Apple /// restoration

Only way I can imagine that resistor blowing up is if it was already damaged; it should never have enough of a voltage drop across it to cause that in this circuit.

As an aside, I think that Q9 in the schematic might have its base and collector pins reversed mistakenly. Don't have an Apple /// of my own to know for sure, but assuming KVCC is just used to power the keyboard lamp, I would expect it to be tied to the collector, and for R43 and the line from H12 (74LS257) to be tied to the base. Edit: assumptions, making an ass out of myself . Not sure where KVCC comes from on these but pin 10 on H12 is an input so the schematic does make a little more sense as drawn.

Glad to see it's showing some signs of life now and that the new oscilloscope is working better.

AwkwardPotato said:

Glad to see it's showing some signs of life now and that the new oscilloscope is working better.

Click to expand...

It's probably kicking and screaming as I take it through it's timing paces

But I'll be damned if it's not working! Just a few hiccups What's a fun project without hiccups though.

I'll admit, I took the whole thing apart, labeled every IC, and gave it a nice scrub, soap and water. It'll get another over in 91% IPA after it's dried for a bit.

Just some house cleaning as I now have to wait for IC / new resistors.

AwkwardPotato said:

Only way I can imagine that resistor blowing up is if it was already damaged; it should never have enough of a voltage drop across it to cause that in this circuit.

Click to expand...

Think so? I can see that. I don't think this machine would see differences so massive to blow it out. Especially since I'm using a new power supply / cable. Shouldn't throw anything weird I imagine.

I also had R86 blow, or at least look like it just split in half. Which would make sense why my sound doesn't work now.. whoops. Probably the problem, I'll get to sound when I get there.


From the sound and serial logic.

Dumb question though.

What is the risk of using the machine without those resistors? I assume it would just stop those specific circuits. In this instance things I don't care about at the moment. Sound and keyboard.


Those 2 resistors also I can't get the bands off of. When desoldering the real one that went boom, it basically crumbled to nothingness.

Looks like just a 1k ohm resistor for the kvcc, and a 1.1k for the sound

Sound


Keyboard is on previous page.

I imagine I could use a 1k for the kvcc is:
Brown, Black, Red, Brown. (I can see the last 2 bands red, brown barely on it)

The other one would on sound and logic 1.1k. All I can see on this one is middle brown then red.
Brown, Brown, Red, Brown

That seems right at least.

A deep clean is where I tend to start with faulty boards, especially really grubby ones. Warm water - soap and a toothbrush, scrubbing everywhere. Rinse off with water. Then a 99% isopropyl alcohol rinse/soak.

In the case of your board, a vinegar bath too may help as there was a lot of corrosion.

I wouldn’t assume anything with any of those traces - test every single one and start running patch wires to rule out any issues. The lack of video may be as simple as a dead trace somewhere.

pball52998 said:

What is the risk of using the machine without those resistors? I assume it would just stop those specific circuits. In this instance things I don't care about at the moment. Sound and keyboard.

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Since they both appear to be pull-down resistors for TTL inputs I think you're right that it would only stop those specific circuits from working (and the one around the sound circuit seems to be for the paddles only, so not much to worry about there). At the very least it won't damage anything further to leave the resistors out.

Those replacement resistors sound correct. Brown-black-red-gold, and brown-brown-red-gold parts may be slightly easier to find depending on where you order (for the 4th band, brown = 1% tolerance, gold = 5%, gold is perfectly adequate as these are not critical parts). Probably wouldn't be a bad idea to order a few spares, possibly in some other common values (e.g. 1k, 3.3k, 4.7k, 10k) in case there are any more surprises

A deep clean is where I tend to start with faulty boards, especially really grubby ones. Warm water - soap and a toothbrush, scrubbing everywhere. Rinse off with water. Then a 99% isopropyl alcohol rinse/soak.

Click to expand...

I agree a 100%

joshc said:

A deep clean is where I tend to start with faulty boards, especially really grubby ones. Warm water - soap and a toothbrush, scrubbing everywhere. Rinse off with water. Then a 99% isopropyl alcohol rinse/soak.

Click to expand...

Fully disassembled last night and washed

Photo mid wash
It has gotten a full alcohol bath earlier but didn't get everything.

It got a FULL bath last night, lots of scrubbing to get off stubborn parts, cleaner than ever now.

I might try the vinegar bath. Wait a bit for the regular to dry or just go ahead and toss the whole damn thing in?

AwkwardPotato said:

Those replacement resistors sound correct. Brown-black-red-gold, and brown-brown-red-gold parts may be slightly easier to find depending on where you order (for the 4th band, brown = 1% tolerance, gold = 5%, gold is perfectly adequate as these are not critical parts). Probably wouldn't be a bad idea to order a few spares, possibly in some other common values (e.g. 1k, 3.3k, 4.7k, 10k) in case there are any more surprises

Click to expand...

There will most definitely be extras ordered!

Edit: You know, I was afraid to take this fully apart because some of those IC are dodgy/stuck/bent/legs missing. In full send it mode now and just making a shopping list

Thankfully most of the IC come out just fine after being sanded. I guess I missed a few somehow(???) or never got sanded and put back in. Ah will I forever hate the creaking and crunchy sound of pulling these chips. (Every chip sounded like that, now only a select few)

So far on the list of replacements.
B12 - this one isn't broken but acts a little odd? It gets 14.3mhz from B13, divides everything else properly it seems. But spits out C1M at .89mhz. Other times it'll be 1.0. So I then see the CPU drop to 1.8mhz rather than the 2.05 I expect. Seems dodgy, so I'm going to try a new one.
G12
H11
H10
C12

Just picked up an Apple /// and watching this thread with great interest.

ried said:

Just picked up an Apple /// and watching this thread with great interest.

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Hopefully yours actually works! Or at least more life than mine

Mine still hasn't been put back together yet.

Extremely busy week at work leading up to the holidays

Hoping to dive back in either next week or after new years.

Well, now that the holidays are out of the way.. my board has been sitting lonley for a bit as I've been out of town. Traveling, family, etc.

I had the day off so I decided to give the /// a vinegar bath, yet another scrub, and a alcohol bath to displace anything.



Scrubbed in a bath with vinegar for 5 or 10 minutes. Washed the board with soap and water to get everything off. Then 99% alcohol bath.

More results to come finally!

Can't wait to have more resistors blow on me and chips legs snap in half

That must be the world's cleanest Apple /// board by now!

joshc said:

That must be the world's cleanest Apple /// board by now!

Click to expand...

From the dirtiest to the cleanest!

Maybe I'll have more luck now

Well, back at it again. All chips back in their sockets.

A different problem now.

The CPU is clocking at 1mhz instead of 2. I'm trying to make sense of this and maybe I'm looking over something simple.
https://www.apple3.org/Documents/Schematics/Timing Logic.jpg

So here's where the signal for the CPU is produced.

F7 sends a 1m signal to pin 13 -> D5. It's received on D5. (Is this correct? Or is it supposed to be another one?)
E7 Q0 is flat. I don't know what this signal is supposed to be. RAS is 2mhz. Leaves pin 11 at 2Mhz. Recieved on D5 at 2mhz.
It leaves D5 at 1mhz -> 9/E7 1mhz
So E7 pin 9 is 1mhz, pin 10 is 2mhz. But it leaves over pin 8 at 1m?

Then goes to A11 and of course to the CPU at 1m.

What am I missing here?

Edit:
My only assumption might be stuck in a reset? Maybe? That's a long stretch I feel.


Data and address lines are fully active and grooving. Should I worry about this later? And continue down the video troubleshooting?

Curious to hear anyones thought.

I haven't looked at this in detail, so maybe I'm wrong here, but the Apple /// sets the CPU to 2MHz in native mode and 1MHz in Apple ][ emulation mode, so maybe there is something wrong causing your board to incorrectly either partially or fully enter emulation mode at reset. I think the mechanism for this is the /SEL2M signal entering F7, so I'd have a look at that and make sure it's low, and if not then that is at least one problem.

/SEL2M appears to come from the 6522 at B6, so that should be quite simple to trace back.

Well, replaced got a few IC in the mail and replaced those. B12 because I thought I had a weird issue with dividing signals. But it's still there after replacement.

Instead of 1mhz I get .9, weird.

But I did replace G12, which is the next part in the timing logic,

No matter where I moved the IC it'd show no activity at all. All 4 of these are the same, so I kicked it out.

I now get a signal on v2-5, and can follow that to:

pin 8 and 15. Which now completes the ROM chip for video generation of elements / attributes

After replacing G12, it actually opened a lot of the rest of the video circuit.

Such as I finally see things on F2 and E2:

The worst part about the video circuit. Half of it's under the RAM board! How are you supposed to troubleshoot anything and see if you get video if you can't access both parts at the same time

Time for the question.

What the heck is THIS supposed to even look like on an osciliscope so I could track it down in case something doesn't look right?

Be best to try and see if I can find what those signals look like on my iie plat?
Things like sync, refresh, rdhires, RBL, etc etc

Happy to see the rest of the board slowly coming to life though!

Guess who has another apple iii board coming in the mail...

Don't worry, this project is still taking up my downstairs

More to come!

I started stripping mine down. A trip to the sink has helped a lot, but the keyboard controller IC looks pretty rough. The plastics were grotty but have cleaned up alright with a toothbrush and a baking soda/water mixture. I washed the aluminum unibody in the shower and it turned out okay.



I bought a 30L ultrasonic because the board should fit into it, so I will give it a session with Branson EC before trying to pull any of the socketed chips for testing. I fully expect to be replacing a couple of these sockets.

All of the card slots are very greened-up, so I’ll be looking for a replacement if anyone knows of a good source or part number. I hate cleaning those things and I can’t trust them if I can’t see inside.

Someone removed the battery from mine in the past, but there’s some evidence that it leaked before the thing was stored and got, uh, rodent-based contamination.

Man is everyone's apple iii literal garbage?

I swear every story is "I got it from a dumpster" or "I had grass growing in it" "I had a rat colony"

So interesting to see where these machines ended up!

ravuya said:

keyboard controller IC

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Jcm makes a replacement!

That's a really good tip, thank you. I had assumed I'd have to be the one making a new one, or hunting down a replacement part, but I hadn't done any research yet and wanted to see how bad it would be once I cleaned it. Maybe Jcm has a test method I can borrow

I think this machine was pretty loved, because it was fairly well equipped (two disk drives.) My hope is that it will clean up pretty well, and once it is booting I'll be trying to fix broken key stems (including the reset switch.)

The generic AY-5-3600-PRO as found on eBay, Aliexpress work fine. I resurrected an Apple IIe (with bent keyboard, bent back!), with a new one of these and was happy.

Byrd said:

The generic AY-5-3600-PRO as found on eBay, Aliexpress work fine. I resurrected an Apple IIe (with bent keyboard, bent back!), with a new one of these and was happy.

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Bent? That's one I haven't heard before.