Philco 84 - Printable Version
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RE: Philco 84 - Radioroslyn - 06-01-2012
Here's a better question can you hear it and what frequency is it on? Needs to be 460kc higher than the setting on the dial.
Terry
RE: Philco 84 - Jim Dutridge - 06-01-2012
The 460KC IF comes thru nicely with the signal generator set to the lowest output and being fed thru a .01MFD cap to the antenna connector. The IF condensors #11 and #15 tune it just fine. But no matter what frequency I place the generator on or output level I cannot hear any signal thru the speaker, not even the faintest noise.
Maybe I'm not checking the correct point on the 77 tube for oscillator operation. From what pin to what point do I need to connect the meter to?
RE: Philco 84 - Radioroslyn - 06-01-2012
Ok Take a 1/4"nut driver and screw in trimmer 13 till in is compressed. DO NOT over tighten and break off screw. Loosen it 3 turns. Set dial at 1000KC. Use a transistor radio. Hold it next to the mixer tube. Tune the transistor set till you hear a hum. To make sure you are hearing the mixer (local oscillator) move the transistor set away from the tube and the hum should diminish. Also if you change the dial setting on the Philco you should be able to follow the signal with the transistor set by retuning it. If you still can't here the signal set dial on the transistor set for 1500kc. The Philco at 1000kc adj trimmer 13 to see if you can find it.
GL
Terry
RE: Philco 84 - Jim Dutridge - 06-04-2012
Terry, no good on finding the signal either way you stated. Even tried connecting the generator to the 77 grid using low, mid, and high output and nothing. Looks like my attempt at rewinding the oscillator coil was not successful, even though I show good continuity on the rebuilt winding. Guess I'll be hunting down a replacement.
RE: Philco 84 - Jim Dutridge - 06-12-2012
I decided to rewind the oscillator coil and after installing in the radio I was able to get squells, whistles and a few stations so I guess I did it right this time. However, when i went to recheck the 460 KC alignment i get nothing thru the radio, which i did have before I rewound the coil. I tried injecting at the antenna clip as well as the grid of the 77 and nothing.
RE: Philco 84 - Radioroslyn - 06-13-2012
Go back check plate and screen grid volts and make sure you cathode circuit grounded though the feedback winding.
Once you get the IF working again Try feeding a unmodulated signal into the cathode of the mixer tube 460kc higher than strongest station in your area. Tune the radio dial to the frequency of that station. Hook an antenna to the set and you should be able to hear that station coming from your set. The signal generator is acting as the local oscillator as you tune both the radio dial and generator you should hear all the stations you would normally hear.
Terry
RE: Philco 84 - Jim Dutridge - 06-15-2012
After playing with compensators #11 and #15 I can get a very low 460KC tone thru but thats at the highest output setting of my generator. Also, depending on where the compensators are set I can get squeals, whistles and the occasional 1 station to come in, although its at the upper end of the band and its not always the same station. Sometimes its the strongest here in Toledo and other times a weaker one.
Some voltage readings I took are:
Det/Osc:
Plate to Cathode 229V
Screen to Cathode 98V
2nd Det:
Plate to Cathode 64V
Screen to Cathode 45V
Seems like these voltages are Ok and I did have a good solid 460KC thru the radio with generator set at the lowest output before I rewound the osc coil the second time. YES, I did connect the wires to the osc coil correctly, and even went thru the wiring twive to make sure. I just can't grasp the reason why I can't get that D**n 460 thru now. I've tried going thru a .o5MFD cap to the antenna clip and control grid of the osc/detector tube and even tried a direct connection thru the grid but still only a very low tone thru.
RE: Philco 84 - Jim Dutridge - 10-14-2014
Bringing up an old thread. I put this back on the bench and still can't get a strong 460 KC thru the radio with the generator connected directly to the grid of the 77. Adjusting the compensators makes no difference in volume of the tone and adjusting #15 will give a squeal now and then.
I really need some ideas here. I have tried all the previous ones but they just don't seem to work.
RE: Philco 84 - morzh - 10-14-2014
A dumb question: is your grid clip from antenna xfmr disconnected fom the grid cap while you are applying the signal?
RE: Philco 84 - Jim Dutridge - 10-14-2014
Nope, could that be a problem?
Removed the grid cap and tried again. Best I can get is a signal thru with squeals and howls on the highest output of the generator but when I go to the medium output, its an Eico 324, the radio goes dead silent.
RE: Philco 84 - morzh - 10-14-2014
Jim
It might be a problem, usually you disconnect the gid cap from everything prior to connecting it to the SG.
For starters, when connected, your volume might be at Low and then it will simply shunt the SG via reflected resistance (your antenna coil is a transformer).
Also: if it squeals and howls, this being a regen radio, you need to turn your feedback trim cap (or is it a pod? I keep confusing the two) until it stops. It even might motorboat.
Then see if you could pass your 460kHz.
Also have you checked the tubes? Regens are sensitive to tube quality, especially Det-Osc.