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I’ve been trying numerous different combinations of search words but have had no luck in finding anything regarding my specific issue.
I have a Gibson Titan Medalist amplifier with an unusual problem. The owner said that the amplifier started having volume issues, that it wasn’t as loud as it should be. The first thing that I found when checking it out was that the 2 amp slo-blo fuse needed replaced and one of the 470 ohm screen resistors had opened up, the other three were nicely in spec averaging about 467/8 ohms. The power tubes were old ones and kind of flaky so I replaced them. So after replacing these the volume came back for the most part. Channel one is behaving very strangely, when the volume knob is all the way down I hear a significant amount of guitar coming through… it sounds very warm, clean and pleasant at a volume about equal to an average conversation. But again, this is with the volume turned all the way down. When you turn the volume up it starts to get “flat” sounding just a little bit but I’m able to get it loud now. This effect was much more pronounced with the old tubes, it would get flat sounding but the volume would not increase. When the tremolo is on you do not hear any of the tremolo effect when the volume is all the way down, but again there is that nice warm clean sound that should not be there. I have swapped preamp tubes between both channels and the issue remains in channel one regardless of the tubes used. Channel two behaves pretty much normally, but you do hear just a little bit of sound with the volume knob all the way down. The phase inverter tube checked to be pretty weak on my transconductance tester so I replaced it. I’m not sure if this is much of a factor or not, but on the schematic it says that both plates on the PI tube should have the same voltage, but the voltage on one is significantly lower. The schematic says about 137 volts (if I recall correctly) and one plate is just about right on the spot but the other plate was something like 119 volts. So far I haven’t encountered any other resistors out of spec.
At this point I’m a tad stumped and I’m hoping to save a little time by asking for a little help. Just about every other time I’ve had an issue I’ve been able to find the answer in a search, but not this time. Any help would be appreciated, thanks.
I have a Gibson Titan Medalist amplifier with an unusual problem. The owner said that the amplifier started having volume issues, that it wasn’t as loud as it should be. The first thing that I found when checking it out was that the 2 amp slo-blo fuse needed replaced and one of the 470 ohm screen resistors had opened up, the other three were nicely in spec averaging about 467/8 ohms. The power tubes were old ones and kind of flaky so I replaced them. So after replacing these the volume came back for the most part. Channel one is behaving very strangely, when the volume knob is all the way down I hear a significant amount of guitar coming through… it sounds very warm, clean and pleasant at a volume about equal to an average conversation. But again, this is with the volume turned all the way down. When you turn the volume up it starts to get “flat” sounding just a little bit but I’m able to get it loud now. This effect was much more pronounced with the old tubes, it would get flat sounding but the volume would not increase. When the tremolo is on you do not hear any of the tremolo effect when the volume is all the way down, but again there is that nice warm clean sound that should not be there. I have swapped preamp tubes between both channels and the issue remains in channel one regardless of the tubes used. Channel two behaves pretty much normally, but you do hear just a little bit of sound with the volume knob all the way down. The phase inverter tube checked to be pretty weak on my transconductance tester so I replaced it. I’m not sure if this is much of a factor or not, but on the schematic it says that both plates on the PI tube should have the same voltage, but the voltage on one is significantly lower. The schematic says about 137 volts (if I recall correctly) and one plate is just about right on the spot but the other plate was something like 119 volts. So far I haven’t encountered any other resistors out of spec.
At this point I’m a tad stumped and I’m hoping to save a little time by asking for a little help. Just about every other time I’ve had an issue I’ve been able to find the answer in a search, but not this time. Any help would be appreciated, thanks.
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