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Philco 81 Questions - Printable Version

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RE: model 81 capacitors - ohiobill - 03-07-2017

Thanks, will stay with the schematic values.

RE: Philco 81 Questions - klondike98 - 03-09-2017

I merged the Philco 81 capacitor questions with your other Philco 81 electronic restoration questions. Please keep the thread together. Sounds like you are doing great.

RE: Philco 81 Questions - Radioroslyn - 03-09-2017

I'll mention in passing that all carbon resistors in this set are rated @ 1/2 watt except for #14 (9,000 ohms) and # 16 (16,000 ohms) These should be 3-5watt as they are the voltage divider for the mixer tube.

RE: Philco 81 Questions - ohiobill - 03-16-2017

Hi all, Just got my new caps and resistors. I have a question about the bakelite box #3615-ODG. Listed as #35 on the schematic. The Philco service bulletin #289, shows that it uses 400 volts, using ,05 Mfd. What I took out of mine was showing a number 8 on the two caps. However, The schematics show that I should be at 600 volts using .015 Mfd. Which is the correct cap that I should use. Thanks

RE: Philco 81 Questions - Radioroslyn - 03-16-2017

As you noted there are 2 caps in #35. One is the AC line bypass (connected to the pri of the power transformer). A .015 @ 630v is fine there. The other cap is bypassing the bias part on the power supply. .05 or bigger is good voltage is pretty low, less than 25v. I would use a small electrolytic like 25mfd@ 35v. Connect the positive to the chassis and negative to wire wound resistor.

RE: Philco 81 Questions - ohiobill - 03-19-2017

Electrolytics ? There is a 4ufd and there is a 8ufd. I have been mailed a 10ufd capacitor and been told to use these . Is that correct?. Even for the 4. Sounds like it is a bit overkill. That is what the parts supplier has told me. 450v

RE: Philco 81 Questions - Radioroslyn - 03-19-2017

There fine. I won't tell you what I put in mine.

RE: Philco 81 Questions - ohiobill - 03-19-2017

Thanks Terry, The can cut apart like butter. Drilled a 1'16th hole in rubber next to alluminum rod and another hole in can to run the ground out to the lug that the clamp holds. Now to put can back together.

RE: Philco 81 Questions - ohiobill - 03-26-2017

I have removed the ocillator coil. It looks to have an inner tube and winding on it. Do I have to remove it and how.
The secondary does show continuity. I took the old rotted windings off the primary. Going well.

RE: Philco 81 Questions - Radioroslyn - 03-26-2017

If the 2ndary (large winding) is showing continuity I'd leave it alone. It's much more critical than the primary (small winding) as it determines the operating frequency of the oscillator. All the primary does is create feedback so the oscillator will run. It doesn't have much to do with frequency.

RE: Philco 81 Questions - ohiobill - 03-27-2017

Ocillator Coil on model 81.

My problem is that I am showing continuity from pin #1 first pin from left side of the ground terminal to pin #2 about 3.2 and continuity from pin #1 to pin #4 ,5.5 Now I also have continuity from pin #2 to pin #4 2.8 Is it possible to have three terminals show continuity. I have not rewound the primary winding yet because I do not know which terminals the two ends come out on. They were gone when I unwound the wire which was all corroded. I do know that the first teminal to the left of ground goes to oscillator. 2nd terminal goes to a trimmer top terminal at chassis. Third terminal goes to tube 77 pin 5 of that tube. From terminal 3, it has a resistor to span to terminal 5. Terminal 4 on oscillator coil has a wire going to another trimmer bottom lug.. I just don't know where the primary coil wires go.

RE: Philco 81 Questions - ohiobill - 03-27-2017

The compensating condensors is what I described as trimmers in my first post. Sorry about that.

RE: Philco 81 Questions - morzh - 03-27-2017

If the coil is 5-pin one, then you should have 3 pins showing continuity, 2.7 Ohm and 2.6 Ohm or 5.4 Ohm end-to-end, and then 3.9 Ohm for the remaining two (don't know what numbers they are, the sch does not show them).

RE: Philco 81 Questions - ohiobill - 03-28-2017

Thanks, I have talked to Terry, and he explained which ones. Now if I wound in the right direction on the coil. I am getting a faint hum through the speaker. A little louder at the 500kc end and fainter at the high end. A little crackle but no stations