Hi folks
A few years back I started this thread on this power supply; luckily i found a circuit diagram at the time, which I put up there:
https://www.vintage-radio.net/forum/...ad.php?t=95600
That time it was an easy fault, but now I have let some magic smoke out and I wonder if anyone would hold my hand while I scratch my head over it.
It appears to adjust to a desired o/p voltage, but as soon as I add any kind of load this collapses - even with very small o/p currents.
The 6.5v (relative to +ve meter output terminal) supply which runs the control circuitry is stable, whether there's a load on or not. (This rail sits on top of Zener MR11 on the circuit diagram.)
The +ve side of the bridge rectifier sags a bit when a load goes on, but not enough to (IMO) be a concern - still plenty of headroom there to drive the o/p transistors.
R29 and R30 (ceramic 0.5 ohm current sensing resistors) both measure ok.
Current limit preset RV1 doesn't seem to do anything at the moment.
Any suggestions where to look next would be very welcome - I'm failing to grasp how the feedback works (or should work) from the description in the manual.
many thanks
Mark