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Apple III Boot Glitch [message #386613] Sun, 01 September 2019 14:24 Go to next message
Anonymous
Karma:
Originally posted by: Michael Mann

After several years of looking, I finally found an Apple III Plus! It's in great condition, cosmetically, but it doesn't boot to SOS. I'm looking for suggestions to debug it.

On power-up, it generally does not seek the disk drive, and displays a screen full of 'X's with an empty square in the upper, left-hand corner. I think that's where the built-in RAM self-test displays. If you cntl-reset it a couple times and it seeks the disk drive, then it displays the 'X's but with an inverted line in the middle. I uploaded two pictures to Google Photos; I hope this link works:

https://photos.app.goo.gl/dZ7AHtbyrKWe7Zds5

I'm fishing for a more specific method of debugging, other than pulling each chip one by one, and reseating and testing in my little chip tester. BTW, how do you pull off the RAM daughterboard to get at the motherboard chips below it?

Thanks!
Re: Apple III Boot Glitch [message #386621 is a reply to message #386613] Sun, 01 September 2019 18:10 Go to previous messageGo to next message
Michael J. Mahon is currently offline  Michael J. Mahon
Messages: 1767
Registered: October 2012
Karma: 0
Senior Member
Michael Mann <gmail@ware4.com> wrote:
> After several years of looking, I finally found an Apple III Plus! It's
> in great condition, cosmetically, but it doesn't boot to SOS. I'm looking
> for suggestions to debug it.
>
> On power-up, it generally does not seek the disk drive, and displays a
> screen full of 'X's with an empty square in the upper, left-hand corner.
> I think that's where the built-in RAM self-test displays. If you
> cntl-reset it a couple times and it seeks the disk drive, then it
> displays the 'X's but with an inverted line in the middle. I uploaded two
> pictures to Google Photos; I hope this link works:
>
> https://photos.app.goo.gl/dZ7AHtbyrKWe7Zds5
>
> I'm fishing for a more specific method of debugging, other than pulling
> each chip one by one, and reseating and testing in my little chip tester.
> BTW, how do you pull off the RAM daughterboard to get at the motherboard chips below it?
>
> Thanks!
>

You might try wiggling the connectors from the main board to the DRAM
board. Intermittency there was a common problem on both III’s and III+’s.

--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
Re: Apple III Boot Glitch [message #397394 is a reply to message #386613] Mon, 03 August 2020 01:46 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: ibsev01

On Sunday, September 1, 2019 at 11:24:28 AM UTC-7, Michael Mann wrote:
> After several years of looking, I finally found an Apple III Plus! It's in great condition, cosmetically, but it doesn't boot to SOS. I'm looking for suggestions to debug it.
>
> On power-up, it generally does not seek the disk drive, and displays a screen full of 'X's with an empty square in the upper, left-hand corner. I think that's where the built-in RAM self-test displays. If you cntl-reset it a couple times and it seeks the disk drive, then it displays the 'X's but with an inverted line in the middle. I uploaded two pictures to Google Photos; I hope this link works:
>
> https://photos.app.goo.gl/dZ7AHtbyrKWe7Zds5
>
> I'm fishing for a more specific method of debugging, other than pulling each chip one by one, and reseating and testing in my little chip tester. BTW, how do you pull off the RAM daughterboard to get at the motherboard chips below it?
>
> Thanks!


I spent about 3 years chasing a similar problem, for me it was displaing all P's, then X's and then finally g's. It turns out there was a short on pins 4 and 14 on the 2114 character rams located at E4 and E5. The short wasnt on the chip but under one of the sockets between the character roms at e4 and e5 and the 4 octal latches located at e2, f2, e3, f3. I removed all the sockets and found a tin whisker.

If you need more help, feel free to reply or reach out to me.
Re: Apple III Boot Glitch [message #397439 is a reply to message #386613] Mon, 03 August 2020 23:40 Go to previous message
Anonymous
Karma:
Originally posted by: vintageworld66

Well look at he pictures.

1Picture there where text should be are blanks ( RAM Test)
Where there should be blanks there are X

2.Picture looks like the same , just the text area is inverted


I do not know what the second picter might be , it is not the "Retry" screen

Is there a ROM test? Is it showing a failed ROM location?

Just a thought
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