Apple III screen output issue.

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Apple III screen output issue.

Hello.

I'm new to this site and relatively mew to vintage Apple computers in general. My family was a Commodore household growing up, mainly because of price. Like many other 80's households, we progressed from an "affordable" Vic-20 to a Commodore 64 to an Amiga 500, until conforming to a dreaded 286 MS-Dos-based computer in college. But I always envied a high school buddy of mine who had an Apple IIe, color monitor and two disk drives. (I can still picture him playing Ultima IV and Bard's Tale on it.) I liked my Commodore 64, but I really wanted that Apple.

These days I enjoy collecting vintage computers as a hobby. Like other enthusiasts, I do garage sales, check craigslist, etc. Anyway, a few months ago I was driving after dropping my kid off at soccer practice and I see an old computer sitting by the road next to a trash can. Score! It turns out to be an Apple /// computer, monitor, second drive and printer.

After cleaning it up and plugging everything in (while shrugging off the crazy looks my wife is giving me), the darn thing works. I get an arrow prompt.

Excited, I get a serial cable, order some DS/DD diskettes and download ADTPro, ready to start my first bootstrapping process from "bare metal."

When the diskettes finally come in, bad news. I turn everything on and get scrambled characters on the screen. The computer seems to be booting up fine. Drive still grinds. I still get the beep from the key sequence. I can even sort of see the blinking cursor, but I am getting a bunch of random characters on the screen.

At first I think it's an issue the monitor, so I plug the computer into a Commodore 1702. Same thing. It doesn't seem to be the monitor.

Anyway, still hoping for my first working Apple computer. I admittedly have very limited technical knowledge and ability but would love to try to get the thing up and running again. Any advice?

Thanks in advance!

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Re: Apple III screen output issue.

reseat the chips?

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Re: Apple III screen output issue.

+1 for reseating chips.

Since you don't have any disks, you could try writing and running a few simple programs to determine what kind of state the CPU is in. Since the speaker is still beeping you could write a program that beeps the speaker regularly, or changes pitch. Not really familiar with the Apple ///.

I feel like an ass, but I have a small twinge of satisfaction that your brilliant find turned out to be troublesome. I'll be lucky to find a DVD/VCR combo lying around on the street - finding an Apple /// is like winning the lottery. Why can't I be that lucky?

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Re: Apple III screen output issue.

Cool find.

Don't understand the Bard's Tale and Ultima story, though. The C64 versions were far superior...

(ducking)

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Re: Apple III screen output issue.

Well done on your find.

I would definitely check the ram chips

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Re: Apple III screen output issue.

Thanks for the replies. I really appreciate it. I'll try reseating the chips and will come back with an update on any progress.

I agree that it was a completely lucky find on my part. It was the first time I have found anything like that "in the wild." I look forward to working on it and learning some things.

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I need help.

Repairing this Apple III is beyond my expertise.  I’m also worrried that I am making things worse.  

 

Any suggestions?  I’d really like to see this thing working.  

 

Does anyone repair these things as a hobby?  

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Personally, I've never even

Personally, I've never even seen an Apple /// in person, however, on an Apple ][ the problem you describe could be indicative of an issue with either RAM, ROM or the processor.  Unfortunately, to my knowledge, the Apple /// lacks any form of Basic in ROM, so testing is going to be difficult, but there is a possibility.  Try bootstrapping ADTPro.  If it works, but the characters are still screwy, then your problem is likely an issue with whatever ROM the keyboard characters are stored in, or possibly the keyboard encoder.  If it works, and the characters return to normal, then this might be normal behavior for the Apple ///.  If it doesn't work at all, then your problem is likely something else.  You'll need a proper serial cable for this and a USB adaptor.  You can look up the bootstrap procedures at the ADTPro website: www.adtpro.com

Earlier Apple ///'s used 12v RAM that had a tendency towards overheating.  Later ones used 5v RAM that was slower, but more reliable. In either case, usually reseating the RAM fixed the problem.  Infamously, Apple actually told their customers (back in the day) to lift such machines a few inches off the surface and drop it to reseat the chips.  Personally, I would stick to a chip puller or a screwdriver, and manually work each chip partly out of the socket, and then push it back in.  I haven't been able to find out what RAM chips were used, but odds are that information is out there somewhere, and the chips were likely generic.  Meaning that replacements shouldn't be too hard to find.

Also, should this turn out to be the processor, then the good news is that it's a simple 6502A.  Which is not only readily available but even still made to this day.

Given the collector's value of that machine, however, my suspicion is the ROM, as that would be the most frustrating to diagnose.  You don't usually throw something like that away is there's a chance in hell that you can fix it.  The good news is that, if does turn out to be the ROMs, new ones can be programmed to take their place.  

Good luck with your repair, and congratulations on finding such a rare machine!

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Thanks for the reply.

Thanks again. 

 

I've done a lot of what you suggested.  I obtained a serial cable, DS/DD diskettes and downloaded ADTPro.  I tried resetting the chips and other things, based on advice here a year or two ago.  I even ordered some replacement chips.  I did it all very poorly and I'm worried that the method I used actually made the damaged some of the chips.  At this point, I have very little confidence in my ability to diagnose the problem or fix the problem if I was even able to diagnose it.

Heck, I even went to one of the local retro arcades and spoke to the guy if he knew anyone who would attempt to repair an Apple III.  He didn't know of anyone.

So I'm stuck with this great piece of computing history sitting on a shelf with no idea how to fix it.  It looks really cool, but I'd really like to get it in working order.

I'd pay someone to fix it or walk me through how to try to fix it.

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http://www.arcadecomponents

http://www.arcadecomponents.com/repairservices.html

I have never used them, and I don't know if they have any experience with or the parts for an Apple ///, but you can ask.

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Re: Apple III screen output issue.

If you haven't already, you might want to check out the Apple /// Enthusiasts Facebook group - there's a lot of people over there with repair knowledge that might be able to help you out. https://www.facebook.com/groups/appleiii/

 

 

 

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Thank you.

I will add that the computer turns on, on light lit, floppy drive runs when a key is hit.  You can see the blinking cursor on the screen, but the screen is a jibberish pattern of dots.  

 

Ctrl-OpenApple-Reset and then hitting Ctrl G gets you beeps.

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Sounds like a RAM problem to

Sounds like a RAM problem to me.  Loose RAM chips and/or seating of the RAM board is a common issue on the ///, especially early units.

 

 

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https://www.youtube.com/watch

https://www.youtube.com/watch?v=5qMP6A_U75E&t=84s

Check out this video.  It might hold some of the answers you're looking for. Go to time index 10:22 and see if the screen image is familiar. If so, then there might not be anything wrong.  Apparently, without a disk, the Apple /// boots to a diagnostic mode, and a passing screen looks a lot like what you're describing.

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The screen looks more like this.

https://www.applefritter.com/files/20180423_193013.jpg

But you can see the blinking cursor.

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character generater ram problem?

It looks like it could be something to do with character generater ram. The Apple /// has loadable fonts, and these need to be loaded for the text display to work correctly. Did you reseat the chips under the RAM board? I think the character rams are under the ram board.

 

If you had some other way to make apple disk images, then trying an Apple /// program that booted up into graphics mode would be a good test.

 

/Rob

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I’ll give it a try again re: reseating.

I ordered some Apple III games disks to test the second idea.

Edit:  There’s s a map of the motherboard on page 32 of the following:

http://apple3.org/Documents/Manuals/Sun%20Remarketing%20Do-it-yourself%20Guide%20for%20the%20Apple%20III.pdf

From a google search:

Having deduced your primary RAM bank is functional then iis a video issue. Specifically the character generator is being fed bad data bits.

 

Looking at the schematic the Apple III uses two 2114 static RAM chips as a programmable character generator, their data inputs are fed by two 74ls374's (octal latch) without looking deeper into the circuit I assume one of them is used to program the RAM with the character data and the other by is fed by the video RAM to display what is in video RAM.

I'd be looking closely at those 374's at E2 and F2

Here's the Video Logic schematic:

http://apple3.org/Documents/Schematics/Video%20Logic.jpg

Does that sound about right?  Any help in troubleshotting, fixing or identifying the character ram chips is greatly appreciated!  

 

Seond edit:

 

The following seems to be getting somewhere: 

https://mirrors.apple2.org.za/ftp.apple.asimov.net/documentation/apple3/service_reference_manual/Apple%20III%20Service%20Reference%20Manual-OCR-1982.pdf

 

From page 315:

By far, the most likely candidates, are the 74LS374'a, located at E2, F3, F2, F3, G2, & ClO. These IC's are the cause of >70% of the video problems.
Itisalsoagodideatocheckthetwo214'slocatedatE4andE5.
The next moat frequent failure is the 74LS153 at LB. This is U90 as shown onshet5oftheschematic.
Video problems are also very likely to be misdiagnosed timing problems. For these check the 64Sl95 at DiO and the 74LS374 at Dli.
Ifthevideohorizontalorverticalsyncapearstobemesedup,checkthe 74LS161's located at F10, Fil, Gil, and G12.

 

If none of the above items point you toward the real problem, begin your troubleshotingonshet5oftheschematicwhere80%oftheproblemsocur, andifnecesary,goontoshet9wheremostoftheremainingvideoproblemB wilbefound.

Thanks again.

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Built in diagnostics

Have you tried the built in memory test?

http://www.apple3.org/Documents/Technotes/TA36769.html

 

 

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I reseated all the chips related to video on the schematic.

They were under the ram board.  I also switched the 4 74ls374's around.    

 

This actually altered the garbled screen to where I can make out the “retry” but there are still lines going down the screen.

 

 

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Sounds promising that you are

Sounds promising that you are onto something with those 374s.  I'd buy 4 new ones and replace them.  You could probably get away with just buying one, but they aren't expensive parts.

 

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I don't suppose you have a suggested link on where to purchase?

I'm a little discouraged at this point though. 

Late yesterday I reseated some additional chips thinking that it might clear up the video issue.  Plugged everything back in and got a burning smell. 

Now it won't attempt to boot at all now.  No video.  Nothing.  Argh.

I bought a chip extraction tool to pull the chips and minimize the bending/damage to the pins.  Am wondering if the tool actually pulled the chip mount off the board and somehow fried other stuff.

Frustrating.

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Check this out, it might help.

The following was posted in the 68k Mac forum under "Apple Chip IDs"

 

"Hello folks, some years ago Patrick Schaefer started to collect Apple chip IDs especially the ROMs. I found this collection and added some. This collection is now available (as part of a private wiki):

https://kb.pocnet.net/wiki/Apple_Chip-Bezeichnungen

You know some more IDs with leading 341- or 342- or you recognize an error? Please contact me.

Or leave a comment  if you have some better sources :-)

Regards,

Ralf"

(Sorry, I didn't know how to do a proper quote from or link to another thread in this one)

 

According to the site, the Keyboard Character Generator is the same ROM IC used between the Apple //e, //c, and ///.  If this is true, then it shouldn't be that hard to find a replacement.  The site also lists all the Apple-specific ICs for the Apple ///, as well as their functions.

 

Also, as for the burning smell, if your machine won't boot, then it might be an issue with the power supply.  You'll need to extract it and examine it for damage.  The good news is that typically they're easy to fix.

 

 

 

 

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