Hi all, New to the forum with some questions about a amp I'm working on. Its a push pull EL-34 based on a st-70 that I built from a different driver board I found
kta-hifi.net/projects/amp_page/st70amp/st70.html
and Stock power supply but I used a different power transformer, a Edcor XPWR002-120 it has the same high voltage @ 720 but 5 more volts on the bias
So between the stock and modified circuit I used it has some minor differences the resistor were the negative bias voltage inputs is about 100k more and the cathode resistor to ground is one 15R where the other has two 15R's
so the problem I'm having is that I can't get the bias voltage to go much higher then 400mV and not the 1.56 that it should be.
I read on here that that changing the to 10k's on the bias power supply to 5k might help and it did but not enough should it be lower or do I need to look somewhere else for a problem?
I hope I've given enough info please let me know if more is needed
thanks
kta-hifi.net/projects/amp_page/st70amp/st70.html
and Stock power supply but I used a different power transformer, a Edcor XPWR002-120 it has the same high voltage @ 720 but 5 more volts on the bias
So between the stock and modified circuit I used it has some minor differences the resistor were the negative bias voltage inputs is about 100k more and the cathode resistor to ground is one 15R where the other has two 15R's
so the problem I'm having is that I can't get the bias voltage to go much higher then 400mV and not the 1.56 that it should be.
I read on here that that changing the to 10k's on the bias power supply to 5k might help and it did but not enough should it be lower or do I need to look somewhere else for a problem?
I hope I've given enough info please let me know if more is needed
thanks