Re: Tempest board problems

Did you verify the DAC's? The first picture there looks a lot like a DAC problem.

Jon

At 11:03 AM 2/26/2001 -0700, you wrote:
>Yesterday was a nice cold, snowy day - so I stayed inside and worked on a
>few Tempest boardsets. Got 2 outta 4 sets working - but the following are
>giving me fits, so I thought I would see if anyone has some suggestions:
>
>Both boards have had all the pre-requisite 'maintenance' done to them - all
>socketed IC's cleaned and verifed as working in a good boardset, AUX board
>tested and working, interconnect board working, interconnect pins
>resoldered, etc. Also checked and verified the adjustment pots on the
>vector section as good. Tested in a perfectly work cab with working
>monitor, power supply, etc.....
>
>Board one - plays blind but trips the spot killer when the monitor harness
>is plugged in. All of the IC's in the vector section were replaced by a
>previous owner. I verified all of the chips as working, and triple checked
>the sockets. The voltages on the board at the test points look fine
>(the -15V on the vector section is about -14.7, and the +15V is about
>+15.2V). Any ideas?
>
>Board two - plays (doesn't trip the spot killer), but all vectors are
>trashed as shown in the following examples
>
>www.enetis.net/~wandk/misc/tempest1.jpg
>www.enetis.net/~wandk/misc/tempest2.jpg
>
>First screen is the High Score Table and the second screen is the "Tempest"
>logo. The monitor chatters like crazy - but only horizontal and diagonal
>vectors are drawn. Putting the game into test mode only displays a few
>random diagonal lines. Again, this board has had all but the LF13201's
>socketed and replaced in the vector section. I again verified the IC's and
>the sockets as good. I have spoken to 4 other people who have boardsets
>that exhibit the same problems - so it must be a fairly 'common' failure.
>Any ideas? Could it be a failing ram (I get no beeps in test mode)?
>
>Thanks for any help or suggestions.
>
>
>Walt
>
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Received on Mon Feb 26 13:35:34 2001