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I bought a Fender twin silverface for a bargain as it doesn't power up. Its dead and I've tried going around it with a meter but with no joy ..need a schematic to do it properly. just wondering if anyone can save me some time with suggestions as to where is the best place to start? maybe you have solved this problem before? Cheers...
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A schematic would be helpful. Try schematicheaven.com. There are lethal voltages in your amp even when it is unplugged.
Does the amp blow the fuse when you apply power?
Search the forum for a light-bulb current limiter and build one so you don't have to replace the fuse everytime you power up.
Sometimes power tubes short, so if you have some known good power tubes it is worth a test. If you only have two known good tubes, you can use two outer or two inner power tubes to test with.
If that doesn't do the trick, pull all the tubes and then power up. The light-bulb in your light-bulb current limiter should be off. If not you have a short in the amp... unlikely unless someone before has been tinkering. -
Pull all of the tubes, make sure you have a good fuse in there (and a good pilot lamp), plug it in and turn on both switches. If it blows the fuse, you either have a shorted cap (very likely in an amp this age) or diode in the power supply (there are 7; six for the B+, and one for bias). If it doesn't blow the fuse, then you must check all of the secondary windings on the power transformer for voltage output. If they are all good, then you probably have a shorted tube.
If you have no idea what I am saying and don't have a voltmeter, then you have to start from scratch, or bring it to an amp tech.Comment
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First thing that I would suggest would be to set your meter up to read resistance.
Read the resistance across the ac plug (hot and neutral). With the switch off it should be infinity. Turn on the power switch and you should get a fairly low resistance reading.
If you don't get a reading, check the plug, cord, fuse and then the wiring from the ac switch to the power transformer.
If you do get a reading, then check the power transformer secondaries as John suggested.Comment
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