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Author Topic: 6146??? 6146B - w  (Read 9793 times)
K9AXN
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« Reply #45 on: November 27, 2017, 10:59:04 AM »

Both the TS-830 and FT-102 implement two stage feedback.  The TS-830 also uses progressive swamping for the lower bands.

I believe the FT-102 states an IMD# of -40db and the TS-830 -35db which can be attributed to the two stage feedback design.  That forgives a good portion of the linearity hit when using mismatched or different models of the 6146 at reduced power. 

The single stage feedback in the other radios doesn't have that advantage; they rely on the negative feedback from band to band neutralization which has only a fraction of the effect that two stage feed back provides.

There is one statement in the tube romance sheet that's calls into question the validity of the document; the max Plate to CG capacity is said to be .22pf for both tubes.  Have you ever replaced a pair of 6146's with 6146B's and not had to dial in more neutralizing capacity and bias?

It's easy to say that I stuck B's and all sorts of variations in my radio and they work just fine; but there's a lot of radios out there that were not designed with that latitude of variation.  The users of those radios may not be capable of making the changes necessary to accommodate those tube variations.

   
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G3RZP
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« Reply #46 on: November 29, 2017, 03:34:08 AM »

I've changed a pair of 6146Bs from RCA with another pair of RCA 6146Bs from a different date code and re-neutralisation was not absolutely necessary - it didn't oscillate - but highly desirable.

Looking at the ARRL test results, the levels of IMD from the TS830 and the FT102 really stand out as being so much lower, especially on the high order IMD, than the solid state rigs that followed them.
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AB1MN
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« Reply #47 on: November 30, 2017, 06:40:56 AM »

Hi All,

While a bit off topic, but relevant I think. I recently replaced a pair of 12DQ6b tube in my Hallicrafters SR-150 and found that I could not neutralize the rig with the new tubes (neutralized fine with the old tubes). The problem was that the new tubes (made in Japan) had a somewhat different internal capacitance than the old tubes and the neutralizing circuit did not have enough range to compensate. By replacing the neutralizing cap with one having a greater range I was able to neutralize the rig properly. Clearly, this is not a situation limited to 6146s.

The reason that I think this is relevant is that there are likely differences in the internal capacitance among the tubes in the 6146 family and the neutralizing circuit in some rigs may not be able to accommodate the difference . Other than this, I tend to believe that one can use any of the 6146 variants in most circuits.

I also believe that many problems attributed to neutralization are really other issues. If you can remove the plate and screen voltages and get a proper null at the output of the final amp, the problem probably lies elsewhere and is not a neutralization problem. The method I use for the (preliminary) neutralization is to remove the plate and screen voltages from the final, monitor the output at the antenna jack (I use a wideband scope, but one could use a VTVM with an RF probe) and adjust the neutralizing cap for minimum feed through while in tune mode. This procedure is well described elsewhere and I won't repeat the details here.

Assuming the final neutralized properly with a good null but instability still exists one might consider the possibility of parasitic oscillations (the resistor in the parasitic chokes may have opened up or increased so much in value that is no longer damps VHF oscillations), defective or faulty bypassing, layout, or shielding or instability in the driver stage.

Just my 2 cents worth,

Bob, AB1MN
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KM1H
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« Reply #48 on: November 30, 2017, 01:26:06 PM »

Quote
I've changed a pair of 6146Bs from RCA with another pair of RCA 6146Bs from a different date code and re-neutralisation was not absolutely necessary - it didn't oscillate - but highly desirable.

In the late tube years RCA was known to throw quality out the window including RX, sweep, and power tubes. National Radio had been all RCA from the late 30's and finally dropped them in favor of Sylvania and Telefunken.....no more erratic specs and failures.

On another note I tried a a GE and RCA 6146B in my HT-32B (original specs were for 6146's which were down to 70W) this morning and all was well after a minimal neutralizing cap tweak.

The B is also in several other rigs here from DX-60B, Ranger, Viking II, Valiant, Elmac AF-67, as well as several brands of 2 way FM radios when I helped out a friend with the repairs in his 2 way shop.

Carl
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KM1H
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« Reply #49 on: December 02, 2017, 06:08:24 PM »

Typo corrected:

National Radio had been all RCA from the late 20's and finally dropped them in favor of Sylvania and Telefunken.....no more erratic specs and failures.
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WY9C
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« Reply #50 on: December 09, 2017, 10:33:16 AM »

I dont know my way around this web site but I read where the 6dk6 tubes could be used in place of the 6146s. I cleaned out some buildings this year and have thousands of tubes. I have an old Palimar 150 bi linear amp that I was thinking about putting a couple of these tubes in but I do not remember enough about these old rigs to know what I am doing. If you or anyone needs tubes of any sort let me know. I might have them. Text me at 765-363-0338. WY9C.
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VK6HP
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« Reply #51 on: December 10, 2017, 04:10:54 AM »

I'm guessing you mean a 6KD6 TV sweep tube, since a 6DK6 is a small-signal tube.  6KD6s and 6146s were used in amateur RF power amplifiers but that's about where the similarity ends. The bases and operating requirements are quite different.  However, if you have a stock of 6KD6s you might find they are attractive to collectors of older transceivers from the 60s and 70s.  My old Yaesu FTDX-560, like a number of similar radios of the era, uses a couple of 6KD6s in the PA. Despite a big CW output, the intermodulation performance is pretty terrible and I don't think you'd find anyone throwing out their e.g. Collins 6146 PAs to use a 6KD6-based radio, at least at the power output such radios were advertised.
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KM1H
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« Reply #52 on: December 10, 2017, 06:29:53 PM »

Quote
Despite a big CW output, the intermodulation performance is pretty terrible and I don't think you'd find anyone throwing out their e.g. Collins 6146 PAs to use a 6KD6-based radio, at least at the power output such radios were advertised.

Im partial to TS-830's with their longevity and superb 6146 IMD.

At one time I had a pair of Drake C Lines using 6JB6's, short life since I operated all over 6 bands contesting and chasing DX and a lot of retuning didnt help. A muffin fan on top of the final cage brought life from about 6 to 18 months.

Carl
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VK6HP
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« Reply #53 on: December 10, 2017, 11:07:17 PM »

Carl,

After a severe existential crisis I did manage to part with a TS-530S hybrid which I'd restored - just in order to get some much-needed shelf space.  But the two TS-830S transceivers, one of which was going to be a donor radio before I couldn't help myself and brought it back to full health, are both going strong.  They are immaculate cosmetically and I've fitted 1st and 2nd IF CW filters in both. For various reasons I recently used one of the 830s as a primary radio for a few weeks, and it was fun to run the test gear over it and remind myself of just how well it works.  There's indeed not much to touch it terms of PA cleanliness and I'm going to a fair bit of trouble and expense to do as well with a forthcoming SDR transceiver and LDMOS amplifier.

I do sometimes use an audio DSP filter on the 830 receiver output, just to knock some of the urban noise down.  But with good receiver operating practices, judicious use of the notch and passband tuning, and the processor between the ears, a lot can be achieved.  Listening during the recent worldwide CW contest I used an 830 alongside my TS-590S and I concluded that the 590 had the edge - but not by much, and about half the time largely due to the Kenwood 'NR2' CW noise reduction algorithm.  I guess there has to be something to show for 35 years of progress.

73, Peter.
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KM1H
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« Reply #54 on: December 12, 2017, 01:00:35 PM »

Peter, I have 4 TS-830's, all have a full slot of CW and SSB filters plus several mods to minimize filter blowby and improve 15-10M noise figure.

Three replaced a couple of TS-940's which had excessive TX and RX phase noise even after several mods to be really useable for weak signal and very low external noise VHF to microwave work with transverters. Another mod was to add outboard Jackson Brothers 10:1 reduction drives as I found the 25 kHz per revolution intolerable.
The last one lives on the amp repair and 6M conversion bench where amp problems wont blow up anything plus I give all repairs a good workout for a day or so before shipping back. A very modified 60's transverter covers the 6M side at 50-140W.

The newest rig I have is still old, a TS-950SD. After trying just about everything available and find them wanting, including SDR so far, Im in no hurry to change any longer....I'll be 77 tomorrow Shocked Roll Eyes   

Carl
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HAMHOCK75
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« Reply #55 on: December 12, 2017, 11:47:32 PM »

Happy Birthday KM1H!!!
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VK6HP
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Posts: 186




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« Reply #56 on: December 13, 2017, 02:58:13 AM »

The tuning rate is a funny thing, Carl. I got along fine when using the 830S as my main radio, but it annoys me when I have to mix and match with other radios.  I have two VFO-230s which I use for routine HF work and I might get around to doing the tuning rate modification on those.  But they do detract a little in terms of phase noise, of course.

Having been away from amateur radio for a good number of years, I have a "missing link" period from the 830S era until a couple of years ago, so the 940 and their contemporary's issues passed me by. I've enjoyed the journey back into the hobby and am heading, cautiously and critically, into the SDR/LDMOS era, while keeping my interest in the older gear.

Happy birthday - and we must be close to sharing a birthday.  I have a decade rolling over tomorrow and figure I'm now officially OK with the grumpiness. Might even be obligatory Wink

73, Peter,
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K1DA
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« Reply #57 on: December 13, 2017, 03:00:30 PM »

The Glen Zook article is well worth reading.  He ran a large factory authorized Motorola shop at a time when
many of the VHF products had 6146 or 12 volt filament variants of the tube  as power amps. Was  was also chosen to rehab KWM 2s left over from the  Vietnam era for the first Gulf war.  To dismiss his observations as an internet rumor is a classic example of Dunning-Kruger syndrome. 
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WA5VGO
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« Reply #58 on: December 13, 2017, 03:32:25 PM »

"Was  was also chosen to rehab KWM 2s left over from the  Vietnam era for the first Gulf war."

KWM-2's were serviced by Dennis Brothers, not Glenn Zook. And that's not the only thing you're mistaken about.
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K1DA
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« Reply #59 on: Today at 06:57:19 AM »

You're making it up as you go along, Sparky, Mr. Zook writes of the trailer load of M2s which showed up at his company when he agreed to do rehab work for the military.  Calling him a liar are you?  That's a Dunning Kruger tipoff.  Whatever you do, DON'T read his article on the 6146 family,  it's always best to comment on things you haven't read, right?
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