SC504 INT SYNC queries


1. What is the internal switch behind the SC504 indicator lamp for? Is this the switch referred to at the bottom of p.2-5 of the Specifcation and Performance Check section of the manual? and if so can someone expand on the rather cryptic description?

2. I'm looking into this area because the INT SYNC signal I am providing at 15B/14B of the backplane isn't triggering. It seems to be getting through correctly, because if I rotate the Triggering Level control rapidly through its top dead centre it momentarily syncs, lights the SYNC light, and freezes the display, but there is no position of this control I can find, however slowly, that will keep it that way. The plugins I'm using to provide the SNC vary from two SG505s to an SG502 and an AF501. The main SG505 I use has been adjusted by me to provide 200mV at the front SYNC output with this backplane connection in place, which sucks the level down a bit due to the 50-ohm termination, but even setting it as high as 350mV doesn't fix it, and this is about as high as it can go.

I've checked both 24R loading resistors at this input, they are OK, and all these oscillators can trigger everything in the place via their front panel SYNC outputs.

Any clues?


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