Broken boot screen with lot garbage

[lolof]

I was assembling a finalgrom99 and unfortunately I got a broken CPLD from China.....

The TI with the not working finalgrom99 started with blue screen and strange noise when flashing the CPLD for the first time. 

It's maybe a coincidence but after this, the screen from my TI was broken. See picture. 

 

I replace the FG99 CPLD with another one and it worked on an another TI-99/4A.

 

Problem is, my first TI was my best one ? 

 

What can be broken ? I do not really know where to start.... I never repaired a TI, it's the first problem I have on TI....

 

Edited February 9, 2020 by lolof

[+arcadeshopper]

in the faq here: https://www.arcadeshopper.com/wp/?p=312

 

search for: Scrambled/Garbled screen graphics/text

 

 

[HOME AUTOMATION]

https://www.ninerpedia.org/wiki/Troubleshooting

 

...close

[+mizapf]

We don't have that pattern on Ninerpedia. Too bad the colors in the photograph are not well visible. @lolof, could you please try to take another picture with a better quality?

 

(Usually I'd say, try different shutter times, but this was when photos were taken by devices that were designed for them, and not by devices for communication.)

[lolof]

Thanks, I will have a look in the FAQ.

 

It's connected on a old TV and I can't do a better picture with what I have here.....

 

I have somewhere a LCD TV that should work. I will search for it and try to post a better picture.

[lolof]

@mizapf

 

Done, thanks to a old Samsung LCD TV ! I hope this picture is ok for you.

The TI is connected on TV by Scart cable. It's a french TI....

 

I will start replace the vram one by one and see if it's the problem.

 

 

 

 

 

Edited February 9, 2020 by lolof

[+mizapf]

OK, looks good. I tried to create this output by manipulating the VRAM write function in MAME; the closest hit was when I set bit 0x20 to 1 for addresses higher than 0x0800. This could mean that bit 2 is stuck to 1 starting from the second kilobit of the 16 kbit chip. See the board on https://www.ninerpedia.org/wiki/Troubleshooting to see which chip is affected (number 2).

 

 

[kl99]

usually the faulty chip is super hot.

[lolof]

Thank you very much, I will start with that Chip. I should receive new chip this week.

I will  report the result.

 

I just want to ask, one modified 4164 will work with the other 4116 well or should all vram be changed to 4164 ?

 

The chips I ordered are 4164.....

 

I saw here I could use 4164 with a simple mod :

 

 

 

Edited February 9, 2020 by lolof

[+arcadeshopper]

18 hours ago, lolof said:

Thank you very much, I will start with that Chip. I should receive new chip this week.

I will  report the result.

 

I just want to ask, one modified 4164 will work with the other 4116 well or should all vram be changed to 4164 ?

 

The chips I ordered are 4164.....

 

I saw here I could use 4164 with a simple mod :

 

 

 

awesome definitely report back how it went

[lolof]

I got 8 the new memory (TMS4164-15LNJ) and solder 4 of them. I want to change them all but I have to wait to receive  4 sockets I ordered.

 

It's already working. At least, I am getting the bootscreen without graphics corruption. 

For a complete test, I have to wait to receive the last sockets and put the TI all together again.

 

Unfortunately, I can't confirm 100% that this was the number 2 broken. I did a mistake and removed the wrong one at first (Nr1). And as I cut the legs from IC, I could not test again with the old chips and I removed directly after a second one (Nr2) without testing. So, it's the Nr.1 or Nr.2. But surely Nr.2 as mizapf could reproduce almost the same problem on the emu.

 

Here a picture of the actual status. Waiting the last 4 sockets...

 

Thanks to all of you for the help.