[tmr63]

Self-quarantined with lots of time on my hands.  Decided to take a few Philco boat anchors off the shelf and give them another try.  Finally finished the model 89.  Had to rewind the oscillator and 1st IF transformers. photo attached.

Decided to take on the Philco CT-2 car radio again.  Again, its driving me crazy and I sure could use some input.  The oscillator will not run on its own. The transformer is the original and not the new version that was changed (blue coil not red) in the later runs. (photos attached)
I removed it and it looks ok. Numbering from the ground to the top 1-4 it measures
( 1-2… 1.32 ohms ) ( 2-3…3.74 ohms ) ( 3-4…1.64 ohms )
( 1-2…21 uh ) ( 1-3…149 uh) ( 1-4…150 uh)

I removed the C12 & R11 and put in a decade box.  The oscillator fired up with 1.4K & .0015uf. However, it will not run with my scope probe removed from the top of R11.  I added 2pf which is the scope lead value but no luck.  If the oscillator runs, I can drive a signal from the antenna input to the speaker with volume control using the 260kc offset for the station frequency through the center portion of the band So everything else appears to be working.  Also tried 3 separate 77 tubes

The lower portion of the coil appears discolored as if it was overheated.  I really hate to rewind this transformer; it looks like a pain.  I would guess that Philco changed the turns on the newer coil, but I have no idea what they would be.
I could really use some input on this one
Tom

[fenbach]

tmr63,
if the resistances are good, the oscillator coil obviously isn't open. and, in my experience, is good. check the resistances in the RF transformer [part no. 9]. I don't know which pins are which, but 2 of the measurements should be small, the others infinite. you can check these with the transformer in the radio. i'm guessing that your offset signal thru the antenna is just bypassing the RF and det-osc tubes and going straight to the IF tube. i'm also guessing that the outer coil on the RF transformer is open.
i've also found that if the low frequency padder [part no. 15] is very far out of adjustment, i'll lose reception. pay close attention to it's setting and adjust it back and forth to see if that helps. you could also put a modulated RF signal into the grid of the det-osc tube. set the tuner to match the frequency. if it gets thru, the oscillator is obviously working.
i attached a scan of a document I got from Gary Schneider about open coils. he believed that the celluloid shield between the inner an outer coils released nitric acid which ate away at the outer coil. and turned it green. since the oscillator coil doesn't have a shield, and yours isn't green, most likely it's good. interestingly, Gary's web site is still up and running altho, sadly he isn't.

http://www.oldradioparts.com/

good luck. and keep us posted.

bob

[tmr63]

Bob
Thanks for the input.  I did get the oscillator to run by dropping the 11K resistor all the way to 1K
and changing R3 (70K)….It was out of tolerance.
I also installed a #36 tube for the RF
one of the schematics called for a 39/44

On your suggestion I rechecked the RF transformer.  

It seemed resistances came up defying common sense.
I have Coil #1 out of the radio and it reads  19.3 ohms on the primary
However the secondary reads across the coil 7.57 ohms
from the bottom of the coil to the center tap 6.55 ohms
from the center tap to the top of the coil to the center tap 7.75 ohms

I would expect the total coil resistance to be 7.75 + 6.55...14.30 ohms total ??
I have no clue as to what is going on here?

I will probable unwind  it to try to figure out what gives.

Tom

[fenbach]

tom,
your resistance readings sure don't "add up." but you must be looking at the antenna transformer if it haws a center tap. it's part no. 1 on the schematic attached to your first post. the readings suggest maybe a short in the secondary coil?? even so, i'd wait before unwinding it. you can test the rest of the circuitry by putting a modulated signal into the grid of the 36 tube. i'd leave the antenna transformer out for now in case it is shorted. I still think the secondary of the RF coil, part no. 3, is open. it only has 4 leads, connected in pairs. again, you can check those resistances [2 low, the rest infinite] with the transformer in the radio. double check to be sure you really do have the RF transformer and not the antenna transformer. it's the one connected to the plate of the 36 tube. the antenna transformer is connected to the grid [cap] of the 36.
funny [to me] that changing the resistor would make a difference. you might check the capacitor, part no. 12. those little guys typically don't fail, but maybe it's open.
good luck. and let us know.
bob

[tmr63]

Bob

Thanks for your help.  It got me in the ball park once I could drive a signal from the Oscillator grid.
 
What I found was there are 2 caps marked c35 on the schematics !! Put two in on opposite sides of the chassis making the value x2. And one missing cap needed for isolation.   Gotta love Philco schematics…My Bad! 
Once corrected I was able to get back to the correct values for the oscillator RC timing values
 
Everything trim’d up but couldn’t get through the rf amp
Antenna coil measured crazy on the secondary. I unwound it and it
turned out to be not even close to the schematic.   Ended up unwinding and documenting it then rewind
There were 3 layers separated by parchment paper.  I rewound it.  What a pain! Wish I took your advice and left it alone.
 
Final problem was some sort of resistance wire buried deep in the chassis inside of a covering....(R8).
R8 was open so no bias on the cathode of the rf amp.  I attached pictures of the coil and the (resistance wire R8)
 
Radio is working and trimmed to spec.
Will never go near one of these again!
 
Another Philco from H**l

Tom

[Tim Tress]

Those flexible resistors are not unique to Philco; they turn up in other sets as well. They tend to be fragile, and sometimes open up.