Confirm capacitor polarity - UK Vintage Radio Repair and Restoration Discussion Forum

Brett530 · 16th Feb 2023, 8:03 pm

I'm recapping a Hallicrafters SX-62 and wanted to confirm polarity on one of the capacitors. The parts list says it is electrolytic (10uF 25v) but the schematic does not indicate polarity. There is a little + on the capacitor, but I wanted to confirm the + was for the right side being positive (in the photo).

Brett530 · 16th Feb 2023, 8:10 pm

I should have included it is C107 in the schematic.

Radio Wrangler · 16th Feb 2023, 8:15 pm

It looks so. The end to pin 3 on the valve socket will be the positive end.

You have a fair crop of wax/paper capacitors about too, and carbon resistors are worth a stab with the ohmmeter. The big one in the middle looks to have sweated a bit.

David

Silicon · 16th Feb 2023, 8:29 pm

The photograph does not appear to match the part of the schematic you have selected.

I would expect the positive side of a 'cathode bypass' electrolytic capacitor to be connected to the cathode.
The cathode would be on pin 3 of the 6SL7 valve holder.

The photograph appears to highlight a waxed paper capacitor.

Brett530 · 16th Feb 2023, 8:38 pm

You are right. The capacitor of interest is connected to pin 6 of the valve socket. Let me go back to the schematic. Stay tuned.

Brett530 · 16th Feb 2023, 9:03 pm

The socket the capacitor was soldered to in the photo on the left is V13 (6V6GT). On the bottom of the socket, it was soldered to pin 6 (based on the imprinted label). It looks like pin 6 was just used as a soldering terminal with no connection to the valve.

So, what I think is the positive side of the cap, connects to a terminal on the right that has a jumper-wire to pin 3 of the V-11 (6SL7) valve.

Sorry for the confusion. So pin 3 would be the positive side of C107?

ms660 · 16th Feb 2023, 9:17 pm

Ref. the previous post, folks can see the wiring here, the 6SL7 valve holder being the bottom right one in the group of four:

https://vintagetubeelectronics.com/w...SX-62A-003.jpg

Lawrence.

Brett530 · 16th Feb 2023, 9:23 pm

Thanks for that reference. That is opposite of what I thought. Negative side of the cap connects to pin 3 via the jumper wire.

Uncle Bulgaria · 16th Feb 2023, 9:23 pm

Quote:

Originally Posted by Brett530

Sorry for the confusion. So pin 3 would be the positive side of C107?

Yes. Noticed R76 is grounded, so the negative side of C107 would be towards the 'earthier' side. The cathode is being held positive with regard to ground by the combination of R74 and R76.

https://en.wikipedia.org/wiki/Cathode_bias

Make sure you check the waxed paper capacitors as Radio Wrangler says. They're most likely to be leaky, and rather more of a problem than a cathode bypass capacitor.

Brett530 · 16th Feb 2023, 9:39 pm

Thanks! And yes, I'm replacing about 50 capacitors (a kit from HayseedHamfest).

16th Feb 2023, 8:03 pm	#1
Brett530 Diode Join Date: Mar 2021 Location: Salt Lake City, Utah, USA Posts: 8	Confirm capacitor polarity I'm recapping a Hallicrafters SX-62 and wanted to confirm polarity on one of the capacitors. The parts list says it is electrolytic (10uF 25v) but the schematic does not indicate polarity. There is a little + on the capacitor, but I wanted to confirm the + was for the right side being positive (in the photo). Attached Thumbnails

16th Feb 2023, 8:10 pm	#2
Brett530 Diode Join Date: Mar 2021 Location: Salt Lake City, Utah, USA Posts: 8	Re: Confirm capacitor polarity I should have included it is C107 in the schematic.

16th Feb 2023, 8:15 pm	#3
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,869	Re: Confirm capacitor polarity It looks so. The end to pin 3 on the valve socket will be the positive end. You have a fair crop of wax/paper capacitors about too, and carbon resistors are worth a stab with the ohmmeter. The big one in the middle looks to have sweated a bit. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

16th Feb 2023, 8:29 pm	#4
Silicon Nonode Join Date: Jun 2007 Location: Coulsdon, London, UK. Posts: 2,163	Re: Confirm capacitor polarity The photograph does not appear to match the part of the schematic you have selected. I would expect the positive side of a 'cathode bypass' electrolytic capacitor to be connected to the cathode. The cathode would be on pin 3 of the 6SL7 valve holder. The photograph appears to highlight a waxed paper capacitor.

16th Feb 2023, 8:38 pm	#5
Brett530 Diode Join Date: Mar 2021 Location: Salt Lake City, Utah, USA Posts: 8	Re: Confirm capacitor polarity You are right. The capacitor of interest is connected to pin 6 of the valve socket. Let me go back to the schematic. Stay tuned.

16th Feb 2023, 9:03 pm	#6
Brett530 Diode Join Date: Mar 2021 Location: Salt Lake City, Utah, USA Posts: 8	Re: Confirm capacitor polarity The socket the capacitor was soldered to in the photo on the left is V13 (6V6GT). On the bottom of the socket, it was soldered to pin 6 (based on the imprinted label). It looks like pin 6 was just used as a soldering terminal with no connection to the valve. So, what I think is the positive side of the cap, connects to a terminal on the right that has a jumper-wire to pin 3 of the V-11 (6SL7) valve. Sorry for the confusion. So pin 3 would be the positive side of C107? Attached Thumbnails

16th Feb 2023, 9:17 pm	#7
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Confirm capacitor polarity Ref. the previous post, folks can see the wiring here, the 6SL7 valve holder being the bottom right one in the group of four: https://vintagetubeelectronics.com/w...SX-62A-003.jpg Lawrence.

16th Feb 2023, 9:23 pm	#8
Brett530 Diode Join Date: Mar 2021 Location: Salt Lake City, Utah, USA Posts: 8	Re: Confirm capacitor polarity Thanks for that reference. That is opposite of what I thought. Negative side of the cap connects to pin 3 via the jumper wire.

16th Feb 2023, 9:39 pm	#10
Brett530 Diode Join Date: Mar 2021 Location: Salt Lake City, Utah, USA Posts: 8	Re: Confirm capacitor polarity Thanks! And yes, I'm replacing about 50 capacitors (a kit from HayseedHamfest).