Anyone have any troubleshooting advice?

I figured I'd be swimming in responses from this list? No ?

Regardless, if anyone has any advice I'd appreciate an e-mail.

> Date: Tue, 04 Feb 2003 00:30:02 PST
> To: vectorlist@synthcom.com
> From: Tony Jones <tony@tonyjones.com>
> Subject: VECTOR: tempest AVG troubleshooting help needed
>
>
> Hi.
>
> Hoping someone can help me. I'm trying the standard "trace the signal back"
> methodology without much luck.
>
> Have what I think is a Tempest board with a bad Y output.
>
> Pressing reset (test switch on) and the test screen appears momentarily
> (a little distorted but recognisable) and then collapses into a blank screen.
> Spot killer is on.
>
> Advancing to the checkerboard test screen (4th screen), Y direction is
> "scrunched" into about a 1" area of the screen. Spot killer on.
>
> Checking with a scope:
>
> The output of the X multiplier (C12) looks good, pin 14 (output) is same as
> pin 9 (input) but downscaled.
>
> The output of Y 1495 (C13) looks bad, pin 14 (output) bears no similarily to
> pin 9 (input). Also, the input is perhaps somewhat skewed, hard to tell on
> the scope.
>
> I socketed C13 and replaced it (known good one), with no change.
>
> There is what appears to be a noise? waveform on pin 18 of F10 (Y AM6012
> DAC). There is no equivalent waveform on pin 18 of A10 (X DAC), rather a
> straightline. On a good working board, no output on pin 18 for either X
> or Y DACs.
>
> I socketed and replaced F10 (Y DAC) with no change.
>
> I don't understand the DAC/BIP circuit, the relationship between the IO
> (pin 18 - is this the analog output?) of the AM6012 and the BIP circuit.
>
> If anyone has some beginner level circuit descriptions and troubleshooting
> advice, I'd appreciate hearing it.
>
> Thanks
>
> Tony
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Received on Sun Feb 9 12:37:07 2003