38-8 shadow meter help - Printable Version
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+--- Thread: 38-8 shadow meter help (/showthread.php?tid=3325)
38-8 shadow meter help - jstaf40 - 06-02-2011
Just finishing up a 38-8 and then the sound got a little distorted and the shadow meter got real HOT got it unplugged, my question is how to test the meter and what would cause the meter to get so hot and the ON OFF switch is not working right all at the same time, they could be all connected.....and can the radio play with the meter unplugged,
thanks for your help
john
Re: 38-8 shadow meter help - Radioroslyn - 06-02-2011
Sounds like you've got a little problem. To operate the set without damaging the SG solder a wire across the coil section, not the lamp. Check the plate voltage on the IF amp tube that the SG is connected to. Also check the screen grid voltage on that tube also. I think you're off/on switch just decided to crap-out at the same time, not related. In order for the SG to work properly the set has to be in good working order and properly aligned. With out that being done in won't develope enough agc voltage for the SG to work right.
Terry
Re: 38-8 shadow meter help - jstaf40 - 06-03-2011
thanks terry who ever worked on this radio caused more problem then they fixed a strange speaker trans and funky wiring job.... thanks for your help you guys are a dieing breed
john
Re: 38-8 shadow meter help - Radioroslyn - 06-03-2011
Am feeling a bit dead myself.
Terry
For got to mention, some of the SG have a resistor across the coil. Check it to see if it has gone high in value or open.
Re: 38-8 shadow meter help - Chuck Schwark - 06-04-2011
Looking at Service Bulletin #280, also be sure the .05 bypass cap #17 is not shorted to ground. Will but short full B+ thru shadow meter coil to ground and fry it.
A short in the IF and or Det/Osc tubes could also cause excessive current draw thru the Shadow Meter coil.
A short to ground in the 1st. or 2nd. I.F. primary windings could cause this too.
Obviously, mis-wired by prev owner could be your culprit.
Chuck