Issues with my Vic 20

[PaulQ]

I was working away at my latest program, when, upon testing my program, my screen went all screwy. I turned the computer off and on again, but this is all I get whenever I power up my Vic 20:

http://ca.youtube.com/watch?v=jHeglSK3s2c

Suggestions?

[Jeff-20]

Wow. That's a new one.

[ral-clan]

Eeek. Time to call TPUG. Don't they have a closet full of VIC-20s they can barely give away?

These are the things I would try (in order):

- try a different power supply.
- pop the hood and re-seat the chips
- feel for any chips that get really hot, and if so, try spraying them with that instant aerosol coolant you can buy to see if it remedies things temporarily (this is only for diagnostic purposes).

That should narrow things down.

Sorry to hear things have gone south on you...I wonder if having the 16K RAM expander plugged in might have placed a load on the VIC somehow and accelerated an already impending problem.

[gklinger]

Eeek. Time to call TPUG. Don't they have a closet full of VIC-20s they can barely give away?

Eight in stock as of yesterday's inventory. They're not exactly giving them away though. They're listed as being $25 each on their website.

[6502dude]

I was working away at my latest program, when, upon testing my program, my screen went all screwy. I turned the computer off and on again, but this is all I get whenever I power up my Vic 20:

http://ca.youtube.com/watch?v=jHeglSK3s2c

Suggestions?

You have problems with both horizontal and vertical sync within NTSC signal.

Both of these are derived off crystal based clock circuit and divided down within 6560 CRT chip.

Since you have clock to cpu (since kernel has executed to point of displaying bytes free and setting screen + border colours), then at least you have some output from clock circuit and it is being passed from 6560 to 6502.

I would look for possible clock off frequency, but more likely a bad 6560 CRT chip.

If you have a spare Vic-20, try the 6560 from machine that is acting up in a known good Vic-20 to see if problem follows suspect 6560 chip.

I advise against taking a good 6560 chip and testing in a suspect Vic-20 since 6560 chips are becoming scarce.

[PaulQ]

Unfortunately, I don't own a "Spare" Vic. I wish I did.

It's a shame, because it's otherwise in great shape.

Looks like I may be buying another TPUG system, if I can't source another Vic before WOC.

[eslapion]

I would look for possible clock off frequency, but more likely a bad 6560 CRT chip.

If you have a spare Vic-20, try the 6560 from machine that is acting up in a known good Vic-20 to see if problem follows suspect 6560 chip.

I advise against taking a good 6560 chip and testing in a suspect Vic-20 since 6560 chips are becoming scarce.

Of course, according to you, it can't possibly be because it was let run too hot for too long.

I wonder why it is consistently the 6560 that fails the most often in the VIC and it happens to be the chip that produces the most heat... must be a strange coincidence.

[PaulQ]

Of course, according to you, it can't possibly be because it was let run too hot for too long.

I wonder why it is consistently the 6560 that fails the most often in the VIC and it happens to be the chip that produces the most heat... must be a strange coincidence.

Of course, according to you, your dinky little clip-on heat syncs are supposed to help prevent this from happening:



Must be a strange coincidence.

[eslapion]

Of course, according to you, your dinky little clip-on heat syncs are supposed to help prevent this from happening

ALL heat sinks can contribute to reduce the risk of this happening. Not just the ones I sell.

NONE will EVER completely eliminate the risk.

Anyone who thinks there is such a thing as a piece of equipment that will totally prevent this from happening has either learned his physics by watching bugs bunny and/or Road Runner or learned electronics by sticking utensils up electrical outlets or all of the above.

Of course, the ability of heat sinks to dissipate heat can be nullified if the poor VIC is used on a carpet or any other environment where its top and/or bottom venting holes are blocked.

Some people don't know how convection cooling works so just for them I would like to point out that the BOTTOM holes are the most critical ones that should never get blocked. That's where fresh air is taken in. If the top ones are blocked, hot air can always escape through the keyboard openings.

Have fun, friendly VIC user...

[PaulQ]

Except that I've only ever used my Vic 20 on a solid desk. In a basement. Where the ambient air temperature rarely gets over 21 degrees Celsius. With your heat sync installed. Which means that your assumption that a small little heat sync would have saved a Vic's 6560 may be as flawed as your flawed assumptions about how some people may learn about physics.

6560 overheated and died... as usual.

Just a small little heat sink would have saved it.

Maybe in the world of Bugs Bunny or Road Runner...

[carlsson]

As to the case of possible overheating, I wonder if the 6561 PAL chip is less sensitive than the original 6560 one? I would imagine and hope it to be.

[PaulQ]

What's interesting to me is that I cannot find a single independent reference suggesting that the 6560 fails from overheating, aside from eslapion's assertions.

The Plus/4 and Commodore 16 were much less popular than the Vic 20, but there are plenty of references all over the web stating that the TED chip overheats and destroys itself. There are references to the chips in the Commodore 128 overheating and failing. There are references to the video chip in the PET 4016 overheating and failing with a certain poke value. There are certainly plenty of references to the Commodore power brick overheating and failing. Yet not a single reference to the 6560.

My guess (and this is only a guess) is that it's possibly the power brick that is starting to fail, and has allowed excessive current to flow into the computer, damaging the chip.

[tlr]

I was working away at my latest program, when, upon testing my program, my screen went all screwy. I turned the computer off and on again, but this is all I get whenever I power up my Vic 20:

http://ca.youtube.com/watch?v=jHeglSK3s2c

Suggestions?

Interesting! Note how the border looks correct, although moving. The character data is zooming around the memory, so it's not just a vertical sync problem.

Which VIC-20 version is it? regular or CR?

How about UB9? 251027l1.gif, 251027r1.gif (NTSC CR)

All schematics here: http://www.zimmers.net/anonftp/pub/cbm/ ... index.html

[eslapion]

Except that I've only ever used my Vic 20 on a solid desk. In a basement. Where the ambient air temperature rarely gets over 21 degrees Celsius. With your heat sync installed. Which means that your assumption that a small little heat sync would have saved a Vic's 6560 may be as flawed as your flawed assumptions about how some people may learn about physics.

Its interesting how I clearly mentioned that you can nullify the effect of a heat sink if the venting holes are blocked, which is far worst than using your VIC in a warm environment, and you say nothing about that in your reply.

BTW, it is worth testing your 6560 in another VIC. Sometimes this kind of problem is caused by the 7402 chip which clean out the 14.31818MHz crystal pulses.

Also, if I follow your thinking, I guess its a good idea to suggest to people NOT to put heat sinks on their VIC chip... after all since it is Eslapion who suggest it, it can only be because he wants to rip you off peddling his little junkie metal clips.

A small heat sink on your video chip may not "save" your video chip but it is well known that if you operate a C64 without a heat sink on its VIC-II, its life span will be considerably reduced. The same can be said of the 6560. A prolonged lifespan does not mean infinite life span. Also, the failure of a specific chip can be attributed to a miriad of different things.

Since you owned and used your VIC-20 for a long time before putting a heat sink on its 6560, it is fair for me to suspect that you blame me for all the years this machine was used WITHOUT a heat sink... just like a guy who's got lung cancer blames his very last cigarette for his disease...

My guess (and this is only a guess) is that it's possibly the power brick that is starting to fail, and has allowed excessive current to flow into the computer, damaging the chip.

Well, well, wa da ya know... a pair of wallwarts attached to an extension cord may be the way to protect your old Commodore machine after all...

It certainly is much less likely to damage your precious old machine than original Commodore bricks.

[PaulQ]

Also, if I follow your thinking, I guess its a good idea to suggest to people NOT to put heat sinks on their VIC chip... after all since it is Eslapion who suggest it, it can only be because he wants to rip you off peddling his little junkie metal clips.

Actually, what it is is your arrogance in telling people that your heat sync would have saved their Vic whenever this chip fails. You assume that it overheated and failed, even though there's nothing to suggest that this is actually a problem with this chip outside of your observations that it gets warm.

Fact is, when I got my first Vic 20, I would set it on a carpeted floor in the living room, completely blocking the bottom vents, and it would be left on for hours, if not days, at a time like this. Sometimes, I would bring it into my bedroom and set it on my bed while I wrote my programs. Of course, I was only twelve, and at that point learned a lot about physics from the Bugs Bunny and Road Runner show. One would think that if heat was a huge problem for this chip, it would have had a meltdown during one of those long summer weeks it lived at the end of my bed, powered on.

Here we are, 24 years later. The Vic is used on a desk. This means the vents are not being blocked. It is on, at best, an average of a couple of hours a week. It has a heat sync on the chip. Yet it appears to have failed.

What I am suggesting is that what you are offering may in fact be false sense of security to Vic 20 owners who ought to be watching out for something else. You make it sound as though the only problem with this chip is that it will overheat. I suspect that the power supply may be a bigger issue.

As for my choice of power supply, I have come to the conclusion that the ideal solution will be to modify one of my Commodore 128 PSU's to work with my Vic and C64. You can keep your wall warts and extension cord; please don't try to peddle that solution anymore.