I know this is untimely, but I have a MingDa 34AB Integrated, (The 8 el34 tube bad boy so this may not apply). My manual (brochure really) is in Chinese. My amp has trimpots for all 8 Tubes, so obviously fixed bias, however, I was told by the importer a tale that biasing is extremely dangerous for amateurs, due to some grounding issue?, and must be done by mail, by the importer, or a guitar amp shop.blah blah...
I find this ridiculous, I have no intention of shipping an 80 pound tube amp around constantly to have the bias checked. Their point is well taken that high voltage is dangerous of course. Luckily I live in a big city with guitar shops, so I guess I will take it there. By the way, my request to BUY a schematic, or service manual, or even the learn the bias setting? Forget it! And this for a product with no warranty, and no dealers! They did say that a matched set of tubes should be OK as a replacement. Still I would feel better if I could check the bias....I need to replace all 8 tubes (or 4 in the channel) if one dies? even though there are 8 trimpots? Come on!
Don't get me wrong, Other than some hassles, this is a super killer amp, the steal of the century. I cannot afford a Mac 2102, or a big CJ; and if I could afford one I would buy one, believe me. But this is pretty darn close (and switchable from triode to ultralinear to boot! For one fifth the price!) It's Probably best for advanced tube people with some electrical know how, or a good repair shop nearby, though, since you are REALLY on your own safety wise. To be fair, Mine has worked perfectly for three months now, and is DEAD silent, I suppose due to the dual choke regulated power supply and killer build quality. Thanks MingDa