previous: aris ...and I'm wondering if the PT is b... -- 1130421850

Re: Enzo - Another Marshall blowing fuses....

10/28/2005 12:08 PM

R.G.

Re: Enzo - Another Marshall blowing fuses.... There are two major ways a PT can fail - open windings or shorted. Open windings don't blow fuses. Shorted windings can (although they may not under some circumstances).     If your PT was blowing fuses, it would not stop when you disconnect the secondary wires. So it must be something past the transformer.     Any short past the secondaries could cause fuse blowing - such as:   - shorted wire leading to rectifiers   - shorted rectifiers   - shorted filter caps   - DC overload past the filter caps, which could also be shorted wires, shorted caps, shorted semiconductors, etc.     How do you find it?   1. Quit buying a new fuse for each test. Make yourself a series light bulb power limiter to limit the current that the amp can draw to less than the fuse current. Then go looking for zero voltage where there should be voltage.   2. Divide and conquer. You know it's not the PT ( at least I think it's not) so open the connection from rectifiers to filter caps and connect the rectifiers. Do you now have DC voltage at the output of the rectifiers? If yes, then it's not the rectifiers. So then connect in only the filter caps. DC across the filter caps? If yes, then it's the load.     quote: "...when disconnected, there is continuity between the 2 red secondary wires, and between each red secondary wire and ground. Is this normal in a healthy PT, or is this one bad?"   If it's a typical centertapped secondary for a solid state amp, there is normally continuity as you describe it.

 

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Albert series light bulb power limiter? -- 10/31/2005 5:49 PM