Electron Cumana Disc Interface

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gidandridge
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Electron Cumana Disc Interface

Post by gidandridge » Sun Oct 07, 2018 7:17 pm

Hey All,

I'm fairly new hear, so please be gentle with me. I've introduced myself viewtopic.php?f=13&t=15809, but I have something I need a little help with.

I've managed to get hold of a Cumana Disc Interface for my Elk. I grabbed it off Ebay and it was listed as 'not working'. When it arrived I stripped it down and discovered that in a previous life the Ni-MH battery had leaked and the circuit board had been badly damaged. :(

It looks like someone managed to clean it up and get it running again by soldering a jumper wire to fix a continuity issue.

When I first plugged the interface in it would work intermittently. So I decided I could probably buy a new battery, rework some of the solder, redo the jumper wire (as it was loose) and upgrade the EPROM to Slogger's SEDFS, which I believe was available for these units as an upgrade.

Well I did all that and now it can be detected by the electron, I can run all it's star commands, but the disk drive doesn't respond. :(

If I drop the original Cumana DFS Eprom back in it freeze's. It displays 'Acorn Electron', then 'Cumana Disk System', but the Basic prompt never comes up. Just stops at that point with a flashing cursor. I think the Cumana ROM is looking from a drive, but can't get a response?

So what to do?

Thing is the solder work on the rear of the circuit board is awful! See the pic. I've tried to rework this but there is nothing left of most of the pads and so nothing for it to adhere to. :(

I think the circuit board is pretty shot to pieces.

I wonder if I should remove most of the components, then trace the circuit and rebuild it in Kicad. Then get a new board produced and put everything back on. Thing is I've never used Kicad before, and I've never done anything like that. So it would be a steep learning curve. #-o

Or should I just try and check on the continuity and fix it with jumper wires?

I've included some pictures, and have done a close up of the really bad section.

Do you have any thoughts? tips?

Gav.
Attachments
IMG_20181007_180018.jpg
Top view of my broken Cumana Disc Interface
IMG_20181007_180156.jpg
Rear view
IMG_20181007_180216.jpg
Close up of the really awful section, terrible solder
Last edited by gidandridge on Sun Oct 07, 2018 8:33 pm, edited 1 time in total.
Gav. :D

BBC Model B Sidewise ROM Board, GoSDC, Datacentre, Hybrid Music 5000
Acorn Electron Plus 1, AP6, GoSDC, Slogger Pegasus 400

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danielj
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Re: Electron Cumana Disc Interface

Post by danielj » Sun Oct 07, 2018 9:40 pm

Assume you've found this topic: viewtopic.php?t=15423 - I don't know if Dave got any further?

Buzz out what and use hookup wire to repair? That's probably the approach I'd take. Reproducing a board that size with the gold fingers will be quite expensive. Dave's reworking the AP3/4 at the moment, which is a more compatible disk interface.

That said, nothing like cutting your teeth with kicad :D

d.

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1024MAK
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Re: Electron Cumana Disc Interface

Post by 1024MAK » Sun Oct 07, 2018 9:57 pm

It would help if you can clean the old (brown) flux off the board :wink:
Use either IPA or a flux remover cleaning solvent.

The fault could be one or two bad connections. If you are unlucky maybe more. But even so, it maybe worthwhile trying to repair it.

Mark
Last edited by 1024MAK on Sun Oct 07, 2018 9:58 pm, edited 1 time in total.

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daveejhitchins
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Re: Electron Cumana Disc Interface

Post by daveejhitchins » Mon Oct 08, 2018 11:15 am

danielj wrote:
Sun Oct 07, 2018 9:40 pm
Assume you've found this topic: viewtopic.php?t=15423 - I don't know if Dave got any further?
It's getting Very Near the top of the list again.

IIRC the original ROM "looks" for the date and time from the HD146818P - So if this isn't working that it could be the cause of the hang!

Dave H :D

p.s. Just put the schematic, as I have it now, in the "Restoration of Three Cumana Electron Disc Interfaces" thread, as linked to in Daniel's post, above.

Dave H :D

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gidandridge
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Re: Electron Cumana Disc Interface

Post by gidandridge » Mon Oct 08, 2018 8:36 pm

Thanks Gents,
1024MAK wrote:
Sun Oct 07, 2018 9:57 pm
Use either IPA or a flux remover cleaning solvent.
I think I'm going to give it a go, if I can clean off the old flux I can test the connectivity again - then solder some jumper wires if needed.
danielj wrote:
Sun Oct 07, 2018 9:40 pm
Buzz out what and use hookup wire to repair? That's probably the approach I'd take.
Sounds like I should. I'm going to try and clean it down again, and try this.
daveejhitchins wrote:
Mon Oct 08, 2018 11:15 am
IIRC the original ROM "looks" for the date and time from the HD146818P - So if this isn't working that it could be the cause of the hang!

p.s. Just put the schematic, as I have it now, in the "Restoration of Three Cumana Electron Disc Interfaces" thread, as linked to in Daniel's post, above.
Thanks Dave, that's all really helpful.

Guys, I'm going to have another bash this weekend at fixing it with jumper/hookup wire. I'll give it a clean, try and fix the solder again and let you know how I get on.

Thanks for all the suggestions!

Gav.
Gav. :D

BBC Model B Sidewise ROM Board, GoSDC, Datacentre, Hybrid Music 5000
Acorn Electron Plus 1, AP6, GoSDC, Slogger Pegasus 400

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jms2
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Re: Electron Cumana Disc Interface

Post by jms2 » Tue Oct 09, 2018 6:33 am

It really doesn't look too bad. I think you should be able to fix it. Good luck!

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Leew
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Re: Electron Cumana Disc Interface

Post by Leew » Fri Mar 27, 2020 2:01 pm

Did anyone ever find a copy of the suppoting floppy disk for the Cumana Electron Disk Interface?

I saw one on CJE Micros way before Christmas and even ordered it but it never materialised.

Thanks
Lee
Lee W
------------
Proud owner of many Electrons, some Beebs, a couple of Archies, some Commodore 64s, Amigas, Atari STs and an Atari Falcon 030
Lemmings are for life, not just the 90's... https://www.lemmingsworld.me

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