Weird DSL201 OT problem.

[drewl]

Working on a JCM2000 DSL201 that someone hacked up pretty bad.

Guess the bridge for DC heaters went bad as it and the filter caps were removed and ac filament tied over to where DC should have been.

That was wreaking havoc with the low voltage supplies.

Fixed that but the OT is intermittent.

Someone must have yanked the wires to it while working on main board as the connector tabs are loose.

If I put pressure on it I get full signal out.
Otherwise output drops to nothing.

But the DC resistance of all the transformer taps doesn't change while flexing or pushing on the tap connectors.

Somewhere inside windings of primary must be shorting, but no dc resistance change.

Jumpered in an 18w OT I have ( which is alot beefier!)
And amp works great!

Luckily mounting holes are the same.

Still need to clean up messes someone did, like solder the loop Jack's, yes they soldered the FX loop Jack tabs so you can't even plug a cord in!

[Helmholtz]

But the DC resistance of all the transformer taps doesn't change while flexing or pushing on the tap connectors.

Somewhere inside windings of primary must be shorting, but no dc resistance change.

DCR measurements of windings will only clearly identify open windings. It will not show primary to core or primary to secondary shorts. And a short between 2 adjacent turns of a winding may change the DCR by as little as 0.1 Ohm but will still load down the OT.

[drewl]

That's what I figured.

No shorts to secondary, but I finally did see dc resistance changes of primary center tap to the bad side.

Thanks.