| Author | Message | ||
| Andrea Cola (andreac) Username: andreac Registered: 07-2011 |
Hallo, I just purchased a nice 210-65 HI-OFF-LOW switch, with 12ax7 phase inverter, totally recapped and serviced few months ago. Output transformer not original (but oversized). Other tubes are two svetlana winged "C". my problem is after playing it for a while in the 2nd channel with master on 8/9 and gain on 3/4, set ohm on 4, HI power switch and fuse simply blown. I have to say that my playing was very dynamic and I was hit a chord very very strongly (if this can help...). changed fuse and after thirty minutes re-turned it on: the sound was not so round and nice as before fuse blowing, I noticed a sort of "out of focus sound" (especially on middle frequencies) and a little bit of hiss. But it works. It is not the first time. Anybody had ever experienced this problem? | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
If the amp works but the sound has "changed" , obviously something has gone bad. My first guess would be tube trouble. I would suggest having it checked by a tech who is familiar with Music Man amps. The bias points are radically different than a fender amp and they are NOT set the same. Also, if the phase inverter went bad, THAT could have been what took out the tubes. There's no real shortcut here. Did the power tubes glow when it went out? That was a common problem with them and was the reason they went to the SS driver. I would guess power tubes followed by a COOLER bias setting and see what it sounds like. Mike. | ||
| Andrea Cola (andreac) Username: andreac Registered: 07-2011 |
my tech owns two 210-65, but with ss driver and he told me that mine has a strange circuit that stays in between the two schematics (12ax7 and ss driver) that he found on web. Yesterday evening I have retried, connecting my 115 RH and switching to 8 ohm (12 ohm total)...after one hour or so, and after a series of continously chords a little bit loud(think of neu!), same problem. fuzzy clean sound and then immediately fuse blown. I was checking the2 svetlana during the rearshal, before this happening, and they were fine! maybe the 12ax7 got problems... QUESTION: is it possible to convert my circuit to a ss driver, without change everything? | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
I HAVE converted a amp to a ss driver but I had a factory driver board to do it with. I would NOT suggest it for the faint of heart or a REALLY reliable tech doing it. It requires the complete restructuring of the amp to drive the tubes from the cathode side. Don't try this at home. Fix your amp the way it is. If Lars pops in, maybe he can help because I get the impression that you are out of the US and have an export amp? Have you check the bias of tha amp the way it is? Tried subbing new tubes with bias check? The 12ax7 CAN be the problem so I would try subbing that but you need to be looking at the amp electrically , not playing when it goes out. In other words, it need to be on the bench. Mike. |
Tue, 03/25/2014 - 09:35
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