tech: tempest board

chips4sle

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ok
tempest board looks clean
no pic and the spot killer is on
tried working tempest board so i know monitor and power supply work

x and y do not swing
x= 6.3
y=12.4

odd i think

checked voltage at all the loops on the board and all are good
disabled the watchdog circuit by grounding it

still no picture and no sound
in regular or test mode
 
Put the toggle switch on the door into diag mode and then power up.
Press fire and zap and you might get it to go into self test and give a readout.
 
At this point I'd unplug the monitor. No need stressing that part of the system. If you have a way of checking you roms do that first. Tempest has a audible test for checking ram but you said it is making no sounds in test mode. Time to check your crystal and make sure you are getting a pulse. Check to see they are there on the correct test points. You can do this with a regular logic probe.
Get back to us.
 
Time to make sure you have a good processor. Any change?
I should have also asked if you reflowed your interconnect between the main pcb and math box.
I hope so, It accounts for a lot of the tempest pcb problems I've come across.
 
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Good Voltages
Good Roms
Good Rams
Good Clock
Good CPU
Check to see if you can get a self test screen. You don't need the aux board to be plugged in to get a ST screen.
from here you can trouble shoot video out problems with a scope, working backwards checking to see where the signal is lost.

From this point you need the Aux board.
Cold solder joints on headers
Check header cable, or get new one
Good 2901's
Good Pokeys

Baring any other dead chip problems you should be able to play blind
If you get picture great, if not you need a scope and start checking the outputs going backwards for signal. If none of that helps then the rest is pure grunt work.
 
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If the video output section is dead, and the aux board is bad. You might not be able to tell if you are infact at the self test screen. since no noise will be heard during button presses, and no video will be seen.

So it's a bit hard to tell unless you know for sure the video out section is good.

If it's not booting, then that leads to problems with address decoders, data lines, buffers, bad sockets, bad roms. Bad CPU (which you already tried swapping) or any combination of all that.

If you have a logic probe, you can at least tell if the datalines are pulsing, that would be a good sign, but it's not going to tell you if it's reading data correctly.

For that you need a fluke 9010a, or something similar.
 
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