Commodore.ca: The PET, VIC, 128, 64 & More Forum

Hello, replaced the missing C25 by a new one and direct a different image on the 9" screen.
Again for one second a screen full of numbers, and then bright vertical static lines.
Will someone have any idea what is wrong ??
Thanks for any imput.......

1) Are the "numbers" properly formed, centered, and look about like they should for a PET warm start?

2) Look closely to see if the vertical lines run right through the characters. Do they? Are they perfectly vertical and straight without overscanning to the edges of the bezel?

3) Does typing SYS64795 bring them (numbers) up again momentarily?

4) With the CRT powered momentarily - only the brown wires connected to the CRT - are the lines there?

5) Um 9" 4032... Did this board have the (Um, 654x?) CRT controller?

Yes to 1 - video ram, dot generators, and character ROM prolly ok.
Yes to 2 - character rom prolly bad.
Yes to 3 & 4 - bad CRT analog board.
Yes 3 & 5, no 4 - bad CRTC IC? Guessing.
Yes 1, no 3 - Bad main ram, bad PIA, bad CPU. bad any ROM.

Whatcha got for diagnostic tools? Got a logic probe? What ROMs are socketed, and in what positions (904xxx-xx in socket Ux-x) ?

j1mt3hcop13rwr3nch wrote:1) Are the "numbers" properly formed, centered, and look about like they should for a PET warm start?

2) Look closely to see if the vertical lines run right through the characters. Do they? Are they perfectly vertical and straight without overscanning to the edges of the bezel?

3) Does typing SYS64795 bring them (numbers) up again momentarily?

4) With the CRT powered momentarily - only the brown wires connected to the CRT - are the lines there?

5) Um 9" 4032... Did this board have the (Um, 654x?) CRT controller?

Yes to 1 - video ram, dot generators, and character ROM prolly ok.
Yes to 2 - character rom prolly bad.
Yes to 3 & 4 - bad CRT analog board.
Yes 3 & 5, no 4 - bad CRTC IC? Guessing.
Yes 1, no 3 - Bad main ram, bad PIA, bad CPU. bad any ROM.

Whatcha got for diagnostic tools? Got a logic probe? What ROMs are socketed, and in what positions (904xxx-xx in socket Ux-x) ?

Thanks again for you advice j1mt3hcop13rwr3nch.

I will have a look and try to see if i can answer your questions.
I do not have a diagnostic tool, i can only see if a part has current on it and how much.

Hi j1mt3hcop13rwr3nch,

Her my answers:

Are the "numbers" properly formed, centered, and look about like they should for a PET warm start?
A) No random

2) Look closely to see if the vertical lines run right through the characters. Do they?
A) No, the characters stay for one sec. then the lines.
Are they perfectly vertical and straight without overscanning to the edges of the bezel?
A) Yes, perfect straight, no overscanning, 40 of them.

3) Does typing SYS64795 bring them (numbers) up again momentarily?
A) No

4) With the CRT powered momentarily - only the brown wires connected to the CRT - are the lines there?
A) No, when i pull J7 lines are gone.

5) Um 9" 4032... Did this board have the (Um, 654x?) CRT controller?
A) No

Yes to 1 - video ram, dot generators, and character ROM prolly ok.
Yes to 2 - character rom prolly bad.
Yes to 3 & 4 - bad CRT analog board.
Yes 3 & 5, no 4 - bad CRTC IC? Guessing.
Yes 1, no 3 - Bad main ram, bad PIA, bad CPU. bad any ROM.

Whatcha got for diagnostic tools? Got a logic probe?
A) No, No
What ROMs are socketed, and in what positions (904xxx-xx in socket Ux-x) ?
A) ROMs are 901xx not 904xx
UD9 - UD8 - UD7 - UD6 - UD5 is different, has a high part in the middle.
UD4 nothing - UD3 nothing - UD2 is soldered direct to the board.

Hope this will help.........

Hmm. I'm confused.

Sorry, but you're really not being clear enough regarding the symptoms. Some of my questions were intended to see if the computer was actually working, and it's still not clear.

40 straight vertical lines on a working computer suggest either a bad character generator - or even a pin not making good connection at the character genny socket - or something in the dot generator circuit, (one of four 74LS244's, two 74373's, or one 74166 near the character generator) but this would mean the lines would usually always be there - and with close inspection, you'd see them on the startup overlayed on the random characters too, and over the "*** COMMODORE BASIC... ***" screen "cutting" through the characters. Everything would respond normally though. Ie: you could type a program and run it even with the lines there. Is this in fact the case?

Definately on the board though. this isn't an issue with the CRT board.

UD9 - UD8 - UD7 - UD6 - UD5 is different, has a high part in the middle.

I don't have a clue as to what you mean. My intention was to see what rom set you had and were they in the correct sockets, this means what number in what socket.

Are the "numbers" properly formed, centered, and look about like they should for a PET warm start?
A) No random

Well yeah, But are they FORMED correctly.

Hi j1mt3hcop13rwr3nch,

Sorry i am not clear, english is difficult to make electric issues clear, but i will have a new try this week.....

j1mt3hcop13rwr3nch wrote:Hmm. I'm confused.

Sorry, but you're really not being clear enough regarding the symptoms. Some of my questions were intended to see if the computer was actually working, and it's still not clear.

40 straight vertical lines on a working computer suggest either a bad character generator - or even a pin not making good connection at the character genny socket - or something in the dot generator circuit, (one of four 74LS244's, two 74373's, or one 74166 near the character generator) but this would mean the lines would usually always be there - and with close inspection, you'd see them on the startup overlayed on the random characters too, and over the "*** COMMODORE BASIC... ***" screen "cutting" through the characters. Everything would respond normally though. Ie: you could type a program and run it even with the lines there. Is this in fact the case?

Definately on the board though. this isn't an issue with the CRT board.

UD9 - UD8 - UD7 - UD6 - UD5 is different, has a high part in the middle.

I don't have a clue as to what you mean. My intention was to see what rom set you had and were they in the correct sockets, this means what number in what socket.

Are the "numbers" properly formed, centered, and look about like they should for a PET warm start?
A) No random

Well yeah, But are they FORMED correctly.

middle.[/quote] I don't have a clue as to what you mean. My intention was to see what rom set you had and were they in the correct sockets, this means what number in what socket.


hello j1mt3hcop13rwr3nch, sorry it took a while to reply......

When i startup the PET i DO NOT get the Commodore Basic screen, just for a second a screen full of numbers and then the 40 vertical lines.
The 40 lines are on the screen nothing else and in the first second just the numbers, no lines.
The numbers are properly formed, centered and i do not know what a PET warm start is, sorry......but it is just a split second.

Here the numbers of the chips on the sockets:
UD5 901465-23
UD6 901465-20
UD7 901465-21
UD8 901447-29
UD9 901465-22

UC4 6502 MPS
UC5 MPS 6522
UC6 8622-9
UC7 8622-9

UF10 901447-10

Hope this is better info for you........

Thanks for your effort !