Sandy Q Board problem

[GameroomArchitectsBV]

I have a Sandy Q Board that has ceased working, QL just doesn't boot to any screen when attached.
Dave, are there any specific ic's or things I should check first?

Frans

[Dave]

Do you know which version of SQB it is? Also, does it have memory on it?

[GameroomArchitectsBV]

It is an Issue 1 board and RAM is fully populated...

Frans

[Dave]

Issue 1 is probably the most problematic of all, because it's an all-in-one system.

For the fault you describe, I'd check the 7805 is working correctly and not just shorting to ground.

Next, I'd socket, check and replace the various 74-series logic. That's hard to do with it all soldered in place.

In the rare cases when Issue 1 cards were returned not working to us, we always replaced them with Issue 2 cards. Checking and repairing memory was always a challenge on them. It would have been a lot easier if we had Minerva back then.

[GameroomArchitectsBV]

All right, I'll try those tips... I have a desolderingstation so it should be possible to do...
What could cause the 7805 to short out when it was working fine some years ago?

Frans

[Derek_Stewart]

I have a SandyQboard Mouse 1987 Issue 3 P/N 10-0074C

It turned up at a Radio Rally in the North East of UK, with a CST Q-488 IEEE Board, both appear to working.

Can any ram be added to the SQB Mouse board?

[Dave]

Yes. A 512K RAM daughtercard can be added in the second row, just by adding the pins.

You need to connect as follows in the two pics:

If you need more info, let me know.

[Dave]

I might add, if you have the thru-co on that RAM expansion, you can just squeeze on a Qubide over the top, and the SQB v3 will happily tun all three cards off its own PSU.

The riser on the V3 feeds post regulator 5 volts. Be aware of that.

[GameroomArchitectsBV]

I guess I'll have to drill out the rivets holding the metal shield... How do I replace that after checking the 7805?

Frans

[Dave]

A little heatsink paste and a flat headed nut and bolt work fine. I never did like that rivet arrangement and spoke out against it. But then, I wanted the 7805 to be mounted outside the case at the other end of the board.