Replacing old five pin capacitors - Page 1
Forum section: electronics / repair

author: reddish75
author_rank: Regular Contributor
timestamp: September 22, 2022, 03:19:23 pm
content: I am finally thinking about refurbishing an Audio Research D76 someone gifted me and am wondering on the best way to replace the power supply caps (x6 600uf 300v) they are five pin I think old Mallory caps. I have seen an adaptor someone made for a broken Tek scope but I'm not sure they would be suitable for the voltage I need as they replaced 75v caps (please see pic) the other option seems new caps of that value and voltage tend to be snap on would be to drill the pcb and jumper one terminal across. Any thoughts?

author: Grandchuck
author_rank: Super Contributor
timestamp: September 22, 2022, 05:09:18 pm
content: http://www.rsdsound.co.uk/product/axial-to-radial-electrolytic-capacitor-adapters/

author: james_s
author_rank: Super Contributor
timestamp: September 22, 2022, 05:18:19 pm
content: A lot of guys just install new modern capacitors under the chassis and leave the originals in place but electrically disconnected. If you want to get fancy you can disassemble them, pull out the guts and stuff modern parts inside them, usually new capacitors are smaller and can fit in the old can.

author: wraper
author_rank: Unknown
timestamp: September 22, 2022, 05:22:16 pm
content: Imho you could just put a new capacitor into positive and one of the negative holes which match the pin pitch the most. Of course it does not work if you want to retain original look.

author: Gyro
author_rank: Super Contributor
timestamp: September 22, 2022, 05:31:03 pm
content: Irrc, on some Tek 400 series scopes, the PCB uses capacitor negative tabs for trace continuity. Not a problem, but you do need to check and, if necessary, jumper the pads to maintain continuity.

author: floobydust
author_rank: Super Contributor
timestamp: September 22, 2022, 05:41:03 pm
content: I've made adapter PC boards then foolishly realized the new snap-in cap has 7.5mm or 10mm lead-spacing and can just fit right on the main board between two (old) pins. Try measure it. I add jumpers if required to join the extra case pins.

author: reddish75
author_rank: Regular Contributor
timestamp: September 22, 2022, 06:10:52 pm
content: Quote from: james_s on September 22, 2022, 05:18:19 pmThis was thought about and I do like the idea in keeping the original look but I don't think I'll go down this route as I like to know everything is installed properly and will last.Quote from: Gyro on September 22, 2022, 05:31:03 pmGood information to keep in mind but it's not a Tek scope it's a valve amplifierQuote from: floobydust on September 22, 2022, 05:41:03 pmProblem is the caps have individual cut outs on the chassis which they go through although one pin will line up the other wontQuote from: Grandchuck on September 22, 2022, 05:09:18 pmThats a good adaptor but not the type I was looking for

author: reddish75
author_rank: Regular Contributor
timestamp: September 22, 2022, 06:17:55 pm
content: Has anyone used the adaptor in post one for 300vdc + or have an opinion about its suitability?

author: wraper
author_rank: Unknown
timestamp: September 22, 2022, 06:27:27 pm
content: Quote from: reddish75 on September 22, 2022, 06:10:52 pmThen I would lead form negative lead very close the the can, maybe put some insulation on the lead. Then before soldering put a blob of electronics grade or just usual neutral silicone under the cap for mechanical support.

author: Gyro
author_rank: Super Contributor
timestamp: September 22, 2022, 07:32:37 pm
content: Quote from: reddish75 on September 22, 2022, 06:10:52 pmThat doesn't mean it's the only place it has ever been done, always check. The consequences of an open 0V trace on a valve amp PCB could be considerable.

author: reddish75
author_rank: Regular Contributor
timestamp: September 22, 2022, 07:39:15 pm
content: Quote from: Gyro on September 22, 2022, 07:32:37 pmAbsolutely! Just wasn't sure you realised it wasn't a scope

author: tkapusta91
author_rank: Newbie
timestamp: January 17, 2025, 03:59:15 pm
content: Hi!I know this post is older so there may not be a reply.I was curious if you discovered a solution to this problem? I have an ARC D76 as well and would like to replace the cans as well. The date codes are 10/88 so they're not original at least but still old enough. Im running into the same issue finding the 5-pin capacitors. Did you just use the 2 pin ones and jumper the other traces? Thanks in advance!

author: GLouie
author_rank: Regular Contributor
timestamp: January 17, 2025, 05:03:11 pm
content: Not affiliated, but CE in the USA still manufactures some can capacitors using the old Mallory equipment. Otherwise, you may have to resort to one of the alternatives mentioned above.https://www.cedist.com/products/capacitors?filters=2341a2356https://www.cemfg.com/can-capacitors

author: Stringwinder
author_rank: Contributor
timestamp: January 17, 2025, 05:34:41 pm
content: The only time I've come across five-lead electrolytes caused a alot of headscratching.The PCB design used the internal connections inside the capacitors as jumpers tosimplify the copper traces. Not easy to replace and jumpers and a plywood crosswith waxed thread holding them in place (four in all) was needed for mechanical stability.Two pins compared to five gets wobbly and sensitive to vibration and shocks.The products resurrected were lab power supplies - Switchbox SB 15-20 and SB 30-10 (from Powerbox).300 watts in a box 30x22x9 cm leaves little room for changes to the layout.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 17, 2025, 05:56:55 pm
content: to resumeyou have the choice to find identical pinouts ... if they still existsfind pcb adapters / converters, to mimick the old pinouts with new modern capsto cut them open, and fit more recent in them, to keep the look ...and yes thoses who used the casing pins to transfert traces / conductors dang messy situations when you forget that "small detail"had problems in Fluke equipment's because of that "small detail", took me a while to remember that