Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old August 13th 19, 02:23 PM posted to sci.electronics.repair
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Default Commodore 1702 Monitor, Intermittent Display Issue

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




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Old August 13th 19, 02:44 PM posted to sci.electronics.repair
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Default Commodore 1702 Monitor, Intermittent Display Issue

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
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Old August 14th 19, 12:31 AM posted to sci.electronics.repair
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Default Commodore 1702 Monitor, Intermittent Display Issue

On Tuesday, 13 August 2019 14:44:08 UTC+1, wrote:

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


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


NT
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Old August 14th 19, 12:00 PM posted to sci.electronics.repair
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Default Commodore 1702 Monitor, Intermittent Display Issue

Might be Martian invaders....

Peter Wieck
Melrose Park, PA
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Old August 15th 19, 01:08 PM posted to sci.electronics.repair
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Default Commodore 1702 Monitor, Intermittent Display Issue

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


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



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Old August 15th 19, 01:44 PM posted to sci.electronics.repair
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Default Commodore 1702 Monitor, Intermittent Display Issue

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

Peter Wieck
Melrose Park, PA
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Old August 16th 19, 02:22 AM posted to sci.electronics.repair
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Default Commodore 1702 Monitor, Intermittent Display Issue

On Thursday, 15 August 2019 13:13:06 UTC+1, wrote:
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


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


that was easy


NT
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Old August 16th 19, 01:32 PM posted to sci.electronics.repair
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Default Commodore 1702 Monitor, Intermittent Display Issue

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


On 8/15/2019 8:08 AM, wrote:
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


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


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Old August 16th 19, 01:50 PM posted to sci.electronics.repair
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Default Commodore 1702 Monitor, Intermittent Display Issue

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.

Peter Wieck
Melrose Park, PA
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