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Re: URSA Power Supply Noise



>. . . Has anyone seen a low level unlocked low
>frequency signal drifting through the video of URSA machines?  It tends to
>look like residual noise generated by a switching power supply.  Does anyone
>know of a fix for this?
>Dave Corbitt / Manhattan Transfer

I had a Bramberg (I think) EHT unit that causes this problem. You can see
it with the PEC supplies switched and the EHT on. Could be seen with the
coax from the cell box removed and the input to the afterglow cards
terminated. Lift the blacks in POS and run the gain right up. I could see
it change switching frequency for a short time after switching EHT off then
on as the supply stabilized. The normal frequency seems to be around 4-8
times the line sweep rate (I doubt it is a sub-multiple.)

BTW, after replacement (I have a couple of spares) does the EHT need to be
adjusted? Would you know of a Rank procedure and specification for this?

I also changed out the lower switcher PS before I found the bad EHT supply
and cured part of a similar problem that didn't follow the EHT.

--- David Tosh  dlt at earthlink.net  (CIS 72167,1376)
--- Video Engineer, Complete Post, Hollywood