pball52998
Well-known member
Welcome to the club! Started with no knowledge of schematics/how an oscilloscope works.
Making my way slowly through it. It's a beast for sure, not as much out there as the ii
-
Updated 2023-07-12: Hello, Guest! Welcome back, and be sure to check out this follow-up post about our outage a week or so ago.
Apple /// questions
- Thread starter ried
- Start date
Making my way slowly through it. It's a beast for sure, not as much out there as the ii
ried
Well-known member
Could this be caused by faulty PROM chip(s)? Found an interesting video in the Apple /// Facebook group that shows a similar power on condition.
www.facebook.com
Log into Facebook
Log into Facebook to start sharing and connecting with your friends, family, and people you know.
www.facebook.com
ried
Well-known member
Ordered one. In part because I want to have a working Apple ///, yes. But an even bigger part of me wants to find out what the heck is indeed wrong with this machine. We shall find out.
pball52998
Well-known member
Ordered an extra apple iii? Got one off ebay/found another one locally?
ried
Well-known member
eBay. It arrived and works. When I have time I'll swap chips and hopefully figure out what's wrong with the first one. If I get lucky it'll just be one chip and an easy fix. If it's multiple chips, that's going to be a real PITA.
ried
Well-known member
It also complicates my effort to diagnose the first Apple /// board. I can't just swap out the ROM chips, for example, since 3 of the 4 on the second board have been replaced by the upgrade. I also don't want to mess with them too much, because if one of them goes... yikes.
So I may end up putting repair of the initial Apple /// on hold for now.
I think Pascal could use all the available memory. I remember an Apple II friend who loved the /// because he could have more memory for Pascal. I don't know if that was native, or Pascal in the Apple II emulation. It _was_ a long time ago
Very cool! If anyone else can remember an use for all of this memory, I'd love to hear about it.
CC_333
Well-known member
Probably, but a standard Apple ///'s II emulation is intentionally crippled by restricting RAM to 48k or something like that.
If I understand correctly, II emulation was implemented, restrictions and all, in hardware, and is thus virtually impossible to "fix" via ordinary means, but maybe this upgrade finds a way?
c
ried
Well-known member
The On Three 512K Memory Board User's Guide is available online, and it reads "By using the included update programs, almost all of your Apple Ill programs will be able to directly use the extra memory afforded by the 512K memory board."
3 disks were originally delivered with the upgrade, and one of them, "Apple III 512k Memory Test.dsk" is available at the same website. I have not found the other 2 disks yet.
The user's guide also indicates that "Part of the 512K Memory Upgrade consists of a new disk drive for your Apple Ill, a RAMDISK. The RAMDISK driver allocates 140K of your Apple ///'s memory and uses it as a very fast electronic disk. The RAMDISK is optional, so if you want to have a lightning fast disk drive, you can!"
3 disks were originally delivered with the upgrade, and one of them, "Apple III 512k Memory Test.dsk" is available at the same website. I have not found the other 2 disks yet.
The user's guide also indicates that "Part of the 512K Memory Upgrade consists of a new disk drive for your Apple Ill, a RAMDISK. The RAMDISK driver allocates 140K of your Apple ///'s memory and uses it as a very fast electronic disk. The RAMDISK is optional, so if you want to have a lightning fast disk drive, you can!"
Tallyappleiii
New member
Oh man. I finally found someone having the same problems with their Apple III. Would love to know the answer if you ever figure it out.
I get the same garbled screen.
I get the same garbled screen.
ried
Well-known member
Working on it. I did find another (third) logic board that I'll try swapping chips with, and it should arrive next week. Will keep this thread updated.
Side note: Someone reached out to me about dumping the PROMs from the unit featuring the 512K memory board by On Three. I do not have any experience with that, but am happy to work with someone local to me (San Diego area) who might like to do so for benefit of the community.
ried
Well-known member
Well, it's fixed. The original Apple /// that started this thread. I received a donor board yesterday that's in so-so condition, but good enough for chip swaps, so I replaced all four of the PROMs near the CPU as well as every IC on the board that looked better / less corroded than mine. Probably about 30 or 35 chips, in total.
Powered it on and it was in the same non-functional state as before. Hmph.
As a Hail Mary, I swapped the 6502 CPU and that fixed it.
So, the original CPU was not working properly and that caused the power on state to look like this:
I pulled and cleaned each and every chip on the board, cleaned everything with alcohol and Deoxit several times, installed a replacement memory board and new all 5v RAM chips, eventually swapped corroded ICs and... no change until I finally swapped the CPU.
I'm glad it's fixed - currently running the Apple /// demonstration disk from its slightly squeaky internal floppy drive.
This is the only computer I've been so frustrated by that I actually started to dislike the machine. I wanted to toss it, but at the same time could not give up, hoping the solution would arrive eventually. I'm disappointed that it was something so simple, too. I wanted to feel a sense of accomplishment after all that, like "Whoa. Can't believe I figured that out." But now I'm thinking to myself "Oh... duh. Should have done that sooner."
I know some others have encountered this issue when powering on the machine. Some have fixed it with swapping PROMs. Try the 6502 CPU, too. Save yourself the trouble.
Fixed 256K unit running on the right.
To add insult to injury, just after that photo and as I finish writing this update, the thing just popped another RIFA cap! I thought I changed all of them in its power supply...
I do not love the Apple ///.
Powered it on and it was in the same non-functional state as before. Hmph.
As a Hail Mary, I swapped the 6502 CPU and that fixed it.
So, the original CPU was not working properly and that caused the power on state to look like this:
I pulled and cleaned each and every chip on the board, cleaned everything with alcohol and Deoxit several times, installed a replacement memory board and new all 5v RAM chips, eventually swapped corroded ICs and... no change until I finally swapped the CPU.
I'm glad it's fixed - currently running the Apple /// demonstration disk from its slightly squeaky internal floppy drive.
This is the only computer I've been so frustrated by that I actually started to dislike the machine. I wanted to toss it, but at the same time could not give up, hoping the solution would arrive eventually. I'm disappointed that it was something so simple, too. I wanted to feel a sense of accomplishment after all that, like "Whoa. Can't believe I figured that out." But now I'm thinking to myself "Oh... duh. Should have done that sooner."
I know some others have encountered this issue when powering on the machine. Some have fixed it with swapping PROMs. Try the 6502 CPU, too. Save yourself the trouble.
Fixed 256K unit running on the right.
To add insult to injury, just after that photo and as I finish writing this update, the thing just popped another RIFA cap! I thought I changed all of them in its power supply...
I do not love the Apple ///.
Last edited:
ried
Well-known member
Thank you, @Byrd! I'm just glad this one's done and dusted.
The 5MB ProFile drive also gave up the ghost at some point in the last few days. No more steady red status light, and a bit of a metallic screeching sound from the inside. Shoot, I was hoping to find out what (if anything) was on it.
And so, the cycle repeats. The circle of life... or something like that
The 5MB ProFile drive also gave up the ghost at some point in the last few days. No more steady red status light, and a bit of a metallic screeching sound from the inside. Shoot, I was hoping to find out what (if anything) was on it.
And so, the cycle repeats. The circle of life... or something like that
pball52998
Well-known member
Good stuff on getting it to work!
I hope I'll get there someday..
Maybe I'll win/find a donor board and really get going!
What 5v ram chips did you use? Model no?
I need to probably replace all of mine..
I hope I'll get there someday..
Maybe I'll win/find a donor board and really get going!
What 5v ram chips did you use? Model no?
I need to probably replace all of mine..
Similar threads
