01-11-2024, 03:36 PM
>The switch just puts each subsequent cap in Parallel, which increases the Capacitance as the switch increments. Right?
Yup sure does!
The values of these caps are not all that critical they just determine how muffled the audio sounds. With the control all the way to the left there is no cap in the circuit. To me that position sound pretty good. I looked at the diagram and saw that the caps listed seemed large when you add them all up w/the switch to the far right. I opted to shrink them down to .005 ea (ymmv).
A lot of modern set will have a .01 mfd cap across the opt and sometimes I would augment that w/a series resistor to brighten the sound a bit. Usually a couple of hundred k will do it.
> I also had the extra capacitor block across the Choke. It was a #4989-J, 0.01mf.
Funny you should mention it mine had it too. But I couldn't find it in any of the diagrams. It was badly over heated tar had melted all around it. It isn't a necessary part as it's used the make a tuned circuit w/the filter choke to buck the 60cy hum. If you up the value the filter caps by just a few mfds like from 6 up to 10 your good. The previous owner just thew in some filter caps and a fuse kept playing the thing till it dyed. It burn out filter choke. Fortunately I had the model 70 pasts set and the according the lists it was the proper the for the 90 and the one in the 90 was for the 70. The bad one in the 90 looked bigger and had more inductance. Swapped the choke the p/s was back in business.
de N3GTE
Yup sure does!
The values of these caps are not all that critical they just determine how muffled the audio sounds. With the control all the way to the left there is no cap in the circuit. To me that position sound pretty good. I looked at the diagram and saw that the caps listed seemed large when you add them all up w/the switch to the far right. I opted to shrink them down to .005 ea (ymmv).
A lot of modern set will have a .01 mfd cap across the opt and sometimes I would augment that w/a series resistor to brighten the sound a bit. Usually a couple of hundred k will do it.
> I also had the extra capacitor block across the Choke. It was a #4989-J, 0.01mf.
Funny you should mention it mine had it too. But I couldn't find it in any of the diagrams. It was badly over heated tar had melted all around it. It isn't a necessary part as it's used the make a tuned circuit w/the filter choke to buck the 60cy hum. If you up the value the filter caps by just a few mfds like from 6 up to 10 your good. The previous owner just thew in some filter caps and a fuse kept playing the thing till it dyed. It burn out filter choke. Fortunately I had the model 70 pasts set and the according the lists it was the proper the for the 90 and the one in the 90 was for the 70. The bad one in the 90 looked bigger and had more inductance. Swapped the choke the p/s was back in business.
de N3GTE
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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