Re: How do I boot a Model 4 from disk?

Christopher Noyes wrote:
Blake Patterson wrote:
On Apr 27, 12:20 am, "Bill Plenge" <B_Ple...@xxxxxxxxxx> wrote:
Blake Patterson wrote:
On Apr 26, 11:59 pm, "Tom Lake" <tl...@xxxxxxxxxxxx> wrote:
"Blake Patterson" <blakes...@xxxxxxxxx> wrote in
messagenews:19008afd-f196-4da2-b5f8-fdfa05e8cb20@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

I just received a TRS-80 Model 4 from eBay. My first TRS-80 ever
(and I've been into computers since '82). How do I boot it from
disk?
I have TRSDOS 6, LDOS, etc. But I turn the machine on and am greeted
by "CASS?" and then a request for sys memory levels and then a
prompt. The two drives are spinning at this point. How do I boot the
DOS?
If you're getting the CASS? message without holding down the Break
key,
either the disk drive interface is defective or the Break key is
stuck down
somehow. A working Model 4 should display a Diskette? message if the
Break key isn't held down.
Tom Lake
Several keys are bad: 2 r j ; z v b ...BREAK seems to work tho - it
CR's when I hit it.
So is the disk system dead? Steps to diagnose? Oy... Tnx. :-(
bp
Sounds like your problem is caused by the keyboard issue. The Model 4 would
boot to Model III cassette mode if a certain key was held down at power on.
That's why you were getting the Model III message. I don't remember what
key it was, it's been a long time. It sounds as if once the keyboard issue
is resolved it should fix your booting to disk problem too.

Best,
Bill

I see dated photos of this unit on the eBay auction item listing.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260230790905

It would seem something in shipping caused this to happen - certain
keys to die and perhaps something sticking preventing booting in
normal disk-based mode. I wonder what it could be? Opening up the
unit worth anything here? Thanks...



bp


You could try unplugging the keyboard from the system board to see if it boots from disk then(connects to the right side of the system board when the front of the unit is facing you).


-CN
You might also try simply moving the various connectors inside & gently lifting, not removing, socketed ic's then gently pressing them back into position. One of the additional problems that appeared from time to time was oxidation on a connector or in a socket. This would cause erratic operation at times. The model I keyboard to EI was particularly problematic this way due to the gold plated edge card connectors meeting with the solder plated PCB fingers. This appeared to be a random & unpredictable problem when these machines were in frequent use & there is no reason to think it has become better over the decades.

BTW when you get it working you might look around for a pair of Mitsubishi double sided 80 track drives. They worked particularly well and provided a great deal more storage capacity. I still have them in my original Mdl I and a MDL III/IV and they still work. TRS-DOS 6/LDOS & the Mdl III LDOS 5.x OS's, among others, work well with them. NewDOS 80 had to be told where the directory was and what the configuration of the disk was in order to find it but the others worked directly. Of course unless you use a double-step routine you will not be able to read the 40 track media on the 80 track drive.

For the switch there was also a version that had a small plunger that pushed a movable metal contact against the stationary one. The assembly was very similar to the one in the picture but it did not have the conductive rubber membrane, it had a tendency to develop a film on the surface, over time, that would increase the contact resistance until a failure. Cleaning would generally bring it back into operation. The metal contact version was much more reliable. Some also had 4 solder points while others had just 2. If you do try the repair path get a length of sold-wick material or a solder sucking tool to clean the solder out of the hole before trying to remove the switch. There are still some local, small, electronic stores where these can be obtained. If you have not used these before get an old trashed board of some kind and practice a bit first before going after your good board. To much heat will damage the through hole plating and possibly lift the circuit material off the board surface causing more repair to be needed.

Good luck with it. Anything can be repaired it is just a question of how much time, and energy, we want to devote to the effort.

JamesSoCal
.

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