I got my OTS 50 today without any mods. Im more of a player then a tweaker so i dont know mutch about the technical stuff of this amp. Im giving my amp a "burnthrough" as i make this post.

I tried the Clean chan and it got everything that i was expecting out of it, But for th OD chan, i would liek som more gain, the way it is now its a bit crunchy and not verry OD. If someone could tell me where to look for the OD trimpot and how to modify it for a bit more OD with a lot of punch and edge with a nice headroom i would be verry greatful.

Thanks, from Sweden

Here it is my good man - black trim pot


also here


addjust for your taste and have major joy - more gain than Marshall.

it's easy
unsrew the back panel
unscrew the 4 screws on top (carefukll cause this will lower the amp a bit.
Carefully slide out the amp itself.  make sure you don't bump the tubes.
Put it on two wooden blocks or 2 stacks of books.
look for the black part on the board (carefull there are 2 or 3 of those trimmers. You need to adjust the one on the 2 pics above. Use a small screw driver and just turn the white part. If you tunr it all the way down there is no sound in the OD channel. if you set to 9-9.30. you get a nice overdrive with not much distortion. setting it highter will give you more and more distortion.
If I were you I'd switch of the amp when adjusting.

ps for a good tech it's simple to make a pot on the back of the amp. then you can adjust with the amp on


here's another picture  http://home.kpn.nl/s.scholten17/inside.jpg
it's the pot on the left half of the board. If you look from right to left to the pot you'll see it's probably set to somewhere around 10 or 11 o'clock.

What is the Ground switch for? and where sould it be, at 1 N or 2?

Don´t worry about it. If you look inside the amp chassis, you´ll find out that the ground switch is not connected to anything. It´s just "there". Probably for cosmetic reasons..