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Connecting Test Equipment to AA5 radio
05-07-2010, 11:50 AM
It's been a few years since I worked on AC/DC AA5 sets. I use an isolation transformer when I work on them. I have forgotten how to safely connect test equipment such as a signal generator and VTVM to these sets. I have a Heathkit VTVM that has a 3-prong cord. With the radio connected to the isolation transformer, how do I connect the negative test leads to the set?
05-07-2010, 05:14 PM
With the isolation transformer you can connect the - lead right to the chaiss. Without the use of an isolation transformer you can measure the voltage from earth ground to chaiss ground. If you get 120vac flip the ac plug around and you should measure a small amount of ac, the difference from neutral to earth ground. Just make sure you don't have 120v from the chaiss to ground and you will be fine.
Terry When my pals were reading comic books I was down in the basement in my dad's workshop. Perusing his Sam's Photofoacts Vol 1-50 admiring the old set and trying to figure out what all those squiggly meant. Circa 1966 Now I think I've got! Terry 
05-07-2010, 11:14 PM
Poor Man's Method = Battery operated DMM and link coupling from the signal generator to the loop antenna.
05-10-2010, 08:16 AM
I haven't found it so much with radios but DMM will drive you nutz on TV's. If the measured volt isn't pure (mixed with a little rf or ac) the DMM will give an incorrect reading. Also vom's and vtvom usually are what the manufacture used way back when the set was built to make up the voltage charts for testing. I do like the DDM for resistor checking.
Terry When my pals were reading comic books I was down in the basement in my dad's workshop. Perusing his Sam's Photofoacts Vol 1-50 admiring the old set and trying to figure out what all those squiggly meant. Circa 1966 Now I think I've got! Terry
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