SSLV1.1 builds & fairy tales

V 1.1 build problem.

Just fired up a mosfet BiB +/- boards, and I am not able to adjust voltage on either board. One is at ~ -13 V, and the other ~ +20 volts. Checked the trim pots (5K) and they are fine. Using 2 red LEDs, and 1K8 R203/103 with the zener position jumpered. Test load is 75R 5W, with sense wires hooked up.
BOM says Q104 is BC550 and Q204 is BC560, but the schematic appears to be confusing me? Clearly I have made the same mistake on both boards. Ideas?
 
Sorry...

Merlin, I am on dial up here, with an iffy connection to boot... No way am I going to try and post any picks from here. Looks cool though!
I ahve double checked thta the trim pots are not backwards, they are definitely correct. Everything seems like it should be fine, just weird that there is no voltage adjust???
 
diyAudio Chief Moderator
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Do you have big sinks so to run briefly without a dummy? In that case all the CCS current is going to burn across the shunt Mosfet too, times output voltage. It must be shorted between F0 & S0, F+, S+ for positive, F0 & S0, F-, S- for negative. But before you try such dangerous stuff, do you have enough DC voltage after rectification? Also is the CCS working? How much voltage drop across the 5R6s?
 
Yes...

~1.0 V across R1. Big sinks, .125" angle stock 1.5"x1.5"x4", should not be a problem-I understand all the current will have to be dissapated. I can only run it briefly to get the voltage close, and test, then I can hook it up to my real load. I understand the sense wires must be hooked across to the corresponding output.
Thanks Salas!
 
diyAudio Chief Moderator
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High Vgs gives 1V across R1. That means 178mA, not enough current for the 75R dummies, they would ask for ~270mA @ 20V. What is your output voltage target? Use a jumper instead of the 47R R108(208,308) so the Leds get more current to up their Vf a bit to give you slack.
 
diyAudio Chief Moderator
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What it looks like is the 9610s are high Vgs and the difference from 3xLeds is small. So the CCS current ended up small. Do you have extra 5R6s to run in parallel to the ones installed? That would be the safest. Using the 75R dummies, no changes. I think the regs are simply current starved now for the targets testing. If its a trend with the CCS Mosfets batch, I will have to revise the Rset recommendations to half. But lets see what is it first for sure.