Capacitors form factors change over time, and I have a 1989 Carver amp that needs new PS capacitors. Hole spacing on the PCB is 1/2" or 12.7mm, while snap-in capacitors are standardized at 10mm. It appears that the PS capacitors with the best specs are mostly snap-in these days like Nichicon LKG.
Is it workable to bend snap-in capacitor leads down and then back up at a slightly wider spacing, or will this make a mess? The traces on this PCB are such that moving the hole spacing is not an option.
Is it workable to bend snap-in capacitor leads down and then back up at a slightly wider spacing, or will this make a mess? The traces on this PCB are such that moving the hole spacing is not an option.
I don't want to seem ungrateful for the offer of help, but there is a wide trace carrying AC voltage to rectifier diodes in-between the capacitor leads. The holes for the original capacitors are placed such that if you moved them closer together, you'd run into the trace between the capacitor leads.
I'd really have to see the foils, but if I had a model number to go by, I'd pull up the service manual from my database.
Additionally, the parts list would have the specifics on replacements.
What exactly makes you determine the need for replacing them?
Once I flattened, or made straight like pins the snap-in leads and also filed them to fit the holes in a standard protoboard.
They can be filed a bit wide or narrow, filed to the inside or outside.
I don't think there will be enough metal to get 2+ mm.
I also think they will be too brittle to bend as much as I believe you want.
You can probably find some in a old PC supply and see how much abuse the pins will take.
They can be filed a bit wide or narrow, filed to the inside or outside.
I don't think there will be enough metal to get 2+ mm.
I also think they will be too brittle to bend as much as I believe you want.
You can probably find some in a old PC supply and see how much abuse the pins will take.
The amp is a Carver M-4.0T. I've determined the need for replacement based on tests with my diagnostic equipment that includes an ESR meter, an impedance bridge, and a scope I've used to check the ripple waveform. Age and known failures of the original rail caps in this amp also point to replacement being a good idea. The lower voltage rail caps were replaced years ago by someone else, and there is evidence that one of those leaked or blew its contents (electrolyte that was not completely cleaned up).
I've decided not to try to bend the snap-in pins on snap-in capacitors, partly due to advice I got on another forum and partly due to reading some of the capacitor datasheets that warn against putting stress on the terminals.
Plan B is getting good radial caps with the proper lead spacing.
Maybe some spec of the snap-in ones is slightly better than others, but in my book that does not justify the mechanical hassle.
0r in other words: forget the snap-in ones.
Maybe some spec of the snap-in ones is slightly better than others, but in my book that does not justify the mechanical hassle.
0r in other words: forget the snap-in ones.
Not maybe. In almost all cases snap-in caps (and screw type caps) are considerably better than their "normal" cheaper brothers with the thin ferro lead wires. Todays screw type electrolytic capacitors still have 12.7 mm lead spacing. It would require to file the current snap in holes to the right diameter of the screws. Easy job, solved. Please use washers to spread pressure and reduce contact resistance. In high power industrial devices this is the default way of mounting capacitors.
OP forgets to mention the main parameters (Car for sale: red) as capacitance and working voltage do narrow down matters.
OP forgets to mention the main parameters (Car for sale: red) as capacitance and working voltage do narrow down matters.
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Maximum diameter is 22mm, so that rules out pretty much all screw-type capacitors. I'm not new to this type of work, and I can use all the same Mouser and Digikey search parameters you can. I just usually work on older equipment, mostly vacuum tube, so I needed to refresh myself on what's available for specific PC board spacing in 2022. And a lot of products are out of stock right now, which reduces options.
And a hi to J.M. We've known each other for years on two FB groups, plus Music Electronic Forum.
Ah now we have data. It seems external caps with external rectifiers will be a viable solution. Not only are you are as keen as us: just like us you won’t find 22 mm snapin caps with 12.7 mm lead spacing.
If the newer caps are shorter, which would give you some vertical spacing to play with, how about using a small board - there are a variety of small boards available from China with a myriad of holes - as a transition device? Make larger holes on the small board to hold the snap-in cap, then solder across to pins which will fit your existing boards holes. If done carefully, it shouldn't look like a hack job.
The way these caps are mounted, horizontally with RTV between them and the chassis, I think it would make more sense to solder short extension wires to the snap-in terminals and solder them to the PCB. You're correct that "vertical" clearance is not a problem here, although cap height becomes horizontal. In the past, I've soldered wires directly to snap-in terminals when adapting them to PTP amps with no PC boards. It worked fine.
