Model I woes

[Erik]

I recently obtained a TRS-80 Model I that has been upgraded to 16K and Step II ROMS.

The system came with an expansion chasis and a single disk drive as well as the base unit and the monitor.

The machine works great when the expansion interface is off and boots properly to a 16K BASIC. When the interface is on, however, the machine fills the screen with garbage and will not boot.

My first guess is that the RAM in the expansion is bad. I've ordered replacement 4116s for one row to see if that resolves the problem. If not, I am stumped.

Does anyone have any suggestions?

Erik

 

[fjkraan]

The garbage is standard if no bootable disk is present.
Two questions:
- Does the machine work when the BREAK key is pressed during switch on?
If so check the memory with ?MEM should be about 48k for a full system.
- Do the drives rotate and is drive 0 selected? Then your floppy controller
is stil working. Try again with a proven working bootdisk.

 

[Erik]

Should there be something recognizable as BASIC or should the screen garbage be there regardless until a boot disk is in the drive?

I tried it with and without disks in the drive and with the drive on and off. It always displayed the same garbage.

I'll try to find time to pull out the machine again to check a few different disks. The only one I ever tried was a TRSDOS 2.3.

Thanks!

Erik

 

[fjkraan]

The garbage is standard when no bootable disk is present. By pressing
BREAK during startup you should get BASIC again, but then you know the
Expansion Interface doesn't block the bus.
If the drive 0 is selected during startup, you probably just need a boot
disk. At http://www.tim-mann.org/trs80faq.html you can find information
on how to obtain disk images and how to make disks from them.

 

[Erik]

Well. . . I come to find out that it was just operator error all along.

Just minutes before trying to snipe a friend on this auction I decided to pull out the Mod I and give it another go.

I just obtained 8 4116s, so I swapped out one row of RAM and tried again. No dice.

I then swapped back the RAM I'd removed with the row I hadn't touched. Still no dice.

I then re-re-checked the cables and lo and behold, the damn disk cable was upside down on one end.

After spending 30 seconds calling myself a doofus, I put the cable on properly and booted both TRSDOS 2.3 and NewDos like the day the machine was built.

Saved myself at least $60 in the process too.

Now it's time for some ScarfMan! :D

Thanks for all the help!

Erik