[Warren]

Thanks, Morzh...Thats pretty much what I thought but I wanted to ask since it has been so long since I did much with electronics. I think the lady on the phone just didnt want to go look the info up.

[Warren]

OK, Maybe I have been reading to much or worrying to much about this but I read something about most caps that are rated above .001uf are probably mica caps so they wouldnt normally be changed. I see caps that look like normal paper caps rated above that in my radio. I have about 23 - 100pf caps, for example, but they dont look like the "dominoe" type caps usually refered to as mica caps. Is what I read something that doesnt mean much or should I not replace those caps above .001uf unless obviously bad? Thanks for your time on this probably dumb question. Warren

[Chuck Schwark]

Any cap smaller in value than 0.001uF, not greater, is most likely a mica type cap.

The parts listing for a particular radio model may also indicate a mica type. Post-war models, like yours, most
certainly had a parts listing in the multi-page service bulletin.

Philco did, on occasion, use rolled wax paper caps in pF sizes instead of mica, but usually inside bakelite blocks.

Chuck

[Warren]

Im sorry, smaller in value,....
Yes, i have a parts listing but it doesnt say much more than the value of the cap and maybe what it is used for. It does not say, paper, mica, etc. it does say if electrolytic though.
It would be easier if they did specify which kind of caps they were, I agree. Actually there is one cap that just says .003 ... no mf or mmf by it, just .003 then "high frequency". I am hoping looking at the cap itself will tell me if its a uf or pf cap.

[codefox1]

My post got lost, .003 almost certainly a paper capacitor. You can use 630 VDC mylar or poly capacitors to replace just about any paper cap in old radios, save the one from the plate of the output tube. Use 1000 VDC type for that one. I keep 450 VDC electolytics around, because, again, they can be used for almost any set with equal or less B+.

Micas are generally below .001 mf, or basically less than 1000 pf. (same!) Generally OK to leave alone, but seen enough bad ones that for a simple set with only a few of 'em I replace with recently manufactured 500 volt silver micas. I also routinely replace carbon resistors whilst doing capacitors, easy and cheap enough to do. Result is long term reliability, easier alignment, and usually much better performance. I'd order all the stuff you need at once to keep shipping delays and costs in check. Lots of good places to order online mentioned all the time here; Mouser, Digikey, Jameco, Just Radios and lots of others.

Best!

[Warren]

Thanks, I just have to find out if the .003 is uf or pf. Being new to tubes, im not sure which is the output tube, maybe I can figure it out by the schematic.
My set has like, 23 - 100pf caps, are you saying I should replace those with mica caps? Also, yes I was planning on replaceing all the resistors at the same time as the caps. Im sure to some its a dumb question but Can someone tell me the reason for useing mica caps instead of film caps? Is it because they are more reliable at those values? If so it would be a good idea to replace anything smaller than .001 uf with mica? Just trying to make a little sense in my mind so I understand how it all works a bit better. Thanks Chuck and Codefox for your answers, and anyone else that might add here.

[BrendaAnnD]

Most of those look to be RF bypass caps. For that, you don't need mica caps. Disc ceramic caps will do nicely. 100pF disc ceramics can be purchased by the 100 lot for just a few dollars.

[Warren]

Hmmmm, now disc ceramic caps. Can someone explain to me how to choose which type of caps is best to use for what? Paper caps should usually be replaced with newer film type caps , I hear. I can get film type axial caps at 100pf, now I am told to use ceramic disc caps. I would like to understand how we are deciding which types are better for what. Maybe I need to study up on the different types of caps to understand what to use for what types or values. Thanks for all replies.

[BrendaAnnD]

The rule of thumb I go by is:

High frequency RF bypass (under 100pf): Disc ceramic
Low frequency RF bypass (120pf-500pf): Silver mica
ALL tuned circuits: Silver mica
AF coupling and bypass caps: poly caps

Others may have other criteria, I defer to those such as Ron and others who have more extensive experience with these radios.

[Mondial]

Different types of caps have different strengths and weaknesses:

Disc ceramics are very good for RF bypasses, but unless they are NPO (COG) temperature stable types, their capacitance value may vary greatly with temperature and applied voltage.

Silver micas are typically used in RF tuned circuits as their capacitance value is stable with temperature and over time. Disadvantage is that they are somewhat expensive.

Film types are available in larger values and typically used as low frequency bypasses and coupling caps. Not the best choice for very high frequency RF as they have higher parasitic inductance than ceramics or micas.

Your radio operates at FM broadcast frequencies (88-108 MHz) so the RF caps can be more critical. If it were my radio, I would leave the low value caps alone for now, as the original caps are certainly either ceramic or mica. They are quite reliable and replacing them in the FM front end may cause problems with oscillations and instability.

[Warren]

So you are suggesting not replacing any caps below .001uf? I can start with that, my only concern is this radio survived a house fire and I was a little worried about whether they were good or not. I suppose I should probably buy a capacitor testor to check any caps below .001uf. If I understand right about the value and to replace just the caps @ 001.uf and above let me know if you can. Thanks everyone for your help, I appreciate any info anyone has to tell me.

[Mondial]

My suggestion would be to replace all the wax paper caps first. These are the ones that are problematic, and in your radio have values of .003 uF and larger. C215 with a value of .001 uF also seems to be a paper cap, along with line bypasses C100 and C101 which should be replaced

Looking at your earlier chassis photo, the 100 pF bypass caps appear to be tubular ceramics as do the 1000 pF and 1500 pF values, and as such are very reliable and would be unaffected by the heat from the fire. I would leave these undisturbed. There are also some postage stamp micas which I would also leave alone.

[Warren]

Thanks Mondial, I was wondering about the 100pf that were little round ones, now I know those are tubular ceramic. I was thinking to leave the postage stamp ones there, I will also leave all the 100pf tubular ceramics to for now. From what I understand the c100 and c101 need to be Y rated so I will buy them Y rated. I will replace all others and the resistors. Thanks for yours and everyones elses help for me to understand.

[Warren]

Well. I'm Happy to report after replacing the Caps and most resistors My tuner is receiving both AM and FM stations. Didn't get anything on the SW band but not sure if it just needs an alignment and maybe a better antenna to receive anything (maybe there just wasn't anybody out there, don't know), what do you think? Also, is there anything besides doing an alignment that I should do since it is receiving stations? Should I check the different voltages or because it is receiving well I shouldn't worry about anything except doing an alignment? Then, to get it all back together and looking good with new dial glass, etc and finish the cabinet. I want to thank everyone for their help, it probably wouldn't be working this far without all of your help. Warren

[Warren]

I take it since I didn't get any answer that I probably only need to worry about doing an alignment on the radio at this point. I guess that's my next step. Thx, Warren