[sdiy] Korg DW-8000 power supply help?

[Tony Kalomiris]

Nice job Eric,

Are you saying C11 was shorted ? Or did you just find it by substitution ?
I've seen tantalums short but don't recall this happening with electrolytics.
That's the longest time constant I've ever seen - half an hour !
I'd change that regulator and re-test.

Tony Kalomiris


On 2010-11-04, at 4:25 AM, Eric Frampton wrote:

> Resolved!
> 
> On Nov 3, 2010, at 1:43 PM, Harry Bissell wrote:
> 
>> ohmmeter across the power supply outputs... look for short circuits.
>> 
>> Suspect failed electrolytic caps...
> 
> then Andy Jury wrote:
> 
>> This PSU has two bridge rectifiers. One block device and another composing
>> D8/9/11/12, so check these. Other suspects are IC1 and C11. Looks for dead
> 
> Bingo. It was C11, the electrolytic that comes right after the block bridge rectifier.
> 
> Interesting, I replaced that one cap and every rail came right back up. Re-connected the CPU board to the PSU, and one 5V supply immediately dropped to about 3.5V. Then, over the course of letting the machine sit for about a half hour, it kept rising until it finally settled at about 4.95V and remained there ever since. Might that be a result of bypass caps on that CPU board re-forming, or...? That was a new thing for me.
> 
> Thanks for the help, y'all.
> 
> Eric
> 
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