Tube Amp Care
Hi fellow Gearheads,
As Doug knows I run a small business in the Claire and Gilbert Valley of South Australia, doing a variety of things involved with music, most of which are legal, and one of which is repairing valve amps (are there any other kind!!), and guitars.
During the last week I have had a number of Marshall's in for repair and they are all suffering from faults related to the same problem.
When a valve amp is switched on it should be run in standby for at least 30 seconds, preferably a minute before applying the DC rail voltage to the power amp valves.
On Marshall's, Fenders and most other valve amps, this is achieved by switching on the power at the main switch, leaving it for the necessary time, then switching from standby to normal operation.
The results of not carrying out this procedure can vary from annoying, to downright expensive.
(1) Power Supply fuses may blow, particularly the DC fuse.
(2) Stripped cathodes in the power amp valves will degrade the sound of your amp
(3) Power Supply capacitors may fail.
(4) Bypass capacitors may fail.
(5) Your power amp valves may only last half the time.
(6) When items 1 - 5 cause your amp to let you down in the middle of a gig, frustration may lead you to doing serious harm to your amp, as per Pete Townsend.
(Note PT can probably afford it, most of us can't).
All this can be avoided by following the above procedure.
One common problem that leads to not following the above is switching off the amp at the end of a show/rehearsal by just switching off the main power switch. Next time the amp is turned on the standby switch is already on and DC is applied to the power amp valves before the heaters have had time to warm up.
I am probably doing myself out of easy money as I am quite happy to repair all the amps which fail due to the above problem but that's not the way I like to do business. Follow the above and save yourself money and frustration.
By the way, the above does not apply to solid state (WHAT!!!) amps, just turn them on and play.
Regards, Bob Charman
Stockport Sound Studio
PO Box 1, STOCKPORT SA 5410, Australia
Telephone 08 8528 2098
See also: AMPS @ GuitarSite.com
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