Mesa-Boogie D180 modified!!

[FinBass]

I went and bought a D180 with 2 15 Diesel road ready yesterday. I plugged it in and tested it worked at a low volume. Was happy all was in order. The amp came with a bag of tubes and some paper work.

I got back very pleased last night and started to read through the old manual and found a service report from 1998. 
It appears that the service tech was a bit of an idiot and has done quite a few significant alterations!
 

I have attached the report

in summary they have carried out an investigation and thought that the wiring was suspect- and that the master volume arrangement was irregular!

 

Looks like they have essentially replaced the master volume circuit, and messed with the cascading gain stage wiring.

 

I am going to take it to the practice room later  to see how it sounds with these mods, however I am thinking I want these modifications reversing so the amp is as designed!

[Owen]

8 hours ago, FinBass said:

I went and bought a D180 with 2 15 Diesel road ready yesterday.

Thunder o'clock.

[Downunderwonder]

I think it might be more a case of Mesa lost the designs for the weird Master vol. There is a narrow band of useful overdrive between 9 and 10.

 

The pirated preamp schematic is freely available but it stops short of the Master.

 

Either a bunch of stuff was replaced on your amp or the tech is one of the ones who makes everyone's life difficult doing mods to perfectly good amps when we would all be better off if he took a job at McDonald's.

 

Some of the D180 did come with a full set of 12ax7.