TRS-80 Model III Monitor Issues

[TheGrandEmperor]

I'f you've read any of my other posts you will know that I haven't had any luck with my vintage computers this weekend. So I just got a TRS-80 Model III really cool looking system, I particularly liked seeing it in Halt and Catch Fire season 1. Anyway, I plug the badboy in last night, and the monitor pops up with angled lines and nothing else. The seller I got it from on eBay, showed it loading to a prompt and everything in his photo's, so I'm a little miffed its not even getting that far. So if anyone has any ideas please let me know.

[R.Cade]

First, hold the break key and press reset, and you should get a "Cass?" prompt on the screen.

 

Adjust the pots on the bottom left side of the PC (under the edge) to get the brightness and contrast to your liking.

The lines could be normal if it's adjusted too bright. They sometimes start out bright then darken after a minute.

 

On most of the old TRS-80 III's, I find these pots have frozen and I have to work in some WD40 and "force" them to turn again.

Edited April 20, 2016 by R.Cade

[TheGrandEmperor]

First, hold the break key and press reset, and you should get a "Cass?" prompt on the screen.

 

Adjust the pots on the bottom left side of the PC (under the edge) to get the brightness and contrast to your liking.

The lines could be normal if it's adjusted too bright. They sometimes start out bright then darken after a minute.

 

On most of the old TRS-80 III's, I find these pots have frozen and I have to work in some WD40 and "force" them to turn again.

Break Key?

[Turbo-Torch]

Your brightness and/or contrast controls are turned all the way up or the pots are just bad as mentioned above.

 

The break key has break written on it, you can't miss it.

[Omega-TI]

 

The break key has break written on it, you can't miss it.

 

Yeah, but I can't find the "ANY" key to continue.

 

[Turbo-Torch]

It's right by the TAB key.

 

[TheGrandEmperor]

First, hold the break key and press reset, and you should get a "Cass?" prompt on the screen.

 

Adjust the pots on the bottom left side of the PC (under the edge) to get the brightness and contrast to your liking.

The lines could be normal if it's adjusted too bright. They sometimes start out bright then darken after a minute.

 

On most of the old TRS-80 III's, I find these pots have frozen and I have to work in some WD40 and "force" them to turn again.

Ok, I got it to work the sequence for me seems to be -> Reset and than the power switch, then with finger still on reset hit Break. Got Cass to come up with some coaxing of the dials. have no software yet anything cool to try out on it?

Edited April 21, 2016 by TheGrandEmperor

[Turbo-Torch]

There should be absolutely no reason to go through all that. Pressing break while turning on the computer or holding break while pressing the orange reset button should bring you into Cass? prompt.

 

As far as recommending things to try out, it would be nice to know what you have. We can assume it's a disk based system since you need to need to hit break to get into the Cassette baud rate prompt. How many drives? Do you at least have a trsdos disk that's bootable? How much memory, 32K? 48K? Is it equipped with the RS232 board? Do you have the cassette deck and cable?

 

Easiest way I've found to get software to it is to download what I want off the net to my PC and then attach the Model III to my PC with a null modem. I then use a terminal program on the PC and XTERM on the III. It's exactly like logging into an old BBS and downloading the files I want directly to a 5¼ disks. It does well up to 4800 baud.

 

If you're into games, you can't go wrong with anything from Big Five Software.

[Caterpiggle]

Hello

R.Cade

First, hold the break key and press reset, and you should get a "Cass?" prompt on the screen.

 

May I ask you why my Model 4 has behaving this way ? At first, when I turn the computer on, it was appearing in normal display without re-adjusting brightness or contrasts. But somehow, when I insert the CP/M diskette then the display had acting so weird with "?@" everywhere on the whole display then it had been disappearing. When I was forcing to hold down "Break" when I press on Reset button and re-adjust the brightness & contrasts for the first time ever. SO MY QUESTION is WHY my Model 4 acts in this way due of poor internal monitor itself ??

[Turbo-Torch]

Hello

R.Cade

First, hold the break key and press reset, and you should get a "Cass?" prompt on the screen.

 

May I ask you why my Model 4 has behaving this way ? At first, when I turn the computer on, it was appearing in normal display without re-adjusting brightness or contrasts. But somehow, when I insert the CP/M diskette then the display had acting so weird with "?@" everywhere on the whole display then it had been disappearing. When I was forcing to hold down "Break" when I press on Reset button and re-adjust the brightness & contrasts for the first time ever. SO MY QUESTION is WHY my Model 4 acts in this way due of poor internal monitor itself ??

 

You need to provide more information. When you hit reset, does everything boot back up normally? Do other disk based programs work or is it only a problem with that CPM disk? Can you spin up a disk drive by doing the DIR command? Does the directory show?

 

If the monitor is dimming, along with strange characters showing up (especially during disk access), most likely caps are failing inside the power supply.

 

Also likely:

Oxidized mylar flex cables that go from the motherboard to the RS232 board, another to the disk controller and possibly another smaller one used as a jumper on the motherboard.

Pull and reseat them in their connectors.

I would also pull and reseat every socketed IC.

 

Better yet, when you pull any component, give the socket and pins a light spray of DeoxIT.

 

If you don't know what you're doing, don't even try to take the IV apart. You're dealing with hazardous voltages and a picture tube neck that will break if you separate the cabinet wrong.