+12V power on Promise VLB controller & bad cap \ VOGONS

+12V power on Promise VLB controller & bad cap

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First post, by mpe

Posted on 2019-04-22, 22:10

mpe Offline

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Location: London, UK

I bought a nice looking Promise VLB EIDE controller for my 486 project.

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I installed it on to the motherboard, powered on and suddenly one of tantalum capacitors literally exploded.

The capacitor sits between +12V line and GND on the ISA part of the card. The 12V line then continues to the Winbond W83758P chip on the ISA side of the board. I guess it is a filtering cap for +12V power line.

The attachment DSC_7541.jpg is no longer available

Anyway, despite the bang the card appears still to be working. At least as far as I could briefly tested it.

I was wondering what could be broken on the card and how exactly the +12V line is used on a multi-IO card? I was actually a surprised to see there is +12V (and even -12V) power line used on the card.

Should I be bothered replacing the capacitor? There are 5 more such caps on the board? Would you expect them to be exploding as well any time soon 😀 ?

Last edited by mpe on 2019-04-22, 22:18. Edited 1 time in total.

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Reply 1 of 1, by retardware

Posted on 2019-04-22, 22:18

retardware Offline

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If one exploded, the chance that the others follow is considerable.
I'd replace all of them, as they are apparently degraded.
Be careful to not mistake their polarity, as they'll bang if connected wrong way.

The +-12V are needed for RS-232, i.e. com1, com2,...

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