Model 4 won't write to floppy disks. Ideas please.

[acollins22]

Hello Folks,

I recently got my first TRS-80 model 4 and thanks to the help of people on this forum I know have two bootable disks. I have CP/M and TRS-DOS. Both will boot to their respective prompts.

I now want to backup these disks and now I've run into problems.

Starting with CP/M I've booted the machine and started DUP.COM. I then get it to format a new disk. I can use any of three different disk drives and any number of diskettes from different sources and all will claim to format but all will fail immediately on the verify pass.

It's as if it's not writing properly but reading is fine.

It feels as if the controller isn't telling the drive to write properly. After all, I get the same result with three different drives.

Does anyone have any suggestions as to how to check out what's going on?


Thanks,

Andy.

 

[JonB]

Ah yes, those Model IV drives, what a pain. I get similar problems, but I think these are caused by bad media. I suppose you tried several disks, and that you attempted to write on both drives.

You can plug a different drive into the external floppy port (which helpfully maps drives 1 and 2 to drives 3 and 4). These aren't too difficult to come by. I have a set of 5.25" and 3.25" DS/DS drives that I often use for this sort of thing. I was going to direct you to somewhere where you can buy them (cheaply) but it looks like the guy isn't making them now. You may be able to use a BBC Micro floppy (easy to come by in the UK).

Another solution for you. Buy the HxC floppy drive emulator from Lotharec, then splice a 34 way IDC connector into the TRS80's internal ribbon cable. Disconnect one of the internal drives and see if you can write to the HxC. I use this one I use this one, and it has been very handy indeed. It's is how I first managed to create a Montezuma CP/M boot floppy on physical media. You can also, with the correct cable, connect HxC to the external drive port per the previous suggestion, this may be a better bet (insofat as there is no need to take the Model IV apart). The cable you need is a ribbon connector with a 34 way edge connector at one end and an IDC plug (female) at the other.

 

[JonB]

..like this one

 

[pski]

Hello Folks,

I recently got my first TRS-80 model 4 and thanks to the help of people on this forum I know have two bootable disks. I have CP/M and TRS-DOS. Both will boot to their respective prompts.

I now want to backup these disks and now I've run into problems.

Starting with CP/M I've booted the machine and started DUP.COM. I then get it to format a new disk. I can use any of three different disk drives and any number of diskettes from different sources and all will claim to format but all will fail immediately on the verify pass.

It's as if it's not writing properly but reading is fine.

It feels as if the controller isn't telling the drive to write properly. After all, I get the same result with three different drives.

Does anyone have any suggestions as to how to check out what's going on?


Thanks,

Andy.

Try the same with TRSDOS and see if you get the same result.

 

[acollins22]

Thanks Folks,

Surprisingly I do get different results using TRSDOS and the difference is in the order in which each OS does things.

CP/M formats the whole disk, from track 0 to track 39 and then verifies each track from track 39 to track 0. When I format using CP/M all of the tracks are formatted and then track 39 fails the verify, followed by track 38, 37 etc. until I loose interest and break out.

TRSDOS verifies a track straight after it has written it and so it formats track 0 and then verifies track 0, format 1, verify track 1. etc.
TRSDOS wizzes through formatting and verifying until it has worked its way into the disk and then it starts to slow down and fail as it gets into the inner tracks.
I also see different results under TRSDOS with different drives. My newer half-height drive gets further through the process before it starts reporting errors and so I _think_ what it is telling me is that my drives need some attention. I've cleaned the heads and lubricated the slides but I don't think I've done enough.

I'll re-group and then try again.


Cheers,

Andy.

 

[JonB]

Hmmmm, tricky.

Loose or dirty connectors? Socketed chips loose? Tough one to call, but if you do get the HXC you can at least eliminate the drives.

 

[acollins22]

Hi All,

I think I've got to the bottom of the problems and I'll finish the story so for those that come after me.

There were several problems here...

The usual capacitors in the PSU were faulty and cracked, even though they hadn't blown up. Replacing them improved things.
The drives needed a very thorough clean. I wiped the heads with IPA, lubricated the slides but very carefully.
I had new-old-stock floppies with bit-rot.

I have now been able to read all of my disks, including the originals provided with the machine. I can format now and copy. Drive B is still not perfect and tends to fail on the inner tracks but basically we're up and running.


Thanks everyone for your help and suggestions.

Andy.