Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Garrett335 on March 22, 2023, 09:24:57 am
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Howdy Chaps,
I'm working on a Blackstar HTStage 100 head that came in. It was blowing mains fuses. I guess the owner took it to Blackstar, they told him it was fixed, came back and kept blowing fuses.
I traced the short down to the power transformer, the IEC has a little PCB where the PT connects, it has a Thermistor, Cap and Resistor, I was thinking one of those components was damaged, however they all read within tolerance.
I disconnected all leads from PT (The Primaries are White/blue, Black/Brown and they are connected together like that on the circuit board (Attached photo from below to see traces).
I disconnected all of the leads from the amp, and plugged the primaries into my current limiter. Short is still there, so is it safe to say the primary has a short in the winding? Are there any other tests I need to do before I tell this customer he just inherited a boat anchor?
(There is no continuity across the PT, I tested each primary to each secondary)
Thank you!