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RG501 Ramp Generator running at double speed?

 

Hi,

I am currently repairing an RG501 Ramp Generator and have found it seems to be running at double speed, that is, when I set it to 1ms, it produces ramps of 500us width, this double speed is true for all ranges.
I have set the relevant adjustment pots to center range and it's sitting squarely at this double speed, and the trimpots don't have enough adjustment to correct the issue.

So far, I've checked the voltage rails, all are spot-on. I've replaced the couple carbon composite resistors (all out of tolerance) with metal film, cleaned all the push button switches, and replaced the Sweep Control and Miller integrator IC's with brand new parts (U30 155-0056-00, and U50 155-0042-03 respectively) as they were faulty.

It seems to work fine now, besides the double speed pulses....

Here's the schematic for reference:


Can someone give me some pointers of where to poke? I can't find much data on the Sweep Control IC around.


Thanks!
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