ampage Tube Amps / Music Electronics |
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Matt![]() |
Marshall 4140 Club and Country I just purchased a Marshall 4140 2x12 combo made in 1981... When I power on, the light comes on and I can hear a very quiet hum... but none of the preamp tubes light.. and when I switch on from standby nothing happens... So basically, as far as function: only the on light comes on. I've checked the fuses and they are fine... also, the tubes are new, and I've reseated each. Where should I go from here? |
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Matt![]() |
Marshall 4140 Club and Country, ALSO Also: I'd love it if anyone has a schematic for this amp. Thanks a lot. |
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Mark Black![]() |
Dr Tube has the schematic: http://www.drtube.com/marshall.htm Search for "4140 & 4145 amp" on the page to take you to the right spot. |
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Mark Black![]() |
Check continuity (power off & at least 10 minutes for discharge) of the power supply transformer windings. You should get some kind of continuity across the ends and end to center of each of the 4 windings. Probably the primary and heater windings are most pertinent here given your symptoms A quick way to check the primary is across the power plug (not plugged into power of course) with the power switch on - you should get some fairly low ohms reading between the legs and infinite resistance from either leg to the ground pin. Heater winding can be checked by measuring across pin 9 and pins 4/5 of the preamp tube sockets, with all tubes removed. Reading should be very low ohms. It's a place to start... Good luck! |
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Matt![]() |
Thanks for the advice... I'll see what sort of reading I get and go from there. |
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