Hello MM people. Any opinions are gratefully welcomed, as I know next to nothing about amp repair. I own a RD50 amp, and last evening when I turned it on, one of the 6L6 tubes flashed brightly, giving off a pink-white glow. I quickly turned off the amp and pulled out the tube to inspect it, but I can’t see anything physically wrong with it. I plugged it into the other tube socket and got the same thing, so I think I can safely assume the tube is shot. I then tried the other tube in both sockets. It did not flash, but it does glow blue and heats up rather quickly. I’ve never noticed whether this blue/heat is normal, because I’ve never really checked to see what the tubes look like back there when the amp is on. Also, with only the one tube installed, the amp hums. Does that sound right...would an amp produce a hum if one of its tubes is missing? Obviously, the simplest thing to do is to replace the tubes, but I’m fearful that if I just put a new set of tubes in, they’ll get immediately fried if there’s something wrong with the amp itself, and there goes $50 or $60 worth of tubes. I understand that it’s difficult to find repair people that will work on MM amps. What to do? I really like this amp! I really appreciate any guidance here. Thanks very much to all.
Thu, 03/16/2017 - 10:51
#1
While I've never seen anybody
While I've never seen anybody try to run one on one tube, THAT LOOKS like it wouuld be dangerous. That amp uses the SS driver but with the transistors driving the cathode and it's ALMOST plu and play but with TWO tubes. You need to either try a new set of tubes or get it to somebody who could watch it as it fires up. I'm betting you just have a crap tube and a new set would fix it. There's no adjustment for bias on that amp at all, not even like the early SS versions. Mike.
Thank you for your input,
Thank you for your input, Mike. I tried a different set of tubes, some old crappy ones I had lying around that I'd forgotten about. Same thing happened when I put them in, so it must be an amp problem. I got the contact for someone in the area that said he's worked on MM amps before, so that's fortunate! I'm gonna take it to him. Appreciate your time and help.