General Stuff(tm)

[stephen_usher]

Hopefully the Enterprise won't be a complete basket case, but we can all find out together :)

It may be more fun if it is. :-)

[rubber_jonnie]

Hopefully the Enterprise won't be a complete basket case, but we can all find out together :)

It may be more fun if it is. :-)

Very true :)

[stephen_usher]

So, what have I been doing recently which is retro?...

Well, I've been getting a "trash" black Microvitec CUB renovated as much as possible for use with Sinclair machines.

I was given it at RetroFest as a non-working monitor for me to see if I could get it working. It's an unusual "IBM PC" model, which means it has a CGA compatible TTL input, so RGBI with horizontal and vertical syncs. It was in a filthy state, having been stored at "The Farm" (not exactly sure where it is). It also had a penetrating impact on the base, but not deep enough to effect the PCB.

I managed to fix the case using UV cured resin and 3D print a new front flap.

I got it home can cleaned the outside quickly and then plugged it in and turned it on. Other than the power light at the front in the switch there was nothing. Opening the back I found that the two fuses had blown. So, I replaced them both, switched on and one glowed for a bit and then blew, the other was fine. Seeing as I was guessing a high initial current and the degaussing coil was on that circuit I disconnected it, replaced the fuse and tried again... success! Plugged the degaussing coil in again and it worked fine. So I think it was all the old capacitors reforming.

I made up an RGB adapter cable for the QL, but I couldn't get sync whatever I tried. The CUB in this configuration should take composite sync on the h-sync line and work... Then I checked the PCB jumpers... it was set for inverted sync, which CGA generates. Changed the jumper and it worked, sort of. Blacks were grey and yellows were brown. It was also washed out. Still I had an image.

It was a bit ripply on the horizontal lines and there was a slow ripple down the picture as well. Recapping the horizontal and PSU output caps fixed those issues.

Looking at the CGA adapter board and reading the documentation showed that the board drove the main monitor by generating an analogue output using the TTL signals to address values in a 32x8 ROM. So, to replace the CGA mapping to pure RGBI would just require replacing it. Of course 32x8 bit ROMs are not really available, so I created an adapter PCB so I could use a 27Cxxx ROM instead. It would also allow me to read the original ROM's contents and analyse it.

I did this, worked out the mapping, created my own and installed it.

IMG_5234.jpeg

IMG_5249.jpeg

The result? Success!

IMG_5236.jpeg

It needed pull-ups on the address lines but nothing else.

I managed to adjust the picture size so that the whole of the QL's display is shown as well.

The only real problem with the monitor is that there's a discoloured area in middle right which shimmers if the monitor is tapped. I think the impact which cased the case damage caused some of the mask suspension wires to break, which is a pity because the tube is otherwise bright and sharp.

IMG_5243.jpeg

Today I've finally got the DIN plugs and cable so I could make up a ZX Spectrum+ 128K RGB cable. This allowed me to tune the monitor for full RGBI, rather than just RGB. Took quite a bit of adjustment of the neck board to get something which worked acceptably both on the QL and Spectrum though.

Doesn't look half bad though.

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IMG_5257.jpeg

[HigashiJun]

Well done !

[mrbombermillzy]

I must admit, I have a soft spot for CRTs.
Well done on getting the RGBI output working. That display looks great. :dualthumbup:

Like you say, a shame about the wobbly mask, but is it a problem when the monitor is not moved?

[stephen_usher]

Like you say, a shame about the wobbly mask, but is it a problem when the monitor is not moved?

Unfortunately it gives a colour cast, which is worst for blue, in that area. A bit like having a magnetic problem, except degaussing isn't going to solve it.

[PhilC]

It's still a great looking monitor and really suits the style of that spectrum and no doubt the QL too.

Iust get myself a decent RGB CRT once I've got space for one again, not enough room as I've got too much stuff needing to be sold now it's fixed.

Anyone wanna buy 6 130XEs?

[rubber_jonnie]

Anyone wanna buy 6 130XEs?

Only 6?

[alexh]

Anyone wanna buy 6 130XEs?

I never owned an 8-bit Atari but I could be tempted in 1. These are like mini Atari ST's in shape no?

[PhilC]

Anyone wanna buy 6 130XEs?

Only 6?

Well I was going to keep one for myself :D