[QuadList] AVR 2 TBC Problem

[Kenneth Zin]

David, look at the frequency of the bits, are they  (4.43Mhz or 13.3Mhz)
all of the memory is clocked at subcarrier.
If you have all of the twenty four bits, make sure that there is no
clocking in the output bits, just clean hi or low.
look's like the third bit ( counting from the MSB down) is the fault.
either memory or two line delay would be my guess.

Regards,

Ken Zin

On Tue, Nov 17, 2015 at 3:08 AM, David Willis via QuadList <
quadlist at quadvideotapegroup.com> wrote:

>
>
>
> ---------- Forwarded message ----------
> From: David Willis <david.willis at tvt.biz>
> To: quadlist at quadvideotapegroup.com
> Cc:
> Date: Tue, 17 Nov 2015 11:07:51 +0000
> Subject: AVR 2 TBC Problem
> Hi,
>
> Currently working on an AVR 2 (it's been a while since I last worked on
> one of these) that's got a TBC problem. I tracked down and replaced the
> dead chip (A32) that fed clocking to registers at the front of the D-A and
> found the non working chips (A4 and A56) on the two line delay that I
> replaced with working spares from a non working board. I appear to now have
> all 24 bits going into the memory, out again, through the 2 line delay and
> into the D-A however please see attached photo of TBC out when fed with the
> ramp from Bd 17. It appears I'm still missing bits.
>
> Fortunately I have some spare boards and have tried swapping out the A-D,
> Clock Gen and Burst Store Gen in turn each with no change. I don't have
> another working D-A. For info I've got the TRW A-D with associated bypass
> board.
>
> The machine is better than when I started but not yet fit. If anyone with
> greater experience has any ideas where I should be looking I'd be grateful
> for the advice.
>
> Thanks.
>
> David
> Engineer, TVT
>
> [image: Inline images 1]
>
>
>
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