what do people do about these "special" footprint capacitors? - Page 1
Forum section: electronics / repair

author: aarons
author_rank: Regular Contributor
timestamp: June 12, 2025, 11:35:18 pm
content: I have a failed capacitor in an HP 3455A (I'm hoping that's the only problem). It's a 5 pin Sprague and one of the pins is a fatty. I hate doing a bodge (as Dave would call it) but there isn't really any other choice, is there? Were these 5 pin footprints ever a standard? I certainly can't seem to find them at my normal suppliers. At least only 2 of the 5 pads are actually used, so it won't look too crazy.Third picture is just admiring the sculpture that is one of the PCBAs in this unit.

author: coromonadalix
author_rank: Super Contributor
timestamp: June 13, 2025, 12:52:08 am
content: and some makers used the body pins as traces, when you remove the capacitor(s) the traces get open and you have problemssome cut open their body and inside they put more modern and smaller caps for the same values and voltages, since the technology evolved,warning it could be a messy job, but keep the looks and usage

author: floobydust
author_rank: Super Contributor
timestamp: June 13, 2025, 01:40:57 am
content: Two approaches with these caps - make/buy a custom adapter PCB.Another is to measure the pin spacing possibilities (first discharge that cap lol) on the old cap, see if there is a 10mm or 15mm set of PCB holes you can use, whch are more standard with snap-ins today. I did this on a Tektronix scope. Had to jumper the ground pin because not all 4 were connected on the PCB.

author: squadchannel
author_rank: Frequent Contributor
timestamp: June 13, 2025, 01:55:56 am
content: Quote from: floobydust on June 13, 2025, 01:40:57 amsame method. adapter board and Nichicon 105°C. sometimes 3D printed housings.axial capacitors with radial and wire.RIFA to EPCOS/TDK.

author: Psi
author_rank: Super Contributor
timestamp: June 13, 2025, 02:02:43 am
content: You may find a modern capacitor is much smaller for same value and you dont need so much mechanical support like the old cap did.It does look rather large for its specs.But yeah may need adaptor pcb or jumper wires if it uses the case tabs for traces.You might even be able to cut up the old cap and use its base as an adaptor for the new cap.It looks like the outer terminals are all one piece of metal in a ring. So that bit could stay.You may even find that there is already a physically smaller cap soldered inside.16.00mm x 26.50mm for 7500 µF 16 V 105C electrolytichttps://www.digikey.co.nz/en/products/detail/chemi-con/EKYC160ELL752ML25S/10486441

author: floobydust
author_rank: Super Contributor
timestamp: June 13, 2025, 02:42:55 am
content: I can see most offerings are LS=7.5mm and a few 10mm parts. They are much smaller in size which is a nice bonus, and some are tall and slim, others shorter and fatter.7,500uF ±20% is 6,000-9,000uF I think. I would also recommend upsizing to the next standard value like 8,200uF because although you really got your money's worth at least rated 7,500uF back in 1979, today's manufacturers are literally at -19% all lower than expected but within spec.I liked UHE1C822MHD or EKYB160ELL822MLP1S kind of cap. See what height you have some are 33/37mm but slim.

author: Psi
author_rank: Super Contributor
timestamp: June 13, 2025, 02:48:50 am
content: What's the voltage it has top handle? 10V?

author: aarons
author_rank: Regular Contributor
timestamp: June 13, 2025, 05:35:07 am
content: Cutting open the old one is an interesting idea.i may do that to satisfy my mild obsessiveness.But meanwhile I had a new 10000uF, 35V chemi-con sitting here so I put that in and this DMM went from a crazy freakout on power up to working perfectly. The old cap measures a capacitance (@120Hz) of 134.46 nF, so basically all 7500 μF have escaped since 1979. It also has an ESR of 78k, so really as dead as can be.The current replacement isn't as sturdy, but it'll do until I cut open the old one.What is a good method for cutting these open so it ends up going back together in a pleasing way?