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Marshall 4140 Club and Country

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12/19/2005 4:34 PM

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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12/19/2005 4:36 PM
Matt	Marshall 4140 Club and Country, ALSO Also: I'd love it if anyone has a schematic for this amp. Thanks a lot.

12/19/2005 4:53 PM
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.

12/20/2005 12:41 PM

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!

12/20/2005 3:03 PM
Matt	Thanks for the advice... I'll see what sort of reading I get and go from there.

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