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Re: CST Thor 1

Posted: Tue May 30, 2017 11:51 pm
by bagpuss22
Does anyone know where there are a decent set of manuals for the Thor 8?

User manuals etc. in PDF format?

Thanks

Russ

Re: CST Thor 1

Posted: Wed May 31, 2017 1:56 pm
by dilwyn

Re: CST Thor 1

Posted: Mon Jun 19, 2017 11:40 pm
by bagpuss22
OK looks like my QL motherboard has just gone down! :(

It was booting OK as I put a Minerva ROM in to test and it was showing that only
128K was seen not the 640k as expected so there was some issue with memory.
Was working with an external mdv and a keyboard membrane.

Then it all stopped!

Now all I get is random sounds and changing patterns on the screen!!!! Arrghh.
Pressing reset sometimes gets the tartan pattern for memory but it does not get
past that..

OK, best place to get my motherboard repaired? Does anyone have a fully
functional issue 5 spare?

Cheers

Russ

Re: CST Thor 1

Posted: Tue Jun 20, 2017 12:46 am
by bagpuss22
@Derek,

I did manage to quickly test the 3 Thor expansion boards, you sent me, before the QL motherboard
went Pete Tong!

The one that says DEAD is definitely that! Nothing at all.

The other 2 boards booted and had similar issues to what I was seeing with mine although
they did both register 640K with the Minerva ROM fitted where mine only registers 128K.

Once I get my QL motherboard repairedI will get back to testing again.

Russ

Re: CST Thor 1

Posted: Tue Jun 20, 2017 8:43 am
by Derek_Stewart
HI Russ,

I was going to test individual components on the expansion board(s), replace where necessary.

This process is a slow painstaking process, but it is the only way I know.

There was some damage due to battery leakage, also maybe worth looking at any electrolite capacitors that maybe shorted out due toe leakage. It might be a reason to buy an ESR meter to measure the capacitor values.

Re: CST Thor 1

Posted: Tue Jun 20, 2017 9:26 am
by RWAP
bagpuss22 wrote:
OK, best place to get my motherboard repaired? Does anyone have a fully
functional issue 5 spare?


I have 3 x Issue 5 motherboards - one has the JM ROM chips piggybacked, but I would need to test them all. None have microdrive units, but I guess that does not matter. £30 each plus postage :)

Re: CST Thor 1

Posted: Tue Jun 20, 2017 11:37 am
by bagpuss22
RWAP wrote:
bagpuss22 wrote:
OK, best place to get my motherboard repaired? Does anyone have a fully
functional issue 5 spare?


I have 3 x Issue 5 motherboards - one has the JM ROM chips piggybacked, but I would need to test them all. None have microdrive units, but I guess that does not matter. £30 each plus postage :)



Hi Rich,

I would definitely be interested in one of the boards as a replacement/spare for the Thor. If you could give it the once
over that would be great as then I can be assured that the mainboard is not the issue.

Many Thanks

Russ

Re: CST Thor 1

Posted: Thu Jun 22, 2017 12:19 am
by bagpuss22
Anyone seen this before?

Image

This is on my Thor which provides its power via the expansion connector. Unfortunately this
board is now failing with pretty patterns and noise, but the ROMS are OK.

IC35 (7805) missing.
IC37 (7812) missing.
Big resistor goes from IC37 to L5 which has been lifted one end.
Track cut on negative part of IC37 -> IC38.

I was planning on replacing with a board which is a standard Issue 5.

Re: CST Thor 1

Posted: Thu Jun 22, 2017 10:06 am
by Martin_Head
From a quick look at the circuit diagram. I would think it's to supply any Microdrive units that are connected with power.

It looks like it takes the +12v power line from the external PSU, passes it through a resistor to drop it to around 9v, then injects it into the +9v power that would have driven the 7805 regulator, and Microdrive units.

Re: CST Thor 1

Posted: Thu Jun 22, 2017 2:52 pm
by Dave
As Nasta loves telling me: The QL was not designed to be backfed power.

Removal of the 7812 and 7805 prevents the release of the magic smoke when you have power at the output and nothing on the input. The Thor doesn't use the microdrives so there's no need to ensure power there. From my recollection (I have misplaced my Thor reference manual) the board is fed regulated 5V power and +12V/-12V at the J1, and there are modifications along the board, bridging the 9V line to the 5V line.

(Mine's a Thor 16, so it is very different to yours.)

Can we have a large, hires image of both sides of the board, then detail photos of all modifications?