Now that I've fixed enough items that I can actually receive radio stations, and while waiting for some wire to rewind coils properly, I have two issues where I need some advise.
First, the audio output transformer primary is open. Has anyone rewound this transformer and if so, how hard was it? I'm using a filament transformer and spare speaker temporarily.
Second, the radio dial is warped in a few places, which I assume happened due to heat. I am thinking about heating this dial with a low heat source and trying to flatten it out by placing a weight on it. Does this make sense?
Thanks.
Hi Harv! Welcome! Ive never rewound a philco audio out transformer, but have bypassed a few open-primarys in the past by using the R/C method to make the origs work again. Im sure someone here will be able to give you specific directions for rewinding it.
As far as smoothing-out warped plastic philco dial scales, never try using a heat-gun! Even the low heat setting is more than the vintage dials can handle! Instead of "flattening", they shrivel-up and actually start burning-up real fast! Ive never tryied using a clothes type iron before, but it may work set on a real-low heating temp, using a damp towel between iron & dialscale? But then again, be careful how damp the towel is also, or it will dissolve the orig ink printed.
There are several different model vintage Philco re-pro plastic dialscales now avail at:
http://www.radiodaze.com if all else fails, they may have one to fit?
Best of luck with your mod 60!!
Thanks for the warning. I guess I forget that some of the materials used in these old radios are rather fragile. Maybe I'll just try a weight on the dial and see if it flattens out by itself.
I'm curious what the R/C method is to bypass open primarys. Never heard of that one.
Another source of dial scales is Mark Oppat, Old Radio Parts:
http://www.oldradioparts.net/
His dial scales are translucent, just like the originals, and the color is faithful to the original amber. The Radio Daze scales are laminated, and a pale yellow in color.
I have never gone to the trouble of rewinding an audio output transformer, although the idea certainly has merit.
I will share info in a new "thread" here on the Philco Electronic Restoration thread, on how to use the R/C method ( resistor & capacitor), to bypass defective orig audio & IF transformers. It was written by Norm Leal many yrs ago, and has worked for me very well throughout the yrs of servicing vintage radios, nomatter brand, race, color,creed, religion, or political-party affiliation! Since it takes awhile to type all this in, hope the space requirements on this forum allows? I will try.
I read your write up on using R/C to replace a transformer, and I understand how this would work for a I.F. transformer or interstage transformer. Both of these circuits are high impedance.
When trying to use this technique to match a speaker, I'm bothered by the fact that I'm trying to match a tube output impedance (high) to a speaker that is only a few ohms. I would think that there would be a large loss in receiver volumn using this technique because the low speaker impedance would be reflected back to the output tube. I have to try this technique because I may be missing something.
Harv
A replacement audio transformer from Radio Daze (#HX124- ) is as cheap as $13.26 for a 5 watt rating. The max. output of the Model 60's 42 tube is 3 watts so there's plenty of safety here. There are several mounting sizes available.
On the dial I agree with Ron- Mark Oppat is the way to go; his quality and original appearance are superb. Go to:
http://oldradioparts.net/
Thanks for the transformer info. I happened to stop into one of the remaining radio "junk" houses here on L.I. today and found a Thordarson output transformer rated at 12W and with an output impedance usable with this radio. I also picked up a 8 hy choke in case the I can not get the damaged speaker that was in this radio working. I managed to get both for $15 after some haggling. When I think of what I've thrown out during my 50 years as a HAM, and how much of it I could use now, I cringe. I sure miss Radio Row that I frequented as a young HAM.
I think I've completed the electrical renovation of my radio with my correctly rewinding the oscillator and antenna coils, thanks to help from Ron, but have one question regarding the factory mods made in later models. According to the factory sheets I ordered from Chuck, some production changes separated the 6A7 and 78 cathode connection and changed some resistor values. Due these changes make a large enough increase in sensitivity to warrant installng them? Thanks.
Apparently you have not read the page on my website giving all of the changes to Model 60.
http://www.philcoradio.com/tech/60evol.htm
That having been said, I do not feel the later changes make a
greatly significant difference in sensitivity.
I did read this web page Ron, and looked at the changes to the radio circuitry. I did not see any conclusion on this web page indicating whether these changes made any significant improvement in radio performance. You answered my question. I won't go to the effort to perform these "upgrades".
Hi Harv
Cool, just wanted to make sure you were aware of that page.
