Tempest board problem

scottz29

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Reflowed all header pins on all inter-board connectors. Reseated and cleaned all pins on socketed chips on Aux board.
Mathbox, AVG, or something else?
 
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Hey Scott, could be a monitor issue but we'll make sure tomorrow. I have some working boardsets so we should be able to isolate the problem.
 
Hey Rob, thanks for the offer to test this in your Tempest, but I got a chance today to hook it up to another 6100 which verifies that this is a board problem. Now it's interesting...
 
Typically these type errors are caused from the aux board. One or more of the alu's is most likely bad, or the header/cable.
 
Update...
Tested the board in a working Tempest, and determined the Vector Generator board contains the fault. Aux board and board connector cable are both verified good.

In the machine I tested in, my board showed horizontal collapse, as opposed to what you see in the video.

Since bringing it back home, I cleaned and reseated 5 RAMs that were socketed. Now, I have no X/Y output voltage at all (I had scrolling voltages before). Game still plays blind. I simply have no XY output anymore.

I tested a bunch of chips in the Vector Generator Address Selector, Data Shifter, and Vector Timer sections of the board using a logic comparator, which all tested good. I don't have every 74LS chip that is used on the board so I can't test all sections, but I feel like some main problem areas are eliminated.

Logic probe confirms data is flowing in the RAMs and the vector generator sections.

One strange area is the outputs of D5, D6 and E5 (Vector Generator Data shifter section) which is 3 LS194 chips that go to the Vector Generator XY output section. Data is pulsing on the inputs, but all outputs read low. I don't know if this is normal or not...but to me it seems not.

Any suggestions on what to try next, or did I miss something big here??

Vector gurus....please help!
 
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Have you tried just putting it in test mode? That will bypass the aux board, and if the video out section is working, you will get a picture.

Let's try and determine if you are indeed getting video out, or not.
 
I have had it in test mode with no difference. Here are some tests I ran yesterday:

X Out > +2.765 steady. Can make it go up or down by adjusting size pots.
Y Out > +2.622 steady. Can make it go up or down by adjusting size pots.
Test lug @C88 > -15.18
Test lug @C61 > +15.26
C60 > -15.19
C62 > +15.25
D/E12 pin 4 > -15.19
D/E13 pin 4 > -15.19
A/B12 pin 2 > +15.25
A/B13 pin 2 > +15.25
D10 pin 3 > -15.19
D10 pin 13 > +5.10
D10 pin 14 > 0 (reads +15.25 at R108)
D10 pin 16 > -8.18 <-- ?????

Edge connector
W > -24.18
X > +23.89
readings the same at other +-22v pins

Spot killer's on as there are no scrolling voltages going up to the monitor.

I'm going to test voltage and logic probe some chips (E6/F6) that supply the LS194 chips in the vector generator data shifter section and see what I get. I believe all the output pins of those 194s are stuck low.

http://arcarc.xmission.com/PDF_Arcade_Atari_Kee/Tempest/Tempest_DP-190-2nd-03A.pdf
http://arcarc.xmission.com/PDF_Arcade_Atari_Kee/Tempest/Tempest_DP-190-2nd-02B.pdf

But, based on the history of these boards and from what I've read, my money is on a bad DAC312....
 
Taking a moment to close out this repair thread while perusing old notes...oops! :eek:

This was fixed 10/30/2010:

Tempest lives! Reseated vector ROMs and processor, and game enters test mode. After adjustments, game is playing.

Began with game in test mode, no display. Swapped CPU with known working 6502 and got a single blue vector on screen and activity on the slam switch (switches test screens) and long steady beep. Confirmed activity on CPU pin 37 & 39. Activity on E2 pin 1 & 2. Confirmed ROM activity on the CS1 & CS2 lines. "Theory of Operation" doc said long steady beep in test mode points to bad vector ROMs. Flip-flopped the ROMs (socketed) and test pattern appeared. Adjusting X/Y position, linearity and BIP controls brought test pattern into view. Went out of test mode and game worked.

DAC replacement could have had an effect, but hard to tell since game was dead - DAC outputs never changed, but inputs upstream were still bad at that point. However, after the DAC replacement, I never saw the pattern shown in the video again. Original CPU was later confirmed good. Bad/dirty sockets ended up being the culprit despite cleaning of chip legs and using contact cleaner before they were inserted into their respective sockets.
 
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