Low HT Voltage on the Gyraf G9

[steve]

First, thanks to Jakob for an excellent, well-documented project.

My G9 is working, but with lower than expected gain. The HT sits at 132v, not 245v.

At the output of the TL783 (the new CHK version) I read 136v.

The voltage coming off the rectifier circuit, just before R33 is 250v, and after R33, at the input of the TL783, it is 246v.

Center pin of the off-board caps terminal is correct at 0v.

The voltage at the adjuster of the TL783 is 128v.

Have checked the resistor values, R34 at 100K, R35 at 470R and R36 at 47R and they seem fine.

I would greatly appreciate troubleshooting advice on this issue.

Thanks,
Steve

 

[steve]

the TL 783 I refer to above is the new CKTER version

 

[CJ]

Something should be getting real hot if your dropping that much B+.

You could try by passing the regulator.

 

[steve]

Problem solved. It was incorrect resistor values on the adjustment circuit.

Now, with 230v into the regulator, I am getting 220v out as HT. Much better, but...

This is still low, not 245v. For some reason, the second toroid transformer, the one with the 15vac going in, is only giving me 200 vac output for the rectifier circuit. I am using two 30VA 15V toroids. Line voltage is 220v.

Don't know what else I can do about that other than try different transformer.