The Sinclair QL Forum

Derek_Stewart wrote: ↑Tue Jan 31, 2023 9:17 pmBut looking at the QL Wiki Hardware section, the board looks similiar to a Simplex Ram expansion.

I am just wondering, why there is EPROM firmware and a PAL if it is "just" a RAM expansion.

There is also no sign of any company on the PCB.

I don't think it's just a RAM expansion, but a 256kb + some toolkit in ROM, the "name" of the interface indicate it.

Also, I don't think that this card intentionally kill QL.

I check the tracks, and the circuit looks very, very standard, I suspect that the fault may be in the 7805 (which cause 12V go back to the QL and fryed something) or in any of the aerial wires, it's curious that have several fixes from factory, including providing +5V to one of the multiplexer, and the 74LS266 pullup resitor , which are part of any basic design.

In any case, if it kill QL inmediatelly, is a very risky board to repair.

But if you check, it have the 8 sdram 1x256kb chips, 2 multiplexer for the Address line, the 74ls266 for decoding the ROM address, the tipical 7805 + 2 capacitor power part.

I guest that the PAL, with the capacitor, resitor and diode of the bottom right are used for the CAS/RAS multiplexing signals need for the Dinamic Ram, and also to save 1 or 2 TTL chips.

I have reverse engineered the board and schematic from the pictures, if some one is interested request it, it's obviously incomplete, and do not have the PAL code, I do it only for fun.

I would also check for bend pin shorted with another at the card connector (happened to me once).

No bent pins, I always watch for that

aalea wrote: ↑Sun Feb 05, 2023 9:37 am But if you check, it have the 8 sdram 1x256kb chips, 2 multiplexer for the Address line, the 74ls266 for decoding the ROM address, the tipical 7805 + 2 capacitor power part.

Certainly not SDRAM, which means Synchronous DRAM, and never existed in DIL packages.

Are these enameled wires at the bottom?
They probably made the damage if from age they lost in places their outer isolation film and shorted something.

Peter wrote: ↑Sun Feb 05, 2023 1:41 pm

aalea wrote: ↑Sun Feb 05, 2023 9:37 am But if you check, it have the 8 sdram 1x256kb chips, 2 multiplexer for the Address line, the 74ls266 for decoding the ROM address, the tipical 7805 + 2 capacitor power part.

Certainly not SDRAM, which means Synchronous DRAM, and never existed in DIL packages.

Yes, of course, normal dinamic ram, without the S.

It's up for sale or trade swap if anyone wants a play with it?

I don't know who made this card, but we did have a couple in a parts bin at Sandy back in the day. Arnie used one for quickly looking at ROMs.

I'd say this could be what it is.