Let's Get Technical > Troubleshooting Problems

MP1 Classic Clean Issue

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AndiK:
Hi all,

my MP1 Classic produces hiss/strange sounds in clean tube mode, when the "brown" uses both modes it is not that strong. Solid state and distortion mode are working normal. Battery and tubes are checked and ok...symtoms appear to be clearly limited to the clean mode only...
Any suggestions???

Thanks
Andi

MarshallJMP:
Try to replace R151 and see if that works. There's some info about it on the depot, just do a search for it. You could also try to measure the resistance first, it should be 180k ohm. Sometimes these go up in value.

AndiK:
Just measured R151 - reading 176k, so this should not be the reason for the issues. Has to be in the signal path of the clean tube mode....

Andi

AndiK:
Just measured the testpoint voltage - reading 207 V with my good voltcraft meter....

AndiK:
Issues are solved - changed R151 and R382. Now the voltage for TP34 is 202V....
Soldering on this PCB is a pain (at least for me).....
As stated by others before, it is really essential to desolder the components before measurement!

Due to the infos in this forum i now have also a fully functional MP1 Classic  :bow:

Thanks a lot!
Andi

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