Mmmm baked apple, hope you remembered the cinnamon... ... I seent this happen live some 30ish years back and it looked like it blew caps in the
PSU that time.

thanks! voltages on psu are fine. still could be something in it? any other ideas?

BitWrangler wrote on 2021-11-11, 21:47:

Mmmm baked apple, hope you remembered the cinnamon... ... I seent this happen live some 30ish years back and it looked like it blew caps in the
PSU that time.

PSU is fine. Traded it with known working.

Additional info:

It does a single beep after i turn on. If i blindly type something i get a beep like a syntax error. if i type 'run' i get no beep. So i think something in the graphics department is shot but the main thing might still be running.

DrAlis wrote on 2021-11-11, 21:57:

thanks! voltages on psu are fine. still could be something in it? any other ideas?

BitWrangler wrote on 2021-11-11, 21:47:

Mmmm baked apple, hope you remembered the cinnamon... ... I seent this happen live some 30ish years back and it looked like it blew caps in the
PSU that time.

Probably gonna have to grab a number 18 or 49 and go through the motions... https://vintageapple.org/apple_ii/

Ah, the good old Apple ][ "you're hopeless".
VCfed is probably a better place to ask questions. They have an apple ][ specific section.

DrAlis wrote on 2021-11-11, 21:09:

I messed up. I wanted to install a SD card in my nice Apple II Europlus and since the case was off, I put the 8-bit card holding the SD converter the wrong way around into the slot.

Such deserves punishment.

DrAlis wrote on 2021-11-11, 21:09:

Somebody out there must know what gets fried if you reverse a card in the bus.

You were lucky and apparently didn't destroy the ROMs or any other expensive stuff.
Check the chips on address bus pins A11-A15, mainly '257 and '153.
Ideally using a known-good board, from and to which you can swap the chips, so you can counter-check which ones are still functional.
Or use the TL866's chip testing functionality.

I did this with a 5160. It fried the card but the computer was unharmed.

Thanks for all comments! You are far ahead of VCFED. I got no replies in the dedicated thread there yet - Vogons rule on speed. 😀

I also checked the two books, I am not sure if my issue is covered: It seems to boot with garbage screen. Best match I can find in the troubleshooting sections are sync issues. How does that look? Is that what I have?

Thanks for pointing me to some chips - this is practical advice. I found 9 of these two chip types. I ordered 2 74LS257 and 2 74LS153 and a TL866 - let's see if that gets me forward. Can you elaborate where I would locate what else is on A11-A15?

retardware wrote on 2021-11-12, 04:22:

Such deserves punishment. […]
Show full quote

DrAlis wrote on 2021-11-11, 21:09:

I messed up. I wanted to install a SD card in my nice Apple II Europlus and since the case was off, I put the 8-bit card holding the SD converter the wrong way around into the slot.

Such deserves punishment.

DrAlis wrote on 2021-11-11, 21:09:

Somebody out there must know what gets fried if you reverse a card in the bus.

You were lucky and apparently didn't destroy the ROMs or any other expensive stuff.
Check the chips on address bus pins A11-A15, mainly '257 and '153.
Ideally using a known-good board, from and to which you can swap the chips, so you can counter-check which ones are still functional.
Or use the TL866's chip testing functionality.

DrAlis wrote on 2021-11-12, 09:38:

It seems to boot with garbage screen. Best match I can find in the troubleshooting sections are sync issues. How does that look? Is that what I have?

You didn't say that the monitor does no longer sync.
To me your description looks rather like that the RAM addressing does no longer work and the screen gets some random garbage.
Can easily happen if some buffers/latches are damaged.

DrAlis wrote on 2021-11-12, 09:38:

Thanks for pointing me to some chips - this is practical advice. I found 9 of these two chip types. I ordered 2 74LS257 and 2 74LS153 and a TL866 - let's see if that gets me forward. Can you elaborate where I would locate what else is on A11-A15?

If your Apple II Reference Manual has got lost, you can find the schematics here, for example.

For some explanations of the circuitry, consult the Red Book or the mentioned Reference Manual.
The former contains the Revision 0 board schematics, the latter one the Revision 1 board schematics. The later revisions are almost the same, just some stuff /chips lacking, for example because Apple dropped support of 4kx1 DRAMs with these.
Basically, following the wires in the schematics, check every chip that is connected with A11-A15, as it looks to me like if some buffer/latch chip on these has been damaged.
The TL866 will come very handy for testing other chips, too, so you do not need to buy spares for each of them.

I am not sure how a sync problem looks, unfortunately. I'll attach a picture of my screen. If the RAM addressing is defunct I would not get a boot complete beep, right? Therefor I suspected video circuitry.

Not a sync problem.
Seems switching to text mode fails.
This is controlled by memory mapped I/O in the address range C000-C0FF.
Something from chip F13 onward in the signal paths.

As the beeper works, I guess the 74LS138 might be OK, at least partly. But these like to fail, fully or partly. Back then when Apple II were common, I have replaced quite some of these.

Edit:
I guess you will have several damaged chips. There are quite some that can be affected.
Best to wait for the TL866 and test them, beginning with all ones that are directly connected with the address and maybe also data lines connected with the slot bus.
But don't worry, it will be only cheap TTL stuff to be replaced.

Alright so the TL866 has arrived and I pulled and tested around 20 ICs predominantely the suspects mentioned. I only almost destroyed 2 with my fat fingers after I pulled them not straight. With some I have trouble finding them in the software. Anyway. All ICs seemed good, EXCEPT: Ther is a chip labeled N74LS51N Motorola K8050. That chip fails the test on 3 or so lines. I tested is a "7451" for lack of alternatives. Did I test it right? What replacement is suitable? Thanks!

P.S.: Is there a way to test old RAMs 4164 with the TL866. I have some sitting around where I am unsure which work. Thanks!

retardware wrote on 2021-11-12, 15:02:

Not a sync problem. Seems switching to text mode fails. This is controlled by memory mapped I/O in the address range C000-C0FF. […]
Show full quote

Not a sync problem.
Seems switching to text mode fails.
This is controlled by memory mapped I/O in the address range C000-C0FF.
Something from chip F13 onward in the signal paths.

As the beeper works, I guess the 74LS138 might be OK, at least partly. But these like to fail, fully or partly. Back then when Apple II were common, I have replaced quite some of these.

Edit:
I guess you will have several damaged chips. There are quite some that can be affected.
Best to wait for the TL866 and test them, beginning with all ones that are directly connected with the address and maybe also data lines connected with the slot bus.
But don't worry, it will be only cheap TTL stuff to be replaced.

So I ordered a 7451 and will report how effective the replacement is when it gets here. 😀

DrAlis wrote on 2021-11-12, 20:23:

Alright so the TL866 has arrived and I pulled and tested around 20 ICs predominantely the suspects mentioned. I only almost destroyed 2 with my fat fingers after I pulled them not straight. With some I have trouble finding them in the software. Anyway. All ICs seemed good, EXCEPT: Ther is a chip labeled N74LS51N Motorola K8050. That chip fails the test on 3 or so lines. I tested is a "7451" for lack of alternatives. Did I test it right? What replacement is suitable? Thanks!

P.S.: Is there a way to test old RAMs 4164 with the TL866. I have some sitting around where I am unsure which work. Thanks!

retardware wrote on 2021-11-12, 15:02:

Not a sync problem. Seems switching to text mode fails. This is controlled by memory mapped I/O in the address range C000-C0FF. […]
Show full quote

Not a sync problem.
Seems switching to text mode fails.
This is controlled by memory mapped I/O in the address range C000-C0FF.
Something from chip F13 onward in the signal paths.

As the beeper works, I guess the 74LS138 might be OK, at least partly. But these like to fail, fully or partly. Back then when Apple II were common, I have replaced quite some of these.

Edit:
I guess you will have several damaged chips. There are quite some that can be affected.
Best to wait for the TL866 and test them, beginning with all ones that are directly connected with the address and maybe also data lines connected with the slot bus.
But don't worry, it will be only cheap TTL stuff to be replaced.

Update: So the new 7451 came and I put it in. Same problem 🙁 I took it out again and threw it in the tester. Same problem (PIN 8 gives wrong output). So either I test them wrong, or I got a replacement with the exact same defect. Or what is most likely. My setup/board now fries 7451... I will order another 7451 and this time test it before putting it in. Considering getting an Oscilloscope but am not sure I will have much success with it. Using schematics I just don't have the experience/background in the electronics (more on the software side)...

DrAlis wrote on 2021-11-14, 14:44:

So I ordered a 7451 and will report how effective the replacement is when it gets here. 😀

DrAlis wrote on 2021-11-12, 20:23:

Alright so the TL866 has arrived and I pulled and tested around 20 ICs predominantely the suspects mentioned. I only almost destroyed 2 with my fat fingers after I pulled them not straight. With some I have trouble finding them in the software. Anyway. All ICs seemed good, EXCEPT: Ther is a chip labeled N74LS51N Motorola K8050. That chip fails the test on 3 or so lines. I tested is a "7451" for lack of alternatives. Did I test it right? What replacement is suitable? Thanks!

P.S.: Is there a way to test old RAMs 4164 with the TL866. I have some sitting around where I am unsure which work. Thanks!

retardware wrote on 2021-11-12, 15:02:

Not a sync problem. Seems switching to text mode fails. This is controlled by memory mapped I/O in the address range C000-C0FF. […]
Show full quote

Not a sync problem.
Seems switching to text mode fails.
This is controlled by memory mapped I/O in the address range C000-C0FF.
Something from chip F13 onward in the signal paths.

As the beeper works, I guess the 74LS138 might be OK, at least partly. But these like to fail, fully or partly. Back then when Apple II were common, I have replaced quite some of these.

Edit:
I guess you will have several damaged chips. There are quite some that can be affected.
Best to wait for the TL866 and test them, beginning with all ones that are directly connected with the address and maybe also data lines connected with the slot bus.
But don't worry, it will be only cheap TTL stuff to be replaced.

So look for something shorted on that output that's pulling too much current and frying it.... then fix that... and if that goes wrong... look for what is connected to that and messing it up and so on...

Quick check might be to test for a short to any of the power/ground supplies between pin 8 on the socket. I don't know if the Europlus is different, but a quick look at the Apple II schematic shows pin 8 as being the sync signal, which is odd given there's an image on the screen.

There's supposed to be a 2k resistor before the pin 8 output goes anywhere on that page which ought to protect the chip, but it does also show it goes off to one of the slots, so maybe look for damage around the slot?

The problem with the chip testers generally is, they do not test under realistic load conditions.
And maybe there are even bugs.

Repairing an Apple II is easiest with a known good second Apple II.
Just swapping suspect chips and testing function.
Maybe it could be a good idea to invest into a clone (~50 euros) which you can (ab)use as chip tester 😀

snufkin wrote on 2021-11-16, 19:50:

Quick check might be to test for a short to any of the power/ground supplies between pin 8 on the socket. I don't know if the Europlus is different, but a quick look at the Apple II schematic shows pin 8 as being the sync signal, which is odd given there's an image on the screen.
AppleII_7451.jpg

There's supposed to be a 2k resistor before the pin 8 output goes anywhere on that page which ought to protect the chip, but it does also show it goes off to one of the slots, so maybe look for damage around the slot?

Checking the slot might be a good idea, but these were quite good quality, took a lot of abuse, don't remember any failed one.
There are +-12V, and -5V on the bus, and with a card reversed this could have blown buffer outputs as well as any chips inputs.
Some chips might test fine on the TL866 with megaohms input resistance, but different when having bus load.

The green-black moving patterns point at some wrong memory area displayed, maybe because of bad RAM multiplex addressing. Normally this should be static.
If you press and hold RESET, does it still move?

MISSION ACCOMPLISHED! Thanks everybody. OK, so let us finish the story for everybody's closure and potential future card twisters. So while waiting for the second replacement 7451, I decided to test all the remaining ICs. Also a friend of mine was able to look up that the 7451 does not behave like the 74LS51. So almost the last chip I tested was the 74S175 at B1. And it failed the test also but completely. So I get new hope I try to find a replacement. A quick look at the language card reveals it also has a 74S175. I decide to swap them and, BOOM, I get a nice "Apple ][" welcome after power on. So now all I need is another 74S175. Testing of the SD Adapter Card reveals that it is fried and will prevent booting if inserted. Thank you all for helping with my first chip level repair journey and all the helpful resources you provided. Also keep up the PIN level debugging work it was the most enjoyable despite me putting you all on the wrong track because I realized so late that the 74LS51 apparently isn't broken but not the same as the 7451. Kind regards and THANK YOU.

Congrats!
I always enjoy repairing on component level (instead of swapping cards). You always expand your knowledge...