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Wanted: Electrolytic caps for DRSSTC bus

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cjk2

Thu Jul 29 2010, 01:05AM

Registered Member #51 Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263

Does anyone have a pair of 3000-6000 uF, 200-400v caps they would be willing to part with? I only require screw terminals on top and a 2000 or later date code.

Can anyone help?

Barry

Fri Aug 06 2010, 06:30AM

Registered Member #90 Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301

Did you find what you're looking for? I might have a couple big electrolytic caps that may work.
Is the date code requirement important? Does it mean you want something manufactured in year 2000 or later?
Cheers, Barry

cjk2

Fri Aug 06 2010, 05:44PM

Registered Member #51 Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263

I found some caps on ebay that I can use if needed, I would still rather find some RIFA, BHC, AeroM, etc. caps that are actually rated for 50A or so of ripple. It is important to me that the caps were made in the last 10 years. I will likely accept any caps that have large high current terminals on top (not just normal threaded holes), are >=200v, >2000uf, and dated 2000 or later.

The type of caps I am looking for start at around $60 each new, so I would be willing to pay at least $20 per cap provided they are what I am looking for.

I have a feeling that I am too picky to find what I am looking for surplus, so I may well end up just buying new caps

803

Fri Aug 06 2010, 06:02PM

Registered Member #2807 Joined: Fri Apr 16 2010, 08:10PM
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Posts: 191

Can you explain why you need <10 year caps?

cjk2

Fri Aug 06 2010, 09:58PM

Registered Member #51 Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263

I don't trust surging 500 amps out of a cap that could have dried up electrolyte and possibly fail with 200v or so across it.

Data sheets I have seen for these caps only rate the shelf life around 5 years, 10 max for most caps. I suppose I would consider an older cap if it was a RIFA long life series for example with a rated life of 15 years or so.

Barry

Sat Aug 07 2010, 01:46AM

Registered Member #90 Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301

I have a box of Mallory capacitors which I'll sell for $4 each plus shipping. Interested?
The capacitor label reads:
Mallory Type HES, 3500mfd 325vdc, POS +85C, Max Surge 375vdc, ASP1387, 235-8629K
Is one of those numbers a date code?

Cheers, Barry

cjk2

Sat Aug 07 2010, 01:57AM

Registered Member #51 Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263

Thanks Barry, close, but not quite what I am looking for. Those were made in the 29th week of 1986 if I am reading the code correctly. If only those were a bit newer and had fat terminals on top they would be right on.

Perhaps if this link works it will shed some light on what I am intersted in. http://www.audiocap.co.uk/ekmps/shops/audiocap/images/peh169(1).gif

Barry

Sat Aug 07 2010, 03:33AM

Registered Member #90 Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301

Okay Chris, it was worth a try! Besides, I learned something, lol.
I have more capacitors besides these but they are even older, so nvm.
Anyway, if anyone else wants to buy some vintage 1986 capacitors that are (visually at least) in fine shape then just let me know.

Cheers, Barry
So I guess that since girls with big boobs work at Hooters, then girls with one leg work at IHOP.

UbuntuNinja

Fri Aug 13 2010, 08:11PM

Registered Member #2677 Joined: Mon Feb 08 2010, 03:06AM
Location: Palo Alto, California, USA
Posts: 64

I think I read somewhere that you can greatly reduce the risk of catastrophic failure of the capacitors by not immediately putting the full rated voltage across them but instead slowly (over a period of a few days I think) raising the voltage across the capacitors from zero all the way up to rated voltage using a variac. I think this is a trick often applied to tube radios but I think it works for any sort of component in question that has been in storage for an indefinite amount of time or just has not been used in a while. If you were to do that and increase the voltage at a rate of 5 volts/ hour it would take about 3.3 days to get them up to 400 volts which I would imagine is plenty of time. That would mean that every 12 minutes you would turn the variac up 1 volt. Now, knowing that you cannot stay up for 3.3 days without having bad things happen to your health it would be best to rig up some sort of setup with a motor that would always be turning. The other advantage to that would be that the voltage would always be changing so you end up with a linear increase rather than a sudden increase which I would think might cause failure. I may be wrong on this but it seems to make sense if you can get something to turn the voltage up slowly over that period of time. If you do this, the other thing you might want to do is put the whole thing in some sort of box or something affixed with the appropriate warning as to the dangers of the capacitors lurking inside :).

GhostNull

Fri Aug 13 2010, 11:23PM

Registered Member #2648 Joined: Sun Jan 24 2010, 12:45PM
Location: Australia
Posts: 291

Yep, Thats called reforming, though more usually it's not over days. In the silicon chip magazine (electronics magazine here in Australia) they just started a project guide on a full on, MCU controlled refromer. We should see some kits out soon. This will be really useful with all the NOS we use.

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