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Philco model 60 not tracking correct - Printable Version

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Philco model 60 not tracking correct - Dean1673 - 03-14-2021

Hi ,  I have been working on this for a while.  I have replaced the secondary I F , rewound the primary on the oscillator twice I went the wrong way the first time .   18 wines of 39 ga.  Did the small coil on the antenna coil (.7) .   
   On the schematic on the oscillator  (item 13)  110 pf cap  I found a mica mold cap rated at 60 pf  in that place. ( blue, brown, yellow).  I measured it out of circuit with a lcr meter it read 57 pf .  I did install the 110 pf silver mica. Everything was going well in the alignment until I went to adjust the 600 padder .   I found that up at 700. I tried rocking and dragging it down to 600 that did not work.  Peaked strong at 700.
   I put the 60 pf back in and did it all again. This time the wave trap did not work at all couldn’t tune it down like I did the first time.   Tuned in 1400 with the oscillator and the antenna padder on the tuning condenser .   Better with the 110pf.  Found 600 at 700 again. Just as strong as before.  Oh, by the way the 60pf cap is mica. (cut it open ) . I put 110pf back in .  Tried another 6a7 same thing. 
   Police band works. The tracking is off also .     
     Any ideas?                    

         Thanks.        Dean

RE: Philco model 60 not tracking correct - OZ4 - 03-14-2021

Dean
Clearly your oscillator range is too high.  

 I think when you first compensate (align) with the hi end trimmer it drags up the low end.  They do interact a lot.

 clean the contacts in the main tuner assy.  If the trimmer caps and the tuner cap is good.  

 I would try a turn or two more on the coil you just rewound. I think it will lower the overall resonance. 

RE: Philco model 60 not tracking correct - radio1 - 03-14-2021

Put everything back in spec, micas and all. If your correct version schematic shows 410, put 410pf in. Start from the beginning again, check the dial position, down at 55, where does the aircap close - it could have slipped. Then apply your proper if frequency gen again and align the if, how strong an undistorted signal do you get out to the speaker, it should be quite loud, or peg the meter if you are using one. If all is well there, then begin with the rf wave through the radio. You replaced the if coil, was it right, connected correctly? 10kc off high, something not right and many ways to dial one in thinking you have the right adjustment, but it is a black art to dial one in correctly.

RE: Philco model 60 not tracking correct - OZ4 - 03-14-2021

Yes the IF frequency could easily be off 10khz (or more) too low. It helps if the frequency generator is accurate. 

I would think the oscillator should be able to tune even a little below the normal operating range before dying.

If your not sure about the frequency generator try the digital AM radio trick to listen for the local oscillator. When the model 60 radio is showing 700khz the oscillator should be at 1160khz  700+460 the IF. 

RE: Philco model 60 not tracking correct - radio1 - 03-14-2021

When tuning by the instructions fail, check where you stand by ear, what is your current high resonance best point. Tune/trap a high am station, try to trap am 1510 WLAC Tn. -  or whatever you find around there - align the dial at the known station, then dial it in. Then tune the if compensators, aircap compensators, and oscillator compensator until you have that station the best it can be. Tune down to lower station, maybe Nashville 650 - see where the dial is. Retune to see if what best signal you can get. Go back to the high station again and dial it in. Then apply your signal gen to see what if frequency zero beats, might not be what the instructed if calls for. All this gives clues as to where you stand with the machine.

RE: Philco model 60 not tracking correct - Radioroslyn - 03-14-2021

+1 Chris
I think we need to figure out what is actually happening. Is the oscillator dying from lack of feedback at the low end of the dial? Or it is running and it can't cover the proper frequency ranges?

The way to do this is to track w/another receiver. A well calibrated communications set is good, tube or ss. It will have a bfo which makes oscillator easier to hear and a S meter to measure it's relative strength. So you can see if it's dying off. All these features are handy.

Or a counter can be used by wrapping a few turns of wire around the 6A7 to p/u the osc signal. In most cases it will read will out a problem. Some can mathematically subtract the IF frequency out can it reads the same as the dial should. Can be had out of China for abt $20 or so.

Is important that the IF is at 460KC and peaked with the generator output turned down low. Generally all of the trimmers should have a pronounced peak. If you don't have good IF sensitivity and it not on frequency can cause poor tracking, (not as bad as yours) and poor selectivity/sensitivity. And nobody wants that.

As per the alignment the trap is set (dipped) at the IF frequency. If this is done it won't have any affect on the tuning or oscillator. As far I know it was designed to keep LW stations out of the IF where they would be a constant hetrodyne against any signal tuned in. Never tried to tune one up into the bcb.

Before changing parts that are critical you may want to check the service bulletins and update for different runs of your set. It could be that 60mmf cap matched a updated coil for a later run that the diagram you are looking at.
A while back I was working on a 660 and couldn't get the bcb to tune whole band. It drove me nutz! For at least 6 months. I found a used osc coil and I though that had to be the answer. Put it and it was better but wasn't working as it should. A few weeks later I was flipping thru the service notes and found that in the alignment instructions they had switch two of the placement numbers of the trimmers for the osc, bcb and pol bands. When I was trying to adjust the bcb I was tuning the trimmer for the pol band and vise virsa. Ligned dandy after that was sorted.