40-180 tube changes - Printable Version

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+--- Thread: 40-180 tube changes (/showthread.php?tid=12395)

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RE: 40-180 tube changes - codefox1 - 06-07-2015

You could also try subbing another 6J8. Unlusual, but could be in internal short.

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RE: 40-180 tube changes - Patrick - 06-07-2015

(06-07-2015, 11:03 AM)codefox1 Wrote:  You could also try subbing another 6J8.  Unlusual, but could be in internal short.

I pulled the tube, and still had the voltage drop.

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RE: 40-180 tube changes - Patrick - 06-07-2015

(06-07-2015, 10:40 AM)Patrick Wrote:  

(06-07-2015, 10:11 AM)Radioroslyn Wrote:  After taking a second look I think I would unground that resistor. Circuit wise it doesn't make a lot of sense cause it will pull the plate voltage on the osc section of the mixer way down. Tube manual sez the triode section can take up to 250vdc which less than the chassis is providing. Is your 4.7K resistor in spec?

Terry

Yes. I'm going to keep this radio, So I've replaced all of the resistors, and checked the new ones as I install them. I'll go eliminate the possibility of a shorted socket first, then go from there with your second suggestion. But only after another cup of coffee. It's almost 8 A.M. here.

Tanks,

Pat

Ungrounding the resistor did the trick. However, now the pin 6 tap goes nowhere. It should go to the pushbuttons. But the ground where the 150 ohm was, is right next to a pushbutton connector. Even though the solder joint looks untouched, I'll bet the 150 goes there, and not to ground. Still doesn't show up in the schematic, but I DID find it in the production changes. Just says it's in series with the plate.

Just connected the 150 ohm to the pushbuttons, and VOILA. Problem solved.

Thanks everyone.

Pat

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