[Radioroslyn]

No worries simple fix! Take the magnet wire leads from the small winding on the osc coil and reverse them where they are soldered onto the lugs. That should get your osc running.
Terry

[dseverson]

Well, apparently this isn't a simple fix. I think I really screwed up. I rewound both antenna and oscillator coils and I can get one station to come in if I touch the top of 6J7 but that's it. I am amost ceratin I have the correct number of turns on both. I'll double check and check the resistors and caps but I need to put this down for a while and work on something else.

[dseverson]

Ok. So I couldn't keep my hands off this little radio for too long. I took another look at my windings on the oscillator and antenna coils and decided to rewind both - again. Radio still doesn't get reception but static. It's the same up and down the dial. I took more measurements with the DMM and got the following:

Oscillator - 4.9 on #2 and 1.4 on #4
Antenna - 1.6 on #2 and 7.9 on #3.

That 7.9 reading seems high but what do you guys think?

[Radioroslyn]

The resistance sound ok but that doesn't mean much. What you need to know is where is the coil resonant? Or the inductance. This can be found out by using a GDO (grid dip meter).
Terry

[dseverson]

Came back to work on this radio again. Found the output transformer was open so I put in another speaker assembly. The radio pulls in one or two stations at the low end of the dial around 610 -640, faintly.

I measured between the GND and ANT posts with the volume all the way full and it reads 14 ohms. Is that too high? Sound like I messed up on the antenna transformer rewind? The radio was unplugged.

[Radioroslyn]

Hi David,
Have you checked to see or hear if the local oscillator is running? If it is running properly it should be heard 1000kc at the low end of the band (530kc) and at 2170kc at the top end. LO frequency= Dial frequency+IF frequency (470kc). 

As I mentioned before the larger winding on either coil is critical to the operating frequency of that tuned circuit. On the antenna coil the small winding couples the RF signal from the antenna to the input of the mixer. It isn't very critical, the more turns the more signal applied to the secondary.

On the osc coil the small winding is there to provide feedback to make the LO oscillate. Direction is critical. Number of turns, not enough won't oscillate across entire band. Too many will make the oscillator generate harmonics.

Best I remember about 25turns for either coil should work. Is the IF on frequency?? Use signal generator set at 470kc hooked to the grid cap of the mixer. Peak the IF trimmers.

Terry

[dseverson]

Looks like I'll have to break down and buy a signal generator. Know of any cheap ones that work well enough for this type of operation?

When the radio is tuned to the low end of the band around 530 or so and at the top end, it squeals. Is that the oscillator running? Is there a way to check it with a transistor radio?

I'm pretty sure I wound both the antenna and oscillator transformers correctly but I can go back and check. You say that the secondary windings on both the antenna and oscillator coils were about 25 turns. The oscillator only had 14 and the antenna had 19. Think I should increase the number of turns? Also, is wire gauge critical for both the primary and secondary?

[dseverson]

Never mind that last post because I read the entire post again. I see that I can check if the osc is running by tuning a transistor radio to 470kc above the dial reading of the Philco and holding it near the 6J7.

I will go back and check to be sure I have the correct number of turns (about 25) on the antenna and oscillator coils using 38g magnet wire. I do need to know, however, if wire gauge is critical for both the primary and secondary windings. In other words, can I use the same gauge for both primary and secondary?

This sounds stupid but does it matter if I run the wire up or down, right or left, just as long as the primary and secondary are in the same direction?

[morzh]

Wire gauge is only critical in case it needs to take the current. In case of your tubes AWG38 can. Although I think AWG34 or 36 is better.

The length of the coil that is connected to tuning cap (usually in parallel) is somewhat critical, as the length affects the inductance and the latter affects the frequency. Whenever you see a coil that is not coupled with a cap, the length is not critical and only number of turns is.

Now about the direction: you do need to observe the direction of winding if you have an oscillator: the coil should be wound in the same direction and the start and end wires should match too. Or the oscillator won't oscillate.

[dseverson]

Thanks, Morzh.

I wonder if I wound my oscillator incorrectly. I'll have to check it again. My notes say the wires go from the top down and to the left. I really blew it when I took off both wires so I might be looking for replacement oscillator and antenna coils.

[morzh]

If you are talking of #10 coil

http://www.nostalgiaair.org/pagesbymodel...013225.pdf

then the direction should be the same for both coils and both say beginnings should be grounded (pin 1) and then both ends should become 2 and 4.

the number of turns you probably know.

[Radioroslyn]

Here's one:
 http://www.ebay.com/itm/Heathkit-Signal-...463bcdc3da
You will to makeup the cable w/a BNC connector.

Terry

[morzh]

http://www.ebay.com/itm/Heathkit-Signal-...463bcdc3da

This link will work

[dseverson]

I missed it but will keep an eye out for another. They aren't bad prices either. I thought they were a fee hundred dollars. Off to rewind my coils.

[dseverson]

Well, this radio is getting closer to working. I rewound the antenna and oscillator coils and I can hear the oscillator pulsing through a transistor radio. However, it is only pulling in a few stations very faintly and garbled most of the time. Two are near the low end of the dial around 640 and 1100 and one at the upper end but they aren't constant. Sometimes I hear them and then there will be only static up and down the dial. A couple of times, the stations at the low end of the dial came in clear but when I tuned the dial, they disappeared. This is even after attaching a wire to the antenna post - not antenna wire and it isn't very long. If I touch the antenna post, the volume goes up but none of the stations come in any clearer.