The Sinclair QL Forum

Excellent development - I would also like to pledge my interest in this - but as there is no list - I will await it's launch. My passport needs renewing by June, so given the new rules, I won't be able to attend either, but I wish you all well in the conference in Germany and a very happy time!

I have to say - that's one impressive looking VCR !

And Kudos for getting it all working again - I think mechanically they are as complex as electronically!

It should stay triggered once you have raised the gate above the cathode voltage, and only reset once the current flow in the Anode to Cathode circuit has gone close to zero. The resistance reading between gate and cathode seems very low, it's normally equivalent to a diode, and as it's a thyristor ...

If you have a multimeter with a DC input voltage rating of 500v or higher - you should be able to measure across the main capacitor - on DC voltage range - you should see some 350-400V. You could also check the stripe (cathode) side of the rectifiers on the secondary side - these should give some in...

I think the wave forms and voltages may not read well on a multimeter. A scope will be the best way to read these voltages - assuming your probes and or scope inputs have the correct rating to check these - as you are dealing with quite high voltages here!

Yes - provided the main capacitor on the primary side is ok, and the bridge rectifier - you should see the full wave voltage from the mains across it - so it will around 380-400v - for a 230/240 V mains supply. It's not that critical as the power supply works down to 110V by the looks of it. The cap...

Looks like the 12V output from the PSU is used to regulate the PSU primary circuit, and the 5V circuit is further regulated by another IC, and also has a crowbar circuit across the input to that IC. Full service manual here: https://elektrotanya.com/grundig_gv280s-vpt,ft,t_vcr_sm.pdf/download.html#dl

Do you have the service manual for it? Those circled numbers probably have expected waveforms or voltages to measure on the primary side, so if they are ok, the issue is likely on the secondary side of it. It's rare but not impossible for rectifiers on the secondary side to fail, which will obviousl...

Back then Video hadn't even been born, so the Radio star was safe

Happy Birthday - enjoy the vino