QL issue 5, D05 repair - RAM troubleshooting / ROM dongle needed?

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ChalkyNZ
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QL issue 5, D05 repair - RAM troubleshooting / ROM dongle needed?

Postby ChalkyNZ » Sun Aug 18, 2019 10:00 am

Hi all, I'm trying to repair a QL issue 5, with serial D05-XXXXXX (will check exact number & post). No ROM dongle is present.

Problem: At power on, I get a grey screen, that's it.

Background: Don't know history of this unit, and whether it has worked in recent years.

Troubleshooting: Have swapped all socketed ICs (except ROMs) with another working issue 6 unit, no change in behaviour - working unit works, failed unit stays failed. Have probed with oscilloscope, I can see normal RAM activity on address & data lines for a few seconds, then activity ceases. Power still present on all ICs.

Questions: Does the build standard D05 QL need the external ROM dongle? I don't know much about those, and the service manual seems to indicate that might be the case. This unit has 2 x 16k ROM EPROMS only - ROM release 'PM' - starting addresses $0000 and $4000, but obviously not $8000, which I can see listed on the PM ROM dumps.

Related question: If I want to get the Minerva ROMs into this unit to try to troubleshoot the RAM issue, I'll need to jumper it for 48 internally - is that possible, or must I put 16k on the dongle?

Thanks so much, and apologies if my terminology is off/rusty/wrong, it's been a while!


Cheers,
ChalkyNZ.


Martin_Head
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Re: QL issue 5, D05 repair - RAM troubleshooting / ROM dongle needed?

Postby Martin_Head » Sun Aug 18, 2019 10:19 am

Check out the QL Service manual section 4 http://www.sinclairql.net/srv/qlsm4.html#s4-p1.2

If IC 17 is still there, then a lot of mods are needed.


ChalkyNZ
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Re: QL issue 5, D05 repair - RAM troubleshooting / ROM dongle needed?

Postby ChalkyNZ » Sun Aug 18, 2019 10:59 am

Martin_Head wrote:Check out the QL Service manual section 4 http://www.sinclairql.net/srv/qlsm4.html#s4-p1.2

If IC 17 is still there, then a lot of mods are needed.


Hi, thanks for that - would the lack of mods (this has none) cause the issues I'm seeing? Cheers!


Martin_Head
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Re: QL issue 5, D05 repair - RAM troubleshooting / ROM dongle needed?

Postby Martin_Head » Mon Aug 19, 2019 10:33 am

ChalkyNZ wrote:
Martin_Head wrote:Check out the QL Service manual section 4 http://www.sinclairql.net/srv/qlsm4.html#s4-p1.2

If IC 17 is still there, then a lot of mods are needed.


Hi, thanks for that - would the lack of mods (this has none) cause the issues I'm seeing? Cheers!

I've never encountered a QL with version PM. But I think you would need the 'dongle' with a 16K EPROM that plugged into the ROM port, as I don't think two 16K EPROMS world be big enough.

So I don't know what effect powering on the QL with the missing dongle would have. You would have to make some kind of replacement dongle for the other EPROM to stand a chance.

Unless you really want a PM version QL. (which I think had a lot of problems and in-comparabilities with later ROMs) I think you would need to do all the modifications in the manual so you could use JS ROMs or Minerva. I don't know if a Minerva ROM would work in your QL as it is, but I doubt it. I think that the rework of cutting out IC17 changed the address decoding of the ROM sockets.

There are probably people here on the forum, who have much more experience of modifying QL's than me.

A thought about the grey screen. If you are connecting to a TV via the aerial lead, If the +12v supply is missing I don't think you get a display, as the video modulator needs 12V. A RGB connection should be OK.


Andrew
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Re: QL issue 5, D05 repair - RAM troubleshooting / ROM dongle needed?

Postby Andrew » Mon Aug 19, 2019 11:29 am

I do not know if this helps but I have a Ql with serial number D06.. motherboard is an ISSUE 5 - and is as described in http://www.sinclairql.net/srv/qlsm5.html - Build Standard D6, IC33 2 x 16k EPROM, IC34 16k EPROM, AH ROM
I had to do the following upgrades :
    remove IC17
    remove the flying lead (the one conected from the pin of IC33)
    set JU2, JU3 and JU4
    install Minerva ROM
The circuit diagram here has a dotted box to the bottom right that gives the proper jumper setting. You need configuration (7), which was the "standard" one.
Use the component layout from here.


RWAP
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Re: QL issue 5, D05 repair - RAM troubleshooting / ROM dongle needed?

Postby RWAP » Wed Aug 21, 2019 5:59 am

To some extent, it depends what you want to do with the QL.

If you want to use it then you are better to make the modifications as per the service manual and convert it to use JM, JS or MG ROMs (or even Minerva).

If you want to sell it as a collectors item and can find the dongle, then the QL should be fairly special as I have never seen a PM ROM in 30+ years...

The 48K version of he PM ROM can be found on the Sinclair QL Homepage http://www.dilwyn.me.uk/qlrom/index.html so you could split this to make up the 16K dongle EPROM image



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