Re: 577 AC collector supply not reading zero on display

DW
 

Thanks for the reply

With the collector in AC on 6.5V with 2k series resistor, horizontal devision set to 50mV...
A flickering line appears 2 divisions in length
I find if I increase the D1 brightness (Turn the D1 brightness fully clockwise) the flickering pattern goes away into a solid green light which is interesting to note
I plugged a voltmeter into the Emitter and collector terminals and observe 38mV of AC voltage
I short the emitter and collector terminals and find the 2 division line shrinks to a dot and the voltmeter reads about 0mV AC
Obviously some small amount of AC power is getting through and measured on the display and voltmeter

When I put the collector in DC- PNP the line shifts to the upper right corner of the display as a dot with the voltmeter measuring about 9mV AC, barely visible on the display
When the LEFT RIGHT selector switch is switched to neutral position I observe 500mV AC, strange
When I put the collector in DC+ NPN the line shifts to the lower left corner of the display as a dot with the voltmeter measuring about 9mV AC, again barely visible on the display

I find if I select any position other than AC on the collector the display shots a dot.

In the following test I put the collector to 25 volts 2kohm in DC- and DC+ at 0 collector voltage 50mV Division and measure the emitter to collector voltage of any slight DC voltage
(DC+ -0.4mV) (DC- 0.3mV)
Interestingly when performing this test I found if I move the series resistor control above 2kohm the dot starts to become the flickering line I observe before in AC but now it is in DC+ or DC-, If I set the series resistance lower about 2k or below the flickering line becomes the dot.

In AC 25V 50mV Division, changing the series resistance has no effect other than just displaying a line that is 7 divisions long which is pretty bad!

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