Posts: 751
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Joined: Nov 2015
City: Jonesboro
State, Province, Country: AR
I'm working on a Model 144B for friend and fellow member Scott D.
Have run into some issues after doing a re-cap and replacing some out of spec resistors.
1. Wave trap was missing. (Spare 44 chassis has been purchased for parts)
2. Radio is deaf as a post, not even static on all bands except very end of upper SW band.
(I have clipped into circuit a wave trap from a 645 chassis, but part numbers are not the same)
I'm going through and checking EVERYTHING.
I found the B'cast band antenna coil had an open.
(Internal spool looks toasted).
I pulled it and reconnected the end that was broken off, and it now measures 40 ohms.
There are no specs on the diagram. Is this anywhere near what it is supposed to ohm out at?
The other coil (outer winding) checks in at 4.7 ohms. (This is coil 8 on the diagram).
I'm still in process of checking all other coils and making sure all connections are as they should be.
Diagram for reference:
Blessings,
Jeff W.
Jonesboro, Arkansas
http://jeffsradios.weebly.com
God loves you as you are, not as you should be, because none of us are as we should be. - Brennan Manning
Posts: 961
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Joined: Feb 2015
City: Roseville, MN
Hi Jeff - I would try feeding a modulated 460 KHZ IF into the control grid of the 6A7. If that works then you have a large part of the circuit that works. Then you can work backwards through the switch with different frequencies. Or maybe the oscillator isn't running.
If the IF doesn't work then move forward to the next control grid until you get a signal.
Rod
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City: Jackson, NJ
Jeff
1. Ditch the trap, it is not needed.
2. You need to make sure at least that your audio section is alive.
Everything from the speaker, output xfmr and back to the 1st AF (touch grid, hear hum).
Then go about other things.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 751
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Joined: Nov 2015
City: Jonesboro
State, Province, Country: AR
The audio section is working. I do get an audible hum, and a buzz when touching the cap of one of the tubes, and like I mentioned, I did get static from the very top of the upper SW band.
Will continue running tests and checking circuits today.
Thanks for the tip RodB.
I’ll poke around and see what happens.
I have a spare chassis on the way that I can hopefully borrow good parts from.
Blessings,
Jeff W.
Jonesboro, Arkansas
http://jeffsradios.weebly.com
God loves you as you are, not as you should be, because none of us are as we should be. - Brennan Manning
Posts: 102
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Joined: Jul 2017
City: Bakersfield, CA
I am curious why morzh thinks the wave trap is not needed? Was it just a gimmik? I always thought is was put there for a reason - to help tune the signal from the antenna. What am I missing? Thanks for taking time to help me understand.
(This post was last modified: 05-23-2020, 03:23 PM by Scott D.)
Posts: 15,704
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City: Jackson, NJ
Scott
There were some military/govt coastal /maritime stations that worked at frequencies close to the IF, so the wavetraps attenuated the signal from those stations.
These stations no longer are in service so there is nothing to protect from. So a bad wavetrap can be simply removed with no ill effects today.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
(This post was last modified: 05-23-2020, 03:41 PM by morzh.)
Posts: 102
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City: Bakersfield, CA
Thanks! It's always good to know why.
Posts: 751
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Joined: Nov 2015
City: Jonesboro
State, Province, Country: AR
I'm still in a quandary with this chassis. We ordered and received a 44 chassis, in hopes of doing some organ transplanting.
The antenna transformer coil has been replaced. The replacement from the 44 was an exact replacement (Part #2 in the Schematic) and checks out.
It turns out the 1st IF coil has been replaced with a non-Philco part.
I jumpered in the 1st IF from the 44 chassis. The part numbers are not the same.
Radio is still deaf as a post.
A schematic with coil values would be helpful, so I know what to look for.
I'm guessing this chassis was a victim of a lightning strike, since there's a char mark on the chassis near the wave trap, the toasted Antenna Transformer, and now the discovery of the replacement 1st IF.
Any further suggestions? Or Ideas where to look?
Blessings,
Jeff W.
Jonesboro, Arkansas
http://jeffsradios.weebly.com
God loves you as you are, not as you should be, because none of us are as we should be. - Brennan Manning
Posts: 7,283
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Hi Jeff,
You could use the the 2nd IF transformer for the 1st. They are pretty close in an impedance match , the the third is different a it matches the for diode detector. Is everting good up to the 2nd IF IF amp??
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: 07-20-2020, 07:27 PM by Radioroslyn.)
Posts: 751
Threads: 91
Joined: Nov 2015
City: Jonesboro
State, Province, Country: AR
Terry,
Thanks for the suggestion.
Would the fact of different catalogue part numbers
(144: 32-1369, 44: 32-1274) make a difference?
One problem I had was switching over or jumping in the replacement first IF, The adjustable capacitors are external to the coil, and there is no place to mount them in the 144 chassis. On the 44, they are mounted on the back of the chassis with holes drilled for mounting and a hole for adjusting. There is no such place on 144.
Blessings,
Jeff W.
Jonesboro, Arkansas
http://jeffsradios.weebly.com
God loves you as you are, not as you should be, because none of us are as we should be. - Brennan Manning
Posts: 751
Threads: 91
Joined: Nov 2015
City: Jonesboro
State, Province, Country: AR
I took the time to sit down and compare coils and part numbers. With the exception of the first IF and the wave trap, all coils parts numbers are the same, and the coil values are listed on the 44 schematic. So now I need to go through and measure every coil and make sure no other coils are fried From the lightning strike.
Blessings,
Jeff W.
Jonesboro, Arkansas
http://jeffsradios.weebly.com
God loves you as you are, not as you should be, because none of us are as we should be. - Brennan Manning
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