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Apple II Plus partial video, no beep

K

KLund1

Veteran Member
Joined
Jun 22, 2012
Messages
561
Location
Livermore, CA
I just got a very clean A2S2 II Plus. I get no beep on power up. The power keyboard light is lit. I first was able to see a very light Apple ][ rolling up on the screen. I tested with another psu from a working II+ and saw the same thing. I then thought perhaps re-seating all the socketed IC's. Being grounded, did so. Also for testing I pulled out the Softcard and pullled one of those ram IC and put in the empty socket on the motherboard. Now I do not see the Apple ][, just full screen of 1/4" checker board squares.
This machine dose look like it was stored indoors. Very little dust and dirt. Very good condition.
Suggestions on fixing??
Also above slot one it reads S8410 in black ink. Dose this mean this was made in week 10, 1984?
 
Power light doesn't take anything more than the +5VDC rail functioning. What I would try is to test the other power rails: +12VDC, -5VDC, etc. Next, disconnect the keyboard cable from the logic board and power up, making sure that the keyboard isn't permanently causing the CPU to be held in reset. I believe you can also remove all the DRAM from rows C and D, so that it will only have 16K of DRAM, and use the pulled DRAMs to swap with the modules currently installed on row E.
 
Thanks. That helps!
I disconnected the keyboard and it booted!
So now the keyboard is the issue.
The LS373, and LS374 get very hot just after a 30 seconds with power on the keyboard daughter card. I tested both on a tester. The 374 is still good, but the 373 is bad. I had another and put it in. with power they got hot gain, and the 373 has gone bad.
What could be causing this?
 
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