Mr. Do vertical lines

Here is a better picture to show the problem the letter t gets cut off in the diagnostic screen.

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By the way, the diva gnostic said cpu1 & 2 OK and all roms OK
 
I tried using a rgb->VGA converter and hooking up a different monitor but the lines are still there and are more prominent.

1c7f63ac.jpg


I also took out the pcb. No signs of bad capacitors.

I believe this is what it is supposed to look like
0f21c506.jpg
 
I tried using a rgb->VGA converter and hooking up a different monitor but the lines are still there and are more prominent.

1c7f63ac.jpg


I also took out the pcb. No signs of bad capacitors.

I believe this is what it is supposed to look like
0f21c506.jpg

I have the same problem with a different game and I think it is a ram problem. When I cleaned the area near the ram on my board it went away for a short while and then came back.
 
I would try to reflow the solder to the connections before I start replacing the parts. Looks like the one at C/D on pin 4 could use a bit more solder. Piggy back a new part on them chips won't help if they do not make a connection. At least check the connections from top of chip to the trace.

Good call.

Here is what the manual says;

Five of these:
MB8128-150 NMOS 16k bit static RAM access 150 nsec

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One of these:
Mb8128-100 NMOS 16k bit static RAM access 100 nsec

542faef6.jpg
 
Wow! Thanks, I will! Any other tips?

Well I fixed mine.

I put in the kitchen sink, while the kitchen dictator was out, and ran hot water all over the component side. Then put dish soap on it and scrubbed lightly with a soft brush so it would not move any of the frail components. I did this for about 2 mins and while rinsing with hot water. Dried it with hair dryer set on high fan and med to high heat. Dried it really well and finally put some extra heat on the interconnect pins. Plugged it in and voila, I no longer have the vertical streaks. This was obviously a connection problem and was an easy fix. Out of 3 boards I tried this on, 1 worked. So I am not real sure it is a ram problem as much as a connection problem.
 
I reflowed all the ram connections for connectivity and they all tested ok. I powered up the board and still have the same problem. I removed and reseated all the ROM chips I Also cleaned the entire board and still no luck. I think the diagnostic mode tests 3 of the 5 ram chips (according to the manual) with 12 test tones at 3 different pitches all 12 tones for each pitch beeped.

That makes me think it must be one of the 3 ram chips that are not specified as part if the RAM test. One has a lower access time 100ns instead of 150 so I would assume that chip is the video ram. Should I try replacing that one first? Any other tips?
 
I reflowed all the ram connections for connectivity and they all tested ok. I powered up the board and still have the same problem. I removed and reseated all the ROM chips I Also cleaned the entire board and still no luck. I think the diagnostic mode tests 3 of the 5 ram chips (according to the manual) with 12 test tones at 3 different pitches all 12 tones for each pitch beeped.

That makes me think it must be one of the 3 ram chips that are not specified as part if the RAM test. One has a lower access time 100ns instead of 150 so I would assume that chip is the video ram. Should I try replacing that one first? Any other tips?

You can go faster in access times just not slower. 100ns = faster than 150ns. Some times it is the same price or lower for faster chips but not always.

Now would be the time to get some ram chips and piggy back one on top of each until it clears up. You might buy some extras and have some on hand to justify shipping unless you can get some local.
 
You can go faster in access times just not slower. 100ns = faster than 150ns. Some times it is the same price or lower for faster chips but not always.

Now would be the time to get some ram chips and piggy back one on top of each until it clears up. You might buy some extras and have some on hand to justify shipping unless you can get some local.

What do you mean by piggy back on top of each unit? Don't I have to desolder each chip I am trying to replace?
 
What do you mean by piggy back on top of each unit? Don't I have to desolder each chip I am trying to replace?

This is a tech trick but you have to be really careful and have some way to see the video screen or have an assistant. It is just like it sounds, you piggy back good ram chip right on the suspect ram chip and when garbage clears up, you found the bad chip.

EDIT:
Copied this from a search and cut it down to this and explains method much better.

The piggyback method requires that you install the test chip
over a board RAM chip so all pins make good contact and no pins
short together. The test chip must be oriented correctly as well.
There is a notch or dot (or both) on one end of those ICs. Those
markings must line up because if the test chip is installed
backwards, it will likely be damaged when power is applied. You
can press the test chip pins against a tabletop to push all pins
inward slightly, and that will provide some spring tension when
the test chip is inserted over the board chip and can hold it in
place. It's OK if you want to hold the chip with your fingers and
then power up the computer. There is only five volts present and
therefore absolutely no danger of electrical shock. Again, if the
bytes free number changes, that board IC is probably bad and
should be changed. If there is no change when all RAM is checked,
suspect the two RAM control logic ICs mentioned above. They must
be replaced to diagnose a problem there.

here is the page this came from

http://personalpages.tds.net/~rcarlsen/cbm/memory.txt
 
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Oh, it is exactly as it sounds. I thought this would just add to the available ram and the bad chip would still be used Thanks!
 
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