Members Casey Posted January 19, 2011 Members Share Posted January 19, 2011 so what would you guys do in this situation? I've owned tube amps for years, but due to whoring I've never actually had to change tubes. My amp uses a quad of 6L6's and I broke one of them last night. Wat do? I pulled the two inner tubes to be able to do band practice and nothing blew up, everything seemed fine. The issue is I'm stuck with 3 tubes. Can I just buy another one and bias the amp? Do I have to buy a whole new set of matched tubes and keep the other 3 for spares? Recently acquired this amp and the previous owner said he had recently retubed it and never played it above bedroom volumes. Link to comment Share on other sites More sharing options...
Members tommythelurker Posted January 19, 2011 Members Share Posted January 19, 2011 what amp and what tubes? Link to comment Share on other sites More sharing options...
Members Casey Posted January 19, 2011 Author Members Share Posted January 19, 2011 acoustic control model 165. It is supposedly a mesa mark clone built in the late 70s/early 80s. Here's a schematic if that sort of thing helps you out. http://www.schematics-free.com/modules/PDdownloads/singlefile.php?cid=32&lid=141 and i guess im not sure what you mean by asking what tubes. They're JJ 6L6s. Link to comment Share on other sites More sharing options...
Members tommythelurker Posted January 19, 2011 Members Share Posted January 19, 2011 According to the schematic it has a 100/60W switch which actually removes two power tubes from the circuit. So you'd be just fine running it with two tubes at 60W if that works for you. Ideally you want all 4 tubes to be matched but it's not absolutely necessary. You could also run two matched pairs and bias the amp to the hottest pair. Replacing one tube is the least desirable option but can be done. I probably should have been more clear but the reason I asked what the tubes where is that if they have a rating on them and you know who did the rating, you could buy replacement tubes (from the same source) with the same rating and the new tube(s) should match the old ones fairly well. Link to comment Share on other sites More sharing options...
Members Dthraco Posted January 19, 2011 Members Share Posted January 19, 2011 Tubes are like tires. I just replace them when they get old, rebias and keep rockin. Keep the old one's in case you break one again. Link to comment Share on other sites More sharing options...
Members tommythelurker Posted January 19, 2011 Members Share Posted January 19, 2011 Tubes are like tires. I just replace them when they get old, rebias and keep rockin. Keep the old one's in case you break one again. Ya, but what do you do when you have a nearly new set of tires and blow one out Link to comment Share on other sites More sharing options...
Members Casey Posted January 19, 2011 Author Members Share Posted January 19, 2011 According to the schematic it has a 100/60W switch which actually removes two power tubes from the circuit. So you'd be just fine running it with two tubes at 60W if that works for you. would you be able to tell which two it uses? I'm fine running in 60w mode for now. Link to comment Share on other sites More sharing options...
Members tommythelurker Posted January 19, 2011 Members Share Posted January 19, 2011 Can't tell for sure without seeing an actual layout or the amp itself, but if the layout matches the schematic it would use the outer two tubes in 60W mode. To check you could put it in 60W mode, put two good tubes in the middle and leave the two outside slots empty. If it doesn't make any sound then it is as I said above (use the outer slots). Also, if you have or can find the manual you might want to see if it says anything about adjusting the impedance in 60W mode. To get a "proper" match you would normally set the amp to 4 ohms with an 8 ohm cab but depending on the amp it may not be necessary. Link to comment Share on other sites More sharing options...
Members Casey Posted January 19, 2011 Author Members Share Posted January 19, 2011 so damn hard to find a manual for this guy. been searching since i got it :[ thanks though. Link to comment Share on other sites More sharing options...
Members tommythelurker Posted January 19, 2011 Members Share Posted January 19, 2011 Well if you're using an 8 ohm load with it I would go ahead and put it on 4 ohms. If you're using a 4 ohm load I would just leave the amp on 4 ohms and not worry about it. Link to comment Share on other sites More sharing options...
Members Casey Posted January 19, 2011 Author Members Share Posted January 19, 2011 yea it was switched to 4ohms when i picked it up. can't go lower so i just left it there. Link to comment Share on other sites More sharing options...
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