Mounting a floppy drive in an A310

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myelin
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Mounting a floppy drive in an A310

Post by myelin » Thu Jul 09, 2020 7:53 pm

I have an A310 that's missing its floppy drive, and the diagram in the A300 Service Manual isn't awfully helpful.

Screen Shot 2020-07-09 at 11.28.30 AM.png

I appear to have the bracket pictured in the digram, but it only appears to have two screw holes to connect to the drive itself.

Aside from the issue of finding a FDD that will work with the 1772 and all the other interesting stuff I see on the A300 / A3000 schematic, it looks like the FDD is mounted with just two screws, on a bit of an angle... is this correct? It also sounds like I need to take the front facing off the drive and glue an extended eject button to it.

Has anyone here done this -- converted the front facing of an ordinary floppy drive and fitted an extended eject button so it fits in an A3xx case?
Last edited by myelin on Thu Jul 09, 2020 10:39 pm, edited 1 time in total.
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danielj
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Re: Mounting a floppy drive in an A310

Post by danielj » Thu Jul 09, 2020 9:18 pm

You need to have a word with SimonI who's mounted a gotek in his old arc!

d.

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myelin
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Re: Mounting a floppy drive in an A310

Post by myelin » Thu Jul 09, 2020 9:39 pm

Oh interesting -- sounds like it's more complicated than I thought, and the connector is wired up in an odd way on the A300 series boards!
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Re: Mounting a floppy drive in an A310

Post by IanS » Thu Jul 09, 2020 9:46 pm

myelin wrote:
Thu Jul 09, 2020 7:53 pm
I appear to have the bracket pictured in the digram, but it only appears to have two screw holes to connect to the drive itself

Aside from the issue of finding a FDD that will work with the 1772 and all the other interesting stuff I see on the A300 / A3000 schematic, it looks like the FDD is mounted with just two screws, on a bit of an angle... is this correct? It also sounds like I need to take the front facing off the drive and glue an extended eject button to it.

Has anyone here done this -- converted the front facing of an ordinary floppy drive and fitted an extended eject button so it fits in an A3xx case?
In an A310, the drive is held into the bracket with 4 screws, but the bracket is only held onto the drive bridge by 2 screws, offest so two drives can be fitted side by side.

I've seen A3xx machines with the front cut out so a standard floppy front pokes through, like on an A4xx or A540.

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Re: Mounting a floppy drive in an A310

Post by Marvin » Thu Jul 09, 2020 10:21 pm

myelin wrote:
Thu Jul 09, 2020 7:53 pm
I appear to have the bracket pictured in the digram, but it only appears to have two screw holes to connect to the drive itself

Aside from the issue of finding a FDD that will work with the 1772 and all the other interesting stuff I see on the A300 / A3000 schematic, it looks like the FDD is mounted with just two screws, on a bit of an angle... is this correct?
Just removed the drive from my A310 for you, let me know if you want any more pics or measurements etc.

The drive mounts to it's bracket with 2 screws per side, so 4 in total...
A310 floppy side.JPG

That bracket mounts to the bridge over the motherboard with 2 screws that are on an offset, botton left & top right in this image
(the top left hole is one of the two that is used to mount either a second floppy or a hard disc)
A310 floppy mounting.JPG
A310 floppy front.JPG

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Re: Mounting a floppy drive in an A310

Post by myelin » Thu Jul 09, 2020 10:38 pm

Marvin wrote:
Thu Jul 09, 2020 10:21 pm
The drive mounts to it's bracket with 2 screws per side, so 4 in total...
A310 floppy side.JPG
This is perfect, thank you! I guess I just didn't spot the pair of screw holes in the corner of the bracket near the front of the machine.
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Re: Mounting a floppy drive in an A310

Post by steve3000 » Thu Jul 09, 2020 10:56 pm

Marvin wrote:
Thu Jul 09, 2020 10:21 pm
That bracket mounts to the bridge over the motherboard with 2 screws that are on an offset, botton left & top right in this image
(the top left hole is one of the two that is used to mount either a second floppy or a hard disc)
That’s a nice ARM3 you have (I had one of those in mine BITD!) and 8mb in your A310 wow!

Your ARM3 is underclocked at 32MHz though, it’s rated for 35MHz and will probably manage 40MHz+. I had mine ticking over at 36MHz :)

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Re: Mounting a floppy drive in an A310

Post by Marvin » Thu Jul 09, 2020 11:46 pm

steve3000 wrote:
Thu Jul 09, 2020 10:56 pm
Marvin wrote:
Thu Jul 09, 2020 10:21 pm
That bracket mounts to the bridge over the motherboard with 2 screws that are on an offset, botton left & top right in this image
(the top left hole is one of the two that is used to mount either a second floppy or a hard disc)
That’s a nice ARM3 you have (I had one of those in mine BITD!) and 8mb in your A310 wow!

Your ARM3 is underclocked at 32MHz though, it’s rated for 35MHz and will probably manage 40MHz+. I had mine ticking over at 36MHz :)
When I bought it was only 25Mhz, back in the day I tried it to get it to run at 40Mhz and it was far too flaky, 36Mhz was ok but still the occasional glitch and I couldn't buy a 35Mhz locally but could get a 32Mhz so that's what I used. Reliability trumps outright speed when it's your main machine as it was for many years.

After having a lowly 8Mhz Arm2 upgrading to rock solid 32Mhz Arm3 was a joy, a unreliable 36Mhz wasn't worth it.

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Re: Mounting a floppy drive in an A310

Post by steve3000 » Fri Jul 10, 2020 12:03 am

Marvin wrote:
Thu Jul 09, 2020 11:46 pm
When I bought it was only 25Mhz, back in the day I tried it to get it to run at 40Mhz and it was far too flaky, 36Mhz was ok but still the occasional glitch and I couldn't buy a 35Mhz locally but could get a 32Mhz so that's what I used. Reliability trumps outright speed when it's your main machine as it was for many years.

After having a lowly 8Mhz Arm2 upgrading to rock solid 32Mhz Arm3 was a joy, a unreliable 36Mhz wasn't worth it.
Agree! And actually looking again mine must have been different as mine used a 72MHz oscillator and divider to get 36MHz. Possibly this gave a more reliable clock signal...

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Re: Mounting a floppy drive in an A310

Post by IanS » Fri Jul 10, 2020 4:30 pm

Marvin wrote:
Thu Jul 09, 2020 10:21 pm

That bracket mounts to the bridge over the motherboard with 2 screws that are on an offset, botton left & top right in this image
(the top left hole is one of the two that is used to mount either a second floppy or a hard disc)
A310 floppy mounting.JPG
Curious, do you know who manfactured the ARM3 upgrade? The upper board is exactly the same design as that fitted to the combined ARM3 and memory upgrade shown here - viewtopic.php?p=226006#p226006
detailed pic - download/file.php?id=43422&t=1

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Re: Mounting a floppy drive in an A310

Post by Marvin » Sat Jul 11, 2020 11:25 am

IanS wrote:
Fri Jul 10, 2020 4:30 pm
Curious, do you know who manfactured the ARM3 upgrade? The upper board is exactly the same design as that fitted to the combined ARM3 and memory upgrade shown here - viewtopic.php?p=226006#p226006
detailed pic - download/file.php?id=43422&t=1
No idea, there are no clues on the PCBs, the text on my board is the same as the ones in the links you posted.

Ignore the hacked out corner of the lower PCB, I did that to gain access to solder the replacement crystal oscillator. Also ignore the messy track repairs, I was young and didn't have much soldering experience at the time.

The plug that goes into the CPU socket looks rather DIY to me as well, it looks like pin headers with an extra thick piece of blank PCB being used as a spacer to stop the pins getting bent inwards when inserted into the motherboard socket.
ARM3 bottom (smaller).JPG
ARM3 angle (smaller).JPG

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Re: Mounting a floppy drive in an A310

Post by IanS » Sat Jul 11, 2020 11:40 am

Marvin wrote:
Sat Jul 11, 2020 11:25 am
No idea, there are no clues on the PCBs, the text on my board is the same as the ones in the links you posted.
Thanks for looking.

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Re: Mounting a floppy drive in an A310

Post by steve3000 » Sat Jul 11, 2020 11:41 am

Marvin wrote:
Sat Jul 11, 2020 11:25 am
The plug that goes into the CPU socket looks rather DIY to me as well, it looks like pin headers with an extra thick piece of blank PCB being used as a spacer to stop the pins getting bent inwards when inserted into the motherboard socket.
Very interesting!

And the "DIY" plug isn't a bad idea for re-use today, considering how much these PLCC adaptor plugs cost now (eg. https://uk.rs-online.com/web/p/ic-socke ... s/7419669/)

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Re: Mounting a floppy drive in an A310

Post by IanS » Sat Jul 11, 2020 12:01 pm

Yes, very interesting, 1.27mm pitch headers are still available (even in surface mount). Who'll be first to try?

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Re: Mounting a floppy drive in an A310

Post by Marvin » Sat Jul 11, 2020 12:21 pm

steve3000 wrote:
Sat Jul 11, 2020 11:41 am
Very interesting!

And the "DIY" plug isn't a bad idea for re-use today, considering how much these PLCC adaptor plugs cost now (eg. https://uk.rs-online.com/web/p/ic-socke ... s/7419669/)
:shock: flipping eck, how much ?

rather than a lump of thick PCB it wouldn't take much to design and 3d print a spacer to keep the pins apart....

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Re: Mounting a floppy drive in an A310

Post by philpem » Sun Jul 12, 2020 12:32 pm

To be fair the £35 is probably worth it for a plug that's more or less guaranteed to work perfectly every time without knackering the PLCC socket...

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