The Sinclair QL Forum

Yes, that is a modded SGC with a link shorting the 9.5V DC input rail to the 5V regulator output. Unfortunately, even after the briefest period, the ICs are likely toast. If you're very lucky a RAM will have failed short first. Either way, everything is replaceable and a duplicate INGOT can be obtained from Tetroid.

Sorry for your misfortune.

Hi,

I do not understand why the there was a wire soldered to bypass the 5V regulator, when Miracle Systems fitted a external voltage connector to allow operation with an Aurora.

But the previous owner of the SGC must read somewhere that shorting the Voltage on the SGC allows operation with an Aurora... very foolish.

My suggestion, is to remove the wire link on the SGC Voltage Regulator. You might be lucky.

I have some SGC boards with CPU pin problems, so could maybe help with any repairs.

The main problem with the SGC, is the Ingot chip, only certain date specific Ingot chips or EP1810, work with the Miracle code,

I have an adapter that will programme the Ingot chip, but, getting the correct chip to allow the SGC to work is hard.

I did start to try and dissaasemble the Miracle MACHXL 2 JEDEC code and produce converted Verilog alternative. But the QIMSI Gold arrived, and it seemed uneccessary. But may a private project to get an alternative Ingot chip.

Derek_Stewart wrote: Fri Jun 27, 2025 10:14 pm I do not understand why the there was a wire soldered to bypass the 5V regulator, when Miracle Systems fitted a external voltage connector to allow operation with an Aurora.

But the previous owner of the SGC must read somewhere that shorting the Voltage on the SGC allows operation with an Aurora... very foolish.

Many QLs were adapted to work off 5V external power. Any of the QXTs, the first early Thors, etc, all did this. To get the SGC working on these you would bypass the 7805 by linking the input and output pins. Running clean 5V instead of unregulated 9V through the back of the QL to expansion cards gave a much cleaner signal path and noticeably less noise within the QL mainboard.

Far more SGCs were used on machines like this than with Aurora.

Hi,

well, I must of been doing wrong, I followed Mircale Systems guidelines and used the external power connector as stated in the manual.

Stuart Honeyball, did say at a Quanta Workshop, which I organised, that the extersl power connector was fitted to the Super Gold Card to prevent accidental, connection of the Super Gold Card to the QL bypassed voltage regulator.

Clearly in this case, that advice was ignored.

It is more efficient and clean to do this by adding a wire link to the board than by using a whole other 5V PSU, if it's going into a system that has been permanently converted to run directly off 5V and the SGC won't be floating between systems.

There are cases where the Miracle anointed way is better suited and cases where bypassing the regulator and feeding in 5V from the Ql is a better choice. These mods were done by people for their own systems. They could not predict what would happen after they pass and someone else takes in their gear and tries to use it 30 years later.

One problem was that the 7805 didn't like being back-fed power. The input pin was at a lower potential than the output pin. This is also a problem with back-feeding power into the Ql from the expansion connector. Nasta told me this was bad but noooo I had to give it a shot and released the magic smoke. A couple of bypass diodes would have done wonders.Another was that at the time it was not widely standardized for the barrel PSU to have GND as the sleeve, so it was common to see reversed polarity.

Thanks everyone, sounds like I need to ship (from Aus), repair and ship back. It would be cheaper to buy a 3rd and have the 2nd for spares.
By the sounds of it my SGC is similarly gone. But it was having a 2nd QL that is more important, thankfully it was the 100 pound one that broke and not the 200 one.

Edit: I'm not able to fix myself due to lack of experience.

I will sell the SGC for parts and recoup some of what I spent, if that's not a pointless exercise?

Wicksy wrote: Sat Jun 28, 2025 9:26 am Thanks everyone, sounds like I need to ship (from Aus), repair and ship back. It would be cheaper to buy a 3rd and have the 2nd for spares.
By the sounds of it my SGC is similarly gone. But it was having a 2nd QL that is more important, thankfully it was the 100 pound one that broke and not the 200 one.

Edit: I'm not able to fix myself due to lack of experience.

I will sell the SGC for parts and recoup some of what I spent, if that's not a pointless exercise?

Hi,

I might be interested in the SGC, please PM me with costs and shipping to UK

Wicksy wrote: Sat Jun 28, 2025 9:26 am Thanks everyone, sounds like I need to ship (from Aus), repair and ship back. It would be cheaper to buy a 3rd and have the 2nd for spares.
By the sounds of it my SGC is similarly gone. But it was having a 2nd QL that is more important, thankfully it was the 100 pound one that broke and not the 200 one.

Edit: I'm not able to fix myself due to lack of experience.

I will sell the SGC for parts and recoup some of what I spent, if that's not a pointless exercise?

You can repair it by yourself (very probably) if you try to follow some easy steps.
What are you going to loose? nothing. You will gain experience and probably some basis materials for future projects or repairing.

The most common tools for repairing are:
Multimeter (less than 10$)
Hot air gun (less than 10$)
Iron soldering (less than 10$)
Tin sucker (less than 5$)
Soldering Wire (a quality one about 20$ 150grams)

And then the components:
N sockets (less than 2$)
N RAM IC Memory, if we are lucky about 1 or 2, that cost less than 3$

Regardless all those materials will be useful for any other repairing or development. And you would not need all of them.
But it is ups to you.

At any case, have you tried the things that I wrote to you above?
And the last option... pay a local technicians to replace the faulty components for you. But for that matter firstly you would need to know which one is. It could be very cheap when you tell to the tech what to do exactly and with the materials.

I've not had time yet, but I'm already sold on getting another and having spares. Now my disappointment has mostly gone I think having spares and living in a fairly isolated location may have it's upsides.

But I will get a multimeter on the QL soon.

Without the Gold card plugged in, or any monitor, and the lid of the QL off.

Power up the QL. Then go round touching the tops of all the IC's. Any getting unduly hot (watch out you can burn yourself) should be considered as faulty.

If you have some very small side cutters, you can (with the power off) snip off the legs of those IC's next to the body of the chip to remove it. This will also make the later removing the legs easier.

Then repeat the the process of feeling for hot IC's.

This will most likely not catch all the faulty IC's. But will point out the worst offenders.