Jazbo, I'm not sure why you only see a thumbnail. I checked it with Firefox, Chrome, and Chrome on my phone and tablet and all of them show me a full-size schematic.
Where did you find that schematic? I looked all over for one and couldn't find one.
While the tubes are the same and the overall architecture is very similar, it's clearly a different amp. I've got 47K resistors coming off the inputs instead of 100K and the first preamp stage in mine is half of the 12AX7, not the 6GW8 triode. In mine the 6GW8 triode runs the tremolo (which the 6AV6 is doing in your schematic). In mine, the second pre-amp stage in the 6AV6. Lots of other little differences. Bias resistor values, etc.
Where did you find that schematic? I looked all over for one and couldn't find one.
While the tubes are the same and the overall architecture is very similar, it's clearly a different amp. I've got 47K resistors coming off the inputs instead of 100K and the first preamp stage in mine is half of the 12AX7, not the 6GW8 triode. In mine the 6GW8 triode runs the tremolo (which the 6AV6 is doing in your schematic). In mine, the second pre-amp stage in the 6AV6. Lots of other little differences. Bias resistor values, etc.
Very weird. The schematic you posted is almost identical to the Model 101 schematic on that site (including resistor and cap values) except with the tubes changed. The Model 101 has two 12AX7s and a 6BQ5 pentode, and as yours is marked as "draft", maybe the author was merely guessing at which triodes went where.. Still, it might make a good starting point for redrawing the circuit.
Is there any way to test caps while they're in the circuit? The cap tester on my multi-meter is designed to have the cap inserted, which won't work if they're soldered into the board.
My guess is the tremolo is suffering from a bad cap. Reverb might be the same problem. All the connections I've tested seem good so far.
Is there any way to test caps while they're in the circuit? The cap tester on my multi-meter is designed to have the cap inserted, which won't work if they're soldered into the board.
My guess is the tremolo is suffering from a bad cap. Reverb might be the same problem. All the connections I've tested seem good so far.
Not really, I merely edited his schematic and made some changes on it as I said "it is based on..."🙂
The old eletrolytic caps should be replaced given their age. To test the other components including the resistors, you need to lift one of the legs from the PCB, it would not surprise me if some of the capcitors are leaky and the resistors have gone way off spec.
Ah, I see. I misunderstood your post of the schematic.
I'll be taking the amp with me to my wife's uncle's house sometime in the next few months. He's a ham and used to own a radio shack. He's got what amounts to a Radio Shack's worth of stuff in his shop (including tube testers and a small mountain of tubes). I'll replace the caps when we go visit him and I'm sure he can help me get the tremolo and reverb fixed. I may also see if I can lighten his load by a few transformers for some future projects.
I'll be taking the amp with me to my wife's uncle's house sometime in the next few months. He's a ham and used to own a radio shack. He's got what amounts to a Radio Shack's worth of stuff in his shop (including tube testers and a small mountain of tubes). I'll replace the caps when we go visit him and I'm sure he can help me get the tremolo and reverb fixed. I may also see if I can lighten his load by a few transformers for some future projects.
That's great. The old ham guys really know their stuff, working on the amp would be like a walk in the park for him.
I’m in need of this schematic but unfortunately the link is broken anyone still have a copy please