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I finished restoring a 116 b and boy does it sound great but the shadowmeter is giving me fits.
I did the realignment but the meter will not work. The meter ohmed out at 813 ohms and the voltage swings from 0.78 volts dc tuned to .221 vdc untuned. I checked the 77 and 78 tubes and even changed them out for new ones without any change.
? What voltage should I expect to see on the shadow meter and what current should I see?
Bob.
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City: Gladwin, MI
Hi Robert,
I just finished a 116B also. Here is what I can tell you. The voltage across the shadowmeter measures 7.5 vdc with no signal. It measures 1.4 vdc with a very strong signal. Also, when I measure the avc voltage across resistor 68 (330K) to ground, I have -.6vdc with no signal and -14.5 vdc with a very strong signal. You should have close to these readings if the radio is working properly. My shadow meter measured about 1150 ohms, but I wouldn't necessary go by that, because my shadowmeter is p/n 45-2086. According to the parts list, the correct shadowmeter for the 116B should be p/n 45-2083. I hope this helps.
Ed
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Hi Etech
This is readings so far, Across 68 is reads -10.6 in tune and -1.2 out of tune.
Not to far out.
Across the meter is voltage swings from 0.78, volts dc tuned to .221 vdc untuned.
Each leg of the meter to ground reads 195 vdc
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Quote:Across the meter is voltage swings from 0.78, volts dc tuned to .221 vdc untuned.
Robert, it would seem to me that the voltage across the shadow meter with no signal should be more in the order of 7.8vdc, not .78vdc. Are you sure you are reading this correctly? If so, double check resistor 75 (2000 ohm) to see if it is the correct value. You will probably have to lift one of the wires from the shadowmeter to make this measurement. Also, double check the cathode resistors of the RF tube and the 1st IF tube. They should each be 300 ohms. If they are within 20%, they should be OK.
Ed
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ETech
It Works, # 75 resistor was replaced with a 220 ohm some time ago so I replaced it with the right resistor and it came alive.
Many thanks. This taught me a lesson about other peoples work.
Bob.
Posts: 237
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Joined: Dec 2007
City: Gladwin, MI
Robert,
Great! Glad to hear you got it going.
BTW, the 220 ohm resistor is why you were getting .78 vdc instead of 7.8 vdc.
Ed
