ICL OPD

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francoistonic
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Re: ICL OPD

Post by francoistonic »

Hello everybody,

I try to boot my Merlin Tonto without original monitor

I build new PSU with meanwell PT

But I don't see how to build video cable for VGA or scart.

i try to find homemade cable, photos, etc. I see RGB pins on DB15

maybe have you some ideas with pins DB15 to VGA / scart, etc. maybe direct connexion between IC video and cable ?


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Chr$
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Re: ICL OPD

Post by Chr$ »

francoistonic wrote:Hello everybody,

I try to boot my Merlin Tonto without original monitor

I build new PSU with meanwell PT

But I don't see how to build video cable for VGA or scart.

i try to find homemade cable, photos, etc. I see RGB pins on DB15

maybe have you some ideas with pins DB15 to VGA / scart, etc. maybe direct connexion between IC video and cable ?
I have such a cable that allows me to use my Merlin Tonto connected to the appropriate voltages from a PC PSU and with a scart video output. I've looked inside but it's quite a spaghetti and would take a while to work out the connections (they all have black heatshrink on them and there is at least one resistor in there). I got it from a very nice man on Facebook called Matthew Smith who is from Scarborough and in his current pic he's wearing a red top. I seem to remember I had to change one of the chips within the Tonto to generate the correct video signal and it wasn't socketed so had to be de-soldered. There was also a jumper wire to add. But it works perfectly, here's a pic of a screen:
20220214_191003.jpg


https://QXL.WIN
Collector of QL related computers, accessories and QL games/software.
Ask me about felt pads - I can cut them to size and they have proved excellent for mdv data recovery.
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Pr0f
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Re: ICL OPD

Post by Pr0f »

I posted pictures earlier in this thread of the IC that needs to be replaced in the video circuit - along with the link to the icl information that explains which chip is swapped for which other chip (74LS240 to 74LS244) from memory.


techfury
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Re: ICL OPD

Post by techfury »

Hello! I recently picked up a Merlin Tonto/OPD off of UK eBay (I'm just a silly yank) because the phone/computer hybrid perfectly aligns with my interests in vintage telecom hardware and vintage computers.

Here are some pics of the stuff I picked up: https://imgur.com/a/8y5x0sY

I seem to have about 32 microdrive cartridges for this thing... mostly with stuff on them, some are blank with brand new sets of BT labels, and one wallet seems to be a completely unused set of the basic OPD application cartridges. I seem to also have duplicates of at least 3 out of the 4 included OPD application MDVs as well.

Interestingly, this OPD came with a DVD containing a large amount of scanned OPD documentation, including... the mythical OPD Programmer's Reference and various schematics.

I really want to dump all these MDVs but I don't see an obvious way other than either: a) reverse engineering the protocol used by the Interfile ROM capsule to transfer files from MDVs to another computer via modem (I have PBXs and modems here, no issue at all), or b) writing my own ROM capsule to handle dumping MDV files over modem or the "printer" port. Obviously these all also need refelting... need to figure out getting pads. BTW, rollers seem good in both MDVs, but I haven't powered either one up yet. Still need to adapt my OPD's video output and rig up a power supply...

Another thought is adapting oqtadrive to work with the OPD... need to check the schematics more. I noticed the MDV wiring is very very different in the OPD...


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Chr$
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Re: ICL OPD

Post by Chr$ »

I'd be very interested if you find a way of dumping the cartridges properly.

I used OPD2QL (think that's what it's called) to read the files with a QL and then back them up individually.

I also got the DVD a few years ago when I bought something from the same seller. I think he's a member here somewhere.

I can supply felt pieces for them.


https://QXL.WIN
Collector of QL related computers, accessories and QL games/software.
Ask me about felt pads - I can cut them to size and they have proved excellent for mdv data recovery.
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dilwyn
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Re: ICL OPD

Post by dilwyn »

Not sure if it's the same software as chr$ mentioned - there's something called OPD Interchange which runs on QL on my site at http://www.dilwyn.qlforum.co.uk/filetran/index.html

I've never tried it, not having ever owned an OPD.


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Pr0f
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Re: ICL OPD

Post by Pr0f »

techfury wrote: Mon Feb 20, 2023 9:05 pm Interestingly, this OPD came with a DVD containing a large amount of scanned OPD documentation, including... the mythical OPD Programmer's Reference and various schematics.
That may be useful to a few of us on here - how large is the content? I would certainly be interested in the schematics and programmers reference at the very least.

techfury wrote: Mon Feb 20, 2023 9:05 pm Another thought is adapting oqtadrive to work with the OPD... need to check the schematics more. I noticed the MDV wiring is very very different in the OPD...
The OPD used the same ZX8302 chip - so the 2 channel data transceiver for the Microwave data would be the same, but I know from my own research that some repurposing was done on the motor select lines that the ZX8302 uses to control which Microdrive was selected - I doubt the OPD was ever going to have more than 2 - so they may have opted for a much simpler selection logic - as the original select lines are used to control shift registers for general i/o (LEDS mostly). If you can figure out from schematics how selection is done - you are in with a good chance of porting Oqtadrive to it.


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Chr$
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Re: ICL OPD

Post by Chr$ »

I seem to remember the provider of the DVD not wanting it shared openly. I think potentially he was nervous about breaking copyright rules (or other similar laws) - many of the docs being marked as internal use only etc.


https://QXL.WIN
Collector of QL related computers, accessories and QL games/software.
Ask me about felt pads - I can cut them to size and they have proved excellent for mdv data recovery.
techfury
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Re: ICL OPD

Post by techfury »

Chr$ wrote: Mon Feb 20, 2023 9:39 pm I can supply felt pieces for them.
Tried PMing you about this one, but it seems I don't have enough posts yet...
dilwyn wrote: Mon Feb 20, 2023 10:22 pm Not sure if it's the same software as chr$ mentioned - there's something called OPD Interchange which runs on QL on my site at http://www.dilwyn.qlforum.co.uk/filetran/index.html

I've never tried it, not having ever owned an OPD.
Good catch, sadly no QL on hand over here...
Pr0f wrote: Tue Feb 21, 2023 8:29 am
That may be useful to a few of us on here - how large is the content? I would certainly be interested in the schematics and programmers reference at the very least.
A bit over 2 GB. The scans of the schematics are pretty bad quality though.
Chr$ wrote: Tue Feb 21, 2023 11:32 am I seem to remember the provider of the DVD not wanting it shared openly. I think potentially he was nervous about breaking copyright rules (or other similar laws) - many of the docs being marked as internal use only etc.
You're not kidding on that one, the Programmer's Reference seems to be quite literally the internal specifications for the OS and some higher layers thrown into a binder. Every page has "ICL Product Specification" "Company Restricted" at the top...
Pr0f wrote: Tue Feb 21, 2023 8:29 am The OPD used the same ZX8302 chip - so the 2 channel data transceiver for the Microwave data would be the same, but I know from my own research that some repurposing was done on the motor select lines that the ZX8302 uses to control which Microdrive was selected - I doubt the OPD was ever going to have more than 2 - so they may have opted for a much simpler selection logic - as the original select lines are used to control shift registers for general i/o (LEDS mostly). If you can figure out from schematics how selection is done - you are in with a good chance of porting Oqtadrive to it.
So, I've been looking at the schematics this morning. It seems I do not have schematics for the Microdrive boards, but this is what I have been able to glean from the motherboard schematic. Do note that to make this easier to cross-reference against the Sinclair schematics, I've adopted some of Sinclair's signal names...


RAW1: ZX8302 pin 21 -> OPD J6 pin 3
RAW2: ZX8302 pin 19 -> OPD J6 pin 5
MDSELDH: ZX8302 pin 34 -> OPD J6 pin 2
MDSELCKH: ZX8302 pin 33 -> OPD J6 pin 1
ERASE: ZX8302 pin 1 -> gates a driver made up of Q9, D25, and R45, Q9 collector connected to mystery J6 pin (pin not labeled on schematic...)
MDRDWL: ZX8302 pin 3 -> OPD J6 pin 7
PROTECT: ZX8302 pin 7 (normally TXD2) -> pull-up to +5 -> mystery J6 pin (somehow they forgot to label ERASE and PROTECT on sheet 6...)

I don't quite fully understand the original Sinclair write-protect logic, but my intuition here is that ICL wanted something a bit more "sophisticated". My guess is that the drive pulls PROTECT down if selected and the cartridge is write protected...

Edit: Thinking about this harder... the TXD2 pin is an output, so the PROTECT signal wouldn't be something "read"... hm. I wonder what they were doing with it...

Edit 2: I'm an idiot, ZX8302 pin 7 is CTS2L, not TXD2. The PROTECT signal is most likely used to read the write protect switch on a MDV so that it can inhibit the OPD operating system from carrying out the operation.


techfury
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Re: ICL OPD

Post by techfury »

I have no idea if these are even usable copies, but they seem to be... I managed to extract the contents of these OPD Microdrive cartridges last night:

- BT Merlin M1850 Welcome
- BASIC (ICL branded)
- BT Merlin M1853 Xchange Demo
- BT Merlin M1854 Xchange Help

I used the OPD Interchange tools found here: https://www.dilwyn.qlforum.co.uk/filetran/index.html

I found the tools must be copied to a QL-format Microdrive to run (I think it's due to latent copy protection...), but I did a simple OPD->FLP copy to a blank 720k disk image. I have not fired up my OPD yet, so I cannot confirm this works, but the files seem to have been extracted successfully, and I am able to initialize a cartridge in OPD format and write the contents back...
Attachments
OPD System MDVs.zip
(131.63 KiB) Downloaded 358 times


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