Commodore 1702 Monitor, Intermittent Display Issue

[jaugu...@verizon.net]

Hi,

I have a Commodore 1702 Monitor that I used with a Commodore 64 computer
years ago. Now I use it as a video monitor with my cable TV converter.

Recently, it developed an intermittent display problem which is hard to
describe. It is similar to an erratic horizontal sweep. When it happens,
there is NO color and looks like random "streaking" horizontal lines.

The problem sometimes happened a minute after I turned on the monitor.
Other times, it took much longer.

Vibration (rapping the monitor) has no effect on the problem. If I turn
off the monitor, then turn it back on, the problem is gone, but it may come
back soon or much later.

Has anyone ever had this problem with a 1702 (or 1902) monitor?

Thank You in advance, John

[peterw...@gmail.com]

This is an old-style CRT monitor from very roughly the mid-1980s. I would start with the electrolytic caps first. Mind all safety processes prior to working on it. While you are 'in there', clean everything and look for any corroded or loose connections, as the symptoms you describe could also be heat-related.

Best of luck!

Peter Wieck
Melrose Park, PA

[tabb...@gmail.com]

Could also be due to arcing. Which may well be stoppable at this stage by washing the affected area and drying very thoroughly.


NT

[peterw...@gmail.com]

Might be Martian invaders....

[jaugu...@verizon.net]

Hi Peter and everybody,

UPDATE:

The problem turned out to be a series of MISLEADING COINCIDANCES. The
monitor does NOT have a problem. The problem turned out to be a faulty video
source, (intermittent poor grounding/shielding).

When it first started, it was intermittent. Since I have another 1702
monitor, I replaced this one with my "backup". No more problem.
I was convinced the first 1702 has an issue.

With the back off, it finally happened and I was able to "scope"
the video signal (distorted) right to the video input. The problem
was NOT the monitor.

I then used a DVD player as a signal source and by golly,
NO PROBLEM.

John

[peterw...@gmail.com]

Good outcome in any case... Still might want to give it a good (and very careful) cleaning if appropriate.

[tabb...@gmail.com]

that was easy :)


NT

[Tim Schwartz]

Just goes to show you, it is not necessary to replace every electrolytic
capacitor that is over 6 weeks old. I've often found that caps I'm
removing when a customer insists on replacing them all are just as good
or better than the new ones. Depends on brand, and the heat in the product.

Regards,
Tim

[peterw...@gmail.com]

On Friday, August 16, 2019 at 8:32:53 AM UTC-4, Tim Schwartz wrote:
> Just goes to show you, it is not necessary to replace every electrolytic
> capacitor that is over 6 weeks old. I've often found that caps I'm
> removing when a customer insists on replacing them all are just as good
> or better than the new ones. Depends on brand, and the heat in the product.
>
> Regards,
> Tim

Always that is possible. But as-reported, the symptoms were indicative of age. And in a design as (relatively) bullet-proof and simple as the 1702, that would lead, typically, to age and/or dirt. And, if one is 'in there' the cost of a few capacitors now, vs. another tear-down later is negligible.

I restore a lot of vintage solid-state Dynaco products, mostly for fun as they are so basic. To do any level of restoration mostly requires a complete tear-down. So, if part X is bad on channel A, I will do the same part on Channel B as well. There are about US$18 worth of critical parts to be replaced in the typical ST-120, and "doing all" vs. doing only "the one" is about an hour in additional time. I am not paying the bills with my hobby - I am happy that it is self-sustaining at this point. But you get the point, I hope.

[Fox's Mercantile]

On 8/16/19 7:50 AM, pf...@aol.com wrote:
> On Friday, August 16, 2019 at 8:32:53 AM UTC-4, Tim Schwartz
wrote:
>> Just goes to show you, it is not necessary to replace every
>> electrolytic capacitor that is over 6 weeks old.
>

> Always that is possible.

One of my first projects was my parents Artone AM, FM and
Phone.
Put it on the bench, plug it in and turn it on.
Pffft. One of the wax paper caps blew it's guts out.
Replace it, and try it again.
Pffft. Another one of the wax paper caps blew it's guts out.
Replace it, and try it again.
Pffft. Yet another one of the wax paper caps blew it's guts out.
Replace it, and try it again.
Pffft. There goes on of the filter caps.
At this point I'd had enough of this foolishness. I replaced
EVERY remaining paper and electrolytic capacitor.

When I get a radio to work on, the very first thing I do is
replace all the paper and electrolytic capacitors. I am not
going to waste my time "trouble shooting" things I know are
bad, or will fail soon.

It's not called shotgunning, it's called not wasting my time.

--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

[tabb...@gmail.com]

based on a sample of one.
What's appropriate varies a lot. Some are better not messed with, some are best with papers replaced & lytics kept, some are basket cases that need every cap changing from the start, some want some bits changing and some there's no erasn to, etc. One approach suits all is the typical fool's guide.


NT

[Fox's Mercantile]

Do you argue because you're ignorant, or because like Arlen you just
want to hear yourself prattle on?

Apparently, some people think troubleshooting means wasting time
finding "that one part" while risking collateral damage to the thing
on the bench when the "there was more than one" suddenly fails.

The other reasons are equally fraudulent.
"My time is VERY important, I can't be arsed to replace something."
Or, "I saved $0.45 not replacing a part that hasn't failed yet."

Or the hacks that leave the old leads and make hook splices or use
Kwiggs(tm) to install the new parts. "But the old terminal might
fall/come apart if I try removing the old lead." I guess that just
shows a lack of skill on their part.

But go ahead and tell me again how you know everything and the rest
of us are just too stupid to pour piss out of a boot with the
instructions on the heel.

[Ralph Mowery]

In article <vJ6dnbyXyJw4PcfA...@giganews.com>,
jda...@att.net says...

>
> Apparently, some people think troubleshooting means wasting time
> finding "that one part" while risking collateral damage to the thing
> on the bench when the "there was more than one" suddenly fails.
>
> The other reasons are equally fraudulent.
> "My time is VERY important, I can't be arsed to replace something."
> Or, "I saved $0.45 not replacing a part that hasn't failed yet."
>
>

I believe in replacing all the old parts if one has failed if the cost
or time benefits doing it.

At work we had a factory man in to repair a motor speed control. The
motor was 3 phase 480 volts at about 200 or 300 amps. The man found 2
bad power diodes. I asked him to replace the 3 rd one. He said they
were about $ 200 each. I told him it was costing us a few thousand
dollars for every hour the machine was down and lots of money to get him
in the plant. The $ 200 was just good insurance to me. That diode was
probably ok, but I was not going to chance it failing in a day or month
later.

I only work on my own equipment now and if I find one bad part and there
are several more like it of the same age (on very old equipment
especially) I usually replace them all if not too expensive.

I started playing around with the old Heathkit transceivers a year or
two ago. Found out that many times the 1/2 watt resistors have changed
values. While I do not take time to replace all of them like I should,
I do spend time checking every one and replacing the ones that are
slightly or on the edge of the tollorance. If I was doing the repair
for money, I would replace every one of them in the 50 year old
equipment.

[peterw...@gmail.com]

My position is that as a hobbyist, I have two (2) responsibilities when dealing with *my* vintage equipment:

a) That it is as safe as may be practical/possible given its type and vintage. This means that _every_ electrolytic and/or wax/paper cap.

b) Presumably, I will not be the 'last owner' of my goodies - so what I have done, and how I have done it becomes a matter of communication with the future.

These devices are appliances - and we are not limited to using vintage parts and pieces, we are not limited to ancient practices either.

[Fox's Mercantile]

On 8/19/19 9:28 AM, Ralph Mowery wrote:
> I believe in replacing all the old parts if one has
> failed if the cost or time benefits doing it.

A point that some refuse to consider.

[tabb...@gmail.com]

On Monday, 19 August 2019 14:14:21 UTC+1, Fox's Mercantile wrote:

Feel free to keep arguing for your position. I don't think it's well informed personally.


NT

[tabb...@gmail.com]

On Monday, 19 August 2019 16:13:51 UTC+1, Fox's Mercantile wrote:
> On 8/19/19 9:28 AM, Ralph Mowery wrote:
> > I believe in replacing all the old parts if one has
> > failed if the cost or time benefits doing it.
>
> A point that some refuse to consider.

If you think I haven't considered that... whoosh.

[Fox's Mercantile]

I'm sure you have, then dismissed out of hand.

[Fox's Mercantile]

On 8/19/19 5:20 PM, tabb...@gmail.com wrote:
> Feel free to keep arguing for your position. I don't
> think it's well informed personally.
>
>
> NT

Of course you wouldn't.
Say what ever you want, I refuse to argue with you any
further on this topic.