Model Expansion Interface Disk Problems

[Chromedome45]

Hi as some may know I recently aquired a TRS-80 Model 1. I'm having some issues with the disk controller though. When I hookup a disk as drive 0 the motor on the disk drive spins and the activity light is constantly on. I have tried Tandon drives, Mistsubishi drives even Teac 3.5 in floppy all the same. So I don't think it's a disk issue because when I insert a disk in the 0 drive it will boot fine. Now if I have a second drive configured as drive 1 the computer will access it and I can hear the head seeking but after a few seconds I get an "illegal drive"something error. Can't format or even get a directory of any disk in drive 1. I am using a straight through (No twist) floppy cable and even tried the cable with the pins pulled which came with the EI. The EI itself is the latest and newest type. Someone please help I am losing what little hair I have left trying to figure this out!

 

[tezza]

Hi Frank,

Sorry to hear about the problem. I have an issue with a System 80 (TRS-80 Model 1 clone) expansion unit which is also driving me NUTS!

However, I won't hijack your thread with the details

In the System 80 expansion unit The MOTOR ON pin is controlled by several TTL logic chips. I'm assuming this will be the same in the Model I expansion box. It could be that one of these has failed and the signal could be stuck on (low?) thereby switching the motor on. A logic probe (or voltmeter) and a circuit diagram would let you check.

Just a thought.

Tez

 

[Chromedome45]

The thing is I found some documentation on the Panasonic drives I'm trying to use. One of the jumpers is labeled MM/MS which is the motor on jumper and have tried it in different positions and drive 0's motor is always on. However when I set the jumper to MS on drive 1 the motor stops after a few seconds so I don't think the EI's FDC is causing it but i'm just not sure. And I still can't access drive 1! So I'm beginning to think whatever is causing drive 0's motor to be on constantly is screwing up drive 1. More & More hair falling on the floor hence the "Chromedome45" user name! UGH :crazy: Now if someone has a spare 26-1160 & 26-1161 drives they don't need! I sure could use them

 

[Chromedome45]

Got it fixed...You were right Tez turned out to be Z41 in the EI. It is a 7416 chip were the motor control and all the drive selects go through. It's working perfectly now. I am a happy TRS-80 Model 1 owner again. I originally had one back on 1979. Loaded to the gills. Fun little machine.