Hello All,
Newbie here, thanks for letting me in.
My band mate has a Mark IV combo that has recently had the Tweed setting go all but dead. When you switch to it the power bleeds down to almost nothing over about 4-5 seconds. To hopefully correct it he installed a new set of tubes with no change. I pulled the chassis and found the 470ohm screen resistor burned open on one of the center 6L6 power tubes(V6?). I spoke with him about that and he said he thinks it happened a few years ago when he inadvertently installed an EL34 in one of the inside sockets but it didn't affect the amps performance. He runs it in Simulclass/Triode mode. I replaced the resistor but it had no appreciable affect.
I found schematics for most of the amp but not the power supply. I was told it is similar to the Triple Rectifier's Bold/Spongy setting. That schematic leads me to believe it just switches the primary winding of the xfmr so unless there is a weird problem with the xfmr the problem must be a marginalized component down stream reacting adversely to the lower voltage of the Tweed setting ...or am I way off base? Admittedly I'm little more than a novice @ amp repair and this is one hell of an amp.
I would be much obliged if someone could send me the schematic covering the Tweed switch, and does anyone know what the Tweed setting problem may be caused by? The amp works fine otherwise.
Best regards,
Kwall
Newbie here, thanks for letting me in.
My band mate has a Mark IV combo that has recently had the Tweed setting go all but dead. When you switch to it the power bleeds down to almost nothing over about 4-5 seconds. To hopefully correct it he installed a new set of tubes with no change. I pulled the chassis and found the 470ohm screen resistor burned open on one of the center 6L6 power tubes(V6?). I spoke with him about that and he said he thinks it happened a few years ago when he inadvertently installed an EL34 in one of the inside sockets but it didn't affect the amps performance. He runs it in Simulclass/Triode mode. I replaced the resistor but it had no appreciable affect.
I found schematics for most of the amp but not the power supply. I was told it is similar to the Triple Rectifier's Bold/Spongy setting. That schematic leads me to believe it just switches the primary winding of the xfmr so unless there is a weird problem with the xfmr the problem must be a marginalized component down stream reacting adversely to the lower voltage of the Tweed setting ...or am I way off base? Admittedly I'm little more than a novice @ amp repair and this is one hell of an amp.
I would be much obliged if someone could send me the schematic covering the Tweed switch, and does anyone know what the Tweed setting problem may be caused by? The amp works fine otherwise.
Best regards,
Kwall
