CST Thor 1

[Ralf R.]

*The Thor doesn't use the microdrives*

As far as I know: the early Thor's indeed have one mivrodrive.

[bagpuss22]

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?

Hi Dave,

I will sort out some detailed pictures.

I have a bit of a dilemma about the voltage regulators. there are 3: +5, +12 and -12. on my issue 5 board they are removed and the 12v dropped to 9v for the microdrives.

I have a picture from Adrian Graham of his Thor 8 with an issue 6 board where the 7805 is removed but the +- 12v regulators are still in place and his works without a problem....

As the 12 regs are in a smaller package would that make any difference?



Russ

[BSJR]

Anyone seen this before?

(...)
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.

I've compared your board with my issue 5 Thor, they seem identical apart from the big resistor which is lacking.
The QL Service Manual states that ic38 is not used in the issue 5, can't find it anyway, so only the ic's 35, 36 and 37 were removed.
No other mods have been done to the underside than those also done to my BBQL issue 5.
Apart from a failing clock, the NC battery is dead, mine now runs fine on OS v4.21 although I have not tested it fully yet.
I had to replace the PSU after shorting the original but have no -12v at the moment so serial testing has to wait.

Bob

[bagpuss22]

Anyone seen this before?

(...)
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.

I've compared your board with my issue 5 Thor, they seem identical apart from the big resistor which is lacking.
The QL Service Manual states that ic38 is not used in the issue 5, can't find it anyway, so only the ic's 35, 36 and 37 were removed.
No other mods have been done to the underside than those also done to my BBQL issue 5.
Apart from a failing clock, the NC battery is dead, mine now runs fine on OS v4.21 although I have not tested it fully yet.
I had to replace the PSU after shorting the original but have no -12v at the moment so serial testing has to wait.

Bob

Hi Bob,

Apologies that should read: track cut on negative part of C37 -> C38!

On your issue 5 board are pins 1 and 2 of HBC1 and HBC2 wire-linked? Is that for Microdrive usage?
I know the resistor on mine allows 9v to be passed to the Microdrive circuits.

IC35 is the 5v reg.
IC36 is the -12v reg.
IC37 is the +12v reg.

OK looks like I will need to remove these from a 'normal' Issue 5 replacement board I have coming. Its weird that the issue 6 Thor board
still has IC36 and IC37 installed unless there are track cuts under the board...

Russ

[bagpuss22]

Hi Bob,

Maybe you could pop up a photo of the area around the power connector so we can have a look?

Many thanks

Russ

[BSJR]

Hi Bob,

Apologies that should read: track cut on negative part of C37 -> C38!

On your issue 5 board are pins 1 and 2 of HBC1 and HBC2 wire-linked? Is that for Microdrive usage?
I know the resistor on mine allows 9v to be passed to the Microdrive circuits.

Russ

Hi Russ,

I checked again and the C37/38 cut is indeed there. But also on my BBQL-i5 so I think it's mandatory and a board design error. The voltage section diagrams of i5 & i6 are the same but the board layout is different on i6.

The mdv mod is actually pin 1 & 3 connected on HBC1 & 2. Probably to allow external drives to be connected as MDV1 & 2.
It there an opening in your box for this?

Bob

[bagpuss22]

Hi Bob,

Apologies that should read: track cut on negative part of C37 -> C38!

On your issue 5 board are pins 1 and 2 of HBC1 and HBC2 wire-linked? Is that for Microdrive usage?
I know the resistor on mine allows 9v to be passed to the Microdrive circuits.

Russ

Hi Russ,

I checked again and the C37/38 cut is indeed there. But also on my BBQL-i5 so I think it's mandatory and a board design error. The voltage section diagrams of i5 & i6 are the same but the board layout is different on i6.

The mdv mod is actually pin 1 & 3 connected on HBC1 & 2. Probably to allow external drives to be connected as MDV1 & 2.
It there an opening in your box for this?

Bob

Hi Bob,

Thanks for the info. I received a new QL Issue 5 board today and the track cut is there too

For some reason, if you look at my previous photo's, pins 1 and 2 are linked on HBC1/2! I know this works as I tested and
external mdv just for fun and it format/read ok. I will need to see if this is really necessary.

There are no openings for this on the unit.


Russ

[Derek_Stewart]

Hi Russ,

If you look in the QL Service Manual, "APPENDIX C TO SECTION 4 MANDATORY MODIFICATIONS" details the modifications to improve Microdrive performance.

Every Issue 5 board I have has already had this modification done.

[BSJR]

Thanks to "the Team" I now can share my Thor issue 5 detail images.

Bob

[bagpuss22]

Starting to loose the will to live on this one......

Rich sent me a working issue 5 board which I got around to fitting today. Had to remove the power connector, IC35 (7805),
IC36 and IC37 (regulators) as power is derived from the Thor..

And!

All I get is a black screen! On RF I cannot get a signal and RGB goes from black to a lighter black! Nothing!

Not sure what to do now. 8301 tested on another board and that is OK and the PSU is outputting the right
voltages......

Russ