VOGONS


First post, by Perro

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Hi. I have a problem with my old Amstrad PC 5086. The floppy drive started to fail and I changed the rubber on the pulley but it continued to fail and stopped working. I looked for an alternative and found the floppy disk diagram and tried to adapt a normal floppy disk drive, but not the floppy disks. However, the adapter I have built does work on a 5286 PC. On the 5286 I can put a normal floppy drive and it reads floppy disks perfectly. However, in 5086 it fails. The only thing I have not been able to adapt is the 8 READY pin, because normal floppy drives do not generate that signal. Is this what makes it not work on a 5086? I would like to know if someone has faced a similar problem and know how to solve it. Thank you.

Reply 1 of 13, by tecnico

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Hi Perro,
I recently got a PC5086 with a non working floppy drive. After some trial and errors, I was able to use a standard 1.44 drive with the following diagram for the adapter.

(26-pin)   -> (34-pin + power)
Power 1 -> 5V power
Index 2 -> 8
DrvSelA 4 -> 12
Density 6 -> 2
Ready 8 -> 34
MotorA 10 -> 16
Dir 12 -> 18
Step 14 -> 20
Ground 15 -> GND
WData 16 -> 22
WriteE 18 -> 24
Track0 20 -> 26
WriteP 22 -> 28
RData 24 -> 30
Side 26 -> 32

As you can see, I connected pin 8 with pin 34 on the floppy. By setting the correct drive type in the BIOS, I can also use 1.44 megs floppy with the little Amstrad PC.

A side note: the motherboard has some sort of integrated IDE controller. Does somebody know if the integrated controller works with modern hard disks or compact flash cards?

Reply 3 of 13, by Perro

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Hi.

I have not made it work. The floppy drive tries to read, but tells me that the boot disk is invalid. I have tried multiple disks of various msdos and they all say the same thing. They are disks that work on other computers. But I can't get it to be read by the 5086's external floppy drive.

Reply 4 of 13, by tecnico

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after some more tests, I realized that I declared success too early. With my wiring the system can boot and read the first disk inserted in the drive, but cannot detect the change of disk properly. DIR shows the content of the previous disk, and then you get errors when accessing the new disk. Oddly, I have the same behaviour even with pin 8 not connected. I tried with an amiga floppy drive, that it is supposed to produce a ready signal, but then the 5086 tells that the disk is invalid as in your case.

I will try replacing the belt of the original drive. If that does not work, I have at least a partially working floppy adapter. My intention is to use a compact flash as HDD replacement and to transfer files: I only need the floppy to boot the system once to partition and format the card.

Reply 5 of 13, by Perro

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Hi.
I have 5086 x2, 5286 x2 and a 4386sx. They all carry the same type of floppy disk drive. I have put a new rubber on all of them and none of them has worked properly again. Only one of them manages to "dir", but I can't execute files or copy them.

Reply 6 of 13, by Jason_rg

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Hi Perro

Im new here. I have founded this insteresting web.
Im trying to revive my pc5286 with lot of problems with capacitors on power supply and main board finally solved.
But the problem with the floppy drive unit even with already replaced belt "traces" to me the way for standard 34 pins drive replacement, but I followed instruction may by no "compatible" with 5286 on:

Toshiba T5200 mods and upgrades

But the above adapter with pictures gives following error:

Diskette error or non system disk
Please insert bootable diskete and press any key

You spoken about you tried also standard drive with success.
Could you be so kind and share this info?

Regards

Reply 7 of 13, by flufetor

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Perro wrote on 2020-06-08, 10:46:

Hi.
I have 5086 x2, 5286 x2 and a 4386sx. They all carry the same type of floppy disk drive. I have put a new rubber on all of them and none of them has worked properly again. Only one of them manages to "dir", but I can't execute files or copy them.

Hello. Regarding the PC5286, I had one unit that died after a likely capacitor exploding in the PSU. While I was powering it after a long storage period , and you see... this is the usual outcome. Do you know or are able to test voltages at the motherboar PSU connectors?.. people says in the forums that the little one should take negative voltages (-12 and / or -5 and perhaps additional ground, but the only colors are red (1) and gray(3)). The big connector should be 5V pink , ground black , and 12V yellow. Any help would be greatly appreciated.

Reply 8 of 13, by aotta69

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flufetor wrote on 2021-05-05, 23:02:

Hello. Regarding the PC5286, I had one unit that died after a likely capacitor exploding in the PSU. While I was powering it after a long storage period , and you see... this is the usual outcome. Do you know or are able to test voltages at the motherboar PSU connectors?.. people says in the forums that the little one should take negative voltages (-12 and / or -5 and perhaps additional ground, but the only colors are red (1) and gray(3)). The big connector should be 5V pink , ground black , and 12V yellow. Any help would be greatly appreciated.

Hi, i'm in same trouble, bought a pc4386sx with a burned psu and trying to replace it with a picopsu... i checked for continuity with tester between sk106 (the small power connector) and the ISA slot, and found pin 1 (the red one) is -5v, pin 2 is -12v and pin 3 is GND.
But i don't know the right voltage of pin 4, it's not gnd and (following traces in the motherboard and in PSU), it seems has a non standard voltage and it's used by the M/B (i didn't find exaclty by whic IC, without schematics it's really hard).
So, the PC doesn't boot (i got green led on but no vga output at all), and i don't know if it's becouse the mobo is faulty or if the voltages supplied are not rights.

Hoping a pc4386 or pc5286 can check psu output voltages and write down here too!

Reply 9 of 13, by gca

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aotta69 wrote on 2021-08-01, 11:47:
Hi, i'm in same trouble, bought a pc4386sx with a burned psu and trying to replace it with a picopsu... i checked for continuity […]
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flufetor wrote on 2021-05-05, 23:02:

Hello. Regarding the PC5286, I had one unit that died after a likely capacitor exploding in the PSU. While I was powering it after a long storage period , and you see... this is the usual outcome. Do you know or are able to test voltages at the motherboar PSU connectors?.. people says in the forums that the little one should take negative voltages (-12 and / or -5 and perhaps additional ground, but the only colors are red (1) and gray(3)). The big connector should be 5V pink , ground black , and 12V yellow. Any help would be greatly appreciated.

Hi, i'm in same trouble, bought a pc4386sx with a burned psu and trying to replace it with a picopsu... i checked for continuity with tester between sk106 (the small power connector) and the ISA slot, and found pin 1 (the red one) is -5v, pin 2 is -12v and pin 3 is GND.
But i don't know the right voltage of pin 4, it's not gnd and (following traces in the motherboard and in PSU), it seems has a non standard voltage and it's used by the M/B (i didn't find exaclty by whic IC, without schematics it's really hard).
So, the PC doesn't boot (i got green led on but no vga output at all), and i don't know if it's becouse the mobo is faulty or if the voltages supplied are not rights.

Hoping a pc4386 or pc5286 can check psu output voltages and write down here too!

I've got a 4386, when I get a chance this week I'll try and get a list of the output voltages for you.

Reply 10 of 13, by aotta69

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gca wrote on 2021-08-01, 21:07:

I've got a 4386, when I get a chance this week I'll try and get a list of the output voltages for you.

Thank you very much GCA, in the meanwhile i made further test and i got a boot screen when connecting pin 4 to a 3.3V or 5V but, strangely, only if i connect it with a delay of 1 or 2 seconds...

Reply 11 of 13, by gca

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aotta69 wrote on 2021-08-02, 16:17:
gca wrote on 2021-08-01, 21:07:

I've got a 4386, when I get a chance this week I'll try and get a list of the output voltages for you.

Thank you very much GCA, in the meanwhile i made further test and i got a boot screen when connecting pin 4 to a 3.3V or 5V but, strangely, only if i connect it with a delay of 1 or 2 seconds...

Got a few free minutes so I dug out my spare PSU and got the readings, see attached images.

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Reply 12 of 13, by aotta69

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Thank you! I'll work for a psu replacement based on a picopsu and a lm2662 module.
But I confirm the +5v line in the smaller connector need to be pulsed at startup (maybe that's why it's driven by a transistor in original psu?).
At the moment I added a second switch for my testing, waiting for a better solution.
I also repaired the 1287 rtc and configured the 80mb hd: looking the Amstrad booting to DOS from his hdd... Priceless!