Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12, 2025) x

Thread Closed

Philco 89B, Detector coil repair
#1

I posted several days ago on the WANTED forum looking for a replacement coil.  See https://philcoradio.com/phorum/showthread.php?tid=20069.  After reading the posts there and discussing with Terry via PM I may consider trying to rewind the open coil.

The open coil is the small primary winding.  I have posted several pictures of the coils condition.  In PM discussions with Terry it looks like I could rewind with 25 turns of 34 gauge wire and the direction of the winding is not of concern.

My problem is the removal of the old winding and what looks like the melted remnants of the nitrocellulose material separating the two coils.  Also wondering if the secondary coil may be damaged by the melted remnants although it does show continuity.

An comments or quidance is appreciated.

Thanks, Bob


Attached Files Image(s)
       
#2

I've rewound several of these and have never had a problem with the wire underneath the primary.  Once cleaned up, I usually coat the underlying wire with shellac before installing a replacement for the nitrocellulose.
#3

Is there a proceedure for removing the crusty remnants of the nitrocellulose?
#4

After unwinding the outer coil, most of the residue can be removed with your fingernail.

Steve

M R Radios   C M Tubes
#5

https://www.philcorepairbench.com/rewind...-rf-coils/

Ignore the model numbers and # of turns as those are for early sets than yours but the procedure is the same. I've never done the ammonia thing.

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
#6

NO! do not use ammonia. Ammonia will corrode copper.

Steve

M R Radios   C M Tubes
#7

I was able to remove what remained of the coil wire and nitrocellulose.  Still have continuity on the secondary so guess I am good there.  I will follow the procedures outlined in the above reference but avoid the ammonia.  Any recommendation on cleaning other than ammonia? I counted the turns at either 13 or 14 - hard to tell because the wire was in a lot of pieces.  Does that sound about right for the number of turns?

Bob
#8

> Any recommendation on cleaning other than ammonia? 

I would leave it alone. Any sort of cleaning may disturb the enamel coating on the secondary.

>Does that sound about right for the number of turns?

Sound good.

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
#9

The primary isn’t a tuned circuit so the exact number of turns is not super critical. I would go with the 14. If it doesn’t work well,it would be easier to remove a turn than add one.

Steve

M R Radios   C M Tubes
#10

I finished it up today.  Went with 14 Turns.  Will be a while before I will be able to test it.  Thanks for the help.

Bob




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
54C Complete Teardown/Rebuild
Hello Roy, here is this one sincerely Richardradiorich — 12:45 AM
54C Complete Teardown/Rebuild
Richard, Had grabbed it already but thank you just the same.  I find myself wanting to find some way to block out the...glyphmon — 12:03 AM
54C Complete Teardown/Rebuild
Hello roy, here is a link to the schematic . Sincerely Richardradiorich — 11:54 PM
54C Complete Teardown/Rebuild
Richard, The Silvertone 2014 also is a transformerless set, so I am incorporating a 1:1 600 ohm audio isolation transfo...glyphmon — 11:37 PM
Preliminary work on wife's Silvertone 2014
Did an alignment today which was interesting.  IF alignment went great, almost all was already spot-on.  Adjusting on th...glyphmon — 11:35 PM
54C Complete Teardown/Rebuild
The main problem with adding a Bluetooth input is that this set lacks a traditional power transformer to isolate it from...radiorich — 11:19 PM
54C Cabinet Refinish
I started stripping this cabinet before it got super chilly out because I knew I wasn't going to be able to work on ...glyphmon — 11:18 PM
54C Complete Teardown/Rebuild
While I'm waiting to wrap up the final steps on my wife's Silvertone 2014, I started disassembly on the next project.  O...glyphmon — 11:07 PM
Preliminary work on wife's Silvertone 2014
Hello roy, that great news glad it worked out for you !! Sincerely Richardradiorich — 10:50 PM
Preliminary work on wife's Silvertone 2014
Safety caps arrived today.  Soldered one in and had a successful first power-up.  No magic smoke escaped and it tunes in...glyphmon — 09:53 PM

[-]
Who's Online
There are currently 1908 online users. [Complete List]
» 1 Member(s) | 1907 Guest(s)
Avatar

>