Screwed up

[Sterling Spurrell]

It looks to me that you have the two positive ends twisted together. So that tells me you had them installed with both positive leads to B-rail instead of negative . Just look at the arrow and negative symbol on the side of the cap .

• This reply was modified 6 years, 2 months ago by Sterling Spurrell.

[garykuster]

I had read that on the newer caps that didn’t matter. when I test them, they test the same back to front. Only the old caps were directional I thought.

[Jean Marcotte]

Gary, I misled you with testing the filament of the burnt 34W4. I had it reversed. Pin 4 and 6 open means a B+ problem. Now looking at the photo of the caps, I see that you twisted the positive sides of the new caps together. You need to do the opposite. There is a band on the cap with the negative sign and an arrow pointing to the negative side. A capacitor installed with reverse polarity can explode in your face. You were lucky it did not. This beeing said, I dont see how caps with polarity reversed could cause the problem you have. One of the caps may be leaking even if they are new. Testing the capacity won’t necessarily show a leak because the tester is only putting a few volts through the capacitor. If you have more caps try others with good polarity this time or if you dont have more you can even try to reinstall these with proper polarity, you never know.

[Jean Marcotte]

Some condenser dont have a polarity but when the negative side is indicated on one it is important to respect this.

[garykuster]

Thanks, Sterling for your sharp eye. Thanks Jean et al. Until those caps, I had replaced smaller caps where polarity isn’t an issue. Then I read that the newer caps no longer have a polarity issue. partly true, but not for the larger electrolytic caps! Radio is back together correctly and plays loud and clear! Thanks for all that took the time to help a newbie out. I can get a little obsessed when I’m trying to solve or understand the problem and can’t move on until I find an answer. I have ordered a proper capacitor checker ( Circuit Test LCR DLM 260) after reading that my Fluke is too low powered to properly check caps. I will slowly build up my workshop bit by bit.

Thanks again, Gary in Montreal

[John Greenland]

Hi Gary,

I can make one more suggestion after you sort out the caps. Before you power up the radio again, temporarily remove the wire from pin 7 of the 35W4.
This will remove the high voltage from the rest of the radio.
If your 35W4 now seems to be alright, then you now have a high voltage (B+) issue to look for.
If not, then the problem is almost gauranteed to be in the heater circuit of the 5 tubes.

regards John G. VO1 CAT

[garykuster]

Thanks, John
All is good. Radio sounds as good as it can with it’s little speaker. Good if you want to hear excuses why the Canadians aren’t going to make the playoffs, less good for music. Very bright sound.
The AA5’s don’t hold a candle to the old Philcos from the 40’s.

Gary K

[Gary Albach]

Hi Gary – check the polarity of the two new filter caps. From the picture it looks like they both might be installed backwards. The two negative leads should be connected together, not the two positive leads.
Gary A.

[garykuster]

It’s a long string, to read, but It was the polarity on those 2 caps which somehow killed the 35W4. Once that was figured out and repaired the radio plays as great as a AA5 can play with a little speaker.

[Gary Albach]

Oops, sorry for the delay here. Didn’t see the end of all the posts – glad you got it working. Shows me just how tough modern electrolytics can be! But as Jean said, you were lucky this time. Let the radio play for a few hours to make sure the new caps weren’t weakened by being reversed.
Gary A.

[Jean Marcotte]

A friend confirmed that electrolytics installed with reversed polarity can draw substantially more current, confirming your problem. And I learned something ot of this.

[garykuster]

Me too! and it only cost me 2 35W4’s! I won’t make the polarity mistake again!

[Dan Middleton]

Gary,
One or both electrolytics May have shorted under the B+ voltages. If you don’t have a leakage tester connect the capacitor to a source of high B+ through a 10k resistor. The voltage across the capacitor should be the same as your B+. Any lower and the capacitor is bad.
When working on a radio I keep a 40 watt lamp in series with it. If the lamp lights up bright there is a problem and the lamp limits the current to protect the radio.

[garykuster]

Hi Dan, I think that was a micro Emerson that I sold 2 years ago in Montreal! I do plan to make a light for that purpose, but radios are more of a winter hobby for me. I keep buying them all year and stockpile them when I’m stuck in the house.

[Ralph Spracklin]

It seems we were through a similar senario, on this site, a while back. Or did I see this on another site???? While I think this problem started out with a single problem, that of the electros wrongly wired, which somehow overloaded the dial lamp, (the weakest link in the filament circuit) it does nor surprise me that the demise of 35W4 would follow. It seems that the way the circuit using a 35W4 with its tapped filament is designed, the loss of the 35W4 was destined to follow. This can and maybe always, eventually cause the loss of the tube itself. So! If the dial lamp has not been replaced, do so immediately, or you will possibly lose a third 35W4 in the near future.

Ralph

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