

73 de Martin, KB1WSY


Title: RE: All-American Five
Post by: AC2EU on September 23, 2017, 11:35:54 AM
there is no current path to ground with the isolated secondary.
You have to have a legitimate 3 prong service for GFI to work.
I wouldn't trust it in your house!


Title: RE: All-American Five
Post by: KB1WSY on September 23, 2017, 11:39:12 AM
there is no current path to ground with the isolated secondary.
You have to have a legitimate 3 prong service for GFI to work.
I wouldn't trust it in your house!

All these things are good to know. Thanks!

73 de Martin, KB1WSY


Title: RE: All-American Five
Post by: KD1I on September 23, 2017, 04:34:53 PM
AC2EU, respectfully, GFCI works just fine on 2 prong devices because they measure an imbalance between the hot and neutral currents and not a current on the ground wire. Picture that a fault condition can be between the hot line and yourself to ground such as a water pipe. In this case, there is no current flowing in the ground wire but a different current in the hot vs the neutral.    Very Best 73, Jim


Title: RE: All-American Five
Post by: KB1WSY on September 23, 2017, 06:05:57 PM
AC2EU, respectfully, GFCI works just fine on 2 prong devices because they measure an imbalance between the hot and neutral currents and not a current on the ground wire. Picture that a fault condition can be between the hot line and yourself to ground such as a water pipe. In this case, there is no current flowing in the ground wire but a different current in the hot vs the neutral.    Very Best 73, Jim

Interesting. FWIW Amazon sells *two-pin* AC plugs with built-in GFCI: https://www.amazon.com/OAONAN-Replacement-Interrupter-Protection-Conditioner/dp/B073PRH8H3/ref=pd_sbs_328_4?_encoding=UTF8&psc=1&refRID=NVXZD6BH9PEGS13NPB3X (https://www.amazon.com/OAONAN-Replacement-Interrupter-Protection-Conditioner/dp/B073PRH8H3/ref=pd_sbs_328_4?_encoding=UTF8&psc=1&refRID=NVXZD6BH9PEGS13NPB3X).

That sort of device is normally used on relatively high-power devices (hair dryers, pool pumps, air conditioners) but I assume that a GFCI would still be tripped by a low current, normally less than a lethal dose?

Really just an extra safety "crutch" in this case and by no means a fail-safe one. The radio is unsafe by design!

73 de Martin, KB1WSY


Title: RE: All-American Five
Post by: AC2EU on September 23, 2017, 06:19:50 PM
AC2EU, respectfully, GFCI works just fine on 2 prong devices because they measure an imbalance between the hot and neutral currents and not a current on the ground wire. Picture that a fault condition can be between the hot line and yourself to ground such as a water pipe. In this case, there is no current flowing in the ground wire but a different current in the hot vs the neutral.    Very Best 73, Jim

Makes sense,I stand corrected. Thank you!


Title: RE: All-American Five
Post by: W9IQ on September 23, 2017, 07:21:18 PM
But what will not work with a GFCI on a two wire circuit is the GFCI test button. The test button routes some current through the ground to test its efficacy. Probably not good to rely on an untested GFCI when you know the risks from the load are higher than normal.

- Glenn W9IQ



Title: RE: All-American Five
Post by: KD1I on September 24, 2017, 03:15:11 PM
Glenn, I fully agree. An isolation transformer is still the best insurance along with knowledge and experience. And as was mentioned earlier, don't work when tired or after a few beers.   Best 73 All Around, Jim


Title: RE: All-American Five
Post by: N8FVJ on September 25, 2017, 05:07:19 AM
I replaced an AM-FM SS radio in kitchen with a 1960s tube type AM-FM radio. The Tube AM-FM was bought as NOS. The tube radio provides much better sound.


Title: RE: All-American Five
Post by: KD0REQ on September 25, 2017, 01:44:34 PM
hot chassis AA5 in the kitchen, what could go wrong?

most chassis have some room in the case for a little isolation transformer.  they are still availiable.


Title: RE: All-American Five
Post by: N8FVJ on September 26, 2017, 05:33:17 AM
Just got lucky. Found & bought a 1967 AM-FM tube type stereo table radio. Likely last year of these tube type radios. Most were SS design before 1967.


Title: RE: All-American Five
Post by: KB1WSY on September 27, 2017, 03:29:49 PM
For what it's worth --- in case nobody mentioned here (I didn't see any reference to it, anyway), the "Beginner & Novice" section of QST in the early 70's, I believe, featured a piece entitled, "New Life For The All-American 5."

Cool. For those interested, it is in the June 1971 issue of QST (available in the ARRL archive if you are a member).

The article explains how to adapt the AA5 for a ham radio band:

(1) Add an isolation transformer to deal with the "live chassis" issue.

(2) The AA5's loop antenna is replaced with the secondary of a BC band antenna coil (I have one in my junkbox: the Miller A-320-A). The primary is connected to a homebrewed ham-band converter with three transistors: RF amp, crystal-controlled local oscillator, and mixer. The result is a double-conversion superhet using the AA5 as a tunable second IF.

(3) To improve the lousy selectivity of a BC receiver, the AA5's IF stage is modified to be regenerative.

(4) Separately, a one-transistor BFO is added to inject into the AA5's IF stage for reception of CW/SSB signals.

"When the modifications and additions to the 'All-American Five' are completed, you'll have a receiving system that will compare favorably with many commercially built receivers costing a great deal more. In fact you'll have a darned good receiver -- and the hardest part of the job might be wired and tested and waiting for you in your attic right now."

Hmmm. I'm tempted. I'd be happier if the converter were designed around tubes rather than transistors, but vintage transistor designs can be cool too. The project calls for TR19 PNP transistors, which are still available from NTE as the NTE-159 for less than $2 each. Most of the rest of the parts are already in the junkbox, apart from the crystal. Judicious choice of frequency is important: I have some deafening AM stations at my QTH, a news station at 1330 and a Latin station somewhere above 1400.

Yeah, a bit quixotic really, but listening to my little AA5 daily, I am getting a bit tired of the fare doled out on AM radio nowadays....

If I do go ahead with this I am not sure whether it belongs here, or in the "Homebrew" section.

73 de Martin, KB1WSY


Title: RE: All-American Five
Post by: AC5UP on September 27, 2017, 07:34:45 PM
(4) Separately, a one-transistor BFO is added

Heresy!