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hfrazier

SE/30 Pixel 'Snow' Artifacts After 10 Minutes or More

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Interesting! The question then is whether UE8 is faulty, or if it's just sitting on the very edge of spec because of the other load on the PDS slot. I wouldn't bother heatsinking UE8: try replacing it and see if the problems still persist.

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Yea your case is unique just like mine. I have replaced UE8 and all the other ICs with no change with the board I have. So its sitting in the junk pile until I can get another look at it. 

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Ive done it alot of times with a handheld torch for heatshrink, But I prefer the heatgun method. a flame could overtemp the chip and actually damage it if your not careful. 

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On 3/16/2018 at 4:56 PM, apm said:

Interesting! The question then is whether UE8 is faulty, or if it's just sitting on the very edge of spec because of the other load on the PDS slot. I wouldn't bother heatsinking UE8: try replacing it and see if the problems still persist.

That is what I'm going to do... The heat sink didn't work for squat! Got one on order from digi-key. This one will work.. right?

I'm also just hoping that the chip is simply faulty. ... I would think that it is a faulty chip, since even in the lighter test one or two columns look like they are still functioning properly... Hmmm. :/

 

@techknight Yeah I have used a lighter many times for heat shrink so I felt fairly confident that I wouldn't mess it up. :)

 

@joethezombie Thanks! It definitely gave me a definitive answer!

 

 

Edited by hfrazier

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Update - I was able to replace it with the new one that came in, but unfortunately the problem still persists, although much lighter. Dang! It must be juuuust on the edge, just like @apm was suggesting.

 

Of course, removing the pivot makes it go away completely. Is there anything else I should try or just forget about making it perfect? I'm afraid it is probably just a hardware limitation (or at least until I find an accelerator card to put in with Bolle's ProtoCache.)

Edited by hfrazier

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You need a riser card with internal buffers IMHO. I know they make bi-directional buffers without the need for the select or R/W line. Maybe thats the route to go. 

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Here's a weird idea, maybe not a good one but probably not harmful (@techknight?). Try shorting out R29, a 22-ohm SMD resistor on the bottom side of the board, just under UI6 (I think).

 

R29 is in series with the CLK16M signal (i.e. the main system clock), which is generated by UI6. If there's enough capacitance on the bus, for example through too many cards, then the rise time of the signal could be just barely too slow. But shorting that resistor will make the drive just a little bit stronger, which might be enough. I imagine it is there to meet emissions specs and that shorting it probably wouldn't damage anything, though I suppose there's a chance that it could create a stability issue.

 

The even stronger version of this would be to place a 5V high-speed buffer in place of R29.

 

However I still don't have a good explanation for why a laggy clock signal would produce this pattern on the display, so maybe it won't make any difference.

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