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Proper polarity for filter caps in 1936 models - Printable Version

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+--- Thread: Proper polarity for filter caps in 1936 models (/showthread.php?tid=1487)


Proper polarity for filter caps in 1936 models - BDM - 11-11-2008

Gents, just a note. Some may know this, others may not. Ed(etech) pointed out something very important. I'll use my 116B as an example since I screwed up on this model. Cap #101 which filters the negative grid voltage of the P-P 42s and center tap of the transformer, should be positive to ground(meaning the floating ground). The schematics on-line do not indicate this. But Chucks schematics do(sorry I missed that fact) Icon_confused . I had mine connected backwards with negative to ground. Since there is only around 25v on this cap, my replacement cap didn't pop since it's rated at 500v. But, I noticed a low level hum with no antenna connected. I figured I would address this later on since it wasn't noticed with any level of signal.

Just thought I'd point this out since several of you hollow state fanatics(me included), are restoring these sets. The same cap is used on other models such as the 650(cap #77).

Re: Proper polarity for filter caps in 1936 models - exray - 11-12-2008

Ding-ding...

When I recently went back thru my 630 set that I had done back a few years ago as a newbie I found I had committed the same error. And yep, I used a 450v cap so it never popped. Didn't seem to make any difference but who knows what might happen in the future as the cap degrades.

RE: Proper polarity for filter caps in 1936 models - tig1 - 09-16-2014

Hi, i'm doing a 116b right now and just ran into this. So both sections of #101(8 and 10mfd) are positively grounded? I'm restuffing them now. Is the other 8mfd also positively grounded? And do you by chance have a copy of the schematics you used? Icon_biggrin

RE: Proper polarity for filter caps in 1936 models - Mondial - 09-16-2014

Just remember that the most negative voltage of the radio is found at the center tap of the power transformer. Therefore the negative side of all three caps should connect there at that point.

Only the positive of the 10 uF cap (101) should connect to ground. The positives of the 8 uF caps should connect to each side of the filter choke.

RE: Proper polarity for filter caps in 1936 models - morzh - 09-17-2014

This will get re-discovered many times to come..... Icon_smile

RE: Proper polarity for filter caps in 1936 models - tig1 - 09-17-2014

And luckily getting re-solved with this thread. Thanks!

RE: Proper polarity for filter caps in 1936 models - Arran - 09-18-2014

This is one situation in which a non polarized capacitor could be used, if practical to do so. Since it's only 25 volts it would be easier to do then with a typical filter capacitor, more compact and more sizes available to play with.
Regards
Arran

RE: Proper polarity for filter caps in 1936 models - Kenneth F. Besso Jr. - 12-25-2014

    I would like to know if this same thing is suppose to be on the early(March 1935) model 620,,,,I went by the print on Philco page 6-25---,,,,,where # 68 capacitor is showing negative to ground(chassis),,,coming off wire wound resistor #70,,this radio worked GGreat for 3 hrs (Great volume,and sound),,,shut it off,,,turned back on next day,,,can't get 1/4 of the volume back now,,,( NO HUM either).. When I got this set ,,,these's parts were missing,,,didn't know about a floating ground,,,soo you are telling me that it should be (+) positive part of the capacitor is to go to the chassis (ground)????? Icon_crazy ,,thank you for all your Help,,,just a newbie,,,,Kenjr

RE: Proper polarity for filter caps in 1936 models - morzh - 12-25-2014

Yes the 68 cap should have PLUS to the chasis.

BTW on page 6-25 it shows no polarity.

http://www.nostalgiaair.org/PagesByModel/804/M0013804.pdf

RE: Proper polarity for filter caps in 1936 models - Kenneth F. Besso Jr. - 12-25-2014

(12-25-2014, 12:36 AM)morzh Wrote:  Yes the 68 cap should have PLUS to the chasis.

BTW on page 6-25 it shows no polarity.

http://www.nostalgiaair.org/PagesByModel/804/M0013804.pdf

Thank you for your help,,,,I will change this out tomorrow,,,Xmas 2014,,,and hope this fix will get my sound back,,,Happy New Year, to all on this site,,,,Ken jr