[morzh]

Yes, this was my theory, that the oscillator goes into some different mode.
And when you touch the GND to it, you should see it go back to two div amplitude

(addressing your GND not connected: your outside GND IS connected to your Mains. It is, other that the noise, is no different from the GND from your electrical panel).


Now, it'd be interesting to look at the signal shape.
Can you trigger on the signal? What's the bandwidth of your scope? Does it have triggering?

[dconant]

No I can't trigger on the signal. Pretty simple scope. Maybe it is time I got one of those digital ones. Do you have a recommendation?

   

[dconant]

Got it to sync. Here it is when reception good. Waiting for crap out. There is nothing I can measure from. Horizontal range is on third position and sweep speed all the way high. 

   

[morzh]

The shape is a bit weird but maybe it's the scope.

Can you spread it a bit horz, or is this at the sweep's limit?

[dconant]

Sorry best it gets. Radio still playing normal.

[morzh]

Rigol has become a respected name, while keeping the prices down.

DS1202 sells for $369, has 200MHz bandwidth with 1GSa/s rate.

Is a 2-channel scope, so if using 1 channel, it is 200MHz, if two - 100MHz/channel used.

Depends on your budget.

I am sure, there are no-namier ones that will be cheaper, but, as always, the greedy pays twice, so....

[dconant]

Thanks Mike. I don't go cheap on my tools. I ordered the scope be hare end of next week.

Radio is still playing. Going to turn it off for the night and start tomorrow. Think I will use 740 AM in hopes scope will sync to that better. I was using 1180.

[dconant]

While I am waiting for my new scope I decided to take the osc coil out have a look at it. No Philco corrosion in there but I did find a connection that looked bad so I cleaned it and resoldered the connection as well as the rest of them. Put the coil back and the radio came up with good reception and maybe a little better. I noticed on the scope the waveform filled the whole screen instead of previous half screen. That was real encouraging. Played all day yesterday and came right on this morning and still playing well. So maybe it is fixed (knock wood).

[morzh]

That would be great. That oscillator clearly behaved erratically.

[RodB]

Well, I'm glad you found something concrete that's made a difference. Let's keep our hopes up. Stronger oscillator signal is always encouraging.

[morzh]

Would also be nice to see the oscillation waveform. On this same scope.
Could you snap a shot and put it here?

[dconant]

I played the radio about eight hours yesterday without any problems. I will play pretty much all day today and if no problems I'm going to call it fixed. Here is the scope picture with the stronger osc signal. I will let you guys know tomorrow how it went today.

   

[morzh]

Over 60% rise in amplitude. Nice.

When you get your new scope, please also put the waveform here; I am just interested in whether it is the way this scope shows it or it is distorted by the scope.

[dconant]

Ok Mike will do.

[tbone]

Congratulations on getting your radio working properly! Intermittent problems where normal means of testing and repair do not resolve the issue are just frustrating.

Thanks to Mike, I learned something new! It proves how important local oscillator levels are in the mixing process. If I’m thinking right, when you adjust the oscillator padder you are peaking the osc level at the low frequency end of the dial.

The next time I have a radio on the bench I’m going to watch the oscillator level and compare it to the most and least sensitive part of the band. I have a spectrum analyzer that would show a great visual of what’s happening.