Search found 1349 matches

by Pr0f
Sun Apr 28, 2024 12:56 pm
Forum: General QL Chat
Topic: Anouncement for the 40th Anniversary of the Sinclair QL in Dormagen (Germany)
Replies: 50
Views: 9556

Re: Anouncement for the 40th Anniversary of the Sinclair QL in Dormagen (Germany)

I manged to get a flight sorted to Koln, no rooms available at the venue hotel, but I'm booked in at a hotel down the road, so will be arriving Thursday and going back Sunday Evening. Wondering if it's cheaper to get trains and taxi's or book a car at the airport as it's only just up the road. It's ...
by Pr0f
Sat Apr 27, 2024 8:06 am
Forum: Hardware
Topic: Announcing the new "Gold Card" - QIMSI Gold
Replies: 98
Views: 9474

Re: Announcing the new "Gold Card" - QIMSI Gold

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!
by Pr0f
Fri Apr 26, 2024 8:37 am
Forum: The Off-Topic Section
Topic: PSU Primary side issue (non QL)
Replies: 14
Views: 1725

Re: PSU Primary side issue (non QL)

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!
by Pr0f
Sun Apr 21, 2024 2:17 pm
Forum: The Off-Topic Section
Topic: PSU Primary side issue (non QL)
Replies: 14
Views: 1725

Re: PSU Primary side issue (non QL)

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 ...
by Pr0f
Sat Apr 20, 2024 9:06 pm
Forum: The Off-Topic Section
Topic: PSU Primary side issue (non QL)
Replies: 14
Views: 1725

Re: PSU Primary side issue (non QL)

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...
by Pr0f
Sat Apr 20, 2024 5:31 pm
Forum: The Off-Topic Section
Topic: PSU Primary side issue (non QL)
Replies: 14
Views: 1725

Re: PSU Primary side issue (non QL)

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!
by Pr0f
Sat Apr 20, 2024 4:59 pm
Forum: The Off-Topic Section
Topic: PSU Primary side issue (non QL)
Replies: 14
Views: 1725

Re: PSU Primary side issue (non QL)

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...
by Pr0f
Sat Apr 20, 2024 4:45 pm
Forum: The Off-Topic Section
Topic: PSU Primary side issue (non QL)
Replies: 14
Views: 1725

Re: PSU Primary side issue (non QL)

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
by Pr0f
Sat Apr 20, 2024 4:29 pm
Forum: The Off-Topic Section
Topic: PSU Primary side issue (non QL)
Replies: 14
Views: 1725

Re: PSU Primary side issue (non QL)

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...
by Pr0f
Tue Apr 09, 2024 3:45 pm
Forum: The Off-Topic Section
Topic: The Victorian Age
Replies: 5
Views: 902

Re: The Victorian Age

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