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Model 4 display issues.

A

Atari-Collector

New Member
Joined
Jan 18, 2015
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5
Location
Ontario, Canada
Hi, my first post here, this forum was recommended to me by somebody that watched my video on youtube about the TRS-80 Model 4 I just got yesterday that has some display issues.

To summarize, it sometimes goes in to a fast scroll on reset or power up. And there are fine diagonal lines on the screen. I was hoping somebody had some ideas on what's going on? I have it running right now in Model 3 mode with an cassette Model one game running ok. I still have to track down Model 4 boot floppies somehow...

thanks

https://www.youtube.com/watch?v=hA82fPno-6o
 
@Atari-Collector
It looks like the power supply's regulation is poor.
If you are technical , take the top cover off, (With the power cord removed from Power) and reseat all the connectors on the power Supply.
and reseat the connector on the video board by unplugging and re plugging several times.
If you only have 1 Power Supply in the unit please have a good look at the soldering on the pins of the long connector (white)
Good Luck (see you in the AtariAge forum)

Ray W
 
Audronic said:
@Atari-Collector
It looks like the power supply's regulation is poor.
If you are technical , take the top cover off, (With the power cord removed from Power) and reseat all the connectors on the power Supply.
and reseat the connector on the video board by unplugging and re plugging several times.
If you only have 1 Power Supply in the unit please have a good look at the soldering on the pins of the long connector (white)
Good Luck (see you in the AtariAge forum)

Ray W
Click to expand...

Yes, I am kind of of technical, been playing with electronics as a hobby since I was 7.. Oh now I feel old... A power regulation and bad contact issue does make sense. I'll have a go at it tomorrow, I want to pick up some good contact cleaner , the stuff I bought last time attacks plastic, so I need something safer..

thanks
 
On the video board give the pot for H-Hold a wiggle, sounds like its right close to the threshold for stable zone. Other than that the machine looks pretty good to me.

Ian.
 
TRS-Ian said:
On the video board give the pot for H-Hold a wiggle, sounds like its right close to the threshold for stable zone. Other than that the machine looks pretty good to me.

Ian.
Click to expand...

That's the plan for tomorrow, I want to get some contact cleaner in there too. The case was a bit dirty, a number of black scuffs on the sides and back like it was use to keep tires from rolling away. Lots of hard scrubbing with Googone and some rubbing alcohol had pretty much removed the scuffs. A few marks are still visible on the back, but I'm not too worried about that and my arms are tired from scrubbing the other marks out. So I'm pretty happy it's cleaning up so well.
 
Ok, another follow up, the cleaning on the potentiometers for brightness, contrast and hozalat hold helped the original issue I posted about.. But, and there's always a but... I just got DOS disks (Thanks to TS-80.com) and when I boot from them the screen goes crazy. Here's a fast video to show what happens since that explains it far better then I can write. I suspect it's the power supply in need of all new capacitors to stabilize the voltage better, but I'm open to suggestions.

https://www.youtube.com/watch?v=c3h5oAgDQbo
 
@ Atari-Collector

When you boot the Model 4 Ldos disk adjust the brightness and or contrast Down to see if the rolling changes.
or adjust the horizontal/vertical controls in the Model 4 mode to get a lock. and then see if it is stable in the Model 3 Mode (without a disk booting)
Please remember that there are some high voltages near the screen and on the Video board.

Good luck

Ray W__________
 
Audronic said:
@ Atari-Collector

When you boot the Model 4 Ldos disk adjust the brightness and or contrast Down to see if the rolling changes.
or adjust the horizontal/vertical controls in the Model 4 mode to get a lock. and then see if it is stable in the Model 3 Mode (without a disk booting)
Please remember that there are some high voltages near the screen and on the Video board.

Good luck

Ray W__________
Click to expand...

Thanks for the reply, I've already resolved all the video issues on my Model 4:D

The initial issue of the roiling just needed some contact cleaner and a little adjustment. And the boot to Model DOS turned out to be a 60 column screen mode has a timing issues, and a simple adjustment to C210 resolved that. So it's in great shape now:D

I am well aware of the voltages inside a machine like that, but I do appreciate the warning. I'm sure some people won't realize the risks of working on an old machine with an open face power supply.
I was thinking about doing a video of it in it all cleaned up and working right condition.
 
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