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capacitor question? - Printable Version

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capacitor question? - Guest - 10-31-2009

Does it make a difference what the capacitor looks like for the non polorized capacitor. meaning does it have to look like a small can with a wire comming out of each end or can one that looks like a chicklet piece of gum work as well?? I have been recapping my 38-60 radio and the guy mailed me ones that are .1k x 630p but now that I have changed them out my radio now has very low volume. thanks Shawn

Re: capacitor question? - Alan Douglas - 10-31-2009

I see two 0.1 µF capacitors in the schematic, one screen bypass and one AF grid-bias bypass. Neither one has much voltage on it, and neither value is critical, so if the radio worked before, but doesn't now, there must be something else wrong. You didn't wire the grid-bias bypass to the wrong side of the resistor, by any chance? Or damage one of the screen resistors?

Re: capacitor question? - Guest - 11-01-2009

I see two 0.1 µF capacitors in the schematic, one screen bypass and one AF grid-bias bypass. Neither one has much voltage on it, and neither value is critical, so if the radio worked before, but doesn't now, there must be something else wrong. You didn't wire the grid-bias bypass to the wrong side of the resistor, by any chance? Or damage one of the screen resistors?




I am sorry but I will probably have to send this radio to someone who knows what to do! you are speaking a foreign language to me I have never attempted to do anything like this before and I dont know what a AF grid- bias bypass and screen resistors are! I basically clipped 3 of the capacitors out and replaced them first and put the radio back together to test before I was going to move forward. I had plenty of volume before and none now. didn't know if it is because I ordered a capacitor that looked different than the one that I took out.

Re: capacitor question? - codefox1 - 11-01-2009

Please don't give up so easily. I've been tinkering with this stuff part time for over 40 years on an off, and there's a set on my bench that has been eluding me for a month! As suggested, before, measure the resistors and double check your connections. Part of this hobby is being a detective. Sometimes when you solder in a new component, you can cause a resistor that was probably out of tolerance anyway to open up. They cost less than a dime each to replace anyway.

We'll help you if you want to continue!

Re: capacitor question? - Guest - 11-01-2009

thanks for the vote of confidence! do you think that the manual would help me chase the wiring down for this radio? the schematic seems vary confusing to me. If I could see what it is suppose to look like a lot closer up might help me. Shawn

Re: capacitor question? - gary rabbitt - 11-07-2009

HI Shawn,
I doubt that the new caps would be the cause of the low volume. Is there a possibility that you may have miswired one of the three caps? Or, that you replaced the cap with a different value?
The 'manual' for the set probably wouldn't have any wiring diagram to go by. The schematic is the best way, and I can understand how you could find it daunting.

In learning how to interpret these, you must compare what you see on the chassis, to what you see on the diagram. Start with the power cord, it is pretty much self explanitory. Other parts can be identified, such as the tubes and the capacitors.
Select one of the caps you replaced. See where it is connected under the chassis. "One end of the cap is connected to pin 4 of the xxxx tube, and the other end goes to a 470,000 resistor....." Then look at your schematic and try to find it there.

You should see the cap connected to the places you saw physically. Do that with the other caps. If you had good volume before, and only replacedd 3 caps, I suspect that one wire was misplaced. If not, then perhaps you moved another wire so that it is touching something? Check to see if the tubes are in their proper sockets.

Don't give up so fast, you may eventually get it. But I'd suggest that you don't replace any other caps until you have verified everything is in the correct place, and tried to get the volume back. Replacing more caps could add to your problems.
Take care,
Gary.

Re: capacitor question? - Guest - 11-11-2009

thank you for the advice Gary I have been going to sites that teach how to read a wiring diagram and am learning the symbols and stuff. I will take a pic of the underneath and see if anyone can see where I might have gone wrong. thank you for your help. Shawn

Re: capacitor question? - Alan Douglas - 11-12-2009

Some of us just grew up with schematics and take them for granted, like learning a language. We tend to forget how long it took, at the time.

Re: capacitor question? - Guest - 11-17-2009

I'm a Navy trained electronics technician (well versed in good ol analog circuitry), but the existing schematic for the Model 37-640 I downloaded has parts callouts and notes, etc, listed somewhere on a missing page. Is there another data source or website where this information might be available? Also, is there someone who could come up with a bill of material for the electronics restoration? (I'm hoping to restore this unit for a non-profit furniture business, and they wanted a ballpark guesstimate on costs). Thanks! Bill pipern998377@yahoo.com

Re: capacitor question? - exray - 11-19-2009

Did you try here?
http://www.nostalgiaair.org/PagesByModel/216/M0013216.pdf

All of the parts lists, etc seem to be there.

GL,
Bill

Re: capacitor question? - Ron Ramirez - 11-19-2009

Tom Bavis also has the schematic on his site (note that it is in DJVU format):
http://www.audiophool.cjb.net/Philco.html