daveq Posted October 15, 2004 Report Share Posted October 15, 2004 OK, here's a dumb question: Does anyone know how to access the tube in my preamp section ? There's an aluminum box bolted to the back but I don't know what it is. I've tried unscrewing a couple of the bolts but they just keep turning. I seriously doubt that they are stripped though. Do I need to take the whole amplifier chassis out of the cabinet and get at it that way? I'm sure I can handle the rest if I can just find the dag-nabbin tube access . Thanks, Dave Quote Link to comment Share on other sites More sharing options...
thrashncrust Posted October 15, 2004 Report Share Posted October 15, 2004 sounds like your reverb tank thingy Quote Link to comment Share on other sites More sharing options...
daveq Posted October 15, 2004 Author Report Share Posted October 15, 2004 Oh, no - the reverb tank is on the left side. The aluminum box I was talking about is too small to be a reverb tank (if that's what you meant). Thanks anyway though. I managed to find some info on the web for a different valvestate amp and someone mentioned that you do have to completely remove the amp from the cabinet to access the tube. I'm assumming that mine is the same way then. Thanks, Dave Quote Link to comment Share on other sites More sharing options...
ansil Posted October 16, 2004 Report Share Posted October 16, 2004 while you are removing it try replacing it with a pentode/triode or a single pentode to really cook it in the gain section you can do easy mods but then agian i am not sure that hte valvestate actually uses high voltage or not haven't looked at the schematic.. hmm well if it doesnt' gut it and make it tube. Quote Link to comment Share on other sites More sharing options...
Fan O' Zakk Posted October 16, 2004 Report Share Posted October 16, 2004 while you are removing it try replacing it with a pentode/triode or a single pentode to really cook it in the gain section you can do easy mods but then agian i am not sure that hte valvestate actually uses high voltage or not haven't looked at the schematic.. hmm well if it doesnt' gut it and make it tube. What was that?? Quote Link to comment Share on other sites More sharing options...
lovekraft Posted October 16, 2004 Report Share Posted October 16, 2004 Man, you know Ansil can't just replace a tube - if he opens something up, it's moddin' time!! Quote Link to comment Share on other sites More sharing options...
Setch Posted October 16, 2004 Report Share Posted October 16, 2004 Dave, Remove the entire chassis, by unscrewing the four screws on the top of the amp cabinet. You'll probably want to undo the connections to the reverb tank and speaker too, since the leads are a little short, and the chassis a little heavy, so doing any work on it whilst still connected to the cab is tough! From there changing the tube is pretty straight forward - it's the only one, and is in a ceramic base with a retainer clip holding it down. Unclip it, and swap in your replacement. There are no big, highly charged, caps to worry about, since the power section is solidstate, but still avoid poking anything non-essential just in case Hope this helps... Quote Link to comment Share on other sites More sharing options...
LukeR Posted October 16, 2004 Report Share Posted October 16, 2004 Dave, may I ask why you want to change the tube? Most 12AX7s have a really long life- i dont think Ive had one fail. Are you thinking about upgrading and getting a Groove Tube, or something like that? I dont really know how much of an effect changing the valve will have on the sound- obviously it would have a significant tonal effect on a conventional valve pre-amp, but I had a friend who changed his valve in his valvestate (granted, it was one of the early ones) and there was no change in tone whatsoever (I mean, the differnce between 5881s and EL34s are like night and day, and the same even with the preamp valves in my Marshall JCM, but honestly, there was no discernable differnce at all when the valve was changed in the Valvestate. Maybe the valve had the EXACT characteristics as the one that was replaced, but thats a pretty long shot). I wouldnt have a clue why that happened, but could you please post your findings on the new valve once you have it all operational (Just to find out if its a fluke or not). Cheers man, Luke Quote Link to comment Share on other sites More sharing options...
Fan O' Zakk Posted October 17, 2004 Report Share Posted October 17, 2004 Dave, may I ask why you want to change the tube? Most 12AX7s have a really long life- i dont think Ive had one fail. Are you thinking about upgrading and getting a Groove Tube, or something like that? I dont really know how much of an effect changing the valve will have on the sound- obviously it would have a significant tonal effect on a conventional valve pre-amp, but I had a friend who changed his valve in his valvestate (granted, it was one of the early ones) and there was no change in tone whatsoever (I mean, the differnce between 5881s and EL34s are like night and day, and the same even with the preamp valves in my Marshall JCM, but honestly, there was no discernable differnce at all when the valve was changed in the Valvestate. Maybe the valve had the EXACT characteristics as the one that was replaced, but thats a pretty long shot). I wouldnt have a clue why that happened, but could you please post your findings on the new valve once you have it all operational (Just to find out if its a fluke or not). Cheers man, Luke Bingo...I could see someone going to a 12AU7 or a 12AT7 for a softer gain, but you won't gain anything by using another 12AX7 tube. It's not run hard enough in the first place... Quote Link to comment Share on other sites More sharing options...
EVHownsall Posted October 17, 2004 Report Share Posted October 17, 2004 The box on the back that you kept turning was the transformer. Quote Link to comment Share on other sites More sharing options...
ansil Posted October 18, 2004 Report Share Posted October 18, 2004 hmm see if what i was getting at is this.. since pentodes inherintly have more gain possiblities you could squeeze out some more saturation out of the preamp by using say a dual pentode. hmmm do they make one in a 9 pin config.. yes they do also you could use say a 6dx8 like i do and although it would require a bit of re routing and only a slight modification.. the x8 can use the pentode first and slam the crap out of the at7 style second stage that is inside it for some truely EVIL gain sustain compression etc. also if you are game you can come off the output section and then add in a negative full wave rectifier/doubler and use it to control the compression effect and for just a few parts you can have onboard evil compression to go with your new sound.. or you can just change it out. personally i would just gut it and replace it with all tubes. :D.. thats true though lk i can't just replace it man i got to make it ansilfied. lol http://geocities.com/ansilgregory/dictionary Quote Link to comment Share on other sites More sharing options...
daveq Posted October 21, 2004 Author Report Share Posted October 21, 2004 (edited) Sorry - it's been a while since I posted this. Setch nailed it - I had to remove just about everything . The little snap-on nuts that snap into the chassis kept falling into the circuit board when I tried to put it back together - what a major pain in the butt! One of them is now stripped. Is this an industry standard - the way they make you take so much of it apart? The snap-nuts are the worst part of the whole mess. Ugh!!! Dave, may I ask why you want to change the tube? Most 12AX7s have a really long life- i dont think Ive had one fail. Are you thinking about upgrading and getting a Groove Tube, or something like that? I've had it for about 10 years now and never replaced it. I bought a Groove Tubes 12AX7 and it does sound different (better). It's not a drastic change but I can tell that my distortion channel is improved and that was the goal. I read somewhere that the avg. life would be at most 10 yrs at my usage rate. I doubt I'll be able to find that web page again though. Ansil - with my luck any mods beyond what I just did would result in complete destruction. Thanks anyway. Edited October 21, 2004 by daveq Quote Link to comment Share on other sites More sharing options...
ansil Posted October 29, 2004 Report Share Posted October 29, 2004 i know we technically have finished this thread but hmm did we ever discuss if it was real high voltage or not. i have a old valvestate on head on my desk and it is real high voltage. but i had a combo that was just a little newer and it wasnt'.. funny though the valvestate SS sounds better than this terd on the bench now.. i am glad his dad wants me to gut the whole preamp and make it all tube with Gak.. a SS poweramp.. i personaly can have a SS preamp and a tube power but hmmm i dont' like SS poweramps that much for guitar. Quote Link to comment Share on other sites More sharing options...
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