I finished replacing all the components needed in the RCA 56X11, including the IF cans, and moved the switch to the line side of the new polarized plug. I got everything ready to do the alignment, and when I touched the chassis, it tripped my GFCI outlet, which was odd. I looked everything over, and found I had plugged the dim bulb tester into the power strip, and NOT into the isolation transformer. So, remember to double check everything before you apply power to the DUT! That GCFI saved my bacon!
Now I have a question. As I stated, I moved the switch to the hot side, and added the neutral to the “common wiring ground”, at the filter capacitors. In this unit, the “common wiring ground” is lifted from the chassis ground by a 220K 1/2 watt resistor, with a paralleled .1 MFD capacitor. The radio works perfectly after the alignment, and played for several hours just to be sure. Now the part I don’t understand. As I was checking voltages, I found the chassis itself had full line voltage on it while it was on. It was late, and I forgot to check chassis voltage with the unit off, because I was so puzzled. Looking through the schematic, I don’t see how this is possible. Can someone clue me in here? I’m just not seeing it. Hopefully I can attach the schematic.
https://drive.google.com/file/d/1He9tZ0RO6iOeLGS_c6vTI6nj_fc1UUsu/view?usp=drivesdk
I know it’s probably a stupid question, but being a retired Electrician; my first thought was. Your outlet is wired correctly, because believe me I’ve come across some that aren’t?
Woodb180
Remember, GFCIs only need about 5ma to trip. This should only need a 2 prong plug, what is installed? Also, where were the probes when measuring the line voltage on the chassis (AC not DC right)?
Radios + Tubes + Scopes + Cars= Nothing better!
Sorry folks, I see I neglected to state that after the GCFI tripped, I found that I hadn’t plugged the DUT into my isolation transformer, and immediately plugged it into the isolation transformer.
The voltage readings I took, were from the neutral connection of the radio (where both filter capacitors – terminals join), to the chassis of the radio. Then, from the neutral slot of an empty receptacle of the isolation transformer, to the chassis. The radio has a two terminal, polarized plug, and all readings were taken with a Fluke 87V set to AC Voltage.
You did mention that, but it shouldn’t trip being off the transformer. Unless you were completing the path to ground? You also might check resistance from power supply/line to the chassis. To see if somehow the supply is on the chassis, but isolated from the common ground.
Radios + Tubes + Scopes + Cars= Nothing better!
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