Tweet
Howdy All,
Working on a early 90's Super Pro Tube amp (4x10, not Reverb) and can't locate the reason for channel switching to not function. When the pull switch is engaged it stays on the clean channel until I tap on the board a few times with a chop stick, then it either switches from clean, but doesn't get any sound out of the Gain ch (muted still). Or it switches over to the Gain channel okay. I've reflowed all the solder joints in the immediate area of the relay, I've replaced the relay thinking the original was bad, same behavior with the new relay. I read +16.5 volts on the coil of the relay and 16.5 on the other side in closed position and +4.2 volts on that side when the switch is engaged, telling me the coil is drawing current. This amp is wonderfully layed out with all the components underneath and only solder traces on top so the only way to get at any components is to disassemble the entire thing (pain in the arse).
The front panel led's function as they should when switched from the front panel and with a foot switch.
I'm pretty sure it has to do with the relay #1 as that mutes or connects the Gain channel on one half of the relay and then selects either the Clean or Gain to the rest of the circuit. Anyone have any experience with this amp and things to check that might cause the relay to not connect. BTW you can hear the relay latching and unlatching when the switch is pulled. Also, when the relay doesn't switch channels, I can confirm that the relay didn't switch by measuring continuity on the switch legs of the relay, until I pop the board a couple times and the switch works.
http://ampwares.com/schematics/fender_super_concert.pdf
So, any thoughts or things I should check?
Working on a early 90's Super Pro Tube amp (4x10, not Reverb) and can't locate the reason for channel switching to not function. When the pull switch is engaged it stays on the clean channel until I tap on the board a few times with a chop stick, then it either switches from clean, but doesn't get any sound out of the Gain ch (muted still). Or it switches over to the Gain channel okay. I've reflowed all the solder joints in the immediate area of the relay, I've replaced the relay thinking the original was bad, same behavior with the new relay. I read +16.5 volts on the coil of the relay and 16.5 on the other side in closed position and +4.2 volts on that side when the switch is engaged, telling me the coil is drawing current. This amp is wonderfully layed out with all the components underneath and only solder traces on top so the only way to get at any components is to disassemble the entire thing (pain in the arse).
The front panel led's function as they should when switched from the front panel and with a foot switch.
I'm pretty sure it has to do with the relay #1 as that mutes or connects the Gain channel on one half of the relay and then selects either the Clean or Gain to the rest of the circuit. Anyone have any experience with this amp and things to check that might cause the relay to not connect. BTW you can hear the relay latching and unlatching when the switch is pulled. Also, when the relay doesn't switch channels, I can confirm that the relay didn't switch by measuring continuity on the switch legs of the relay, until I pop the board a couple times and the switch works.
http://ampwares.com/schematics/fender_super_concert.pdf
So, any thoughts or things I should check?
Comment