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Did I shoot myself in the foot? Apple IIe Enhanced RAM repair

Stapler

New Member
Joined
Oct 1, 2015
Messages
3
Hello everyone and thanks in advance.

History:

1. Picked up an Apple IIe (enhanced version) to restore.

2. Booted to message and beep but, had infinite repeating key problem.

3. Repaired repeating key problem, booted with message and peep. Also, played a couple of games but, noticed it didn't pass RAM test.

4. Removed RAM and replaced with sockets and new faster RAM.

5. Now it boots to a screen full of garbage and no beep.


Original RAM chips were MT 4264-20 type with (8520N script in top corner)

Replaced with MT 4264-10 type with (8817 A script in top corner)

** After the fact I noticed the MT 4264-10 RAM was 64k x 8 **

Removed the MT 4264-10 and replaced it with MT 4264-15 (433 script in top corner)

No change, still boots to garbage on screen and no beep.



Question:

Did I fry one of the other chips with the 64k x 8 RAM and is the MT 4264-15 (with 433 script in top corner) compatible with MT 4264-20 (8520N script in top corner)?



** The address and data pins on the CPU now have incorrect wave patterns as well **



~Stapler
 

amauget

Experienced Member
Joined
Mar 9, 2011
Messages
84
Hello Stapler,

The 4264 chips are all compatible together. This is just a matter of speed. And it's probably not the problem here.
You can also use 4164, as long as the speed meets the requirement.
4164/4264 are 64 Ko * 1 bit. So you need 8 chips to have the full 64 Ko.

Are you sure you don't have damaged some tracks during the restoration process ?
 

Stapler

New Member
Joined
Oct 1, 2015
Messages
3
I was very careful not to damage any traces but I will verify there is no damage and let you know.

Thanks for taking the time to reply.
 

Stapler

New Member
Joined
Oct 1, 2015
Messages
3
Antony, thank you for your suggestion. I tediously verified all the traces between the RAM chips and it seems there was one damaged trace at the number 10 pin on one of the RAM chips.

I repaired that trace and the system now works perfectly.

All the best
 

g4ugm

Veteran Member
Joined
Feb 22, 2011
Messages
2,746
Location
NorthWest England (East Pondia)
Antony, thank you for your suggestion. I tediously verified all the traces between the RAM chips and it seems there was one damaged trace at the number 10 pin on one of the RAM chips.

I repaired that trace and the system now works perfectly.

All the best

So glad there is a happy ending.....
 

amauget

Experienced Member
Joined
Mar 9, 2011
Messages
84
Hello Stapler,

Well done ! Now you can enjoy the Apple //e's taste :cool:
 
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