PAL red/green color moire, not in NTSC

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rmzalbar
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Re: PAL red/green color moire, not in NTSC

Post by rmzalbar »

After weeks of bright sun, there was none this weekend, so no bleaching possible. It's fully stripped down and I've bathed the case and keycaps, warm-air lifted and set aside the decals. Clean the keyboard frame and mainboard probably tomorrow night.

This weekend I will be out of town, so perhaps I will set up my UV lamps for some controlled indoor retrobriting sometime next week. I don't worry so much with white cases and keys, they tend to respond well to the process. Always go gently.


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banman
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Re: PAL red/green color moire, not in NTSC

Post by banman »

Hi rmzalbar,


I found this interesting video on heat sink compounds....

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Re: PAL red/green color moire, not in NTSC

Post by rmzalbar »

He is already introducing some systematic errors in the flatness of his lapping simply by grinding against a non-involved surface. The best way to get a true flat is to have three units - say A, B and C. You grind any two against each other until they are lapped together - say A and B, then grind A to C, and then B to C, and then A to B again.. repeat several times, rotating them out at regular intervals until all three of them can be wrung to any other and stick.

At this point that's good enough for heat sinks, but if you were making optical flats for telescopes you'd start paying attention to temperature and use a collimated light source to do interference measurements.
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Re: PAL red/green color moire, not in NTSC

Post by banman »

Hi rmzalbar,



I think I heard something similar about that elsewhere.


I found this interesting article on gauge blocks.


https://en.m.wikipedia.org/wiki/Gauge_block

It seems they are able to adhere to eachother just thru their own close contact....


From what little research I've done there aren't too many ways to take the heat away from C64 chips.

The C64 breadbin has more room under the keyboard than the later wedge shaped C64C. Not a whole lot unfortunately considering both.

The main one being a metal heat sink on top of the chip
I did see a video where someone added a fan to the heatsink.

I wonder if there are other novel ways to keep things cool.....

Isn't the IC wafer bonded to the bottom of the dip package?

Could a way of cooling the chip from underneath be explored......

Has any one done stuff with peltier devices?
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Re: PAL red/green color moire, not in NTSC

Post by rmzalbar »

The stock heatsink setup is nothing but a thin strip of copper-plated or alloyed tab (brass maybe?) that is connected at one end to the RF shielding cover, so you really don't need a very good heatsink at all. It's reasonable to imagine a custom-shaped heatsink that is not very thick on top of the chip, but maybe extends to a thicker finned area off to one side.

Simplest thing I can imagine is a piece of flat aluminum bar stock, a few mm thick, laid with part of it overlapping the top of the package, with a low-profile heatsink mounted to the other part facing downward, everything bonded with silicone thermal adhesive. You can make the bar stock and heatsink can be as long as the chip if you like, but it probably doesn't need to be, the middle of the package is the important part. Here's an endwise view of what that might look like. Of course components near the chip might make this problematic.
low_profile.png
low_profile.png (2.11 KiB) Viewed 4412 times
Gauge blocks are calibrated flat, and yes you can get to that level of flatness by doing the three-piece grinding method. More difficult and painstaking would be to get the thickness correct (measuring instrument is now needed) and even more so to control for wedge - non-parallel opposing faces. Anisotropic grinding movements are used to make corrections, good "barrel walking" protocol is then used to keep it from developing once corrected. But all of this work can be done by hand with nothing more needed then measuring instruments and several grades of grinding powder.
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rmzalbar
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Re: PAL red/green color moire, not in NTSC

Post by rmzalbar »

If you wanted to get clever you'd solder a heat pipe to the bar stock instead of a heatsink, and then you could remote the heatsink off somewhere else entirely, where component clearance is not an issue.
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Re: PAL red/green color moire, not in NTSC

Post by rmzalbar »

banman wrote: Thu Feb 20, 2020 8:27 pm Got any photos of the new machine?
De-yellowing in progress.. technique lifted from The 8-bit Guy
20200307_133348.png
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Re: PAL red/green color moire, not in NTSC

Post by banman »

Hi rmzalbar,


That's a great idea the the heat sinks ! That's lateral thinking...

It would certainly free up head room.


I like you suggestion of the heat pipes.

I use this stuff for sticking the heat sinks to the top of chips..

It smells and looks a bit like liquid paper. It's pretty cheap. I would say it's very average ...

IMG_20200308_200039.jpg
I only try to get a very thin scrapping between the heat sink and chip.
The bond seems semi permanent. I can remove the heat sink by twisting it off with some pliers..
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Re: PAL red/green color moire, not in NTSC

Post by rmzalbar »

That's what I use too, I got it along with a heatsink kit for the C64, perhaps you did too. It's perfect, it can be applied and spread thin and sets into a strong - but not permanent - bond, and when you separate it you can easily rub and roll off the residue.
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Re: PAL red/green color moire, not in NTSC

Post by banman »

Hi rmzalbar,


Yes, I agree. It seems do the job.

Do you think it might be silicon based?

I think I got mine from AliExpress. I think I got heatsinks separately.
At the time of purchasing these I really didn't understand what I was doing. Probably still don't..ha! Glad I might have done something ok for a change.



I actually find it great talking about things like this. It helps me get a better understanding of what is going on under the hood so to speak.

By the way how's your C64G coming on?
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