Tube Amps / Music Electronics
|For current discussions, please visit Music Electronics Forum.|
|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?
|And now, a word from our sponsors:
|12/19/2005 4:36 PM|
||Marshall 4140 Club and Country, ALSO|
I'd love it if anyone has a schematic for this amp.
Thanks a lot.
|12/19/2005 4:53 PM|
Dr Tube has the schematic:
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...
|12/20/2005 3:03 PM|
Thanks for the advice... I'll see what sort of reading I get and go from there.
|Page 1 of 1|