Did you checked the supplys for ripple voltge with a scope ? If ripple if excessive the DC can look higher for your multi meter. Is adds the average AC from the ripple to the DC.?
Fred PA4TIM
Op 19 mrt. 2013 om 03:46 heeft "Philip" <
ndpmcintosh@...> het volgende geschreven:
?
In getting started troubleshooting a 2213 with low gain on one channel, I figured I should probably check the supplies just to make sure they were okay -- they aren't.
They are all significantly high and won't adjust (-8.6 is -9.5, 100 is about 110, etc.) The preregulator is good at about 42.7. I checked the primary on the transformer, figuring there is nothing on the secondary side that could cause such a problem, and it is being driven at about 175VAC whereas in comparison to one that is not running at overvoltage I got around 154VAC. This makes sense -- if the primary voltage is too high, the secondary voltages will all be too high too and that is exactly the situation. The transformer windings ohm out okay (low resistance, no shorts and exactly like one that I compared it too)
So, in troubleshooting the inverter with power off I can find nothing wrong with it either. With power on, measuring the voltages on the smaller transformer connected to the switching transistors Q40 and Q42 I see no difference compared to one that is working normally and I see little difference in comparatively measuring the voltages on the collector, emitter or base of those transistors either.
I even followed the troubleshooting chart in the manual as well and it says to check the error circuit in the inverter (which I already did because I was sure I would find an obvious problem there) but no dice. But, I don't have an isolation transformer and Variac so I can't do it quite the way it recommends.
I'm stumped (for now).
Phil...
P.S.
I could still use some advice on whether to build an HV multiplier or I should just bite the bullet and scrap one defective scope (maybe this one!) and cannibalize it for that and other parts.
