Tempest 'M' for math board error

vintagegamer

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Last night i worked some more on Tempest and got it in test mode. The only letter showing is 'm' for math board. I have a spare math board so i moved all of the chips over from the orig math board to the new one, with the exception of ram chips 126 and 131, bc those chips were already present on math board 2. I put math board 2 in and my graphics issues did not change, stayed exactly the same. Should i go through switching out the ram chips one at a time since i have 2 extras? a new big blue is on the way as well.
 
Have you gone over the interconnect cable and header pins that connect the main pcb to the aux pcb ?

Not yet bc i usually stink at anything solder-related but it sounds like i'm running out of options. IMO the techs who used to fix these games didn't get paid near enough!
 
Do you still get the "M" error in test mode?

If you do the problem is still the aux board, cables, headers, or Bit slicers, or proms.

You haven't determined if any of the chips you have swapped are good. So you could just be replacing bad with bad.

And we still don't get paid enough :)
 
Ok i reflowed the pins on the main pcb and no change BUT after removing and cleaning connectors going up to the cage thing by the monitor, i am now able to see the words 'press start', 'high scores', and 'insert coins' which i couldn't before. If i have time tnt i will pull the aux board chips and clean them, and check the pins on that board too. So fing close!!
 
Reflowed pins on math board, no change. And a new bonus is monitor screen display all flip-floppy. Guess that will need the rebuild next!
 
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OK here's an update from today. I cleaned off the main board and aux board edge pins (again) and I'm getting the vid back for the most part (only an occasional flip-flop, but still no vector generation).

I put in my alternate math board again and am still getting the M error, so either both math boards have probs OR it's one of the chips that I'm swapping between the boards.

In other news, I got the voltages from the ARII board, they are as follows:

-5v tab on board reads -5v on DMM
+12v tab on board reads +12V on DMM
-22V tab on board reads -24.7 on DMM
+22v tab on board reads 23.6-24v on DMM
10.3v tab on board reads 10.3 on DMM
36v AC tab on board reads........ 17.6-18V AC

Do these readings look good or bad?

With any luck, I should be getting a big blue in the mail tomorrow and will be doing that swap as well.
 
OK here's an update from today. I cleaned off the main board and aux board edge pins (again) and I'm getting the vid back for the most part (only an occasional flip-flop, but still no vector generation).

I put in my alternate math board again and am still getting the M error, so either both math boards have probs OR it's one of the chips that I'm swapping between the boards.

In other news, I got the voltages from the ARII board, they are as follows:

-5v tab on board reads -5v on DMM
+12v tab on board reads +12V on DMM
-22V tab on board reads -24.7 on DMM
+22v tab on board reads 23.6-24v on DMM
10.3v tab on board reads 10.3 on DMM
36v AC tab on board reads........ 17.6-18V AC

Do these readings look good or bad?

With any luck, I should be getting a big blue in the mail tomorrow and will be doing that swap as well.

Those look good. 18VAC on the 36VAC tab is normal. That's AC juice....so you're only reading half the wave....18 + 18 = 36 :)

Edward
 
OK, the new big blue (or should I call it the big black?) from Bob Roberts went in last night. It may have stabilized the machine in some sense, but I'm still getting the 'M' message on the test screen.

I'm guessing the next step is a hunt for 4 2901 ALUs..

I've also been getting the fold of the Tempest logo on the left side when it is displayed, and I've read that the problem was with the actual game and that an updated ROM revision took care of it. So, I guess that will eventually have to go in the shopping cart also.
 
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