SRM-1/mk2 channel imbalance? Need help

[bwck2000]

Recently i acquired a SRM1/MK2 (B series) Stax amp and a pair of sr404 which is bought for a sigma/404 conversion

It comes with an imbalance issue. I first thought it is the headphone , but after several switches of equipment(amps,headphones etc） im certain that its the AMP.

By observation there is no burnt resistors,measured some of them ,the VR seems to be functional........I tuned the offset and balance

 But the  + to - voltage of the lower-volume channel doesn't change when i rotate the balance pot which is abnormal, it stays on 8v dc

While all other balance and offset pots is fine.

Have anyone once had the same issue ？Any thoughts?I need help desperately from anyone. Thank you

[spritzer]

Might be a bad pot but it is probably something more serious.  Still it wouldn't hurt to replace the pot as they don't age well

[bwck2000]

found out why

four resistors on the output(R123-126) on a channel are of strange value

The eight (four each channel) resistors on my another flawless SRM1MK2 are all in 230K But the eight resistors on this one  varies with each other.

one 1M in ohm, two 300k,other 230k something

After switching them ,it singsNow just waiting for the new one to arrive

But i wonder if the problem is solved completely or will it happen again?

[spritzer]

There is no telling if something else is damaged so just enjoy that it works for now.   

[Makoto]

On 11/22/2016 at 3:49 PM, spritzer said:

There is no telling if something else is damaged so just enjoy that it works for now.   

I'm also having a SRM-1 MK2 with imbalance problem due to the pot. Too late for me to see this thread that I've already tear it apart. There's also some problem with the humming transformer. Bad grouding may cause that I guess. But how can I get it modded for balanced input? I remember seeing some saying that one just have to replace some resistors...hmmm

[spritzer]

I've posted the schematic for the amp so on there you can see that one side of the input fet has the gate tied to ground via a resistor.  Remove that one and copy the other side of the fet (two resistors and a cap) and it is now ready to take a balanced input.