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 Post subject: Ceramic trimmer capacitor helpl
PostPosted: Nov Sun 10, 2019 1:54 am 
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Joined: Jul Sat 20, 2019 10:38 pm
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I’m restoring a Philco 42 PT7 radio as my very first radio restoration. I unfortunately was dumb and took the I.F out of its can to replace a couple shotty wires and managed to accidentally disconnect all the coil wires from the capacitor... I took pics before hand but I can’t for sure recognize where they all went. I’m hoping someone on here can guide me so I can make sure they get put back in the proper spots please?

Thank you!


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 Post subject: Re: Ceramic trimmer capacitor helpl
PostPosted: Nov Sun 10, 2019 3:04 am 
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Location: Santa Rosa, CA
I think this is for a tube radio, not a transistor radio?

Rich


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 Post subject: Re: Ceramic trimmer capacitor helpl
PostPosted: Dec Tue 03, 2019 4:16 am 
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Location: Port Orchard, Wa 98366
The Schematic is in Riders Vol 14, Philcopage 17-18.
The PDF page is 697

You will see the coil resistances which you will have to measure. Then you can determine which coil is primary and secondary.
Did you mark the I.F. can as far as which way it was before removal?
I don't think (however I may be wrong) it matters which lead goes to which side of the coil. You may have to try swapping those fragile wires. If the two coils interact (induction). Resulting in a Weaker signal throughput.

The coils along with the trimmers make a filter to remove the RF frequency from the mixture of RF-IF frequencies. It will allow the IF frequency to pass to the next stage. The primary coil is the output from the prior tube and the secondary coil Transfers that signal to the next tube's grid.

You may have to see if the other IF can could be used as an example as far as lead position and connections from the coils, inside the can to caps connections.

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 Post subject: Re: Ceramic trimmer capacitor helpl
PostPosted: Dec Mon 09, 2019 2:08 am 
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With the resistor on the trimmer assembly, this is the output IF transformer. The first thing to do is find the wires to both windings. The 47k resistor will be connected to one of the trimmers, one of the lugs on the outer edge of the trimmer assembly. One of the wires from one of the coils will connect there. This lug will be adjacent to one of the adjustment screws on the top. Directly opposite that lug, on the other side of the screw, is where the other wire from the coil will connect. Examining the trimmer assembly closely, you will be able to see that the trimmer lugs are in two pairs.

In the same way, the wires from the other coil will connect to the other pair of lugs; this is the primary winding, and connects to the plate of the IF tube and B+.

Back to the resistor! The other end of the 47k resistor will be connected to another lug on the trimmer assembly; this is where the wire to the volume control connects. There will be one remaining terminal on the assembly, and that will connect to B-. I hope that this is clear enough; see the schematic.

Before reassembling the transformer, make sure that both windings have continuity, measured across each trimmer.

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Last edited by Tim Tress on Dec Mon 09, 2019 2:21 am, edited 1 time in total.

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 Post subject: Re: Ceramic trimmer capacitor helpl
PostPosted: Dec Mon 09, 2019 2:16 am 
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OP asks a question, then doesn't come back to see any answers -last visited Nov 9- just love these drive by one post wonders... :roll:

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 Post subject: Re: Ceramic trimmer capacitor helpl
PostPosted: Dec Mon 09, 2019 2:23 am 
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Well, maybe my post will help someone else out, down the road.

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 Post subject: Re: Ceramic trimmer capacitor helpl
PostPosted: Dec Mon 09, 2019 3:25 am 
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I'm sure it will.

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