![]() Hi Guys First of all, Im very naive when it comes to technology and the associated terminology so bear with me Ive had my amp for 9 years from pretty much new and never had it serviced or had any problems with it. Then recently it lost a lot of power, no crackels hisses etc, just a loss of volume overall. Of our JCM 2000 Dual Super Lead valve heads. Stylish looks and above all great Marshall tone. The DSL 100 and DSL 50 are our latest all valve heads. Nov 25, 2017 How is the Marshall JCM2000 DSL. JCM-2000 DSL's are fine amps. But ultimately Marshall made a replacement PC board available that fixes all of. I was told about a guy who did repairs locally, so took it to him, who diagnosed the fault, and said i needed a new set of valves. I expected as much, and although a little disappointed at being quoted £120 for 4 pre an 2 outputs (its a 50 watt amp) as well as fitting, didnt have much in the way of options so went with it. I mentioned that Id heard theyd need biasing, and asked if he could do that, and he said that as he was getting a matched pair of mullards, he wouldnt need to bias them. This worried me, but hey, hes the expert. I went today to check it worked with my cab and guitar and to pay and bring it home, but on plugging in there was just crackling and we couldnt get a sound from the guitar. He ummed and ahhhd, took off the back and felt the output transformer which was hot, and he said it looks like your output transformer has gone. He was however getting a signal with his signal generator, but it was very weak, and he said it had been much louder before Id arrived. He mentioned the cause might have been that he had been using an 8 ohm load, and me plugging into the 16 ohm cab must have pushed the transformer over the edge. Now, I dont have the knowledge to know whats going on, and feel a bit trapped into the situation, and worried about how much Im going to be charged now. Does all this sound ok or should I be concerned? As far as i can tell this guy knows his stuff electronically, and he comes recommended from a friend who i trust very much, but he is not a musician at all and doesnt work solely with amps. I have now left it with him to test the output transformer and see where we go from there. If anyone could chime in about the type of issue Im having and confirm if the output transformer should be the first suspect, and whether the rest of the work so far sounds reasonable itd really put my mind at rest. Thanks in advance, Kris. Well, First of all, which JCM 2000 is that amp. JCM number are just like a series designation. The other numbers might be a chassis number like 2202 or TSL-100. That is a bit weird to have the OT go bad like that, espically if you weren't playing all that loud at the time. I think the jury will be out on that one for a while. As far as replacing tubes with matched set not needing biasing, he's got a problem there. The Matched set only means tjhat all four power tubes will be drawing the same current at a specific bias voltage setting. That could be 100ma for one set (which would be low for 4 tubes) or 220ma for another set (which would be too high for 4). Either way, the bias being off doesn't ususally take the OT out. If it is of the TSL or DSL variety, there is a common anti-oscillation disc capacitor that shorts & could mimmic a bad OT to an unexperienced tech.so I'd be careful at accepting this 1st diagnosis. Get a second opinion from a tech that at least understands how biasing works! Thanks guys, wnet and got the amp back, and found a good guy elsewhere. However, before I went to get the amp, i told him to take out the new valves, send them back and put mine back in. Shock horror, it works. Like it did before I even had a problem, like its fixed. Could this be to do with the fact that hes probably changed (by accident) the positions of my preamp valves? Im sure Ive heard that one of the four preamp valves deals with the drive or something, I could be completly off with this, but if that one was dying this would make sense. Im still going to take it for a service with the real tech, just pondering thats all. Thanks so much for your input. Thanks guys, wnet and got the amp back, and found a good guy elsewhere. However, before I went to get the amp, i told him to take out the new valves, send them back and put mine back in. Shock horror, it works. ![]() Like it did before I even had a problem, like its fixed. Could this be to do with the fact that hes probably changed (by accident) the positions of my preamp valves? Im sure Ive heard that one of the four preamp valves deals with the drive or something, I could be completly off with this, but if that one was dying this would make sense. Im still going to take it for a service with the real tech, just pondering thats all. Thanks so much for your inputSounds more like a loose connection or something, not a dying preamp tube. Could even be loose socket pins. I've got to tell you that these amps are notorius for cracking solder joints at varying locations.
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