Trouble with two interfaces

[schombi]

I would need some help with two faulty interfaces.

- An Expanderam 512K memory expansion: Once plugged into a working QL, I get a white screen. Interesting enough, there´s a mix of two different types of memory chips on the board. Eight of them are TMS4256-15NL, where the second eight are TMM41256AP-10. Is that normal? What can be done to rectify a white screen error?

- A CST Q-Disc: When the QL boots, I get the Q-Disc message displayed. Also a Dir flp1_ is taken, so I assume the ROM is working. However, none of the (working) drives seem to respond. Even more strange, the LED on the drive(s) is (are) always on, once the ribbon cable is plugged into the Q-Disc - also when there´s no power on the QL. Therefore I tried to turn the cable, but I´m pretty sure that would be the wrong way, as both the cable and the connector on the Q-Disc are keyed. By filing the cable and using some force, I could insert the cable 180 degrees twisted, but still no response from the drive. Anything else I can do, rather replacing the (socketed) WD1770 chip?

[RWAP]

The white screen with the expanderam suggests that one or more of the memory chips is faulty unfortunately... They should all be the same speed, but I too have seen some with a mixture, so I guess it doesn't matter too much...

The CST issue sounds very similar to ones I came across a couple of years ago - the cable had to be turned upside down (despite the keying) but even with a replacement WD1770, I could never get them to format....

[schombi]

Thank you Rich! I´ll try replacing the RAM chips, once they arrive from China.

I still hope the CST Q-Disc can be healed. Strange you also had some odd findings with this interface - I cannot believe CST sold the Q-Disc with the connector mounted incorrectly. Finally you had to bin yours?

[RWAP]

Yes unfortunately mine were both binned in the end

Dilwyn has used the CST Q-disc without any problems so it looks as though it is either something that fails on the cards, or maybe one particular version (there were at least 3 revisions).

[Derek_Stewart]

Hi,

That is a pity about "binning" the expansions, it is probably the quality of the logic chips on the board.

[schombi]

One more question while I´m waiting on the WD1770 to arrive. The label on the ROM says "CST QDisc 1.06". I had a look at Dilwyn's page and there´s only 1.13 and 1.16 (Sinclair QL World from 5/1987 even mentions 1.19), so mine is pretty old. Are there any limitations, so I cannot/should not put a higher version on mine?

[1024MAK]

I don't know enough about this interface to say, but keep in mind that with some expansions for other retro computers, there were differences in hardware, so a later firmware version may not be compatible.

Once you get it going, then is the time to try a later version. Or if every effort to get it to work fails, try another firmware version. Just don't bin or reprogram that EPROM (yet).

Mark

[dilwyn]

During the early years, I had three different versions of Q-Disc (I think there were 4 versions in total) and all worked well from what I remember. Can't remember what the differences were, maybe more toolkit extensions and/or ramdisc included, aparat from any hardware changes).

There was one version where the disk cable had to be upside down as someone has mentioned, I think (not 100% sure) it was the early version sold via Computamate name.

I *think* that the Q-Disk version was etched or printed onto the PCB somewhere, but it's so long ago since I had the various versions I can't remember how to tell the difference. There are manuals for three of the four versions on my website http://www.dilwyn.me.uk/docs/manuals/index.html#disks, you may be able to glean some understanding of the firmware differences at least from these manuals. The Toolkit 2 manual also contains some information about differences between flp driver versions, e.g. v1.15 contained some changes to allow for WD1772 being used instead of the WD1770 commonly used.

[chriskgnr]

I had this exact Qdisc controller with the 1.06 firmware and worked like a charm with a dual cumana 5.25 disk drives set(Mitsubishi drives). I updated the firmware with the 1.13 and still everything fine(i think it included more tk2 extensions)! And yes, i had to turn upside down the disk drive cable plug to work correct! BUT, i never managed to make work this controller with 3.5 disk drives, except once with a chinon 3.5 one sided 360k disk drive taken from an Acorn Electron Plus 3 Interface! I replaced almost everything, including the euro connector the disk drive connector, put ic sockets, cleaned the pcb, checked the pcb for cut traces, replaced the 74LS series ic's with military specifications ic's, replaced the wd1770 with other wd1770 and later with a wd1772, reprogrammed the eprom with varius firmwares, but no avail. For some reasons it does not like the newer 3.5 disk drives, pc disk drives with modifications or old ones like chinon, panasonic, teac etc. I think it can work only with very old 3.5(maybe 1982 'till 1984) shuggart compatible disk drives. All these points to that this version controller is a poor electronic and pcb design.

qdiskif_cst.jpg (33.66 KiB) Viewed 4928 times

cumana_double.jpg (9.33 KiB) Viewed 4928 times

[1024MAK]

Bit of a guess - It sounds like it may need the READY signal. Most 5.25 in and 3 in drives provide this, but most 3.5 in drives do not...

Mark