VIC20 colours off & checkered image

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mrr19121970
Vic 20 Nerd
Posts: 873
Joined: Tue Jan 19, 2016 9:22 am
Location: Germany
Occupation: IT service manager

VIC20 colours off & checkered image

Post by mrr19121970 »

Did anyone see an image like this before?

Image

Possible contenders?

http://personalpages.tds.net/~rcarlsen/ ... /vic20.txt

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UB7		6560-101	VIC	VIDEO/AUDIO
  White or blank screen, garbled or no video, screen full of (or few 
random) "garbage" characters. "Blind" disk commands may still work.
Partial failure: Dark or smeary image, loss of color, garbled or no 
sound, game paddles or light pen doesn't work.

UB9		7402 (M53202P)	OSC	MASTER CLOCK OSC
  White screen... no RF interference in AM radio (see text). Partial 
failure can produce missing color or incorrect colors, slight or severe 
tearing of picture or diagonal lines, sounds play at incorrect pitch. 
Symptoms may only appear after warmup.

UC2		74LS04		LOGIC
  Screen character colors incorrect (scrambled). If very bad, entire 
screen becomes garbled with flashing characters, vertical bars and 
random colors.

UD1 		CD4066		QUAD SWITCH (LOGIC GATES)
  (UC2 in very early version) Screen characters have incorrect colors.

UD2-UD6
UE1-UE6		2114 or TMM314A	SRAM	MEMORY
  Blank screen. Partial failure: less than normal "3583 BYTES FREE" at
startup, sometimes will produce "garbage" screen or screen freeze after
warmup. Shorted chips may get very hot. NOTE: UE1 is used to generate 
character color. 
VIC-I was swapped out and same symptoms.
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MCes
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Re: VIC20 colours off & checkered image

Post by MCes »

Old quartz becoms low frequenzy , try to trim che cap that fix xtal frequenzy clock that is used to color encoding
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." (Albert Einstein)
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mrr19121970
Vic 20 Nerd
Posts: 873
Joined: Tue Jan 19, 2016 9:22 am
Location: Germany
Occupation: IT service manager

Re: VIC20 colours off & checkered image

Post by mrr19121970 »

MCes wrote:Old quartz becoms low frequenzy , try to trim che cap that fix xtal frequenzy clock that is used to color encoding
Thanks, I passed on this info. It was right. Colour is now back after altering the trimmer.
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