Apple II Plus That runs, passes diags but has thin vertical lines

[VERAULT]

I am in the process of repairing one of the dirtiest and worst Apple II plus computers I ever saw. IT was tucked away in a corner and was essentially a mouse nest/Toilet. Replacement PSU, lots of Bad RAM replaced, Lots of TTL logic replaced and a replacement keyboard (borrowed from my other II plus). The unit is 95% working and done except for one problem. The display (regardless of what monitor I use, I have tried several) shows thin vertical lines that get brighter as the computer processes or uses the floppy drive. Here is the image of the bars prominent while it is doing something:
Here is an image of it idle:

I seem to recall something I read a long while back about some failing IC that would cause this, but I cant seem to find anything now on the issue, was it the 9334 IC perhaps? I dont know,
Let me know what you guys think

 

[rpiguy2]

Have you tried adjusting the video pot? Sometimes just adjusting it down can reduce vertical lines. Probably won't solve it since it sounds like something not properly isolating the 5v and/or 12v lines (not sure if the drives use both) from the video circuitry, but worth a try.

Also, of course, try running it without any expansion cards in it.

 

[VERAULT]

Which Pot as there are two, The color trim pot which is labeled "C3" for some reason and another towards the back of case which I believe is R11? I will try without cards

 

[iz8dwf]

I am in the process of repairing one of the dirtiest and worst Apple II plus computers I ever saw. View attachment 61587IT was tucked away in a corner and was essentially a mouse nest/Toilet. Replacement PSU, lots of Bad RAM replaced, Lots of TTL logic replaced and a replacement keyboard (borrowed from my other II plus). The unit is 95% working and done except for one problem. The display (regardless of what monitor I use, I have tried several) shows thin vertical lines that get brighter as the computer processes or uses the floppy drive. Here is the image of the bars prominent while it is doing something:View attachment 61585
Here is an image of it idle:View attachment 61586

I seem to recall something I read a long while back about some failing IC that would cause this, but I cant seem to find anything now on the issue, was it the 9334 IC perhaps? I dont know,
Let me know what you guys think

First of all: what revision is the actual PCB? Assuming a common Rev. 7, check UA3 ground connection on the socket or check for oxidized pins.
UB2, UA9, UB10 could be also involved, but less likely.
Frank IZ8DWF

 

[VERAULT]

Frank the board says 820-0044-D RFI and 606-X548

And it does the lines with all cards removed.

 

[iz8dwf]

Frank the board says 820-0044-D RFI and 606-X548

And it does the lines with all cards removed.

RFI is newer than the rev.7 I think it was the last Apple ][ revision (afair). The char dot shifter and the other chips should be in the same positions as in the Rev. 7, so the chips I suggested still apply.

Frank

 

[VERAULT]

Well The 74166 (ua3 Right) down near the char rom was faulty so I replaced it with one that tests good. I have pretty much been through every socket just for contact cleaning and troubleshooting.

 

[VERAULT]

Frank I will check the other IC's and sockets. Which IC is the Char dot shifter?

 

[iz8dwf]

Frank I will check the other IC's and sockets. Which IC is the Char dot shifter?

it is UA3, maybe check the char ROM outputs continuity to the UA3 inputs (you really need to look at a schematic for proper troubleshooting).
It could be also marginal char ROM or marginal socket, bad solder joints etc.

Frank

 

[rittwage]

That's bus activitiy leaking into the signal. The lines is down the middle of every character, so you'll have to track down what signal correlates with that, or just shotgun it. Normally the Apple II doesn't have what we call "jailbars" so that is a new one.

 

[VERAULT]

Ok Guys give me a little time to check these IC's. It is not an original Char Rom. Its a homemade job, and by the looks of the label and old one at that. So I will try a known good char rom as well.

Edit: While working on this unit I had some problems with Disk II interface cards (650-x104) I have one that havtuall has bad P5 and P6 Proms. Is this something I can burn another copy of? They are small 20 pins IC's

 

[iz8dwf]

Ok Guys give me a little time to check these IC's. It is not an original Char Rom. Its a homemade job, and by the looks of the label and old one at that. So I will try a known good char rom as well.

Edit: While working on this unit I had some problems with Disk II interface cards (650-x104) I have one that havtuall has bad P5 and P6 Proms. Is this something I can burn another copy of? They are small 20 pins IC's

They are 256 x 8 bipolar TTL PROMs.
https://www.mikesarcade.com/cgi-bin/spies.cgi?action=url&type=info&page=PromRef.txt

Here you should find a quite complete cross reference. I believe Apple used mostly the TI 28L22, but I don't see any reason why another
pin-compatible chip wouldn't work.
Now, the programmers that can actually program the old TTL PROMs aren't many. I do have one anyway.
Frank

 

[VERAULT]

They are 256 x 8 bipolar TTL PROMs.
https://www.mikesarcade.com/cgi-bin/spies.cgi?action=url&type=info&page=PromRef.txt

Here you should find a quite complete cross reference. I believe Apple used mostly the TI 28L22, but I don't see any reason why another
pin-compatible chip wouldn't work.
Now, the programmers that can actually program the old TTL PROMs aren't many. I do have one anyway.
Frank

Yep both of these are 28L22. Ill see what I can find as far as availability.

edit: So Something I saw got me thinking. I was looking at some posted ads for an apple II plus and check this out, it has lines as well This isnt my machine, its just a photo from one online.

I hooked up another of my II plus units (this thing is really dusty and oxidized but works fine and it has faint lines too I adjusted the monitors brightness and contrast to make it visible of course

So the One I am working with has very bad lines by comparison. Here is my question. Are these lines a natural degradation on all II Plus' (and possibly II's) caused by aging chips or oxidation/corrosion?

 

[VERAULT]

That's bus activitiy leaking into the signal. The lines is down the middle of every character, so you'll have to track down what signal correlates with that, or just shotgun it. Normally the Apple II doesn't have what we call "jailbars" so that is a new one.

Arent Jailbars the thick solid lines you would get if you pulled the CPU out for instance?

 

[VERAULT]

First of all: what revision is the actual PCB? Assuming a common Rev. 7, check UA3 ground connection on the socket or check for oxidized pins.
UB2, UA9, UB10 could be also involved, but less likely.
Frank IZ8DWF

Ok Frank. I have checked continuity on all these IC's and sockets. I already cheaned the pins when I was getting the board working but I deoxit'd the sockets as well. All sockets have continuity and the ohm difference between the board and question and my other II plus system is marginal. I also tried another PSU and a genuine character ROM. No change.

So I noticed on the bad line apple II there is a blank rectangle in the upper left corner (lines are much fainter)
But on my other ii plus the there are just two small squares where the lines are dimmer

 

[iz8dwf]

This is my Apple ][ (europlus), though the board revision I have is older than yours. This is cranking up the monitor brightness. I think I can barely guess some vertical bars in the picture, but in real life they're not visible. It might be a known artifact of the Apple ][ that I'm not aware of. I'm sure the signals must
be visible on an oscilloscope though.

Frank

 

[cjs]

I've got a friend who's running into this problem with an Apple II as well. Given that the problem doesn't occur with no expansion cards installed, and is particularly bad when the drive is running, we were reckoning a power supply issue. But we swapped that out with a modern Meanwell 4-rail PSU and still saw the same issue.

Looking at the various PSU rails, there was a lot of ripple when significant power was being drawn. Both the Apple and the Meanwell were at under 200 mV ripple when not plugged in. This went up to about a volt when plugging into the motherboard, 1.2 V with the Language Card installed, and over 2 V (!), about 4.5 - 6.5 V range, with the disks installed and one drive spinning.

I'm kind of feeling that this isn't about any issues with the video circuit, but that the video circuit may just be displaying symptoms of bad power that's affecting the entire system. I'm open to thoughts about how to further debug this.