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UM486V - Capacitor Specs

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First post, by Aui

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Hi everyone,

today I tested a UM486V board but it (spectacularly) failed during power on.

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Two of the metal oxide capacitors exploded so I want to replace all of them (there are altogether 27 on that board)
I think the rating is 4microF and 16V - Is this correct ?

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There is a group of 4 additional slightly larger caps (reading 475 + 25K) . What are the specs of those? Do they need to be replaced as well?

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I see large boxes (e.g. BOJACK 300 or 600 pcs) of such capacitors for sale. Are those recommended and working well?

Thanks for the help

Reply 1 of 3, by wbahnassi

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Remove the sad cap and measure for shorts on the power connector. If no shorts then you can put in the replacement cap and try your luck. I recommend replacing that entire group though, if one of it failed like that, there's a good chance the others will follow.

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Reply 2 of 3, by Aui

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Could you please give some details on the cap specs (I will first need to order them). Is 4microF and 16V correct? The ones close to the AT power connector have not failed (yet) They are also slightly larger. What is their rating (in terms of voltage and capacitance) ? thx

Reply 3 of 3, by Horun

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The large 475 +25k are 47 x 100000 pf = 4700000pf = 4.7uF 25v the k is +/-10%. The small are 4.7uF 16v looks like letter H then +/-3%.
Tants last a long time but if one goes of a type, the rest will soon, so minimum replace the one and have some spares

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

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