• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

preamp 6J1 used separate, transformer ct hot

try to repair the 6j1 preamp, the same scheme follows the original, only there is a modification in the psu, the plate voltage is 28 volt ct, the output of the regulator is lm317 and 337, the transformer is 3 ampere, the heater uses 1 ampere, the voltage using 9 volts is turned down using lm2596 to 6.3 volt dc... which makes I'm confused, originally I used 12vac 1 amper (it's safe) then multipliered it to 28 vdc. When using a model like this, it often makes noise, so I modified a separate PSU (the hum is gone, the noise is gone). The question is why the 3 ampere transformer heats up quickly even though the regulator IC is still there. It's just cool.....maybe someone can help

AX tech editor
Joined 2002
Paid Member
There may be a problem in the rectifier bridges.
I suggest to disconnect the load, disconnect the inputs to the regs.
If still hot, disconnect first the trafo to the pos rectifiers, if still hot also disconnect the trafo to the neg rectifiers.
In the end, if still hot, get a new trafo.
Otherwise, you have located the problem.