Members FarToMany Posted February 18, 2009 Members Share Posted February 18, 2009 I need help as i am getting fustrated. I own a Crate GXT amp which has two 12ax7 tubs in the preamp --1 for each gain channel so the instructions say. About a month ago it started squealing, i was told could be bad tube, so i replaced them. I used a set of groove tubes from guitar center---the only two matching ones they had. I put them in and all was well. The amp when in the house doesnt get moved at all, and i havent moved it since i put the new tubes in. Last night i moved it so i could go try out for a band and when i set up and turned it on, it started squealing again. If i took the gain channels off, it would be alright---which makes sense if the tubes only drive those channels. It either wouldnt squeal when i played or i was just playing over the squeal, and if i had the volume set at 3, that was alot. But dang it, can these tubes be bad already and or be damaged just from moving it? Its a combo type amp and i have to lay it down in the back of my truck to get it to fit under the tonneau cover. I use a moving blanket to pad under it too. I am really getting fustrated with this thing. And to top it off, they want me back on sunday to play again. I need to remidy what is going on and fast. Tonight when i get home, i plan to plug it in and see what it does. I tried to move it in different parts of the room last night thinking it was somehow interfering with the PA, but it made no difference. The only other issue i had was alot of buzzing latter on last night when i took the gain channels off. Like there was interference around--it didnt happen at first, so i am hoping thats what it was---i'll find out like i said later tonight when i plug it back in here at home. Sorry for the long winded post, i wantyed to give as much info as possible to get the help i need. Thanks. Link to comment Share on other sites More sharing options...
Members ¤ Matt ¤ Posted February 18, 2009 Members Share Posted February 18, 2009 Check you cables, try some more valves. It might also be your pickups - if it does it again turn the guitar down and see what happens. Link to comment Share on other sites More sharing options...
Members FarToMany Posted February 18, 2009 Author Members Share Posted February 18, 2009 If i turned the guitar down (some, all the way--didnt matter), with the gain channels on, it would still squeal---untill i turned the gain channels off I could try another cable, never thought that would do it. This amp and guitar and cable have been fine before in the last band i played in---always dependable. Untill the first time it started squealing like i said about a month ago, then has been fine again untill now---but it wasnt moved untill last night since the new tubes were installed. I hope having to lay it down in my truck isnt an issue, it never has been before though. Link to comment Share on other sites More sharing options...
Members steve f Posted February 18, 2009 Members Share Posted February 18, 2009 Are the tubes seated in the socket ok? Loose preamp tubes can cause feedback/squealing. I've even seen it where one channel would be ok, but when you switched to another channel you'd get all kinds of noise. If the tube sockets are mounted directly on a circuit board (not chassis mounted) make sure the board hasn't come loose. I've seen a couple of amps where a circuit board has come loose inside the amp, and a tube wouldn't seat properly since when you pushed the tube into the socket, the board would just move backwards. Link to comment Share on other sites More sharing options...
Members FarToMany Posted February 18, 2009 Author Members Share Posted February 18, 2009 OK, here is what i did. I figured out what tube was for what channel. Then, I swapped in one of my old original tubes---squeal was gone. I swapped in the other old tube---again squeal gone. Thats weird as i swapped them both out because it squealed before. I swapped the 2 replacement groove tubes from there original spots---squeal gone. Then i put it back to the way it was last night and the squeal was back. OK, i am not nuts--yet anyways. So it seems that either of the original tubes will work just fine in either spot---weird, and the Groove Tubes will work if i place them in a certian way---leading me to believe one is bad, and one groove tube--the good one, can go in either spot with one of the original tubes in either sopt. So why would either of the original tubes be making this thing work ok, when thats why i replaced them the first time around because of the squeal? The spot in question was for the "high gain" channel, would this matter also? If you see something obvious with this pattern on my tests i did, let me know. I guess yet another set of tubes in less than a month will be bought. I'll pick some up this weekend. I know tube anything is supposed to be great, but my first experience with this so far is leaving a bad taste in my mouth and wanting to go use all solid state again. Thanks for your help Link to comment Share on other sites More sharing options...
Members FarToMany Posted February 19, 2009 Author Members Share Posted February 19, 2009 Alright, why does it buzz (like electrical intererence) on the clean chanel now. unplugged the guitar cord from the amp and it still does it. aggghhh, i am starting to hate this thing. Link to comment Share on other sites More sharing options...
Members FarToMany Posted February 19, 2009 Author Members Share Posted February 19, 2009 Anyone? Link to comment Share on other sites More sharing options...
Members ¤ Matt ¤ Posted February 19, 2009 Members Share Posted February 19, 2009 by some a new set of valves for it but don't get Groove Tubes. Go for something a bit tamer. Link to comment Share on other sites More sharing options...
Members jpaoletti Posted February 19, 2009 Members Share Posted February 19, 2009 A couple of things I learned from my tube (crate palomino)amp. The elements inside the tube can get loose from vibration causing the squeal. Mine did that. The cabinet was too small for such a loud amp. Any way I changed my tubes out and all was well. To prevent it from happening again, I made a head out of the amp and got a separate cab for the speaker and haven't had any issues since.Also those tubes get hot. I hope you let it cool down before taking it outside in this winter cold. It could cause stress or tiny cracks in the glass.Jason Link to comment Share on other sites More sharing options...
Members jaytee123 Posted February 19, 2009 Members Share Posted February 19, 2009 A couple of things I learned from my tube (crate palomino)amp. The elements inside the tube can get loose from vibration causing the squeal. Mine did that. The cabinet was too small for such a loud amp. Any way I changed my tubes out and all was well. To prevent it from happening again, I made a head out of the amp and got a separate cab for the speaker and haven't had any issues since.Also those tubes get hot. I hope you let it cool down before taking it outside in this winter cold. It could cause stress or tiny cracks in the glass.Jason bad design FTL. Hell, its a Crate! Link to comment Share on other sites More sharing options...
Members starsandthesea Posted February 21, 2009 Members Share Posted February 21, 2009 I have the same issue with my $2k plus Marshall JVM 410C no one seems to be able to figure this out. I have replaced all tubes twice still when I turn up either of the high gain channel the amp starts to squeal like feedback from a PA. The amp has been looked at multiple times. I get the call "All fixed" I get it home or at rehearsal or a gig and "EEEEEEEEEEEK". This happens even when the guitar cable ISN'T plugged in. This amp is also so noisy at high gain channels like a hurricane. I want to fix this, sell it and get a Fender Supersonic but no one can find out the issue. Has anyone figured this out yet? Shane Link to comment Share on other sites More sharing options...
Members PlinytheWelder Posted February 21, 2009 Members Share Posted February 21, 2009 Have somebody scope it and see if it's oscillating.....Ultrasonic or RF oscillations can make an amp act REALLY weird. Link to comment Share on other sites More sharing options...
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