Dual Dark 50 Plate Voltage?
Posted: Fri Nov 16, 2018 8:49 am
Hi. I am an engineer from the UK, most of my work being through a Music store in Halifax, Yorks'.
I have a Dual Dark 50 from a customer.
The Plate volts on the 2 - EL34's are at 290v each. Given the 40mA current supposed to be drawn between the Plate and screen, that would mean this 50w amp would struggle to make it to 25w!!
I have it on full power, rather than half.
So what should the plates be seeing volts wise? Seems to me that it should be almost double what it is.
A schematic would be nice as I am used to working on vintage amps and this power supply looks hard to decipher without pulling the whole board and backwards engineering the thing, if the customer could afford that I'm sure he would have sent it to Orange directly!!
Only had a quick look so far but I did notice in initial checks that the HT to the OP was 400v unloaded, 290v loaded no matter which valve set I put in. Strange thing is at the moment the output tubes, and I have tried 2 different sets which both test good in a tester, are only pulling 12mA each, regardless of an assurance from the customer that the bias pots have not been touched. Any help would be appreciated! Thanks.
I have a Dual Dark 50 from a customer.
The Plate volts on the 2 - EL34's are at 290v each. Given the 40mA current supposed to be drawn between the Plate and screen, that would mean this 50w amp would struggle to make it to 25w!!
I have it on full power, rather than half.
So what should the plates be seeing volts wise? Seems to me that it should be almost double what it is.
A schematic would be nice as I am used to working on vintage amps and this power supply looks hard to decipher without pulling the whole board and backwards engineering the thing, if the customer could afford that I'm sure he would have sent it to Orange directly!!
Only had a quick look so far but I did notice in initial checks that the HT to the OP was 400v unloaded, 290v loaded no matter which valve set I put in. Strange thing is at the moment the output tubes, and I have tried 2 different sets which both test good in a tester, are only pulling 12mA each, regardless of an assurance from the customer that the bias pots have not been touched. Any help would be appreciated! Thanks.