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Old 22 March 2020, 08:25   #1
Omolungo
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Amiga 500 rev. 3 doesn't load floppies from disk drive

Hi all,
I have this mobo of A500 rev.3 that apparently works fine, it boots normally to kickstart 1.2 and the disk drive is initializated correctly (classic ticking of disk drive waiting for a floppy).

When I insert a disk it doesn't happen anything: any attempt to load the floppy by disk drive, which continues to click as it was empty.

Naturally I swapped the disk drive with another fully working from another Amiga 500 but nothing changes.

I also changed both CIA chips with others from a motherbord fully working with the same result.

What could be the issue?
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Old 22 March 2020, 09:25   #2
solarmon
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Check the pins and traces for the _CHNG signal - on motherboard, sockets and floppy cable.

This should go from pin 2 of the internal floppy connector to pin 4 of Odd CIA (U7).

You can use http://www.amigapcb.org/ to help identify the pins and traces, although this has only a board view for rev 8A, the floppy connections should be the same.
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Old 22 March 2020, 10:24   #3
Omolungo
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Checked, they seem all fine, there's continuity.

I can try to reflow soldering of pin 2 of the internal floppy connector to pin 4 of Odd CIA (U7), since continuity seem a little weak there.

I noticed that one EMI close to E616 (E601) is badly soldered (on the rear of board pin doesn't come out) but I don't think it's the problem
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Old 22 March 2020, 10:40   #4
solarmon
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Those EMIs are for the external ports, so it shouldn't impact the internal ports, unless they are shorted to ground or VCC or something else - so check for shorts of the floppy traces to ground or VCC, or to another trace.
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Old 22 March 2020, 12:58   #5
Franchute13
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Hello!
When you say you changed the floppy drive. Did you change the data cable too?
regards
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Old 22 March 2020, 14:57   #6
AmigaHope
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Wow a Rev 3. That's a rare bird.
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Old 23 March 2020, 10:35   #7
Omolungo
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Quote:
Originally Posted by Franchute13 View Post
Hello!
When you say you changed the floppy drive. Did you change the data cable too?
regards
Yes, I changed also the cable, they come from rev.6 motherboards.
Maybe the rev.3 uses a floppy cable dedicated for this revision?
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Old 23 March 2020, 10:42   #8
solarmon
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Looking at your second picture and it looks like the pins of the internal floppy adapter looks to have some corrosion on it.

I would suggest to get the corrosion cleaned off and see if that makes a difference.
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Old 24 March 2020, 12:27   #9
Omolungo
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No, any corrosion on the pins. The motherboard is in perfect cosmetic aspect.

I Gary involved in functionality of the disk drive? I could also swap it with another one in order to verify if something changes.
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Old 24 March 2020, 13:39   #10
solarmon
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Quote:
Originally Posted by Omolungo View Post
I Gary involved in functionality of the disk drive? I could also swap it with another one in order to verify if something changes.
Yes, Gary is involved in floppy drive functions - it controls the motor signal.

Have you got an external floppy drive that you can test with too?
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Old 29 March 2020, 09:56   #11
Omolungo
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I swapped Gary with another but nothing changes.

I have an external floppy drive to connect to the mobo, how can I test it if df0 is not working?
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Old 29 March 2020, 10:21   #12
solarmon
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Is it a known working external floppy drive - i.e. it works in another Amiga?

On Kickstart 1.2, you won't be able to boot off the external drive on DF1.

Depending on the make/model of the external drive, you can take out the floppy drive and test it as the internal drive.
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Old 29 March 2020, 20:43   #13
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Perhaps v3 has a problem, I have a V6.5 that's missing the gary chip the CIA B is installed. But have no Gary chip.
Interested?
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Old 01 April 2020, 20:21   #14
Omolungo
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Quote:
Originally Posted by solarmon View Post
Is it a known working external floppy drive - i.e. it works in another Amiga?

On Kickstart 1.2, you won't be able to boot off the external drive on DF1.

Depending on the make/model of the external drive, you can take out the floppy drive and test it as the internal drive.
I already tried with another floppy 100% working from another A500, result is the same.
No need to extrapolate one from external drive
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Old 01 April 2020, 20:22   #15
Omolungo
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Quote:
Originally Posted by StefaanC View Post
Perhaps v3 has a problem, I have a V6.5 that's missing the gary chip the CIA B is installed. But have no Gary chip.
Interested?
Never seen an A500 rev 6.5
Can you show me some pics?
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Old 01 April 2020, 21:05   #16
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Have you used a known working floppy data cable?

Also check your power supply. Check the ground, 5v and 12v lines at the floppy power connector.
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