Bit of an update video here -
https://youtu.be/qHmO9qxaRNo I'm still slogging away at it, winding another mains transformer. I've found a cheap source of big toroid's on ebay, think it was £30 for a 700VA, which is a tad bigger than the other one I wound, IE 625VA. I went over the playing field yesterday to measure out the HT winding's, which are 2 x 243.3ft, but ran out of copper wire. I have some on order from Brocott's. Then it's a case of twisting the two together to form one bi-filar wire, bung it on a foot long "bobbin" then wind it on. With that done the other secs are a doodle.
I've also built a VU meter driver. It uses a TL074 opamp, one as precision rectifier, another as a voltage amp and another as buffer. I didn't use the last bit. The only modification I did was add a 100k preset on the IP, as the circuit as is, loaded the OP off the ECC83 too much. I've also had to add an attenuator SW because with an OP off the ECC83 of 6v RMS, this means the meter tops out , IE FSD, at about 35W. this is just a 6K8 R, with a SPST SW.
I also added a peak/clipping indicator, which turns an LED on at 5.9v RMS, glowing brightly at 6v RMS.
Lastly I've built a protection circuit that fires a triac at around 100mA cathode current. Each EL34 has a wire running off the cathode to the protection PCB. This is just a peak detector in essence. It took a lot of experimentation to get it right. As I said at 1v the triac fires, which supplies 12v to a relay, with cuts the negative mains to the mains tfmr. There is also an ultra bright diode on the front panel to indicate a fault.
These circuits are all on one PCB, with the PSU, which is a half wave rectified +/- 15v, stabilised by two 5W zeners.
If anyone's interested, I'll attach the circuits.
Andy.