Philco 37-60: Opened Antenna Transformer/Coil - Repaired - Printable Version
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+--- Thread: Philco 37-60: Opened Antenna Transformer/Coil - Repaired (/showthread.php?tid=21205)
Philco 37-60: Opened Antenna Transformer/Coil - Repaired - whirligig - 04-18-2020
Well, it's been 8 months since I put this radio on the back shelf. I thank this group for helping me configure a tone control that was absent. Now that the shop is closed down due to the pandemic, the boss asked me to take a couple of radios and work on them at home. The 37-60 with the band antenna coil was one of them.
After some struggle the other evening, I was able to extract this coil out of the radio. Attached are some photos. My evaluation so far:
- The lower longer coil is the secondary and it measures 6 ohms at wires #4 & #5. That would be the lower wire at the bottom and the upper wire directly above it.
- The upper coils is the primary. I would guess it's about 40 turns of #34 but I'll check. It has a center tap and thus three connections. All are opened.
- In two of the photos, you'll see hown one half of the primary windings overlaps the other half. I thought this was strange.
- I believe the coil was mishandled. Possibly someone poked something through the tube and sheared off a couple of wires.
The next thing I plan to do is use a heat gun and melt some of the bee's wax around the primary and see if there are any loose ends that can be repaired. If not, then get a turns count and direction and proceed with the rewind.
Any thoughts?
Thanks
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Update: The primary on the antenna coil has been rewound. 34 gauge wire with 16 turns to the center tap and another 16 turns from the center tap to termination. The radio was aligned. It is sensitive and selective. There was another issue discovered during alignment and that was motorboating on the lower broadcast frequencies. That was resolved by re-routing a wire that away from the Rf section where the oscillator coils are located. See photos on my last post.
RE: Philco 37-60: Opened Antenna Transformer/Coil - morzh - 04-18-2020
The shorter coil doesn't look too menacing.
I would rather rewind it.
RE: Philco 37-60: Opened Antenna Transformer/Coil - whirligig - 04-18-2020
Well, after removing some of the wax it looks like I have no choice but to rewind.
I got the direction of the turns, now I need to get the number of turns to the center tap.
Counting the turns is pain even with an optivisor, loupe, and pointer.
Woohoo, I just found an easier way to count the turns on this coil. I took a photo of it with my phone.
It looks like 16 turns to the center tap. Maybe 32 turns total. That's doable.
RE: Philco 37-60: Opened Antenna Transformer/Coil - whirligig - 04-20-2020
Hey hey, the coil is done. I installed it, reassembled the radio and it plays. After an alignment, I'm picking up stations from 1600 down to 700 khz without an antenna, so sensitivity and selectivity is good. But, I'm ran into an issue during the alignment. I begin to loose signal right around 700 khz. I can't hear KFI 640 and motorboating begins softly around 600khz and roaring when it gets to the lower end.
The other problem is howling around 7mhz on SW. First encounter this during alignment.
I would appreciate any suggestions. I'll probably go over the work my colleague did on this radio. There are a couple of original micas still in the radio that needs to be checked.
RE: Philco 37-60: Opened Antenna Transformer/Coil - Repaired - whirligig - 04-24-2020
Motorboating was fixed by re-routing a wire. See photos. The re-routed wire was carrying pulsating DC from one electrolytic to another.