ADA Depot Too - A Forum To Support Users of ADA Amplification Gear

Let's Get Technical => Troubleshooting Problems => Topic started by: AndiK on January 07, 2019, 09:50:19 PM

Title: MP1 Classic Clean Issue
Post by: AndiK on January 07, 2019, 09:50:19 PM
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
Title: Re: MP1 Classic Clean Issue
Post by: MarshallJMP on January 09, 2019, 01:49:56 PM
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.
Title: Re: MP1 Classic Clean Issue
Post by: AndiK on January 11, 2019, 08:54:27 AM
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
Title: Re: MP1 Classic Clean Issue
Post by: AndiK on March 29, 2019, 11:19:30 AM
Just measured the testpoint voltage - reading 207 V with my good voltcraft meter....
Title: Re: MP1 Classic Clean Issue
Post by: AndiK on April 28, 2019, 10:10:50 PM
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
Title: Re: MP1 Classic Clean Issue
Post by: rnolan on April 28, 2019, 11:37:42 PM
 :whoohoo!: :thumb-up: great news
Title: Re: MP1 Classic Clean Issue
Post by: Dante on April 29, 2019, 02:33:33 PM
+1! Great news!!
Title: Re: MP1 Classic Clean Issue
Post by: MarshallJMP on May 01, 2019, 04:06:36 AM
Classic pcb's are a pain in the ass to desolder