Microdisc Restoration

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This includes generic Oric talkings and things that are totaly unrelated but want to share with people here :)
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jacqu
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Microdisc Restoration

Post by jacqu »

Hi fellow Oricians,

I hope you guys are doing well. It’s a while since my last post on this forum. Meanwhile I was busy with a complete C64 setup restoration with drive, datasette and printer.

I recently won a bid on eBay for a Microdisc and other stuff. So my next project will be to make a full restoration of this drive. I have already ordered the critical chips of the controller that are prone to fail. I will probably upgrade the PSU and maybe power the Oric directly from the extension port.

Before posting all the details of my restoration adventures, I share here with you a picture of the Oric manual that was in the package along with the Microdisc. It seems that the machine belonged to a very tidy person, according to the detailed manuscript notes that I found. I almost had the feeling to find Severus Snape’s personally annotated copy of Advanced Potion-Making :lol:
IMG_1730.jpeg
Best,
Jacques
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Dbug
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Re: Microdisc Restoration

Post by Dbug »

My experience with Microdisc units is that the drive may need grease, and the PSU tends to have problems (be careful with the polarity of the connector, it's a standard 4 pin molex but the +12/+5/gnd are not in the same order as on PCs).

I never had a problem with the caps on the disc controller board, and I never had any problem with any of the caps on any of my Oric 1 or Atmos.
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jacqu
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Re: Microdisc Restoration

Post by jacqu »

Hello Dbug,

Thanks for these tips! I will proceed carefully, especially when dealing with the PSU. I’m currently doing researches on how to copy data from a modern computer to a 3 inch disk using the Microdisc. I still have a whole lot to learn on this subject.

Best,
Jacques
Dbug wrote: Sun Jan 21, 2024 2:05 pm My experience with Microdisc units is that the drive may need grease, and the PSU tends to have problems (be careful with the polarity of the connector, it's a standard 4 pin molex but the +12/+5/gnd are not in the same order as on PCs).

I never had a problem with the caps on the disc controller board, and I never had any problem with any of the caps on any of my Oric 1 or Atmos.
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Chema
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Re: Microdisc Restoration

Post by Chema »

What an interesting thread. I always liked the Microdisc a lot, but I don't have one.

On the matter of reading/writing 3" discs, I think the most convenient way is either using a greaseweazle with such a drive, or fitting the Microdisc with a second 3.5" unit or, better yet, a gotek so you can use the Oric itself to copy discs.

I have a greaseweazle with a 3.5 unit and it works perfectly, so I assume it will with 3" units too.
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jacqu
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Re: Microdisc Restoration

Post by jacqu »

Chema wrote: Sun Jan 21, 2024 5:00 pm What an interesting thread. I always liked the Microdisc a lot, but I don't have one.

On the matter of reading/writing 3" discs, I think the most convenient way is either using a greaseweazle with such a drive, or fitting the Microdisc with a second 3.5" unit or, better yet, a gotek so you can use the Oric itself to copy discs.

I have a greaseweazle with a 3.5 unit and it works perfectly, so I assume it will with 3" units too.

Thanks Chema for your advice. I didn’t know that the 34 pin connector at the back was compatible with a gotek. And I even just discovered after reading your post what a greaseweazle is :) Still lots of things to learn in this area…

Below you will find some shots of the inside. Looks in pretty good shape. No obvious signs of mods or hacks apart perhaps from the ROM chip with the hand written label on it.

Stay tuned for the updates, it will probably need a few weeks before the first trial, since I have a lot of research to make before starting to seriously work on it (and I can only work on this project the weekend).
IMG_1731.jpeg
IMG_1737.jpeg
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Re: Microdisc Restoration

Post by Dbug »

Regarding Microdisc and Gotek, I wrote an article about that on my blog some time ago, including how to switch A<->B easily

See: https://blog.defence-force.org/index.ph ... &ref=ART67
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jacqu
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Sourcing Components

Post by jacqu »

Hello folks !

The project progresses slowly. Even the weekend I have barely the time to work on it. I sourced almost all the components needed for this restoration, and especially the components for the power supply. Indeed, I think it would be a crime to try to power the Microdisc with the old one, since its design seems to be very rough, not talking about its current shape (see picture).
IMG_1760.jpeg
So I ordered 2 tiny but sufficient Mean Well switching power modules, one for the 5V and the other for the 12V (RS15-5 and RS15-12). I checked the specs of the drive and these modules should be able to sustain the peak current.

I also ordered:
* a Greaseweazle to test the drive separately,
* a female DIN 4 pins since the original one was missing,
* some 3 inch floppies,
* a FDC1793 chip and a FDC9216B chip since they are prone to fail.
IMG_1759.jpeg
Next step: design the housing of my new custom built power supply with Fusion 360 and 3d print it.

Best,
Jacques
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iss
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Re: Sourcing Components

Post by iss »

jacqu wrote: Sat Feb 10, 2024 9:01 pm...one for the 5V and the other for the 12V (RS15-5 and RS15-12)
Two PSU's will work but why not a single one with Dual Output like RD-35A?

Else the original PSU is not so bad. It has independent 9V output for the Oric and 5V/12V output for the Microdisc. You need only new good wires and maybe new capacitors. Take a look HERE - I've restored 2 old PSU's and they work just fine.
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Re: Sourcing Components

Post by jacqu »

Thanks for the tips iss. Yes, one PSU would also do the trick of course. I considered this option, but did not find the right form factor and amperage. Furthermore, I prefer to be able to fine tune the voltages separately.

When I say that the design is rough, I mean in fact that it is way too outdated and also too unsafe. A bridge rectifier generates a lot of harmonics on the mains and is now forbidden for new designs. Furthermore, it seems to have no over-voltage or over-current protections. This may lead to catastrophic failures. I don’t want to take this risk.
EDIT: I checked the data sheets and it seems that the linear regulator LM323 is pretty fool proof in fact. Maybe I have to reconsider my choices.

Finally, I plan to power the Oric directly through the extension port: having a common 5V PSU for both the drive and the main board is probably the best way with respect to EMI/EMC.

Sure, the final setup will not be totally period accurate. But I plan to leave the Microdisc untouched externally so that its external aspect remains as the original.
iss wrote: Sat Feb 10, 2024 9:49 pm
jacqu wrote: Sat Feb 10, 2024 9:01 pm...one for the 5V and the other for the 12V (RS15-5 and RS15-12)
Two PSU's will work but why not a single one with Dual Output like RD-35A?

Else the original PSU is not so bad. It has independent 9V output for the Oric and 5V/12V output for the Microdisc. You need only new good wires and maybe new capacitors. Take a look HERE - I've restored 2 old PSU's and they work just fine.
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jacqu
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Re: Sourcing Components

Post by jacqu »

jacqu wrote: Sat Feb 10, 2024 9:01 pm Next step: design the housing of my new custom built power supply with Fusion 360 and 3d print it.
In fact I will probably follow my original plan: to retrofit the original casing of the Microdisc PSU
IMG_0835.jpeg
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Re: Sourcing Components

Post by iss »

jacqu wrote: Sun Feb 11, 2024 11:50 am In fact I will probably follow my original plan: to retrofit the original casing of the Microdisc PSU
It will work! :)
Post the progress here...
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