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Hi All - I've got a Working Dog Boxer (6V6 version) - have to admit that I've never really been happy with it and, over time, have had a couple of things done to it - added a cut control to tame the high end (there's a lot of it), got rid of the creamy/jangly switch, few other small things. Anyway, somewhere along the line, before I knew enough to just do it myself, a tech tweaked the phase inverter resistors - no idea what they were originally - anyone got one that they can check? - might try to put it back to stock.
In all honesty, the amp has been mostly sitting around for a couple of years because it's amazingly noisy (I could hear at least two different hums and a lot of hiss) and rarely gets played - have recently decided to try to do something about it and have been looking under the hood.
There are some things that surprised me - mains ground and heater CT are tied together on a transformer lug - everything else, including the first filter cap, is connected to one ground point by a bus wire, heater wires are barely twisted - there was no grid stopper resistor on the input - added one at 33K and it got rid of one of the hums (at high volume it cancelled out the other hum leaving just hiss), so that was a step in the right direction - now I'm left with a hum that increases with volume - sounds like mains hum, kinda raspy - seems to be distorting as amp gain increases. BTW, this thing has 5 - 47uF filters and a choke.
Going to reground it (separate ground for the mains, first filter separated from the rest, preamp to its own ground on its side of the amp, rewire the heaters - maybe elevate the heater CT ground, check for bad caps....anyone ever poked around in one of these? Any similar experience?
AJ2000
In all honesty, the amp has been mostly sitting around for a couple of years because it's amazingly noisy (I could hear at least two different hums and a lot of hiss) and rarely gets played - have recently decided to try to do something about it and have been looking under the hood.
There are some things that surprised me - mains ground and heater CT are tied together on a transformer lug - everything else, including the first filter cap, is connected to one ground point by a bus wire, heater wires are barely twisted - there was no grid stopper resistor on the input - added one at 33K and it got rid of one of the hums (at high volume it cancelled out the other hum leaving just hiss), so that was a step in the right direction - now I'm left with a hum that increases with volume - sounds like mains hum, kinda raspy - seems to be distorting as amp gain increases. BTW, this thing has 5 - 47uF filters and a choke.
Going to reground it (separate ground for the mains, first filter separated from the rest, preamp to its own ground on its side of the amp, rewire the heaters - maybe elevate the heater CT ground, check for bad caps....anyone ever poked around in one of these? Any similar experience?
AJ2000
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