Re: Tempest AVG board problem

I checked the first three, D5, D6, and E5.

Pin 1 - pulsing Hi, fast
Pin 11 - pulsing Lo, kinda slow

________________________________
From: Kevin Moore <talon.k@gmail.com>
To: vectorlist@vectorlist.org
Sent: Tue, August 24, 2010 11:54:56 PM
Subject: Re: VECTOR: Tempest AVG board problem

What do you have on pins 1 and 11 of the ls194's ? Probe those with the logic
probe. You may have a bad 12Mhz clock, or a bad latch.

On Tue, Aug 24, 2010 at 10:38 PM, Scott Zeiser <scott@zeiser.org> wrote:

Hi guys,
>Got a Tempest board problem I've been struggling with. Took me a while to get
>the 6100 rebuilt, only to find out I've got a board problem. Here's a video of
>the problem I was originally having.
>
>http://www.youtube.com/watch?v=Bt4Hj9NEdRM
>
>Problem 1:
>I've tested the board in a working Tempest, and determined the Vector Generator
>board contains the fault. Aux board and board connector cable were both
>verified good.
>
>In the machine I tested in, my board showed horizontal collapse, as opposed to
>what you see in the video.
>
>Problem 2:
>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 lost my XY output voltages.
>
>I've been having another local friend/collector help me with this, and here's
>what we've done so far... 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.
>
>I have had it in test mode with no difference. Here are some tests I ran
>yesterday (you'll notice I now have voltages as of yesterday, but they are not
>scrolling):
>
>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.
>
>Am I warm? Is there anything else I should be checking? Not exactly sure what
>I'm missing, but my money is on a bad DAC312 somewhere...
>
>Thanks,
>Scott
>
>
>

      
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Received on Wed Aug 25 00:26:20 2010