| Attachment | Size |
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| MonitorDump.png | 220.7 KB |
Yes yet another Apple II+ boot problem.
Before I get jumped on, I did search the forums and came up with 67 pages of possible links regarding "Apple II Boot" but none of them that I saw seemed to match this set of circumstances.
I am trying to help a friend get an old Apple II+ up and running. He received it totally dead and non functional.
I have recapped the Power Supply, and removed and re-seated all of the chips.
I only have the first bank of RAM populated, and I have run these RAM chips through a hardware tester and all pass without any problems. (The kit to build the tester can be found here: http://neoloch.com/products/Inquisitor.php)
When the Apple II+ is turned on, it beeps twice and dumps to monitor mode with C012 (or thereabouts - the address changes slightly)
Expanding the effort I used another known good Power Supply and get the identical result - so I know the power supply isn't the problem.
This is booting without any cards, and only 16K of RAM on the motherboard.
I know from other posts that this area is related to IO. ("$c000 - $cfff : I/O")
And a picture of the motherboard in question:
Any thoughts?
Jennifer
Hello Jennifer,
Quite a bit thoughts.....
First of all Gratulations, that you allready solved a quite large portion
of the tests....
the next steps would be related to reading the Applesoft ROMs to the RAM and
moving that contents to the Card
( cable to languagecard inserted correct ? )
first there are few chips for decoding the ROMs for reading:
J7 74LS257
F12 74LS138
E2 74LS139
F2 74LS139
does the move of single chips from that list with alternating chips at other
positions of the mainboard change behavior at startup ? That might indicate
a damaged chip.....
if all that tests don't change behaviour at startup it might indicate a damaged ROM....
at this stage you should consider the following things:
1. After startup the Apple II starts to load Applesoft to the languagecard...
- and scrambles at that stage.... ( assuming that at this stage the rest of the RAM
has been inserted....
It's a pity that a picture of the "test-setup" is missing...
so next check if all 3 banks of RAM are present...
examine if the RAM determined to be relocated to the language card
from the position A3 ( from the motherboard ) is located correct in correct orientation at the languagecard...
sincerely
speedyG
Hi Jennifer
good to know the ram is good.
Does the screen get cleared on boot?
When in the monitor does keyboard entry work?
Also consider checking B5 & B8 (74LS174) and B6 & B7 (74LS257) as these sit between the ram and the databus. The databus is also shared with the slot and roms.
Regards
Geoff B
Hi Jennifer
good to know the ram is good.
Does the screen get cleared on boot?
When in the monitor does keyboard entry work?
Also consider checking B5 & B8 (74LS174) and B6 & B7 (74LS257) as these sit between the ram and the databus. The databus is also shared with the slot and roms.
Regards
Geoff B
On this great site "Apple II Box"
is a very good guide that gives you an overview
http://www.appleii-box.de/H198HomeRepairGuide.htm
Hello Geoff,
the chips should be O.K. -
Otherwise RAM could not have passed the testing succesfully....
sincerely
SpeedyG
Hello 6502enhanced,
thanks for spotting to my site...
the link you issued points to later stage of the process....
the initial page is:
http://www.appleii-box.de/D04_resurection.htm
and it seems that Jennifer allready has performed the instructions from that page in the
first part of her task....
sincerely
speedyG
Hi speedy,
did you note that Jennifer used a device to check/test the ram.
I haven't seen you about recently and it's good to see you back.
Regards
Geoff B
Hi Goeff
missed reading that... sorry.
to Jennifer:
in that case the text from Goeff is still valid
yeah, had 2 months ago a severe traffic accident.... riding my e-bike a lorry nearly killed me...
resulted to breaking the top of my right leg bone....
got a artificial right hip joint implanted and weeks of medical treatment thereafter.....
at least I'm now back home and i got rid of the need to walk with crutches...
speedyG
Hi Speedy,
that's really bad! Hope you will be fine as soon as possible!
Thanks for the great link!
Hi SpeedyG! Sorry to hear about your accident, I hope you are doing well!
Thanks for the information, so there are no cards inserted at the moment, and only that single bank of RAM which has been tested with a hardware tester.
I will do the check on the chip locations you suggested (J7, F12, E2, F2) just one quick question - I do not have a keyboard attached I am thinking that shouldn't cause a problem but wanted to run that by you folks.
Thanks again!
Jennifer
Hi again!
Ok, so there is no chip at J7, but I do see a 74LS257 at J1, so I replaced it - no change.
Replaced 74LS138 at F12, no change.
No chip at E2, its an RFI motherboard so don't know if that is the reason why or not. (No socket either)
Replaced 74LS139 at F2, no change.
When turned on it does present "Apple II" on the screen but immediately below that it dumps to a monitor prompt "*" with an address around C012/C014, etc.
Still chasing this. Any other ideas?
Jennifer
Hi Geoff!
Tried that, swapping one chip at a time and no change.
I am going to try to post some pics, in the hope that helps with the troubleshooting.
Thanks again!
Jennifer
Hi Jennifer
the screen picture helps as it shows the screen has been cleared and the APPLE ][ shows. As you found B5 & B8 were working, these latch the data from the ram during both video access and cpu access. If there was a problem there the displayed screen would have had issues. Maybe there is an issue with one bit of the address bus buffers H3, H4 & H5 (8T97). The other most likely area is the address multiplexer to the ram. I would also check C1, E11, E12 & E13 (74LS153). E13 is less likely to be faulty due to screen output as it multiplexes the cpu address lines A0, A1, A5 & A6.
If you still have issues could also test the keyboard input from the monitor prompt.
Regards
Geoff B
Hello Jennifer,
after examination of the picture 3 remarks:
A: Pin 1 of the 74LS139 in position F2 does not seemto be tight in its socket....- reseat it
B: the red marked sockets are not original - it seems there has been former trouble and
that sockets heve been desoldered, removed, and replaced by other sockets - I'd have to inspect the solderside
of that sockets by picture..... often such repairs damaged the pads or traces at the solderside...
carefull inspection is demanded !
C: the 74LS174 in position B5 suffurs by a lot of dirt/oxydattion of its pins - its pins should be cleaned carefully.
waiting for the posting of the mentioned sockets soldersides.....
sincerely
speedyG
Hi speedyG,
I recently did a repair on a system and had sockets that looked like that. There is a plastic piece that clips inside the socket and it is the top of the plastic piece that you can see. It is easily removed an then the socket looks like the others in photo.
Regards
Geoff Body
Hello Gggb,
i've seen them too - but these have been replaced and the solderside demand inspection....