03-14-2021, 09:58 PM
+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.
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.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got it!
Terry
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