Stax SRM-1/MK2 Pro refurbish
Jun 6, 2013 at 12:28 AM Thread Starter Post #1 of 5

konagold

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Hi
 
I picked up a SRM-1/MK2 Pro (series A) off of ebay for $299. It had been stored away for at least 10 years (lots 'o dust!). Cleaned it and it works. It's dead silent, no hum at all.
 
I now want to do a full refurb. I've seen the post(s) on replacing the power caps but don't know what else to check/replace.
 
What voltages should I check and where? Replace all caps? resistors? diodes? what brands/series? anything else ......
 
I've searched these forums for a few days and have found bits and pieces but not enough info to avoid reinventing the wheel.
 
Any help would be appreciated.
 
Thanks in advance.
 
BTW: I found schematics for this box, quite comfortable with HV, soldering etc.


 


 
Jun 6, 2013 at 5:08 AM Post #2 of 5

spritzer

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You could replace the diodes (just match the current and voltage requirements) but I only do it if there is something suspect.  They are run far under their rated values so there shouldn't be any issues.  If you replace the diodes then I'd replace the bypass caps next to them as well. 
 
Normal offset and balance adjustment as for all other Stax amps (well most) but remember that the pot marked offset is actually the balance and vice versa. 
 
Jun 6, 2013 at 12:42 PM Post #3 of 5

konagold

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Quote:
You could replace the diodes (just match the current and voltage requirements) but I only do it if there is something suspect.  They are run far under their rated values so there shouldn't be any issues.  If you replace the diodes then I'd replace the bypass caps next to them as well. 
 
Normal offset and balance adjustment as for all other Stax amps (well most) but remember that the pot marked offset is actually the balance and vice versa. 

Thanx Spritzer
 
Do you see any advantage in replacing the 100uf power supply caps with something larger, say 200uf or even 500uf caps? The power supply seems to be unregulated ....
 
Jun 6, 2013 at 3:05 PM Post #4 of 5

spritzer

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Quote:
Thanx Spritzer
 
Do you see any advantage in replacing the 100uf power supply caps with something larger, say 200uf or even 500uf caps? The power supply seems to be unregulated ....

 
220uf is what Stax would put in there now but too big could cause issues.  Unregulated is an understatement, there is nothing but the caps.  Same for all Stax amps including the SRM-T2. 
 

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