I’m still very new to radio restoration and am working on a Philco 19X that I believe has problems with the detector and oscillator coils. I’m not sure how to properly test coils but I did a sound continuity test between the 5 pins of the detector coil and got continuity between #2, #4 and #5, nothing between #1 and #3. The ohm readings between those pins are on the enclosed photo.
I would appreciate it if someone could confirm that what I assume is the secondary, needs to be rewound and if so, what gauge of wire I require. It looks to be about 14 turns but my eyes are older then the radio so it’s hard to tell. ?
I’ll leave the oscillator coil for a later post just in case my assumptions on this coil are wrong.
Also if anyone can lead me to a post or even better, a video as to how to properly test coils, it would be greatly appreciated!
It would appear that the feedback winding is open which will render the local oscillator inoperable. It's the small winding on the outside of the oscillator coil. Remove that winding, insulator, and discard replace insulator with a replica made from thin plastic. Rewinding requires 38 or 36g wire at about 14t. You can run a needled over the existing winding and count the bumps to ascertain the correct number. Direction is important. Wind it the wrong way around and won't oscillate.
Before you pull the trigger do check the wires going from the winding to the terminals that they go to that winding that is suspect. Since the diagram doesn't list the pin connections vs what winding. I can't make a absolute answer that coil is open but there's a real good chance.
GL
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
(This post was last modified: 08-19-2022, 03:36 PM by Radioroslyn.)
Thanks for the information Terry. Does it make a difference though that this is the detector coil and not the oscillator coil. I haven’t pulled out the oscillator coil yet but I believe I have similar issues with that one as well. The antennae coil seems to be fine.
I checked and the windings do go to the suspect terminals.
I'm talking about the coil #12 the oscillator coil for now. #8 doesn't have a tertiary winding just two windings one with a tap.
Since there is no pin out for the coil base go ahead and tack #8 back in place and we can figure what pin go to what components. Then this will tell what sections are open on #8. Or just count the turns, measure the size of the wire with a micrometer and rewind.
One thing to look for is green dots on the windings. This is where the copper has rotted and that portion is no good. You can clean the wire just past that area and check the resistance to the other end for continuity. If good you can solder new wire (splice) for the repair.
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!
I ended up rewinding both the detector coil, 14 turns and the oscillator coil which was 27 turns. That was the best estimate my eyes could figure out. Glad I did a count before I tried to unwind them because the wires were broken in quite a few places. I used 32g wire for both coils and everything worked out well! The radio plays great and just waiting for some dial cord to complete the radio.
Glad to hear you got it sorted and working well. Some would say those sets (89/19) are tougher than the average bear to fix. The mixer circuit tends to be problematic. But you nailed it.
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!
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