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    Electrolytic packaging questions

    I know and can easily identify the basic (large) electolytic type caps, easily. But, having found this site wondering why my BP6 was a bit flaky (and a BE6-II also) and having the revelation that some of my other 'bad' hardware could be suspect I figured it was time to start checking.

    In this pic, I show a section of a Digital Alpha (22164A, 500MHz RISC) motherboard that decided it didn't like ANY kind of memory anymore (bios beeps out 'no memory' code even if loaded up with approved types). I stored it away for the last couple years (packrat, yes) and went and dug it up and checked it out. I noticed what appears to be a toasted resistor package (by where it's labelled "OUCH!", obviously would repair this first and then retest) and then there are a couple banks of these other type of capacitor and I don't know if they're electolytic in some different casing, or tantalum, or... can someone ID them for me and suggest if they might be bad and causing the memory detection problem? Note the discoloration/watermarking pattern around the right bank of caps... could be drool or something that got on it during the years it's been floating around outside of a case, but I was suspecting electrolyte (if those are electrolytic, and could leak somewhere like the cans)... Also do you recognize the manufaturer logo (assuming that's what the "A" with a flag thing on it is)? Obviously they are 330uf, 6.3V whatever type they are, and the 'banded' end makes me think electolytic...


    Then (yes, that's not it, yet) I have a 'dead' old GeForce256 (yeah, prolly not worth fixing, but now I'm back on an even older Voodoo3 3000 so it would be an 'upgrade' if I can make it work again). I had thought the RAMDAC toasted because the symptoms were proper operation, but a very dark and shadowed output with extra dark ghosting/shadowing horizontal bands across the full width of the screen, following 'bright' regions like dragging window around and such - barely legible. But now you have me wondering about caps on it as well, but they are more of a surface mount style:

    The cap in question (there is another identical one elsewhere on the board as well) is the silver part, with the numbers paraphrased next to it for legibility... how can I tell what type this is and/or who made it? There were no markings on the sides at all either. It would seem to be a 330uf, 6.3V maybe? The item above it and into which circuit it is connected is a voltage regulator so I'm thinking if the cap went bad that could drop the voltages eventually output to the monitor and thus end up being very 'dark' and difficult to 'lock' onto (basically the problem). Also wondering if the superminiature surface mount types like the one circled could be suspect (but I think those are similar to the ceramic disc style, just surface mount packaged) as there are buttloads of them all over it. Here's another shot of some other type on the same card, similar to the ones on the Alpha board:


    Suggestions? And, thanks a metric ton! Can't wait to fix up my BP6 and make it fully happy again (still operates OK, but flakes now and then).

    #2
    Welcome to the forums...

    Those yellow caps are micro surface mount electrolytics... The gold stripe indicates the negative pole of the cap. If you remove one and break it open, you will find it has electrolyte in it.. The one marked OUCH is obviously toast.... Finding exact replacements for those might be a little on the tricky side.... They're 330uF 6.3v, you could just get regular low-ESR electrolytics and replace them, they'll work. It might look a little dicey, but it will be good enough for testing anyway.

    The video card is a different story... those are not electrolytic. Like you said, they're either ceramic or tantalum. However, without the white papers for the device, there's no way of telling it's value. Most aren't marked. If those are burned up, your device probably has some serious issues. Most of the time, they won't burn up unless there's a serious problem somewhere else. A lot of the time I see them knocked off the board from careless handling, and unless the cap was retrieved, or you have the white papers, there's not much that can be done. You can 'trial & error' and sometimes get lucky, but I've not seen much success with that...

    Ypur BP6 on the other hand, that will be an easy fix!!

    TC
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      #3
      Awesome, I knew you'd know it all.

      So I'm going to forget about the video card, it also had the fan die on it (stupid bushing based fans!) and it 'cooked' the chipset pretty well just before this happened (in the midst of a game)... that was why I assumed the RAMDAC part of the wafer melted itself (but wasn't sure why that didn't bomb out the rest of the cards function). Lost cause. Was going to be more of a soldering practice exercise whereas if I melt everything it doesn't matter since it's basically something I should have tossed a while ago.

      The motherboard I might try to fix up, it runs Linux pretty well if I remember correctly and also ran NT4 pretty good (last MS OS to support Alpha, I think). Actually has a "DIMM" mode but takes SIMMs (parallel banking, 8 slots, 72-pin) which was a pretty cool idea (until 'real' DIMMs came out of course). That was probably one of the only gains that made it faster than what seemed fast back then, it probably crawls now compared to GHz and DDR, etc, despite the RISC being 'better' than CISC thing. But the newer Pentium cores are RISC anyway, with a CISC compatibility 'wrapper' I guess so there is not as much of a difference as there used to be. blah blah blah I guess I'm rambling too...

      Anyway, thanks again for your help and input, I'll be back to share my experiences once I procure a soldering iron that isn't an industrial 9000000 watts like the monster I have now (for antennas, large gauge car wiring, etc). Seriously, it's like the sun with a tip attached.

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        #4
        the yellow ones are tantalum .
        you could salvage one from a junk mobo.
        make sure you scrape the carbon out of the burnt area.
        i wonder if the cap is really bad.tantalums tend to totally incinerate themselves when they go.and stink bad.

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          #5
          btw the band on the tantalums is positive +

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