Berzerk ZPU repair [2]

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This is the second ZPU board I'm working on.

This one actually gave three beeps/flashes when it was still in the machine. AFAIR it _didn't_ give 3 beeps when I powered on the machine, but it did when I removed the power plug and put it back on:

http://www.youtube.com/watch?v=LUCDVHoXYHM

I kinda messed up that first power-up, the second one is good.

After I removed the board it doesn't give 3 flashes on my AT power supply anymore....
 
Berzerk ZPU #2

Hi,

See my post on your #1 board.

Update: I looked again and see that you actually have to have at least 9 Volts or so, on your "+5 V UNREG" line to make it come out of reset. (the reset line is after the 5.6 Volt zener on Q1 so you have to have the Q1 drop + the 5.6 Volt zener + about 2.6-3 volts to pull up the reset line and another diode at 7G = 9.4 Volts... give or take)

This one looks like it has a bad cable or a RAM problem. Will it go into self-test?

Kenneth
 
Thanks Kenneth,

I tried this board with the +12V jumpered to the +5V unreg input too.

Still same response, the LED is burning very very dim.

I actually did have a high on the reset line a couple of times and was able to "reset" it with the reset button (Saw the reset line go low, and high again), so it looks like the reset circuit on this one works _sometimes_ because it simply doesn't work every time I boot up the board....
 
Berzerk #2

See also the Berzerk #1 reply... it is really long.

This is the board that gave 3 beeps in the video right?

I read another post about Berzerk that said there was a bad connection from the ZPU to another board that gives that screen. It also said that 3 beeps was right. i will see if I can find it again and send you the link.

Kenneth
 
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