C64 letter artifacts/ glitches

[Tpapp54321]

Ever since I got my C64 powered up its been working perfectly fine for the most part minus this one glitch. Lines flicker over various letters and characters on the screen. They appear in no organized order and almost sort of flicker. Although it doesnt seem to make garbled text as the letters are displayed perfectly fine under the flickering lines/ blocks. Heres a video of what Im trying to describe:

 

So what is my problem?

DD93088F-CE8C-4291-8E2F-BE58049590D2.MOV

9D9CEA1B-CD03-422B-A644-EFFEF59D0826.MOV

[Tpapp54321]

Also, graphics seem to be completely unaffected for the most part. (I noticed some flickering in Commando though)

[+OLD CS1]

Ain't seen that one before. My guess would be failing character ROM since it only affects built-in characters and not graphics. If it is socketed try re-seating it.

 

YMMV, void where prohibited, results not typical, and consult with your doctor.

[shoestring]

Looks like a bad character rom to me too. I've had a very similar issue.

 

There's some troubleshooting you can do by typing in this short basic program.

 

http://www.devili.iki.fi/Computers/Commodore/C64/Programmers_Reference/Chapter_3/page_110.html

 

The above program will copy the character set from the ROM into RAM, then type the following.

 

POKE 53272,(PEEK(53272)AND240)+1

 

The flickering should stop because you are now mapping the VIC2 chip to use the character set from RAM but you will still have some corrupt characters.

 

Type in the following to change the letter T to a smilie face.

 

10 FOR I=12448 TO 12455: READ A:POKE I,A:NEXT
20 DATA 60, 66, 165, 129, 165, 153, 66, 60

 

 

here's an example..[ note every character has a line through it ]

 

 

 

After reprogramming the letter T to a smilie face [ note.. no line through that character ]