Hi Beanbag, welcome to the forum and great report on your amp.

I guess we all experienced the same as you have -  a new dumble clone amp sound very harsh and unforgiving.

Nice mods the 82k slope and 750pf on V2a.... I'll bet in two month you won't need the 750pf on v2a, in fact I have just removed the additional 220pf on my #183, leving me with 22pf on both v2a and v2b and no the OD top is much more open. However, like you , when the amp was new it had much to much OD top.

I have 20 years experience with DIY tube amps and repairs and untill 2 years ago I wouldnt have believed in the fact that these amps need burn in time.

I have got an OTS as well Plus a D'lator (made by Erwin)
I experimented with tubes a lot but still found the OTS a bit to  much "in your face" Erwin now changed the amp and made it into a combination between a Bluesmaster (cleans) and an OTS (lead). He also added a 0,47pf cap on the (push pull) master volume.
Great mod.

There's got to be something wrong with your amp, either construction error, faulty component or improperly adjusted bias. Not something some mods are going to fix. Did you make it yourself?

I have no idea what he did to my amp. I can't even solder a guitar cable. Perhaps you could pm him (Erwin_ve).

I just tried biasing the OTS via black to earth point and red probes into the test points either side of the power tubes, flicking the amp on to Operate and switching the digi MM on. The readings kind of baffled me somewhat. The reading on one side was 150.6mv and the other was 170.6mv, surely I must be reading this wrong, but it's a simple thing to do. I also turned the dial to one end to the other and not much of a difference in readings. Maybe 20mv difference. Please help on this cos I seem to be doing something totally wrong.

Yes, the amp is fully operational. I replaced the HT fuse which cured the problem of no sound. Now the amp is back like it used to be - loud and proud. I put the black probe into the black test point in between the two power tubes, then the red probe into the red test point of each tube left and right. I switch on the multimeter on to read 'mv' and begin testing.....then the readings baffled me.....don't know what else to do!! I don't want to blow the amp again. If anything, I'd rather run the amp 'cold' to prolong tube life, I just don't know which way to turn the dial, it's either 'blow' the amp again or 'cold'. But I'm not taking a chance in guessing! Please help.

@ babybear, it sounds like you are reading both tubes at once, or possibly reading ac current, which is possible if you are reading both tubes via the reds. you will want to insert a red probe in one red socket at a time, and the black probe in the center black socket. Also you will want to make sure that all front controls are set to zero and that you have a speaker or dummy load plugged in. You will want to set your multimeter to the mV or smallest scale on the DC side. You will want to adjust your current to somewhere between 35-40 mV as a starting point. You can adjust up or down to taste, with 47-48 mV (mA in reality) being the upper safe limit for most 6L6 tubes.

If you're getting 170 mv you're basically destroying those tubes. You'll need to check the wiring around the power tubes and/or the transformer extra carefully, find what you've done wrong and fix it. Then most likely replace the power tubes. It probably needs to go to a tech for this.