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Re: CST Thor 1

Posted: Fri Oct 06, 2017 6:54 pm
by bagpuss22
ON the board removed today

I added the regulators I took off the board I was installing to the Thor.

I have also noticed on this Issue 5 board I removed, that memory ICs 3, 5, 9 and 10 are getting
very hot, +60 degrees within seconds.

The screen seems to be constantly changing with different patterns, I assume this would be
a valid fault display for faulty RAM?

Would anything else be damaged? If I populate these 4 RAM ICs then hopefully the board will be
useable again...

Russ

Re: CST Thor 1

Posted: Sat Oct 07, 2017 10:52 am
by Martin_Head
bagpuss22 wrote:ON the board removed today

I added the regulators I took off the board I was installing to the Thor.

I have also noticed on this Issue 5 board I removed, that memory ICs 3, 5, 9 and 10 are getting
very hot, +60 degrees within seconds.

The screen seems to be constantly changing with different patterns, I assume this would be
a valid fault display for faulty RAM?

Would anything else be damaged? If I populate these 4 RAM ICs then hopefully the board will be
useable again...

Russ
Four RAM chips all going short at the same time seems very suspicious to me. As if the board had been supplied too much power, or something sparked across somewhere.

I would remove the four overheating RAM chips, and see if anything else is getting warmer than expected.

Have you got a Minerva ROM you could fit, this does a RAM test and displays graphically on the screen any errors. If you try it with the faulty RAM's removed and get a display that shows the removed RAM's are faulty. It will suggest that the rest of the logic on the board is working. If you don't then you have other problems than just the RAM's.

With four RAM chips gone so badly faulty, I would be tempted to replace all 16 of then in one go, fitting IC sockets in their place.

On the subject of the new issue 5 board you just received, Did you try it as a stand alone board before fitting it into the Thor. If it did you would at least know that if something has now gone wrong with it, It was caused by something in the Thor. Either the power supply, or if you connected anything to the edge connector.

Are you absolutely sure that the Thor Power Supply is OK, I would also check that all the power supply wiring goes where it's supposed to. Also make sure the ground (0 volt) rails are all correctly connected, and continuous.

Re: CST Thor 1

Posted: Sat Oct 07, 2017 1:54 pm
by bagpuss22
Martin_Head wrote:
bagpuss22 wrote:ON the board removed today

I added the regulators I took off the board I was installing to the Thor.

I have also noticed on this Issue 5 board I removed, that memory ICs 3, 5, 9 and 10 are getting
very hot, +60 degrees within seconds.

The screen seems to be constantly changing with different patterns, I assume this would be
a valid fault display for faulty RAM?

Would anything else be damaged? If I populate these 4 RAM ICs then hopefully the board will be
useable again...

Russ
Four RAM chips all going short at the same time seems very suspicious to me. As if the board had been supplied too much power, or something sparked across somewhere.

I would remove the four overheating RAM chips, and see if anything else is getting warmer than expected.

Have you got a Minerva ROM you could fit, this does a RAM test and displays graphically on the screen any errors. If you try it with the faulty RAM's removed and get a display that shows the removed RAM's are faulty. It will suggest that the rest of the logic on the board is working. If you don't then you have other problems than just the RAM's.

With four RAM chips gone so badly faulty, I would be tempted to replace all 16 of then in one go, fitting IC sockets in their place.

On the subject of the new issue 5 board you just received, Did you try it as a stand alone board before fitting it into the Thor. If it did you would at least know that if something has now gone wrong with it, It was caused by something in the Thor. Either the power supply, or if you connected anything to the edge connector.

Are you absolutely sure that the Thor Power Supply is OK, I would also check that all the power supply wiring goes where it's supposed to. Also make sure the ground (0 volt) rails are all correctly connected, and continuous.
OK,

Replaced the for hot ICs, and powered up. Not getting hot anymore but still not booting.

Put a Minerva ROM in and it fried it! Hot within seconds!

Not a happy bunny.

Re: CST Thor 1

Posted: Sun Oct 08, 2017 9:09 pm
by bagpuss22
It was a shorting link put in by CST, by the main connector!

So far I have had to replace the 4 x DRAM and the 8049, just the ZX8302 to check and then
maybe some power can be applied.

Re: CST Thor 1

Posted: Mon Oct 09, 2017 10:18 am
by Martin_Head
If that was a shorting link between the 9v rail and the 5 volt rail, I would expect mass death and destruction amongst the logic circuitry. Watch out for the 74LS... chips, they really shouldn't like more that 5 volts up them at all.

Re: CST Thor 1

Posted: Wed Oct 11, 2017 12:19 am
by bagpuss22
I am hoping that I may not have to change too much. My worry would be, if the board would be
better scrapped or rebuilt!

:?

Re: CST Thor 1

Posted: Sat Jan 25, 2020 2:41 am
by bagpuss22
OK, back to looking at this one.

Recently socketed all of the logic and put in a new 8046 and ZX8302.

Just recapping the board and then I will fire it up and see what is what....

Might socket all of the RAM too and then we are easily replaceable on all the ICs....

BP.

Re: CST Thor 1

Posted: Fri Jan 31, 2020 2:14 pm
by Derek_Stewart
Hi,

I have found my old Thor 1 case, floppy drives, eprom expansion board.

Just: QL board ( got a few of these), Thor expansion board, psu.

Do you have any of thr Thor boards I sent to you spare?

Condition is unimportant, I have been performing a lot of PCB track repairs on other computer equipment, udually battery leakage and through hole barrel replacement.

Re: CST Thor 1

Posted: Thu Mar 14, 2024 11:50 am
by brefeldin
Does anyone have images of the 3 floppy disks coming with the original CST Thor ? Especially the System and the Tutorial disks would be great.