ingeneri Posted March 27, 2011 Share Posted March 27, 2011 Seeking amp guru: My DRRI has been suffering hum and breaking up with a harsh crackle at moderate volumes that are normally clean. I bought matched and balanced 7025 and 12at7 tubes from the tubestrore's premium deluxe reverb package. But immediately after swapping the tubes the amp ceased to function at all. I get power but can't get any volume with the guitar. The hiss on the vibrato channel is about the same, but it's worse on the normal channel. And I get a nasty crackling sound when I turn on the standby switch. I thought this was a pretty risk free operation, but seemed to have just spent a ton of cash to kill my amp, Appreciate any help or advice. Link to comment Share on other sites More sharing options...
Steiner Posted March 27, 2011 Share Posted March 27, 2011 Are the tube heaters glowing red? Is everything plugged in correctly (especially the rectumfrier?)? Link to comment Share on other sites More sharing options...
pushover Posted March 27, 2011 Share Posted March 27, 2011 Aarrgh.. Lots of variables to consider. What I always do is to go back to where I started and then proceed forward again from there. If you still have 'em, try putting the original tubes back in, and see what happens? Maybe in the process, get some contact cleaner and spray all of the tube pins before reseating them (to try and clean out the sockets). If the old tubes don't work to get you back to where you were, then it implies it may be something else. After trying the contact cleaner try the new tubes again, and maybe cleaning the sockets will help Beyond that kind of simple stuff, I don't like to mess with amps that much. If you think you need a professional to take a look, in the greater DC area, I recommend Eric the Viking (google viking amps). Knows his stuff, and is honest. Hopefully some of our more amp savvy folks will be of more help. Good luck. Link to comment Share on other sites More sharing options...
kbp810 Posted March 27, 2011 Share Posted March 27, 2011 Yeah, I agree with the above I would swap V1 first and see what happens before changing them all back out If it still does it with the old tubes in... time to take it to a tech; otherwise, I'd play the trial and error swapping game to find the bad tube. (I've had bad tubes new out of the box before, it can happen!) Link to comment Share on other sites More sharing options...
Steiner Posted March 27, 2011 Share Posted March 27, 2011 Link to comment Share on other sites More sharing options...
DetroitBlues Posted March 27, 2011 Share Posted March 27, 2011 Wow, too bad about your amp, but I think you are in good hands here. Link to comment Share on other sites More sharing options...
tulk1 Posted March 27, 2011 Share Posted March 27, 2011 Did you bend a pin plugging them in? Hope you get it worked out. New tubes shouldn't give you that reaction. Link to comment Share on other sites More sharing options...
DetroitBlues Posted March 28, 2011 Share Posted March 28, 2011 Sounds like there might be a problem with the tubes being crap right out of the box or you put the wrong tubes in. Link to comment Share on other sites More sharing options...
ingeneri Posted March 28, 2011 Author Share Posted March 28, 2011 OK, here's an update: I inspected each tube and found one of the 7025's had a seriously bent pin. After fixing that I was able to get rid of the loud crackles and pops. But the normal channel still hissed like crazy and the vibrato channel got nothing. So, I put the reverb 7025 in the normal channel and that seemed to eliminate the hiss. Then I swapped in my old 7025 into the vibtrato channel and was able to get a very very soft signal. Then I swapped the new 7025 into the vibrato channel and got nothing and the old Fender tube in the normal channel produced the loud hiss again. I'm going to try swapping the 12AT7s next, but I'm wondering if I need to get the power tubes changed as well given the loss of volume. Any thoughts or suggestions from the resident amp gurus is appreciated. Link to comment Share on other sites More sharing options...
DetroitBlues Posted March 28, 2011 Share Posted March 28, 2011 OK, here's an update: I inspected each tube and found one of the 7025's had a seriously bent pin. After fixing that I was able to get rid of the loud crackles and pops. But the normal channel still hissed like crazy and the vibrato channel got nothing. So, I put the reverb 7025 in the normal channel and that seemed to eliminate the hiss. Then I swapped in my old 7025 into the vibtrato channel and was able to get a very very soft signal. Then I swapped the new 7025 into the vibrato channel and got nothing and the old Fender tube in the normal channel produced the loud hiss again. I'm going to try swapping the 12AT7s next, but I'm wondering if I need to get the power tubes changed as well given the loss of volume. Any thoughts or suggestions from the resident amp gurus is appreciated. Looks like you're on the right track. You'll have to keep swapping tubes then. It may be a case of the a component that went bad with the bent tube. I sure hope its not like that, but KBP810 is a good amp tech for advice before you spend you money at a local shop. Link to comment Share on other sites More sharing options...
tulk1 Posted March 28, 2011 Share Posted March 28, 2011 Did you bend a pin plugging them in? Hope you get it worked out. New tubes shouldn't give you that reaction. OK, here's an update: I inspected each tube and found one of the 7025's had a seriously bent pin. After fixing that I was able to get rid of the loud crackles and pops. Ha!! I win, I win ......... well, kinda. Link to comment Share on other sites More sharing options...
Hfan Posted March 28, 2011 Share Posted March 28, 2011 I'm no tube amp expert, I've fixed and modded a few amps (mine) and really haven't read up on this stuff in a few years but several things come to mind. Other guys here know more on the subject then me so please correct me if I'm off. If one of your 7025s had a bent pin, I'm assuming it was straight prior to you installing it. You may have bent it while trying to press it into the socket, since one pin was bent, the remaining unbent pins may have gotten pushed into the wrong holes, each one pin from desired position. If this occurred I would think that improper loads where placed on the interior tube components and possibly the amps components. Was it severely bent? Did it feel like it was seated properly? If you labeled the origional tubes prior to dis assembly you may want to reinstall them to their origional positions. This may enable you to start from scratch with the swapping deal, though I would hesitate to re use the one with the bent pin. Does this bring you back to your original problem condition? If yes then I would try swapping out one at a time, if the condition doesen't change, put the origional tube back in and try the next one. The tube with the bent pin may be hosed. If you put the tubes back to their origional positions and the problem is much different, then something may have occurred during your prior swap attempts. How old is the amp? Power tubes do wear out with time and use. If you do change the pwr tubes I believe you would have to re bias the amp. Involves getting around hi voltages and currents (I'm assuming the amp has no exterior bias points) I have used this forum for amp advise on several occasions. There are pro amp techs there who give good advise http://music-electronics-forum.com/. if you don't want to tinker anymore it may be time for a local tech. Good luck. Link to comment Share on other sites More sharing options...
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