Re: Curve Tracer 576 - current consumption

Bob Koller <testtech@...>

I think you have a problem with the CRT HV module. The burned resistor is a clue. If the HV oscillator is not running properly, or is overloaded, the mains current will be very high. Disconnect the 100V source to the HV module and see if the mains current is low.

From: Dr. Matthias Weisser
To: TekScopes@...
Sent: Tuesday, May 1, 2012 6:28 AM
Subject: Re: [TekScopes] Re: Curve Tracer 576 - current consumption

Thank you Albert for this hint. I tried all those
settings but the problem remains with all of those.

No problem to see if I turn mains voltage to zero
switch then on and turn voltage up to 220V.
Also seems to be better when some time the 576
was on and then switched on and off.

Problem comes again when 576 is some time off.

Now I changed all of the power supply diodes on
the rectifier board and I cut off all the bigger 0.022uF caps
from Sprague to be sure they are not the problem.

Also the upper cap 4200u 30V from Maxwell got
replaced. Did not change anything. The capacitance
was still there - only ESR not so good compared to
newer ones. So may be the other huge caps are also
ok. My ripple measurements some weeks ago did
not show a problem. Also the voltages were ok these days.

The problem only is there when powering up in a very
short instant. Not so easy to measure because there
are just some seconds before the mains current goes up
really steep. No smoke to see up to now.

May be another cap defective somethere? 


Am 01.05.2012 12:16, schrieb Albert:
I vaguely remember that my 576 had a rattling relay sound (and didn't work) in one of the front panel choices (polarities NPN or PNP, or maybe Display polarity). It was a fault in the relay driving voltage, not in the relay itself. Did you try different front panel settings?

--- In TekScopes@..., "matthias_weisser2002" wrote:
> ---
> The problem now is a bit more tricky. When I switch power on there is an initial current draw of about 0.5A at 220V. This is going up steeply to 2A or so when I let it switched on for just 30 seconds or so. Therefore I am switching off quickly. When I am ramping up mains voltage manually no such current draw can be seen. I can hear some relais clicking. May be a relay fault when switching on immediately? Seems to be hard getting to the relais.

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