A1200 freezing and DF1: can't write

[MrClump]

I've bought an A1200 after selling my old one almost 25 years ago, so far I'm loving re-learning everything I forgot and all the new developments since 1996! I used to be a bit of a power-user back in the day.

I've got two main issues with my A1200 and could do with some sage advice. It's a stock 1200 with a 4GB CF drive and a newly fitted 8MB ram expansion purchased from Amiga Kit a few days ago. No other bells and whistles (yet).

First problem: With the ram expansion installed, the machine is unstable and frequently freezes. Once the computer has been switched on for a while, this behaviour stops, it is then rock-solid; it is also stable without the RAM expansion installed. I've read this sort of issue can be caused by dodgy caps, or a poorly seated socketed component. The previous owner has said the machine had been recapped, although not until after we'd completed the purchase (which was odd). I'm a bit puzzled why it would only act like this with the ram installed. Could (another) recap be the order of the day?

Second problem: the Amiga came with an external floppy drive. It reads disks just fine, but can not write. Attempting to format a disk fails as does attempting to write any files to an already formatted floppy. I plan to fit a Gotek as DF0:, so would really like to get the external drive working to retain the ability to read and write floppies. The internal drive works just fine.

I don't know what make or model the drive is, as I can't find any branding inside or out; but this is a picture of it. The vents are quite distinctive.

[Nightshft]

Originally Posted by MrClump

Second problem: the Amiga came with an external floppy drive. It reads disks just fine, but can not write. Attempting to format a disk fails as does attempting to write any files to an already formatted floppy. I plan to fit a Gotek as DF0:, so would really like to get the external drive working to retain the ability to read and write floppies. The internal drive works just fine.

I have the same external drive. It works fine reading and writing disks. I guess there's some (hardware?) failure in your drive. You could open it and check if you find something suspicious. Good news is they are quite cheap now AFAIK, so I guess you could easily get another one.

Originally Posted by MrClump

First problem: With the ram expansion installed, the machine is unstable and frequently freezes. Once the computer has been switched on for a while, this behaviour stops, it is then rock-solid; it is also stable without the RAM expansion installed. I've read this sort of issue can be caused by dodgy caps, or a poorly seated socketed component. The previous owner has said the machine had been recapped, although not until after we'd completed the purchase (which was odd). I'm a bit puzzled why it would only act like this with the ram installed. Could (another) recap be the order of the day?

I'd open the machine carefully and look if everything on the motherboard looks good. If there are ceramic capacitors you'd know it had been recapped. If there are electrolytics maybe someone here on the forum could tell by the brand/pictures if they are original or recapped.

Also the psu could be faulty and fail when more current is drawn, although I don't think it's much more current with the extra-ram installed.

Although less likely on a new ram-expension it could still be failing ram. Typically the machine would run stable until it utillises ram areas that don't work correctly. Use Keir Frasers Test Kit to test all your memory, cold and hot and multiple times. I'd probably also confront Amigakit with the problem (warranty).

Have fun with the machine and good luck.

[solarmon]

Regarding the floppy write issue - it sounds like an issue with the /WGATE signal, similar to what is shown in this video:

[ Show youtube player ]

For the instability look in to 'timing fixes' - I had to perform a partial timing fix to my A1200:

http://eab.abime.net/showthread.php?t=98149

[MrClump]

Originally Posted by solarmon

Regarding the floppy write issue - it sounds like an issue with the /WGATE signal, similar to what behavior in this video:

[ Show youtube player ]

For the instability look in to 'timing fixes' - I had to perform a partial timing fix to my A1200:

http://eab.abime.net/showthread.php?t=98149

I'll take a look at the video later, thanks.

The instability behaviour you described in your post is almost identical to mine, even down to it hanging when doing pretty much the same things. My memory tests also check out fine. The only difference is that the seems to resolve for me once the machine has warmed up, did you observe similar?

I should really strip the computer down and have a good look over the mainboard, something I haven't done yet.

[MrClump]

Originally Posted by Nightshft

I have the same external drive. It works fine reading and writing disks. I guess there's some (hardware?) failure in your drive. You could open it and check if you find something suspicious. Good news is they are quite cheap now AFAIK, so I guess you could easily get another one.


I'd open the machine carefully and look if everything on the motherboard looks good. If there are ceramic capacitors you'd know it had been recapped. If there are electrolytics maybe someone here on the forum could tell by the brand/pictures if they are original or recapped.

Also the psu could be faulty and fail when more current is drawn, although I don't think it's much more current with the extra-ram installed.

Although less likely on a new ram-expension it could still be failing ram. Typically the machine would run stable until it utillises ram areas that don't work correctly. Use Keir Frasers Test Kit to test all your memory, cold and hot and multiple times. I'd probably also confront Amigakit with the problem (warranty).

Have fun with the machine and good luck.

Thanks for the tips. I am going to strip the machine down and give it a good looking over. The odd thing with the drive is I think it was working fine, but then stopped. Although I'm not 100% certain, as I didn't specifically test it and haven't had it for long!

[solarmon]

I'm not sure on the stability after it has 'warmed up' - I would soft or hard reset it after the issue anyways. But I don't really leave it on for long periods of time - I'm always tinkering with my Amigas!

[MrClump]

Originally Posted by solarmon

Regarding the floppy write issue - it sounds like an issue with the /WGATE signal, similar to what is shown in this video:

[ Show youtube player ]

Excellent, video and for the first time gave me the confidence to start poking around inside a computer with my multimeter! But, I am now slightly more confused.

I've checked the voltage on the /WGATE line for DF1: between the resistor behind the floppy connector mentioned in the video to the matching pin on the floppy connector in the external drive while formatting a floppy. It rises to around 4.0v and falls to 0v on each movement of the disk head, but the disk does not format. It appears to complete successfully, but all the data is still on the disk.

HOWEVER, when I disconnect the floppy cable to DF0, DF1 can then write, although the voltage on /WGATE is exactly the same, rises to around 4.0v and falls to 0v on each movement of the disk head.

I'm really not sure what this tells me! I do have a GoTek arriving in a day or so to replace DF0, so if it's a problem with the internal drive this should prove it.

[MrClump]

So, my miggy is back from being recapped (thank you Steve at Retropassion), and my stabilty issues have vanished! Bad caps!

My issues with DF1: not writing persist, however I have made some progress in isolating the issue. This is what I have found:

1. With DF0: (in the form of the original internal floppy or a Gotek) and DF1: both connected, DF1: cannot write. It appears to write, but once completed the disk is unchanged.
2. With DF0: disconnected, DF1: can then write just fine.
3. If I replace the floppy drive in DF1: with a Gotek then it can write just fine even with DF0: connected!

I am assuming this rules out my Amiga, and the controller in my external floppy (seeing as it works fine with the Gotek) and points the finger firmly at the floppy drive itself. But why would it work without DF0: connected, and not work when it is?

I am pretty mystified, not sure where to proceed from here.

[MrClump]

Originally Posted by MrClump

So, my miggy is back from being recapped (thank you Steve at Retropassion), and my stabilty issues have vanished! Bad caps!

My issues with DF1: not writing persist, however I have made some progress in isolating the issue. This is what I have found:

1. With DF0: (in the form of the original internal floppy or a Gotek) and DF1: both connected, DF1: cannot write. It appears to write, but once completed the disk is unchanged.
2. With DF0: disconnected, DF1: can then write just fine.
3. If I replace the floppy drive in DF1: with a Gotek then it can write just fine even with DF0: connected!

I am assuming this rules out my Amiga, and the controller in my external floppy (seeing as it works fine with the Gotek) and points the finger firmly at the floppy drive itself. But why would it work without DF0: connected, and not work when it is?

I am pretty mystified, not sure where to proceed from here.

I just realised there was a combination I had not tried. The Gotek as DF0: and then replacing the floppy in the external enclosure with my internal floppy. That combination also works just fine! So definately an issue with the external floppy drive itself. Hmmmm.

[Firthy2002]

Clearly the drive isn't getting enough power to magnetise the heads during write operations. Sadly I don't know much about the electronics side of things to give you any pointers as to where you go from here.

[MrClump]

Issue resolved! I've obtained a new floppy drive to put in the enclosure, which just happened to be the very same Citizen model when it arrived. This drive can write just fine, so clearly the weird issue was with the drive. I am still totally mystified what it could be, but at least I now have a spare unit to rob for spares in the future if ever needed.