On Wed, Jun 28, 2017 at 2:04 AM, Warner Losh via cctalk <[email protected]> wrote: > Had a static discharge event with my VR-201 and suddenly the background is > 'grey' rather than 'black'. By this I mean I see maybe 50% of the color > (where before I saw maybe 1%) and maybe half a dozen solid diagonal lines. > This replicates across the two rainbows I tried the monitor with. > > This seems like it would be a common thing, but my google fu has turned up > little. I get why I might not find a how-to on fixing a VR-201 (though I do > have the prints), you'd think that I'd be able to locate the proper jargon > to find the answers, but so far goose-eggs. I can't even find a good > monitor repair FAQ, though I guess I need a primer on terminology as > well... I've done a lot with video over the years. But it's all been > digital, I've never repaired analog gear.
'Digital circuits are made from analogue parts' as Don Vonada said. I still wonder how anyone can understand digital circuits properly without understanding analogue stuff. But anyway... This sounds like it should be a simple fault to fix. At least the HV circuitry is still working (you have a raster, albeit an over-bright one). My thought is either a problem in the video amplfier or in some of the supplies derrived from the flyback transformer. The video amplfier is remarkably complicated, it consists of a CA3046 transistor array (4 of the transistors are used) and 4 more transistors. But start by measuring the CRT voltages (not the EHT, so you don't need more than a normal multimeter). I noted down the ones in one of my VR201s (working normally, normal brightness picture) and got : Pin 1 (Green) Control Grid : -25V Pin 2 (Yellow) Cathode : 35V Pin 6 (Red) : 1st (accellerator) anode : 560V Pin 7 (Blue) : 2nd (focus) anode : 200V Pins 1 and 2 are the important ones at this stage. Look for pin 2 being more -ve (lower voltage) that this or pin 1 being less -ve than here. Can you adjust pin 1's voltage with the user brigthness control, and if so, can you make it a lote more -ve? When I have an idea of which area of the circuit is the problem, I will look into debugging it more. > -tony
