[sdiy] Disassembling MKS-70 Power Supply

Dino Leone dino.leone at stanford.edu
Mon Nov 3 22:23:53 CET 2008

that's so interesting. Mine has the exact same problem. I found that  
after it has turned off, it comes on again when I touch one of the  
power transistors (even with an insulator). I need to check those  
solder joints again.  Thanks for posting this!!


On Nov 3, 2008, at 6:38 AM, Csaba Zvekan wrote:

> Thanks, Bob.
> That's exactly what it was . It wasn't hard to get to the board  
> either. If you think they put two Roland JX-10s in a 3 HE Rack mount  
> unit. That's pretty cool :)
> So I put some flux on the regulator solder joints and added fresh  
> solder . I should have desoldered and removed  the old tin and  
> cleaned pads. I was thinking of that later. Oh , well it works now  
> under several hours of testing it seems fine.
> I have ordered some 6800uF and 4700uF that I want to replace them as  
> well. They took a lot of beating over the last 20 years, I assume.
> When I open up the unit again for that I will sure remove the old  
> tin and clean pads etc.
> Again thanks for the hint, it was very helpful.
> Csaba
> On Nov 3, 2008, at 7:13 AM, Bob Weigel wrote:
>> I don't recall off the top the circuit details but common problems  
>> are regulator solder joints on those.  If it shuts off after a few  
>> seconds that MIGHT be the problem..  On the other hand could be  
>> some leaking electrolytic or something.  But you have to pull a few  
>> things out as I recall to get that board out.  Get under there and  
>> verify the solder before you go to a lot of research time though  
>> and I'll bet you'll find the problem. If you have an esr meter it's  
>> nice to check the caps. -Bob
>> Csaba Zvekan wrote:
>>> Hi Group,
>>> My Roland MKS-70 (SUPER JX) 's power supply is failing . After  
>>> two  seconds it shuts off. I am suspecting capacitors on the power  
>>> supply  board. Can anybody tell me an easy way to get to it.  
>>> Before I make  some stupid mistakes?
>>> It looks like I have to loosen the VOICE boards that are on  
>>> hinges ,  right ?
>>> I googled the MKS series and they seem to be a bit flaky in age.
>>> Also maybe one of you knows already the problem. What's the deal  
>>> with  the sensing in the circuit ?
>>> Any help greatly appreciated
>>> Csaba
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