Flicker and red band on Commodore 1702 monitor

[Frank Cox]

I never bother to watch tv but I do some work for the local cable company. I have "all the channels" and occasionally one of the folks at the NOC will phone me to check channel number XXX if someone in town phones in with a problem so they'll know if the problem is just that customer or town-wide.

I have a Commodore 1702 monitor attached to the digital cable box and that's my TV.

It's probably been ten years since I've turned that monitor on for more than a few minutes to check a channel, but tonight my wife and I decided to watch Thelma and Louise on one of the commercial-free movie channels.

Thelma and Louse. Just as good as I remember it being from the last time I watched it. "I'm in deep shit. Deep Shit, Arkansas."

After the first hour or so the picture would occasionally flicker and a horizontal red-to-pink band about one-third the height of the screen would appear on the screen for about one second. The band formed a background to the picture, i.e. the picture was still there and the band was behind it.

I assume the issue comes from the monitor having warmed up over that first hour and something went haywire. Does an occasional horizontal reddish band ring any bells for any of you electronically minded folks? I hope my monitor isn't dying; for the little that it gets used I'd just as soon keep using this one if there's any easy fix that I could do. Though I suppose after about 40 years of service it really doesn't owe me anything.

It is about -40 degrees here tonight so I suppose it could also have been the channel but that was one of the digital channels and it seems to me that those channels should either work or not work. I guess I should crank it up on a warmer day and see what happens then; maybe it's not the monitor.

[Marcel Birgelen]

I guess nobody in your town really likes watching HD? I'll have to take my Comodore 64 along to test it properly.

How are you feeding the thing? I guess via the standard composite in? If there is an input on both the front and the back, have you tried using both? Also, you have nothing else around that accepts a composite in to check the original signal?

The last time I debugged CRT gear, those things were chunky CRT projectors about the size of a casket. :P

[Frank Cox]

My digital box automatically downsamples the signal for my monitor. So I can view the hd channels to the extent that I can tell the NOC guys that there's a picture on the screen and it's not distorted. There's a picture and there's sound. That's all they want to know.

Thelma and Louise was in fact on one of the hd channels.

It's connected through the composite input. The digital box that I had prior to this one had s-video output, but they changed their encryption standard a while back and gave me a new box that doesn't have s-video any more. Now I'm stuck with composite.

It was just one movie on one channel for one night so I suppose I should do a bit more experimenting to see if it's really the monitor at fault before I get too carried away with doing stuff.

One of the younger cable tv techs was here a while back getting some readings and when he saw my setup he asked me if he could take a picture of it to show some other people since he's never seen anything like that before.

[Carsten Kurz]

I'd suggest a card cage board reseat. Make sure you have the tamper and marriage passwords at hand. If that doesn't solve the issue, I am afraid you have to shell out big $ for a new light engine.

[Randy Stankey]

Y'know... I get it. TV just isn't as important to some people. I'm mostly the same way but I also see the TV as a source of information.
What if there's a big storm or, God forbid, a war or civil emergency? You'll need to have a way to find out what's going on. That's the main reason why I have a TV, at all. If I had my druthers, I wouldn't have a TV but my girlfriend "needs" a TV.

You could get a cheap, Chinesium television at Walmart or Best Buy, etc. If you look, you could probably find a small 24-inch model for somewhere in the neighborhood of $100 to $150.

I like your Commodore monitor and I think it's cool, the way you keep it running but, sadly, there comes a time when you just need to upgrade. I think you are fast approaching that time.

Did I correctly hear you say that the problem only happens on one channel?
If that's true, I would suspect the converter box first. Possibly something upstream. I'm not certain but that's where my thoughts go.

Do you have another device that you can hook the TV up to? An old DVD player or VCR that has compatible hookups with your monitor?
If the TV works with a DVD but not the cable box, it's the box's fault. I think you know the drill.

[Frank Cox]

I've only tried it on one channel so far so I don't know if it affects any others or not. My first thought was that my poor old monitor is on its way out but now I've realized that there are a number of other potential causes, including "just one of those things" and it's also within the realm of possibility that might never happen again.

Prior to this I haven't actually used that monitor for anything more than a few minutes once or twice every few months over the past ten years or so.

I suppose my next step should be to do a bit more testing and see if it happens again and under what circumstances. Maybe I should check the tv listings and see if there's another good movie on.

[Tony Bandiera Jr]

Two words:

Bad capacitors.

The symptoms point to that, as dried out or failing caps may start out ok (or not) but as they heat up, things go south. Another clue is caps that are old and have sat unpowered for long periods of time need to be electrically "reformed" now and then to keep them perky. One hour of continuous "on" time per week should do the trick.

Open that beast up and look for signs of swelled tops, leakage or the dreaded brown glue around the caps and other components.

Can probably get saved with a handful of new caps.

[Leo Enticknap]

I'm all for maintaining and enjoying older equipment wherever possible for personal enjoyment. I'm much less for trying to do that when the equipment is being used for a mission critical and/or revenue earning business function, though. On work-at-home days, I listen to John and Ken in the afternoon on this:

85T1.JPG

An RCA model 85T1. I can't give you an exact manufacturing date, but per online research, this model was in production from an unknown date until October 1937. After buying it from a thrift store for $25, I needed to replace one of the five tubes (a 6D6), and swapped out all of the caps on spec (cost insignificant, and if they were still OK, capacitors almost a century old likely wouldn't be for very long). The dial illumination light was also blown: I went a bit inauthentic, and replaced it with a LED. Thanks to the revival of interest in analog audio and tube amps, all of the other four tubes, or substitute models that would work, are now easily available if any of the others should die.

The station I mostly listen to it with (KFI) is even older than the radio, having been broadcasting continuously on AM640 since May 1923!

[Frank Cox]

I think there would be a market for an mp3 player that looks like an old fashioned floor or table radio.

But on the other hand I think there should be a good rack mount mp3 player and those don't seem to exist either, so what do I know...

[Fraser Falconer]

Hi Frank,
What Tony said, he hit the nail on the head. Sounds like bad caps in the vertical scanning circuits or dreaded dry joints. (Intermittent Vertical collapse and linearity issues.) Could you post an image if the issue. I could then help to point you in the right direction.

Cheers Fraser

[Randy Stankey]

... I went a bit inauthentic, and replaced it with a LED. ...

If they had had LEDs back in the day when that radio was made, they probably would have used them. Don't you think?
I think that it's good to make "sensitive restorations" whenever you can but you have to face facts. Sometimes those old light bulbs and things are unavailable and you have to make due.

If you can answer the question, "Would they have done it this way if they could have?" to the affirmative, there's no harm in it.

As long as you don't change the original form or function of something, I don't think its a sin to (thoughtfully) modernize an antique if you have to.

When I worked at Mercyhurst, my boss had an old, console radio in his office. The "Power-On" light had burned out and we couldn't find an original replacement.

Somewhere, online... I forget where... I found a place that sold LEDs in original style packaging. I found a red LED in a bayonet base, just like the original. It was a literal drop-in replacement. Worked perfectly!

If you ever wanted to restore the radio to "Museum Condition" all you needed to do was find an original style incandescent lamp.

[Ethan OToole]

Hello! You can buy a cap kit for the 1702 prepackaged from console5 and some others. There are also lists of the capacitors needed if you wished to source higher quality Pansonic 105c or Nichicon caps from someone like Newark/Digikey/Mouser/etc. Console5 makes it easy.

As I am sure you know, be sure to discharge the tube before working on it and be careful as some of the other caps may still hold a charge. If you are not familiar with this process there are videos online.

Another thing could be cold solder joints, usually around components that have large swings in heat or size differences but you never know.

I am lucky enough at this point I haven't had to work on any of my crusty computer monitors or recap them but I know the day is coming. I think I can think of 7 of them that will need it at some point not too far off (Atari ST, Amiga, Apple II/IIGS and C64.) I have done a number of arcade game monitors though.

There is a pretty vibrant scene for all that stuff and new innovations every day. Just saw a Coleco Adam and Atari 800XL playing Connect 4 against each other via internet server (FujiNet project.)

[Marcel Birgelen]

I think there would be a market for an mp3 player that looks like an old fashioned floor or table radio.

Amazon.com: Victrola Aviator 8-in-1 Bluetooth Record Player & Multimedia Center with Built-in Stereo Speakers - 3-Speed Turntable, Vinyl to MP3 Recording, Wireless Music Streaming, Mahogany : Electronics

But on the other hand I think there should be a good rack mount mp3 player and those don't seem to exist either, so what do I know...

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