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Old 22nd January 2012, 01:40 PM   #61
jrobson is offline jrobson  South Africa
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Yeah I can, I'll do that now, I've also found some 12xK resistors, quite large probably around 3w each, in parallel I'm measuring 43K
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Old 22nd January 2012, 01:48 PM   #62
jrobson is offline jrobson  South Africa
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Okay, with OPT's off, B+ cut from Mosfets, same as before, 0.
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Old 22nd January 2012, 02:04 PM   #63
jrobson is offline jrobson  South Africa
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Okay with the resistors I'm at 80v...
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Old 22nd January 2012, 02:06 PM   #64
jrobson is offline jrobson  South Africa
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Make that 146v when the coupling cap is connected.
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Old 22nd January 2012, 02:31 PM   #65
jrenkin is offline jrenkin  United States
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Maybe try more in parallel if you have them.

I haven't run the sim yet, everyone woke up.

You probably want a little higher plate voltage, and set the cathode voltage around 3v, recheck the plate and calculate current through the tube. If you can get 160--180ish plate voltage and a current 7--13mA you should be able to trust your tubes and try it in the whole circuit.

You may have already have proved the ccs bad.
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Old 22nd January 2012, 02:47 PM   #66
jrobson is offline jrobson  South Africa
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Looks like around 31K-32K, I get 172v without the output tube in.
There is a difference between left and right though, I reconnected the coupling cap and still only getting 85v or so on one side.

Can you pm me your price and paypal info and I'll take your board and 2 CCS's, I'll just rebuild with a new pcb and see if I have better luck second time around.
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Old 22nd January 2012, 03:54 PM   #67
jrenkin is offline jrenkin  United States
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There can be big differences between tubes, if you can't get one of them right by adjusting the bias resistor circuit, it may need a different load, a problem with 5842 tubes that George solved with a ccs and variable cathode bias.
I don't need to make any money on the parts. Maybe $30 plus shipping total? How best to ship to you? I can send them and then give you a total, not today though.
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Old 22nd January 2012, 03:57 PM   #68
jrobson is offline jrobson  South Africa
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Well I figured I'll use this board to find the problems and fix on the new one, sent you a pm.

I'll play around a little more and swap some parts from left to right see where it all goes.
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Old 22nd January 2012, 04:08 PM   #69
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honestly I haven't read the whole thread but if it helps I'll share this bit of information:

Sometimes throughholes in pcb get damaged or are damaged from production. I experienced lack of gain from my pmillet red board and it turned out everything was correct (values, types of components ecc) but because of desoldering and soldering some connections were missing or damaged.
Difficult to explain but maybe this is what the issue is. I solved my problems by soldering a new board and adjusting soldering temp to less than 300C if soldering small leads.

Hope it helps, good luck
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Old 22nd January 2012, 04:16 PM   #70
jrobson is offline jrobson  South Africa
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Thanks Alex...

It is quite possible, there is certainly a lot of damage
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