08-05-2025, 11:56 PM
Hi and welcome,
Two quick service notes for your mdl 20. The filter caps in #26 should be replaced with mylar style cap and not electrolytics. They can't take the ripple current and will overheat causing one or more to short, not good.
Use an ohm meter to measure the resistance from one pin on the spkr plug against the other 3 one by one. Should less than 4,000 ohms. That's the field coil's resistance (3,100)+ the output transformer (abt 500 total). It's not uncommon for the fc or 1/2 opt to be open. Doesn't hurt to know where you stand. Sometimes it's a bad connection.
Two quick service notes for your mdl 20. The filter caps in #26 should be replaced with mylar style cap and not electrolytics. They can't take the ripple current and will overheat causing one or more to short, not good.
Use an ohm meter to measure the resistance from one pin on the spkr plug against the other 3 one by one. Should less than 4,000 ohms. That's the field coil's resistance (3,100)+ the output transformer (abt 500 total). It's not uncommon for the fc or 1/2 opt to be open. Doesn't hurt to know where you stand. Sometimes it's a bad connection.
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 it!
Terry
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
