• Please review our updated Terms and Rules here

Apple II Clone Keeps Repeating Keys - Help?

Joudan

Member
Joined
Apr 15, 2018
Messages
21
Location
Sydney, Australia
Hey all,

I bought a Japanese Apple II clone recently and am in the process of restoring it. It appears to have a dead power supply, so I've rigged a PC/AT PSU for the time being and sure enough it powers on to the Apple ][ prompt. Everything seemed to be working at first... until I hit "Shift" + "/" to get a question mark, at which point the computer started beeping rather rapidly and filling the screen with a combination of "?" and "/" line by line. Sometimes when this happens, the backgrounds of the characters are coloured too. Hitting Return stops it, and hitting the "/" key without shift works fine. It also happens with some other symbols such as ">", but it doesn't happen with every Shift-modifiable symbol key - every alphabetical and top-row number key works fine with and without Shift.

I tried removing each logic and rom chip, dusting them and their sockets, and reinserting them but nothing changed. I also tried doing the same to the two chips on the keyboard PCB but still no change.

Here's a photo of the problem: https://i.imgur.com/QTMXTFH.jpg

I'm 99% sure the weird colour bleeding/artifacting/whatever is due to the cable I'm using. This clone has a 3.5mm headphone jack for video, and the cable it came with is fairly old and stiff, so it should probably be ignored unless you think it might be related to this key repetition problem.

Also, it occasionally starts spewing question marks immediately on boot until I hit enter, but this isn't a consistent problem like the one I described above.

So, any ideas? Could the rom chips be failing, or is it maybe a memory problem? How would I go about diagnosing this? It might be worth mentioning that I have a Spectrum Micro Engenho 2 (Brazilian II+/IIe clone) that I could try stealing the chips from to test things, but I haven't confirmed that it even works since the internal power transformer is dead (another thing I need help with! But this Japanese clone comes first :p).

Thanks!
 
My IIe platinum would repeat key-presses, but just occasionally, and just certain keys. In my case, the switches are just dirty. I was able to just work the keys a bit and most behave now. Eventually I'll pop all of the caps off and hose down the switches with deox-it. Supposedly this is a pretty common issue. When I was googling it, another common issue was the keyboard encoder IC.
 
The problem is not in the keyboard.

It's maybe a stuck /IRQ. But someone more familiar with Apple ][ theory of operation will likely know right away what it really is.
 
It is a little odd that only certain keys cause this. I'd examine the key switches first.

But a seemingly common mode of failure involves the chips associated with the keyboard "strobe" line. Apple II/II+ and clone style keyboards usually connect via a DIN socket. This includes lines for power, ground, parallel data lines, and a strobe. The when a key is pressed, the keyboard asserts the ASCII value of the key pressed in parallel on the data lines and then signals a "strobe" to indicate that the value is ready to be read.

Unfortunately, if the DIN connector is ever plugged in backwards the power gets connected to the strobe line and can damage it. The end result is often that all keys repeat (or no keys register at all). Partial damage can also result in intermittent repeating behavior - I had a keyboard that was doing something sort of similar a while back.

Anyway, if it is not the key switches, I'd check along the strobe line. Both the chip on the motherboard, the chip on the keyboard controller, and the cable itself.
 
Because it is only a few keys that do it it is unlikely to be the keyboard strobe/clear logic.
It is most likely to be a keyboard problem. Without knowing what type of clone keyboard it is, guessing the cause it a bit of a stab in the dark because the implementations vary quite a bit.
However given that most keys are fine but a some keys that are probably grouped on a single scanline as the issue I would look for a dry joint at the keyboard controller/ROM decider or the pullup resistor.
 
I'm wondering what connector the clone board has for power? Why are you using a AT power supply and not the original? or another Apple ][ PS.
I would want to start with known good power first then go from there.
 
The original power supply is dead, it was quicker for me to use an AT power supply than diagnose the old one - that comes later. The power is good, I highly doubt that's the problem.

In other news, I tried reflowing the solder on each switch and nothing changed. I also tried triggering the problem and then disconnecting the keyboard, and it continued (aka. the question marks kept scrolling across the screen). But now there's a new problem: I tried reseating all of the chips again and discovered that a few of them had broken legs, but even after bridging the connections between what's left of those legs and the socket, the computer now boots to a solid screen full of question marks. I neglected to mention before, but this is essentially what I got when I turned the machine on for the first time but it had some flashing squares amidst the question marks back then.

I've tried removing each chip and cleaning their pins to no avail (some required a bit of scraping).
 
In other news, I tried reflowing the solder on each switch and nothing changed. I also tried triggering the problem and then disconnecting the keyboard, and it continued (aka. the question marks kept scrolling across the screen). But now there's a new problem: I tried reseating all of the chips again and discovered that a few of them had broken legs, but even after bridging the connections between what's left of those legs and the socket, the computer now boots to a solid screen full of question marks. I neglected to mention before, but this is essentially what I got when I turned the machine on for the first time but it had some flashing squares amidst the question marks back then.

I've tried removing each chip and cleaning their pins to no avail (some required a bit of scraping).

Powering on with a screen full of question marks is a completely different scenario than a screen filling with question marks after pressing a key.
You need to be really clear on the fault description for advice to be good enough to be of any help.

Did the fault change after you reseated the chips or did it always have a screen full of question marks at power on?
Does it power on normally without question marks with the keyboard unplugged?
Does it power on normally without question marks with the keyboard plugged in and olny starts generating question marks after you press the "?/" key?

Also when I suggested the reflow, the problem is more likely on the scanlines and the associated pull up resistors not the individual keys. Posting a photo of the chips on the keyboard will allow me to point you at the chips most likely to be the problem.
Due to the inaccurate description of the fault you probably should expand your fault search and check the mainboard IC's at B5, B6, A12 and C11
 
Last edited:
Powering on with a screen full of question marks is a completely different scenario than a screen filling with question marks after pressing a key.
You need to be really clear on the fault description for advice to be good enough to be of any help.

Did the fault change after you reseated the chips or did it always have a screen full of question marks at power on?
Does it power on normally without question marks with the keyboard unplugged?
Does it power on normally without question marks with the keyboard plugged in and olny starts generating question marks after you press the "?/" key?

Also when I suggested the reflow, the problem is more likely on the scanlines and the associated pull up resistors not the individual keys. Posting a photo of the chips on the keyboard will allow me to point you at the chips most likely to be the problem.
Due to the inaccurate description of the fault you probably should expand your fault search and check the mainboard IC's at B5, B6, A12 and C11

The screen was filling with question marks after pressing a key, I re-seated some chips and the problem changed into a pre-filled screen on boot.

Using some bodge wires I managed to get it back to regular boot + screen filling with question marks upon pressing a key, so to answer your questions:

1. The very first time I powered it on, the screen was full of question marks with some flashing squares scattered here and there. I re-seated some chips and it booted normally, which is when I encountered the problem where trying to type a question mark would progressively fill the screen with them.

2. Sometimes on boot the question marks begin to scroll immediately and can be stopped by hitting Return. Powering it on with the keyboard unplugged doesn't change this, it seems completely random. Other times it boots just fine until you try to make a question mark. Occasionally the "<", "7", and ";" keys trigger the exact same problem as the question mark one, but with those characters instead. This isn't all the time though, the only constant problem occurs when trying to make a question mark.

3. See above.

After fiddling with it for a few days it's clearly above my current skill level and I'd rather have money for other projects, so it'll be going on eBay on Sunday. Thanks to everyone for your help! Hoping the next owner figures it out.
 
Actually ignore that last part of my reply, I can't edit it because it hasn't been posted yet (pending moderation due to my account being fairly new).

I think I'll persevere with this and try to figure it out. The clone is pretty cool and I'd like to hang onto it and get it running properly since I'm passing on my Apple IIc soon, and I just got a good deal on a Disk II (still need an interface card though, any Australians got one to spare?) - I'll check those ICs and report back. I'll also take some proper photos of the board.

I was looking at some photos of real Apple II boards online and the positioning of some of my chips appear to be different, but it should be easy enough to figure out which are which.
 
If this clone is designed like an Apple II / II+ with 3 rows of memory, try pulling out all the memory and put a different set of chips in the row closest to the front. Memory is usually outlined by a white square.
Failed memory in the first row will give the symptoms you describe. It should beep and show a title with good memory only in the 1st row (16K of memory). Share a photo of the motherboard if needed.

Larry G
 
I left this alone for a long while and moved onto other projects, but since my last post I've worked on two IIe Platinums and a IIe Enhanced and eventually gathered enough confidence working with Apple II's to have another try at this. And I figured it out!

It ended up being the keyboard. I got another II Plus clone for free from a friend (non-working) and tried its keyboard, which worked perfectly with very extensive testing. So now the Japanese clone is back together with this new keyboard after modifying the case a bit, swapping some switches from the old keyboard to this new one, and swapping all of the old keycaps over (some switches and keycaps were missing from the new keyboard originally). The switches were the right height, but the legs didn't line up with the holes/pads of the PCB, so I dremelled them flat and soldered wires to each one which I then fed through the holes in the PCB, cut to length, and folded over + soldered. I also stole some chips from the dead board to replace the ones in this board that had broken legs and bodge wires previously. Everything appears to be working fine now.

eKQzD0L.jpg


BWoMccG.jpg


b9WxLY9.jpg


dAnKGwO.jpg


mWzoWmm.jpg


6L82mKn.jpg


taHwadw.jpg


jACPZ0i.jpg
 
Last edited:
Iv ran into this problem and have solved it, my problem was that I'd get repeating cherictors of the last key pressed I found that I had 1 key shorted swapped it out and it worked again so if you look t this and have the same issue check your switches
 
Iv ran into this problem and have solved it, my problem was that I'd get repeating cherictors of the last key pressed I found that I had 1 key shorted swapped it out and it worked again so if you look t this and have the same issue check your switches
i replaced the 74LS273 and the 74LS123 when i had the same issue of it repeating the last key pressed. :) I think the solution was actually the 74LS123 you may want to try that first, if this is a clone keyboard that uses an eprom instead of a keyboard controler chip :)
 
Back
Top