Hello,
I'm new here and this is a place of gurus. Forgive me for troubling you.
I have a Microvitec Cub monitor, acquired several years ago. The Microvitec label on the back has a serial number but where the model number should be, it's blank. If it helps, there's also a 'National Power' stock label on it.
A hand-written sticky label on the side says "1441MS4". The obvious answer is that it's a 1441 M series 4. It's definitely an M series but I can't be certain whether it's a 1441 or a 1431 and whether it's a series 3 or 4. From circuit diagrams obtained for the series 3 and 4, it looks more like a series 3 but I'm uncertain and likely need to look harder. Did the tripler change from the series 3 to the 4 and is this the easiest way to tell the difference? How does the 1441 differ from the 1431 internally? Any help would be gratefully received. Apart from a Microvitec label on the edge of the main board, there is no other labelling to help. From the series 3 circuit diagrams, the tube base board appears to match the hires rather than standard res diagram and so my inexpert conclusion is that it's a 1441.
It worked nicely for several minutes when it arrived and then displayed a single thin line in the middle of the screen without even a phut to accompany the change. 2 years later, I've finally got around to thinking about it. I've been looking at the circuit diagrams and trying to determine the cause of the frame collapse and I've been looking in the area of the frame coils circuits, fusible resistors, electrolytic capacitors and the vertical control IC, IC301, a TDA1170s. No damaged components leap out on a visual inspection but what does that really tell me as there could be dry joints and cracked traces: 1983 was a long time ago and no doubt it was stored in a loft for a long time before it travelled in the back of a courier's van to me.
I'm trying to drag my electronics knowledge back through a 25 year void and it wasn't the greatest then anyway: much textbook study but very basic practical and little in the way of diagnostic repair. Any help in guiding my thinking through this would be great. I'd like to work it out rather than throw components at it and the hope is to understand it, repair it and then use it with the BBC Micro that I've fettled. The problem has already gotten under my skin.
I've been looking at building a safe discharging method for the capacitors and CRT. Buying resistors of sufficient wattage to cope is proving more of a challenge than I'd expected but I clearly don't know enough. Any help there would also be appreciated. I was concerned that the instantaneous wattage of the CRT discharge through 10 M Ohm would be initially in the kWs for a fraction of a second before diminishing.
I've attached a top and back view of the monitor's internals. The tube base board is loose and the main board is off the stand-offs with most connections removed as I had dismantled it to look under the main pcb - just to explain the photos.
https://jmp.sh/TC8HQ1U
https://jmp.sh/D1eECTb