Hello again - I hope it's ok to keep the subjects separated in different threads.
I have tonight put together my Apple monocrome monitor - filter caps had gone - and unfortunately I still experience the same weird graphic issues I was observing on my LCD monitor. It looks like one vertical line is missing.
Please see below, can you help me? I believe the switch on the motherboard is set to monocrome (it doesn't say which is which but in this mode it seems more suitable for the screen).
Text mode seems ok.
I'd be checking your RAM. Seeing as it likes to appear in both text and HGR, not sure what else they share in common.
Hi Spectre,
Text is fine. What you see above is - I believe - text in graphic mode. See below for an actual text screen.
I re-seated the IOU chip yesterday after checking the repair guide but it didn't change things.
IMG_0684.JPEG
IMG_0685.JPEG
It's most likely either bad RAM or a bad IOU chip, or a cold joint on a RAM chip or the IOU socket. I usually see issues lie this on the ][+, not the //e.
The Apple Dealer Diagnostics disk has them. I may be posting a new image of that soon to the asimov database, that strips the copy protection nonsense. IDK if the version on Asimov is protecte, or not, but the protection is not difficult to circumvent, as it is in the actual ProDOS kernel and disk bootstrap code.
There are other good testing utils on Asimov:
https://ftp.apple.asimov.net/images/disk_utils/diagnostics/
XPS is a good one, as I recall. MECC Computer Inspector and Apex II are good, but XPS was specific to the //e.
I also suggest reading this:
Apple II Plus and IIe Troubleshooting and Repair
Start at page 158 (155 of the PDF file itself).
P.S. Looking at the highlight of 'View Readme' on your ProDOS bsty boot screen, the INVERSE text suffers from the same atefacting as your GFX mode video. It should be a solid white background with dark text.
Hello Timelord,
Good catch, so it seems that there is a line missing at the end of everything!
I have tested the system with MECC, XPS and Apple diagnostic.
The 80-col/64K board is being marked as BAD by MECC (Error 04/01158F) and Apple Diagnostic test. However the latter marked the board as faulty this morning but not now and not yesterday. XPS says it's fine.
Main memory is marked OK by everything.
XPS says that Rom C0 and E0 are bad...
XPS also seems to suggest that one of the drives is weaker as over a number of tests it failed on a couple of sectors while the other drive - same media - did not. The same drive also showed a "speed error" but only once. Both drives were adjusted and speed is ok so maybe this is an intermittent issue or a glitch.
I have removed the 80-col/64K board to test but the graphic glitch is still there.
I am a tinkerer when it comes to electronics but one of the reasons I got this Apple // is to enjoy repairing it so I'd like to take a rational approach and study how graphic is generated. Once I know that, I'd like to probe the relevant lines to observe the issue and hopefully come to a solution. I'll start reading up on the guides!
I've also tested the memory using some lines of code under Monitor that I found on this forum and all seemed ok.
Quick update:
I went ahead and did some soldering on the 64K/80-cols card as one socket had been previously BADLY reworked (first picture). I changed that socket and re-seated all chips, which don't look in great shape to be honest.
I'd say there is no change. A question for you is: how much should I trust those software tests? Since not 100% of software is telling me there is an issue, I don't want to chase ghosts here. The picture issue is there anyways, 80-column mode seems to be working and AppleWorks seems to be working ok.
Thanks!
IMG_0697 (Small).jpeg
IMG_0701 (Small).jpeg
IMG_0702 (Small).jpeg
Another update. I am reading up on how the system works and also found another thread about the very same issue
https://www.applefritter.com/content/text-not-appearing-correctly-apple-iie
I have removed, cleaned and re-installed my memory chips - shifting them by one position. The line is still there and it's in the same position. So I doubt the memory is at fault EVEN THOUGH I noticed that two modules have been already replaced with faster chips, which I read around is not recommended.
My next step is to probe the Video bus, I expect to find a dead line there (the black line on screen) and then I'll move to find out whether it's coming from the ROM (as in the previous link) or it's due to an issue with 74LS374, IOU, 2732 or 74166.
More tests. I've moved the Apple //e on my workbench and started poking with the scope. Let's say I am not a massive expert when it comes to electronics but I love it and I love learning things. I have checked the video area and so far I haven't seen anything massively out of the ordinary - I thought I found a dead video bus line but it turned out my drawings are incorrect! :) My board is a 820-0073-A which appears to be an "early Apple //e PAL" as on this link https://finapple.hho.fi/finapple/index.php/2019/01/12/apple-e-early-pal/ does anybody know where to find the correct drawings for it?
Can someone also please confirm that the "2732 carachter generator rom" is indeed the "Video rom" on the board? It is not clear on the Troubleshooting and repair guide. I have followed all the traces and I do have continuity in between the chips as per drawings.
One issue I have is that my scope is an old analogue one and it's not easy to see digital data with it - you see whether there is something happening but that's it :)
Any ideas, please let me know! :)
https://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Books/
Have a look at Jim Sather - Understanding the Apple IIe.pdf and Sams ComputerFacts - Apple IIe.pdf
Before you spend an absurd amount of time on this, desolder the RAM, install sockets, install a set of fresh 4464-150s.
Thanks Timelord - I am indeed educating myself on how the system works.
The "absurd amount of time" is to be honest great fun for me so it's not a big deal, it's one of the reasons I got this system, to learn and hopefully repair it! But yes, I see your point!
All IC's on my motherboard are socketed - how lucky I am! They seem not to be the best sockets though as IC's do not slide in easily.
I was indeed thinking of buying a set of RAM chips - I'm sure I'll need some at some point. Please see my other post where I mention that my current RAM chips are 8264 - a mixture of 150 and Apple genuine 200. Would a set of 4464 work ok? Would 8264 be a better choice so I can keep the ones I removed as spare?
Both 4464 and 8264 are fine. Use a a fully-matched set of eight, same manufacturer and speed.
No //e was sold with mixed RAM ICs on the mainboard, so I suspect that this has been repaired before, possibly wrongly.
As your RAM is socketed, you could also 'shuffle it'. Move ICs around and see if it affects this. If you have loose 64x8 RAM ICs, you can try swapping them one at a time, but a full net set at the currect speed is cheap, and a wise way to save energy. |
While I admire learning in general, in this field, it is also crucial to learn that spendiing extraneous time in diiagnostics overall, is unwise. If you have a ssimple solution to use as a test, try that first. Likewise, if you have a workiing system, swap in the IOU and see if it changes anything. One bad RAM IC has a compound effect on every aspect of the system.
Hi Timelord
Yes, the system must have been repaired before as the two different memory chips don't have an Apple logo on them - all the others do.
I have already shuffled the chips - I believe I mentioned it on this thread. I shifted them all one position but the line did not change position.
I completely appreciate your advice and indeed if I were to repair this unit professionally the fastest way would be the best way. However, I am very keen to improve on my electronics skills so studying the schematics and poking around with my scope one way to learn things. Anyways no, I do not have any spare parts available.
I did some more studying and more poking today. All the memory lines are doing something and all the lines involved into video are also active - that is, not stuck low or high. I also made sure that all RAM chips had continuity to the LS 374 - and the LS374 to the IOU as I now understand how the memory works on the Apple //e and I see why a bad joint may cause this issue. Everything checks out ok.
This comes from a not very competent person but I begin to suspect the Video ROM. I have a ROM burner coming for other projects anyway so I will be able to test.
Thanks again for your continued help! :)
The video ROM is responsivle only for text generation. It is RAM, IOU, or a broken VIA.
Ok, It looks like I need to study more even though on the thread below a user had the same identical issue which was solved by swapping the ROM. It could be a coincidence of course.
https://www.applefritter.com/content/text-not-appearing-correctly-apple-iie
I read that the Video rom has a section of straight-through bit mapping for the graphic modes and the Video bus indeed goes through it. I wonder if that mechanism could go wrong and affect all modes somehow. Again, just thinking aloud.
Do you have a second system mainboard? If so, you can use it to shift parts and test them.
Unlike earlier Apples with a CHARGEN ROM, the Video ROM on the Apple //e IS also used for graphics. If you've already verified that the LS166 at location F5 is working, then it's most likely the video ROM or IOU causing your problem.
Timelord,
No, I don't have it.
Jeffmazur,
Interesting, thanks.
Hi all
Just to follow up, the issue turned out to be the 166 shift register. As recommended, I could see all lines in being active but I could see a pixel missing on the serial out.
Thank you for all the ideas!!
Now I am on stabilising the picture on screen - I see online people regularly using LCD monitors with the apple so I am confident it can work. Another challenge. I'll make a video and post it here!
IMG_0828.jpeg