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Apple II (Not Plus) Board has Issues

DistantStar001

Experienced Member
Joined
May 8, 2019
Messages
208
Recently got a Rev.2 Apple II board. Originally had AppleSoft ROMs, But the AutoStart had a bad pin (broke off) so I replaced them with an Integer set I had on a II+ board. The board boots to the Machine Monitor, and with a ROM switch card (AppleSoft onboard) in Slot 0, it will go to BASIC. I connected a Disk II in Slot 6, and put in a copy of Apple-cillin II. It loaded fine, so I tried a copy of DOS 3.3, and it either hangs after splash screen or crashes. I figured that it was a RAM issue, and indeed several of the chips had corroded legs, but even with good replacements, the issue continued. I tried rotating chips, DeoxIT in all the sockets... I even replaced the CPU, drives and Disk II Cards. No luck.

So I tried loading from "cassette" (Apple II Game Server). And it also crashed out mid load (with or without any card installed).

Eventually, I tried changing my configuration. First, I tried changing the disk controller slot. But that has no effect. So then I moved the ROM Switch Card to slot 3 and suddenly, IT WORKS!!! To be sure, I removed the ROM card, booted up, dropped into BASIC, PR#6 and it loaded DOS too. So I seem to have an issue with Slot 0.

I installed a Z-80 Soft card clone into the suspect slot (tested on a II+), but get a "SOFT CARD NOT FOUND" error. Moved it to slots 1, 2, and 4, but only got garbage screens.

So far, I haven't managed to load any games. BattleZone, Centipede, so forth... All disks tested on my //e, but nothing's loading on the II. I do have a little sine wave program in BASIC that makes use of high-res graphics on my DOS disks and that loads and runs fine.


To recap: Computer boots with ROM card in Sot 0 (in both the on and off positions), but won't load DOS. DOS loads with no ROM Card, or card in slot 3. Games won't load from disk, and "cassettes" crash mid load. Disk II Cards work in Slots 5, 6, and 7. Z-80 Cards (tried two, both tested in another machine) aren't recognized in Slot 0, and fail to boot in any other. Both upper and lower RAM passes Apple-Cillin tests.

Any Ideas? Also, on the off chance I need to replace Slot 0, any idea where I can get a matching edge-connector? It's kind of a dark green that I've ever seen before. So no idea where to get it.
 
I suspect you still have issues with your memory.
Not ruling it out. I've replaces all the chips that had corroded legs and rotated them all into the socket at D3, which I believe is the first (bit 0) RAM (but I could be mistaken), on the theory that if the chip were bad, then the computer wouldn't boot. I know it's hardly a conclusive test, and Apple-cillin isn't the most thorough RAM test either, but I'm limited in what I have. Maybe there's something I can try typing into BASIC or machine monitor that can help me locate the suspect chip? The other possibility are the multiplexers.

Still, bad RAM or not, I'm not sure why that would have an effect on which slot the ROM card is in. Oe why the Z-80 Card isn't being seen in Slot 0.
 
Not ruling it out. I've replaces all the chips that had corroded legs and rotated them all into the socket at D3, which I believe is the first (bit 0) RAM (but I could be mistaken), on the theory that if the chip were bad, then the computer wouldn't boot. I know it's hardly a conclusive test, and Apple-cillin isn't the most thorough RAM test either, but I'm limited in what I have. Maybe there's something I can try typing into BASIC or machine monitor that can help me locate the suspect chip? The other possibility are the multiplexers.

Still, bad RAM or not, I'm not sure why that would have an effect on which slot the ROM card is in. Oe why the Z-80 Card isn't being seen in Slot 0.

I wrote the following memory test program that can be typed into the monitor (it's an assembly listing but you can just type in the numbers following the addresses on the left side). It was intended to perform a quick and dirty test when I couldn't use any other memory test program.. It's about as basic as it gets (that was the idea) so it's intended for someone with an understanding of low level programming.

If it successfully returns to the monitor prompt without a beep then the test completed successfully. If it beeps and shows the registers then you can identify the memory location by looking at the value of zero page $11 to know which page the failure is at and the Y register will have the location within the page.

Since this program relies on three zero page memory locations ($10 - $12) I recommend manually testing them to ensure they're OK. I would also list the program after entering it and checking to ensure it matches. This tests the memory locations where the program is store to ensure they're OK.

Feel free to ask if you need help.

1 ORG $300 2 0300: A4 10 3 LDY $10 0302: B1 10 4 REPEAT LDA ($10),Y 0304: AA 5 TAX 0305: A9 00 6 LDA #%00000000 0307: 91 10 7 STA ($10),Y 0309: D1 10 8 CMP ($10),Y 030B: D0 29 9 BNE FAIL 030D: A9 FF 10 LDA #%11111111 030F: 91 10 11 STA ($10),Y 0311: D1 10 12 CMP ($10),Y 0313: D0 21 13 BNE FAIL 0315: A9 AA 14 LDA #%10101010 0317: 91 10 15 STA ($10),Y 0319: D1 10 16 CMP ($10),Y 031B: D0 19 17 BNE FAIL 031D: A9 55 18 LDA #%01010101 031F: 91 10 19 STA ($10),Y 0321: D1 10 20 CMP ($10),Y 0323: D0 11 21 BNE FAIL 0325: 8A 22 TXA 0326: 91 10 23 STA ($10),Y 0328: C8 24 INY 0329: C0 00 25 CPY #0 032B: D0 D5 26 BNE REPEAT 032D: E6 11 27 INC $11 032F: A5 11 28 LDA $11 0331: C5 12 29 CMP $12 0333: D0 CD 30 BNE REPEAT 0335: 60 31 RTS 0336: 00 32 FAIL BRK ZP: $10 - Starting byte within page ZP: $11 - Starting page ZP: $12 - Ending page Bank 0: $0000 - $3FFF Bank 1: $4000 - $7FFF Bank 2: $8000 - $BFFF Bank 3: $C000 - $FFFF[/FONT][/CODE]
 
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Okay. There was a RAM issue! I basically had to strip it down to its base 16k and then work my way up to a full set of working chips bank by bank, but it now loads programs from disk and cassette! However, there's still an issue with Slot 0. I tried installing a Language Card and it's not being recognized, either by DOS or diagnostic software, and load failures continue when the ROM Card is in that slot.
 
Do pins in slot 0 have continuity with those in slot 1? I'm thinking especially about +5v (pin 26), GND (pin 26) and device select (pin 41) - note pin 1 (I/O select) is not connected. You were noting in the first post it's looking a little green, so bad connections could be at issue. I assume you've attempted some cleaning.
 
Do pins in slot 0 have continuity with those in slot 1? I'm thinking especially about +5v (pin 26), GND (pin 26) and device select (pin 41) - note pin 1 (I/O select) is not connected. You were noting in the first post it's looking a little green, so bad connections could be at issue. I assume you've attempted some cleaning.
Pins 25 (+5v), 26 ((GND), and 41 (I/O Select) all have expected continuity. Pin 1 is not connected, nor are there any shorts to the adjacent pins.

As for the "green," I was referring to the color of the plastic. The pins are a nice and shiny gold.
What, if any, test equipment do you have?
I have a multimeter, semi-functional logic probe, and an analogue oscilloscope.
 
As for the "green," I was referring to the color of the plastic. The pins are a nice and shiny gold.
Ah! My apologies for the misunderstanding - yeah, I don't think you're going to find those green connectors anywhere, they're very rare (and worth preserving if possible).

Pin 41 of Slot 0 should have continuity with pin 15 of the LS138 at H2 - or there might be a chance that IC is bad. I'm focused on the language card not being recognized, but not sure though why if slot 1 isn't being selected the ROM card would cause boot errors. Can you describe / show the errors?

Also, is the language card known-good?

(PS - just reading up the thread... I don't think the CP/M card can be used in any slots other than 4 or 7)
 
Ah! My apologies for the misunderstanding - yeah, I don't think you're going to find those green connectors anywhere, they're very rare (and worth preserving if possible).

Pin 41 of Slot 0 should have continuity with pin 15 of the LS138 at H2 - or there might be a chance that IC is bad. I'm focused on the language card not being recognized, but not sure though why if slot 1 isn't being selected the ROM card would cause boot errors. Can you describe / show the errors?

Also, is the language card known-good?

(PS - just reading up the thread... I don't think the CP/M card can be used in any slots other than 4 or 7)
Yes, there is continuity between pin 41 of Slot 0 and pin 15 the 74LS138 at H2. Also, I tried swapping it with another, but sadly, no luck.

Also, yes, both the Language Z80 Cards have been tested in two other II+s.

A picture of the load error in AppleSoft/DOS 3.3 Below:
Screenshot 2023-11-02 at 20.40.31.png

This is why I thought I had a RAM issue. But any other slot, it works perfectly.
 
Apologies - when you say 'language card', you mean the Z80 card, not a RAM/Integer BASIC card? As far as I can gather, Z80 cards need to be installed in a specific slot (usually slot 7), not slot 0. Only the RAM card or BASIC ROM card can go in slot 0.
 
Curious.. is this the one that sold on ebay recently? Had the asset tags and other stampings on it?
 
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