Philco F817 All American Five "The Edsel"

[N4NYY]

Nelson,

I replaced C7 A,B,C all with 33uf caps. Would that jack the B+ up too much? The originals were 30,25,20.

The format is in DJVU

http://techpreservation.dyndns.org/schematics/Philco.htm

[KE3WD]

Subbing electrolytics, there is a LOT of leeway as to the microfarad specification, typically as long as you observe "equal or better" than the original spec, not a problem at all. 

To understand why, do a little websearching on the tolerance of the common electrolytic capacitor.  You should soon see that it is typically a lot more on the "plus" side of the listed uF capacity.  The originals may have been as much as 20% higher than that listed on them when they were new. 

Voltage should not change at all from spec. with the slightly larger caps.  Voltage would be a function of the power supply, regulator, etc.

73

[WX7G]

The Philco F817 is the lineal ancestor of the Yaesu FT-817.

[AC5UP]

I replaced C7 A,B,C all with 33uf caps. Would that jack the B+ up too much? The originals were 30,25,20.

Vinnie... I want you to know that I have thoroughly enjoyed our conversations and consider you to be an absolute credit to the hobby. Not only do you have a sense of humor about yourself and the mystic arts of boatanker restoration, but you're more than capable of moving beyond your D'oh! moments to gain more experience. That's what it takes to learn this stuff and as the Halson illustrated, old radios come in a variety of styles and levels of technical sophistication. When you consider that you're looking at 80+ years of development it's unreasonable to expect to learn all the nuances in short order, but on the other hand once you understand the three major components of every radio... Power supply, RF / IF section, and audio... The rest is boilerplate and logical troubleshooting will (eventually) lead you to the fault.

Last night I made the decision that my days here are numbered. Some boards are managed well, others less so. This should explain it http://www.eham.net/ehamforum/smf/index.php/topic,80390.msg569410.html#msg569410

You saw the post that was deleted and can decide for yourself if I have a reason to be offended... We all make mistakes, but if K5TR can't man up and take responsibility for a clumsy response to a hasty judgment call, then so be it. I'm outta' here.

Good luck with your future projects..........................!

[N4NYY]

AC5UP,

I think you are one of the most knowledgeable and gracious people on this forum. And I think you are an asset. So I ask you not to go away. I have always appreciated your advice, and would like for it to continue.

Vinnie

[N4NYY]

Dave WX7G,

Did you see the pic? I think it is pretty cool looking face.

[AC5UP]

Deep down inside this is the radio Vinnie really wants..............

http://www.shopgoodwill.com/viewItem.asp?ItemID=9253251

Sure, the " Edsel " has a pantload of charm, but a classic 60's puke green Admiral clock radio?

* Priceless *

[N4NYY]

I have to replace the speakers in this Edsel. The stepdown transformer to the speakers is mounted on the old speakers. I have to drill it out, but I am going to have to mount it somewhere else.


BTW, that is a nice green color, but the radio is butt-ugly.

[KE3WD]

...The stepdown transformer to the speakers is mounted on the old speakers...

While it is indeed a stepdown, proper terminology here is, "audio output transformer" or just audio transformer. 


73

[KE3WD]

AC5UP --

You're bigger than all that. 

Keep on doing good, posting and helping others. 

Don't let *anybody* steal your joy.


73

[N4NYY]

Dammit. That is what I get for buying a set of AA5 tubes on ebay. The Edsel has a bad 50C5. I ordered a set us used "but tested good" AA5 set. 4 of 5 test fine on my Heathshitz TC-2. The 50C5 is on the edge of the yellow-green. Go figure. That is the only one I needed for the Edsel.

[AC5UP]

I replaced C7 A,B,C all with 33uf caps. Would that jack the B+ up too much? The originals were 30,25,20.

Let's think about this for a moment........... In the case of a half wave rectifier, the DC output is every positive voltage swing - or - every other voltage swing of the AC power line. For the sake of simplicity we'll assume the negative swings are ignored and we have a voltage pulse, nothing, voltage pulse, nothing, etc. 60 times a second. The purpose of the filter electrolytic is to store enough charge to 'float' the DC voltage level between recharge pulses. If the condenser doesn't have enough capacity to keep the output level steady there will be a voltage sag between pulses and the repetitive change of the B+ voltage level will be heard as a 60 cycle hum. The deeper the sag, the louder the hum.

So............. If the ratio of filtered DC to unfiltered half wave AC is 1.414 to 1, a 100 volt input to a 100% effective ripple filter will yield 141.4 volts (1.414 x 100) output. Can the filter be more than 100% effective? No. The electrolytic condenser can do no better than to retain an almost flat charge between charging pulses. Assume that for a given load the output level with a 20uf condenser is 141.0 volts. The output level with a 25uf condenser might be 141.1 volts. The output with 30uf, 35uf, 40uf, etc. should be progressively higher but NO condenser, no matter how large, can be charged higher than the absolute peak value of the DC pulses charging it.

In a practical application you might see a 2% differential between an electrolytic that's big enough and one that's way too big, but you'll never see the voltage go higher than the peak DC value of the ripple.

The 50C5 is on the edge of the yellow-green. Go figure. That is the only one I needed for the Edsel.

In general terms the hotter a tube runs the shorter its service life will be, and that's a broad generalization as some power tubes are built to run hot and will do so for a very long time. The 6080 with graphite plates is an example of this. In the case of the Phugly Philco, the two hottest tubes on the chassis are the 50C5 and 35W4.

Damn shame I didn't think of it back in October when I threw out that big box of brand new mil-spec.......................

[N4NYY]

Damn shame I didn't think of it back in October when I threw out that big box of brand new mil-spec.......................
   

The pain! Oh, the pain!

Anyway, the radio works. The audio is a little low, but that is likely because I have only one speaker in line. The set calls for 2 in papallel. So when I put the other in parallel, it should jack the audio up.

I have to figure out how to mount the audio transformer.

[AC5UP]

FYI: Just for grins I decided to figure out a couple of Mystery Transformers that I've been meaning to test for way too long........

One side has a layer of silicone RTV over the taps of a winding that insulates a set of four 1N400x style diodes wired as a bridge. Interesting primary winding too. Four taps that measure 0, 110, 120 and 130 VAC when using the 0 and 120 combo. Then there's the five tap secondary that tests 0 - 10 - 33 - 56 - 70 VAC --- Or, when measuring between the taps, voltages of 10, 23, 23 and 14 VAC. Also has an 18 volt CT winding which is perfect for a 5 volt regulator.

Anyway............. The winding with the bridge diodes measured 160 VDC. In the clutter on the test bench I notice a 200mf @ 350 vdc electrolytic that tested at 300mf, so now I'm wondering what my 160 VDC unfiltered diode bridge voltage would look like if I whipped that condenser on it?

Surely the jump from Zero filtering to 300mf would make a huge difference, wouldn't it?

Measured voltage increased from 160 to 164 VDC.

Apparently a full wave bridge with no load doesn't see much time when the waveform drops below the maximum peak-to-peak voltage and since I was using a DMM the response time of the meter is way longer than any ripple at 120 cps. Otherwise the display would be a blur of numbers. If you're ever in the mood for playing Mr. Wizard, dig out a scrap transformer, rectifier bridge and electrolytic to replicate this experiment. Measure the output voltage with and without the condenser using both your Extech and 'scope, then try a larger electrolytic to see if it makes a difference.   

[N4NYY]

This is done! Pics will be posted on the 6 o'clock news!