[dconant]

Hello, Working on a Philco 60. I have done a total recap as well as all resistors. I have done a full alignment. I have checked over my work and find no problems. The problem I am having is I am receiving an AM station (not sure which one) all over the police band and no stations that should be there. I normally pickup 3 or 4 stations on this band on other radios. I have cleaned the band switch. My antenna is a 100 foot wire strung outside from tree to tree. This radio only has 4 compensators (12, 17, 18 26). It does not have compensator 26A and in place of compensator 11 is a 1400 PF cap which I changed after verifying my work. Best I can tell this is a code 121 run 4 radio. Anyone have any idea what is wrong here?

[Arran]

It could be that the section of the oscillator coil for the police band has gone bad, on my 60L it was still working, but I haven't powered up that set in 20 years so it may have failed too. As I recall it's not to hard to repair, just a single layer coil.
Regards
Arran

[dconant]

Arran, I had to rewind the outer coil on the antenna coil. I'll check out the oscillator coil. Do you happen to know the wire size and how many turns?

Dan

[morzh]

Honestly, I disregard police band.
This is the only one where the antenna coil was open on my 38-690, and I made no attempt to fix it.

[Arran]

I haven't had the set out in a long time, 20 years or more, that band worked at the time I put it away. The problem with the model 60 is that without the police band working you don't receive the upper end of the AM broadcast band, it stops at 1500 KC or slightly above, so if there isn't anything to hear at the upper end of the B.C band then it doesn't matter. Maybe it was the antenna coil I was thinking of, I may have conflated that with the oscillator coil, my guess is that maybe there is something not right with the band switch as what should happen is that it should shunt the B.C band section to ground to kill that part whilst you are on the police band. I don't know if these sets have mica cap issues or not. Could it have something to do with the rewound section of the antenna coil? I once got two terminals mixed up on an oscillator coil in a G.E, where I only got one station, but in that set it only had one band. Maybe it's best to step back and think about what work you did last, on coils and band switches, it's easy to get clockwise, and anti clockwise positions mixed up with the terminals.
Regards
Arran

[462ron]

Hi Dan, what I use to check if an oscillator is working and on the right frequency is a small AM/FM SW portable digital radio with a signal strength indicator. That way you can tune the radio your working on to say 2.0 MHz and see if you pick it up on 2.46 MHz, which is 460 KHz IF frequency + the 2.0 MHz the radio in question is tuned to. It’s a handy diagnostic use I found for that portable besides just using it for entertainment. It can save you from tearing into your oscillator needlessly.

Ron

[dconant]

Thanks Ron for that nice idea, unfortunately I don't have such a radio. Would another SW tube radio work? I failed to state when on the police band there is a fair amount of static where there is none on the AM band. I was thinking maybe the osc coil arching. I'm going to take the coil out and have a look.

Dan

[462ron]

Hi Dan, yes you could use another tube radio to do that test. I only suggested the small digital portable I use because it’s super accurate. I’ve used other tube radios in the past to do this test!

Ron

[dconant]

Thanks Ron. The coil is out and the winding between pins 2 and 3 are open. I counted the turns and got 18 and so did my wife. I took a picture and zoomed in. The connections to the pins are intact and there is no green corrosion so not sure where the break is. Guess I'll find it when I unwind it. Not sure what the wire size is. Any idea?

Dan

[dconant]

I have rewound the open coil which had lots of breaks. I used #38 wire. While I had the coil out I changed that cap down in the core (110PF). The static on the police band is gone now. The AM band comes in a lot stronger now but the police band still has that AM station (I'm sure it is 550) all over the range except between 1.5 and 1.6. At that point I get two different stations. Don't know if they are regular AM stations or what. So looks like the rewind did some good on AM but not so much on the police band. All the other coils have continuity.

[David]

What is the distance from your place to the radio station you are picking up on the wrong band? Could be some type of secondary harmonic just guessing.  David

[462ron]

Dan I was going to guess #38 guage wire. Did you try doing an alignment on it yet?

Ron

[dconant]

David, I'm thinking about 100 miles.

Ron, I did an alignment prior to the coil rewind. I'll do another alignment.

Dan

[DaleHCook]

To check an oscillator I use an item of instrumentation which few to none of you would own - a Tektronix P6022 current probe. Probing a terminal on an oscillator coil with an oscilloscope probe could disturb the operation of the oscillator. Because of its design clipping the P6022 probe onto a coil lead will cause less disturbance to the oscillator circuit while providing a sample to my 'scope.

[dconant]

Dale, I don't have such a tool and really don't know what it is.

I have another 60 that plays very well so I will be using that to compare with my current one. So far all my parts are in the right place. I have not checked the Bakelite blocks yet to see if put a wrong value in one of them. I did discover I messed up one of the caps in the by pass block (#20). Put a .05 in where should have been .5. Made no difference except maybe a little more volume. I'm beginning to suspect the antenna coil. I thought I had rewound the outer coil but I didn't. Must have done that in my sleep. Measuring pins 2 and 3 to ground on the good radio I get 2.3 megs and on the other I get 4 meg. I hope that is not one of the longer windings.

It is going to be a little slow for a while as I have another project I really should be spending more time on.