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View Full Version : my Intertec Superbrain Status Update



alan8086
April 1st, 2017, 02:02 AM
Hello to all. This post is just an update for anyone interested, on the status of my Superbrain QD. There are people on this forum who keep a back of the mind track of who owns these machines, where shouts they are etc.

I had drawn things to a halt for a while but yesterday I spent a few hours trying to repair the spare psu module, didn't work out so I carried on with the one that works, tried both of my motherboards and I seem to be getting unreliable voltages. Also managed to overvolt the ROM as it got a little hot onnboth boards after upping the voltage on the psu pot. This revealed a weakness on one board as one of the decoupling caps between the -12v / 0v rail blew. Removing it restored a reliable voltage to the RAM banks. Sounds a bit hit and miss but no other harm done since I restored the 5v to where it should be.

My unreliable voltages are due to the ribbon cable that feeds voltages /data to and from the logic board and psu. It has been unplugged/plugged so many times the carbon tracks in the ribbon are breaking down. This is on the working psu. Today I will attempt to swap the ribbon cable off the other non working psu as it is in much better condition.

The main inspiration for all this is that I managed to get the machine to try reading a disk. The floppy light would come on at power on, pressing the red keys make it go on/off and placing a bootable disk in the drive caused the head to move slightly. Nothing on the screen though which may be to do with the ribbon cable.

alan8086
April 1st, 2017, 04:42 AM
...I also worked out what likely killed the machine in the first place. It came from Cardiff Uni originally, came to me dead - hence the non working psu I have. It also came with a Micronex Pixel Plotter board and associated wiring/interface board. I traced the voltage lines on the PixelPlotter board and found the -12V to be shorted to ground - probably a bad cap or IC. All IC's are socketed and of the 74LS variety so it shouldn't be too hard to track down the fault. I suppose having a shorted -12V output wouldn't do the PSU much good if it was left that way?

OK, end of update for now...

JonB
April 6th, 2017, 05:32 AM
Hi Alan

Have you sorted the ROM out, if so, how? I'm collecting one on Saturday, and I would like to "get my ducks in a row".