Uh Oh I think I blew it

[Daven]

Hello fellow tube amp entusiasts,

I thin I blew the output transformer in my Kustom Kraft 600. I was measuring the power output on the 50c5. I first set up the meter to measure the plate current by shunting the output transformer. Then I went to measure the voltage from the cathode to the plate and forgot to change the leads to voltage. The ammeter being basically a short this put the B+ across the primary of the output transformer. Now when I look at the output signal it has all sorts of high voltage high frequency distortion on positive peaks. Any thoughts?

[Daven]

Hello Again,

I'm trying to determine which output transformer to use as a replacement and I am a little confused. I understand turns ratio and impedance ratio, but I am confused about which primary resistance to use. The data on the 50C5 says it has a plate resistance of 10,000 ohms, but another spec says load resistance of 2500 ohms. I thought the idea was to match the plate resistance. What is this load resistance spec and should I be using that instead of the plate resistance?...Thanks...Dave

[Dave H]

Hello fellow tube amp entusiasts,

I thin I blew the output transformer in my Kustom Kraft 600. I was measuring the power output on the 50c5. I first set up the meter to measure the plate current by shunting the output transformer. Then I went to measure the voltage from the cathode to the plate and forgot to change the leads to voltage.

I've done that loads of times. It's one of the hazards of the OT shunt method but I've never blown an OT. Usually it just blows the fuse in the meter. If it has blown the OT the OT primary impedance you need is the 'Load Resistance' in the data sheet not the 'Plate resistance' i.e. 2500ohms not 10000ohms

[g1]

Then I went to measure the voltage from the cathode to the plate and forgot to change the leads to voltage. The ammeter being basically a short this put the B+ across the primary of the output transformer.

I see it as you put B+ across the cathode resistor and cap. I'd expect the cathode cap to be damaged and maybe the cathode resistor too. Have you checked them?

[Daven]

I see it as you put B+ across the cathode resistor and cap. I'd expect the cathode cap to be damaged and maybe the cathode resistor too. Have you checked them?

I changed the cathode resistor and the bypass cap...Problem solved, it wasn't the output transformer...Thank you