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Philco 60 - antenna wavetrap? - Printable Version

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Philco 60 - antenna wavetrap? - winston763 - 04-22-2014

Hi, I can send a EICO signal generator signal from the wave-band switch forward to the speaker. However, when I go back to this capacitor (wavetrap?) between the switch and the antenna, no signal is passed nor of course from the antenna. I also can send a signal thru the antenna connections on the wave-band but when I attach it to the lead with the 10k resistor - nothing. I'm so close. Thanks Rich

RE: Philco 60 - antenna wavetrap? - exray - 04-22-2014

Your terminology is confusing but if you want to inject the signal generator via the antenna teminals simply detune the wavetrap temporarily by a few truns of the trimmer and then reset it when you are done. The wavetrap is only going to affect injection of a 455/465 kc signal.

RE: Philco 60 - antenna wavetrap? - Roger Cole - 04-22-2014

Attached is a pic of my Philco 60 chassis prior to restoration with the wavetrap marked. The flat metal part is the capacitor, and there is an inductor buried back behind the cap. There is an adjustment screw for the cap accessible from the top side of the chassis.

The purpose of the wavetrap is to block IF frequencies (460 kHz here) from entering the antenna circuit. Anything at those frequencies coming in from the antenna is noise, and it blocks this from the RF and IF amplifiers. The later models of the 60 had this, and you can see the updated schematic at http://www.philcoradio.com/tech/60evol.htm

I'm not really sure where you are trying to inject RF, or what frequencies you are working with. Try posting a picture of which cap you are concerned with and I might be able to help.

RE: Philco 60 - antenna wavetrap? - winston763 - 04-23-2014

Hi, I can put a signal in the tube 6A7 and I can even tune the signal via the high frequency and antenna compensating condensers. I can clip the signal generator on the antenna coil wires and hear a signal. I can set up the signal generator to tune to a known channel, checking with a modern AM radio then tune my radio to that frequency when the signal generator is clipped to the antenna coil, yet I can't get a signal from the actual antenna connection. From the antenna connection to the wavetrap then to the wave band, nothing. when I switch between bands, it does change the properly from the switch forward but doesn't change any reception from the antenna. I soldered the wires again but no change. I wonder if the wire going to the antenna coil is broken even though I checked it? Rich

RE: Philco 60 - antenna wavetrap? - winston763 - 04-24-2014

Roger, hope you don't find too much wrong. Thanks, Rich

RE: Philco 60 - antenna wavetrap? - Roger Cole - 04-24-2014

Sounds like you are making progress. I get the sense that your problem may be in the antenna transformer, so here are the notes I made when I worked through that section. The values noted are my measured values.

The antenna input into the primary is a wire coming down from above which does not have a solder tab. In my set, the 0.3 ohm section was open and I had to rewind it. I used 7 turns of magnet wire, being careful to wind in the same direction as the original. I found a very helpful post on this forum about that particular repair.

I would suggest trying to feed some audio riding on a 460 kHz carrier into each point in my diagram. Make a chart of where it works and doesn't work, and you can decide if your antenna transformer is working or not. If you use IF instead of some other RF frequency, you should be able to hear something regardless of the tuning capacitor setting. (In theory all of the 460 kHz should be rejected by the tuning circuit, but in practice some will make it through to the IF circuit and get amplified. This is why they have a wavetrap.)

It's hard to really trace much from your picture given the resolution limits. Simple things to think about would be to check your solder joints (a cold joint can be surprisingly tricky to figure out!) and making sure all connections have good mechanical support.

If you would find it helpful, shoot me an email address and I will send you a full resolution picture of my chassis before after restoration.

Keep trying. You are getting very close!

Roger

RE: Philco 60 - antenna wavetrap? - winston763 - 04-25-2014

Roger especially, but all who helped me. It is a testament to this forum that you guys would take your valuable time and help novices like me. This is really a great community. In return, I hope someday I can help someone else - but I have much to learn. Rich