[sdiy] yamaha spx-90 blown p/s caps

[Tom Wiltshire]

I agree with Graham - that's far too complicated for a linear supply,  
He's also right to point out that the caps often die in switched  
supplies. In fact, I've got a non-functional wireless router here  
which is down to the same thing - dead caps in the cheap switched  
supply.
I'd recommend replacing all the electrolytics with high-temp/high  
voltage replacements starting at the largest values and going as far  
down as you can be bothered. The original caps will have been the  
cheapest they could get that met the spec, rather than anything that  
improves the life of the unit.  I'd have thought you can source some  
caps that would be an improvement.

The only other thing to watch out for is that power supply faults  
sometimes fry a lot of chips on the other circuit boards (like that  
29V you mentioned?) so it might not be worth a repair at all. Can you  
check by powering it up with the other power supply?

T.

On 8 Oct 2008, at 19:06, GRAHAM ATKINS wrote:

> Nate,
>
> Thats far too complicated for a linear supply !. The Xformer would  
> be much
> bigger. Those are inductors. Yes the switching regulator does  
> probably run
> fairly hot. Often the capacitors break down on such devices. Do you  
> have a
> meter that can read capacitance ?. Certainly remove and replace the  
> damaged
> one but I would carefully remove a few more, the biggest first, and  
> check them.
> They may be badly out of spec. replace any suspect ones.....look  
> for signs of
> heating and/or bulging at the ends. If you do have to source any  
> replacements
> (Not in your spare) go for the higher temp 105 Deg caps rather than  
> the 85 Deg
> equivalents. Used frequently in VCRs etc, usually the caps fail.
>
> Now wheres that meter......
>
> Graham
> On Oct 8, 2008, at 17:43, Nate Reeves wrote:
>
>> i think it is a linear supply but here is a pic
>>
>> http://picasaweb.google.com/natere2ster/YamahaSpx90Spx90II#
>>
>> i did notice that the heat sinked voltage regulator (?) was VERY  
>> hot to the touch, with the unit being one for only 10 minutes
>>
>> my hope is that between the 2 boards i can make one fully  
>> functional!  lol
>>
>> cheers,
>>
>> nate
>
>
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