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Hi all, I am a new member amd am building a pair of Mk III clones with the transformers from Triode, purchased the driver board from them too. I searched and can't find anyone that has asked this question so apologize if this is a "known fact".

On the schematic I note that C4/R12 connect to point G and C5/R13 connect to point F however looking at the board its backwards with C4/R12 to F - which is right? Obviously the board is etched and labled but would not the phase of the output transformer be backwards? And should G go to the blue & green side instead of F?

Simple enough to swap and don't think it would actually damage anything but this has me puzzled so I thought I would ask.

Thanks All - Dave

Nice catch! Follow the hook-up (F & G to the colors listed) from the schematic, Dave. I'll try and fix the schematic for the component numbering. Good luck with your build.

Shannon

F goes to the solid blue and green side. G goes to the striped side.

Thank you Shannon, I now have it figured out, the slik screen F and G are correct, its the silkscreen part numbers for C4/C5 and the associated resistors that are flipped, I followed the trace from the V2 PIN and the light came on. I did not look at the input to C4/C5 to see which pin the trace there was going to. Funny - If I was just soldering the parts on they are symertical so it makes no difference in practice.

I will send along a picture once I get the 1st one finished, I added a softstart for the filaments and PC boarded the bias supply, I have used a simple softstart with expensive transmitting tubes just so as not to shock the cold filaments, not sure its necessary here but what the heck, diode, 2 48v relays and a couple caps, 2 resistors.

My question -
I plan on using and have panel mount trimmers for both balance and bias voltage (I know this is not really needed) parts Mouser 652-3006P-1-504-LF and 652-3006P-1-103-LF with a panel mount adaptor 652-H83P they are both 3/4W units, is this enough dissapation for the 10K? I actually have no idea how to calculate the current in the negative bias supply. I am a hobbyist and make my living as a systems engineer in IT.

Thanks,
Dave

Dave -- A 3/4 watt rating is more than enough, since the 10K pot actually dissipates something less than .1 watt in reality.

Good luck with your projects!

Dave