The Sinclair QL Forum

Vitaliy,

Do you have any circuit information for the SGC.

I know you were recently asking to borrow an SGC, I can't remember if you got one or not.

Whopper

Whopper, if you'd like me to have a look at it for you, I'd be happy to. I have two here, so I could check if the logic or RAM is bad, etc, and replace the 7805 with a buck regulator.

Nothing to just have a look.

Whopper wrote:Vitaliy,

Do you have any circuit information for the SGC.

I know you were recently asking to borrow an SGC, I can't remember if you got one or not.

Whopper

Yes, I have, but only parts of this. I plan to make PCAD version, but still no time for this.

What happens when you connect SGC to QL ?
Dont work always or sometimes work but not stable ?

Vitaliy,

On power up it makes a horrible sound (from around MDV_1.) The QL doesn't POST or anything else.



Dave,

If you PM me your address I'd be glad for you to have a look at it. Obviously I'd pay for postage both ways, and I think you're in Texas aren't you?

Whopper.

Whopper wrote:Vitaliy,

On power up it makes a horrible sound (from around MDV_1.) The QL doesn't POST or anything else.



Whopper.

Did you try to remove the QL CPU ( 68008 ) ?

Vitaliy,

It's just the same with or without the original CPU fitted.


Whopper

Whopper wrote:mk79,

You do know that Dave is producing a device with similar capabilities to the SGC. Look in the General QL Chat. Proposed cost around £70.

No, he isn't. And besides, as I'm probably the only one who develops SMSQ/E for (S)GC it would make sense to have the hardware for it...

Marcel

Some have been converted to run off 5v. Does it still have the 7805 under the heatsink, or has it been replaced with a wire link?

It's a little hard to tell, but you can usually see the 7805 upside down on the bottom of the heatsink if you look through the gap to the right of the 5V socket.

The way they assembled it was... interesting. They screwed the 7805 to the bottom of the heatsink, bent the pins down, then mounted the 7805 pins through the holes. They screwed the heatsink onto the PCB, then soldered the pins. They did it this way so the heatsink didn't contact the PCB and transfer heat to it - made the CPU and INGOT run a lot cooler. They even used plastic sleeves instead of metal hex nuts to cut down on heat transfer.

Unfortunately, this means it isn't exactly obvious if the heatsink has been replaced with a link. If it has, you just put 9V into it and it is quite possibly toast. :/

Just one of many possibilities, but the most terminal.

Dave,

I thought about the external power supply. I tried a 2.5A 5V wall wart I have, centre negative as per the manual. Just the same though.

Whopper

If there is a wire link, even with an external 5V supply, it still could be shorting 9V QL power to the 5V line.

In this photo, in the exact middle, the row of three pins. If you have a multimeter, can you check across the outside two pins and see if there's a resistance or no resistance?
[edited to clarify which pins]