[sdiy] Korg DW-8000 power supply help?

[Andrew Jury]

Hi Eric,

Glad you got it fixed. You might want to try replacing the 78 series
regulator that feeds that particular +5v rail. That is not normal operation!
You might also want to make sure D4/6/13 aren't leaky.

Bye for now,
Andy


On 04/11/2010 08:25, "Eric Frampton" <eric at ericframpton.com> 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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