TRS 80 Disk Drive Controller Card!

[SnapCraft]

I have been working on my TRS 80 Model III's for some time now. Plural. I own 3 of these monsters. All the innards relatively work (one dead keyboard). I have accumulated 3 Drive Controller Cards. One old style (much longer than the others with a bigger 4 prong power plug) and two regular ones. I have swapped chips, tried to find problems with a temp gun, used many different drive-to-card cables, and used several motherboard-to-card ribbons. I even hooked a HxC Floppy to it.

 

I have about 5 drives. NONE of the cards work with my floppy drives. I am 99% sure it's the cards.

 

My latest card gives me a "Diskette?" prompt with the HxC plugged in (closest I've ever been). Zaxxon is the only disk to boot, after you hit "L"oad new game the tracks count past available tracks! (ie, 120/80 on the HxC display)

 

The HxC is fine. I'm able to use it on a 4P. Although cool, a 4P is extremely annoying (disks need to be transferred to 4P format).

 

When plugged in, drives do light up and spin for about 5 seconds, but I get a "Cass?" prompt.

 

Is it possible to go 0 for 3 on Disk Cards? What really pisses me off is that for all this money I could have gotten a FreHD. However, that's "cheating" in my book.

 

Please help.

[Turbo-Torch]

How many motherboards have you tried? Not only did I have constant issues with the mylar ribbon, the connector on the motherboard had bad prongs in it. I ended up hard soldering a wired ribbon cable from the disk controller to the motherboard and things have been flawless ever since. I was actually looking to replace the disk controller before trying that.

There is also another thin mylar "jumper" cable on the motherboard which went bad. I ended up soldering in a permanent cable on that one too. I believe that was part of the floppy kit and if it's bad, you won't have working drives.

 

That cheap ribbon had been a problem even back in the 80s when my III was relatively new. I removed, cleaned and reset it so many times over the years, that's what ruined the connector. The one that goes to the RS232 card isn't any better but at least it's been functional for a while now.

[SnapCraft]

OK. I replaced the ribbon cables (both) with hard-wires (tried two different Disk Drive Cards). Still I get the first few tracks to boot up. NewDOS/80, TrsDOS, and Zaxxon (bootable), for example, all display their "ready" prompts. However, once I type "L"oad for Zaxxon, or any DOS command the track counter goes haywire and jumps passed the available count. The HxC ultimately crashes.

 

Like it's getting corrupt data...

 

Any other suggestions?

[Turbo-Torch]

Sounds like an out of alignment drive but no way you have 5 duds. I have no experience with the HxC.

Last weekend I picked up Model III off CL for $25 thinking it would be a good parts machine.

Turns out it's like brand new inside and out...even if it were just removed from the original box, I'd have a hard time believing it could be so perfect.

Downside is that one drive is screwed up and it sounds exactly like what you described. If set as drive 0 I was able get TRSDOS to load up to the date/time prompt after adjusting the track 0 stop. After entering the date, it goes to load info off another track towards the center and goes haywire and eventually tries to load past track 39. I think it's off by at least one track. LDOS acts similar.

If I use it as drive 1, I can format and use a disk in it; however, I can't use that disk in the other drive or in my original Model III.

 

But like I said, that should not be happening for you on 5 different drives.

 

I'm going to try and do an alignment on it soon using Floppy Doctor. My oscilloscope probes seem to be missing so I just ordered a new set.

 

One other thing I found odd with this new Model III is the requirement for a ground to each drive! While out of the tower, even the good drive would not work and I could not come close to adjusting the speed on either drive, it constantly changed. Sometimes the motors would also require a push to start. Once I grounded each drive chassis with a jumper wire back to the Model III, everything was spot on perfect. When properly mounted, the screws go through the grounded metal shield.

 

My original Model III has an aftermarket controller with it's own separate drive system power supply and quality double sided Tandon drives (not the Texas Peripheral knock offs that Radio Shack used). I never had to ground them while bench testing outside the towers.