peacemaker Posted August 19, 2010 Share Posted August 19, 2010 My Twin is hissing a lot more than usual with a borderline high pitched howl. At one point, it would do that high-pitched howly thing big time, and I had all the caps replaced and a couple other mods. Black-faced innerds in a silver-face package. Anyway . . . that was several years ago and it's been perfect. There's also this tinkling sound going on. Sounds almost like cracking glass. Makes me afraid to touch it. This amp has travelled a little bit, so I'm wondering if something has gotten knocked loose or I've got a tube going out . . . thoughts? I'm not an amp guru, so thought I'd ask some . . . I just love my Twin! Link to comment Share on other sites More sharing options...
GuitArtMan Posted August 19, 2010 Share Posted August 19, 2010 Sounds like a microphonic tube. One thing that can help pin point microphonic tubes is tapping them with a chopstick. It's not a perfect science, but often the offending tube(s) become immediately apparent. Another thing to try is cleaning your tube socket. Get some Caig DeOxit and spay the socket and/or pins of the tube and then seat and reseat the tubes several times the clean the sockets. Link to comment Share on other sites More sharing options...
slider313 Posted August 19, 2010 Share Posted August 19, 2010 Sounds like a microphonic tube. One thing that can help pin point microphonic tubes is tapping them with a chopstick. It's not a perfect science, but often the offending tube(s) become immediately apparent. Another thing to try is cleaning your tube socket. Get some Caig DeOxit and spay the socket and/or pins of the tube and then seat and reseat the tubes several times the clean the sockets. Agreed. Even tapping it with your finger should work. If you use any electronic cleaner spray on tube sockets or input jacks, be sure it has no lubricant. Link to comment Share on other sites More sharing options...
GuitArtMan Posted August 19, 2010 Share Posted August 19, 2010 Agreed. Even tapping it with your finger should work. If you use any electronic cleaner spray on tube sockets or input jacks, be sure it has no lubricant. True. That's why I mentioned DeoxIT and NOT FaderLube. Looking at their website it appears there have been some name changes (again) and all the product appear to carry the DeoxIT name. Make sure the get the contact cleaner and NOT the lubricant. MG chemical also makes a good contact cleaner. Link to comment Share on other sites More sharing options...
FredZepp Posted August 19, 2010 Share Posted August 19, 2010 This takes me back to when my old Dual Showman would have tube issues. And yes, you could find the culprit fairly quickly, most times, with that technique... knock on wood , I haven't had these issues in a while. Link to comment Share on other sites More sharing options...
peacemaker Posted August 19, 2010 Author Share Posted August 19, 2010 So . . . One of my pre-amp tubes (those are the little ones, right?) sounds like tapping on a microphone when I tap it with a chop stick as advised. I've never tapped my tubes with a stick, so I don't know how that is SUPPOSED to sound. But, none of the others make any real noise through the speaker when tapped, and this one does. It doesn't tinkle or squeal or anything. Just sounds like tapping on a microphone. Is this normal, or have I found a bad tube? Thanks for all the advice guys! Link to comment Share on other sites More sharing options...
yoslate Posted August 19, 2010 Share Posted August 19, 2010 So . . . One of my pre-amp tubes (those are the little ones, right?) sounds like tapping on a microphone when I tap it with a chop stick as advised. I've never tapped my tubes with a stick, so I don't know how that is SUPPOSED to sound. But, none of the others make any real noise through the speaker when tapped, and this one does. It doesn't tinkle or squeal or anything. Just sounds like tapping on a microphone. Is this normal, or have I found a bad tube? Thanks for all the advice guys! By your description, I think you've found the culprit! Link to comment Share on other sites More sharing options...
slider313 Posted August 19, 2010 Share Posted August 19, 2010 Ok. Now which one is it? Starting from left to right looking at the FRONT of the amp; V1 is the first preamp tube and V6 is the one closest to your power tubes. Link to comment Share on other sites More sharing options...
peacemaker Posted August 20, 2010 Author Share Posted August 20, 2010 Ok. Now which one is it? Starting from left to right looking at the FRONT of the amp; V1 is the first preamp tube and V6 is the one closest to your power tubes. It's V1 . . . implications? Link to comment Share on other sites More sharing options...
slider313 Posted August 20, 2010 Share Posted August 20, 2010 Try switching V1 with V5. If V5 is quiet in the first position, leave it there. V5 is a "function" tube and no noise will show up using the noisey V1 tube there. Link to comment Share on other sites More sharing options...
peacemaker Posted August 24, 2010 Author Share Posted August 24, 2010 Forgive me if this is an ignorant question, but are there any potential biasing problems with switching tubes around like that? Link to comment Share on other sites More sharing options...
212Mavguy Posted August 24, 2010 Share Posted August 24, 2010 Nope. Biasing situations tend to occur in the power tubes section of the amp. Link to comment Share on other sites More sharing options...
peacemaker Posted September 22, 2010 Author Share Posted September 22, 2010 Alright . . . been a while since I got the advice and things have been crazy. I just spent a few minutes tinkering. Here's what happened: Switched V1 with V5 as advised. Still had microphonics showing up. Seemed like V2 was the culprit. Figured I'd mis-diagnosed & went back to status quo. Switched V2 with V5. Microphonics still showing up. Reversed that. Switched V1 with V5 AGAIN & will live with what I've got for the time being. Ugh . . . Seems like I've got at least 2, maybe 3 microphonic tubes!? Wha? Methinks it's time for a pro . . . Link to comment Share on other sites More sharing options...
212Mavguy Posted September 22, 2010 Share Posted September 22, 2010 Alright . . . been a while since I got the advice and things have been crazy. I just spent a few minutes tinkering. Here's what happened: Switched V1 with V5 as advised. Still had microphonics showing up. Seemed like V2 was the culprit. Figured I'd mis-diagnosed & went back to status quo. Switched V2 with V5. Microphonics still showing up. Reversed that. Switched V1 with V5 AGAIN & will live with what I've got for the time being. Ugh . . . Seems like I've got at least 2, maybe 3 microphonic tubes!? Wha? Methinks it's time for a pro . . . Just a silly thought, but the last work done on this amp was years ago? Could it be that you have tubes that are several years old in your preamp that all have lots of hours and on/off cycles on them? Often huge numbers of on/off cycles in tubes and the expansion/contaction cycles the tube guts go through will cause things to loosen up, and then add the vibrations induced by speakers in that powerful amp and you do have a recipe for microphonics to begin... Especially if that amp is the only one you play through on a regular basis. Link to comment Share on other sites More sharing options...
ingeneri Posted September 22, 2010 Share Posted September 22, 2010 Alright . . . been a while since I got the advice and things have been crazy. I just spent a few minutes tinkering. Here's what happened: Switched V1 with V5 as advised. Still had microphonics showing up. Seemed like V2 was the culprit. Figured I'd mis-diagnosed & went back to status quo. Switched V2 with V5. Microphonics still showing up. Reversed that. Switched V1 with V5 AGAIN & will live with what I've got for the time being. Ugh . . . Seems like I've got at least 2, maybe 3 microphonic tubes!? Wha? Methinks it's time for a pro . . . I had the same problem with my DRRI a few months ago. I reversed the VI and V5 tubes as advised and dramatically reduced the hissing. Like you, I had never plunked around the innards of a tube amp and was pretty nervous. But it was easier than I had feared. Just stay away from the power tubes. If you've got multiple tubes going though, you might want to get a new set. Best of luck Link to comment Share on other sites More sharing options...
Hfan Posted September 24, 2010 Share Posted September 24, 2010 Some of you guys may know about this site, lots of pro and amateur amp techs here. Friendly site to get answers for amp questions or advise. Helped a lot when I restored / blackfaced my old silverface Twin. Also a link there for a huge number of archived amp threads. http://music-electronics-forum.com/ Link to comment Share on other sites More sharing options...
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