pilot lamp burn out

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pilot lamp burn out

Post by Patrick on Tue Nov 07, 2017 12:13 pm

Recapped a Philco 46-420 code 125 and the pilot lamp comes on slowly then continues to brighten until burn out. All tubes check out and 35Z5 has been replaced several times with no improvement. What is causing the burnout?

Patrick
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Re: pilot lamp burn out

Post by Chas on Tue Nov 07, 2017 8:44 pm

Patrick wrote:Recapped a Philco 46-420 code 125 and the pilot lamp comes on slowly then continues to brighten until burn out.  All tubes check out and 35Z5 has been replaced several times with no improvement.  What is causing the burnout?

http://www.nostalgiaair.org/pagesbymodel/597/M0013597.pdf

Check all the 35Z5's for an open filament tap. Check the filament, both sides, of the tap do so HOT to be sure.

For the pilot lamp, use the Tung-Sol #44, U.S. made not China!

Check ALL other tubes for excessive heater/cathode leakage and C-17 for excessive leakage, 50L6 will run very hot.

Be sure there is not a miss-wire, solder blobs, wire snips. This chassis has a floating ground. The negatives of the filter caps and many other connections are above chassis. The symbol for chassis ground is the horizontal line with slanted hanging "grass" . The symbol with multiple progressively smaller lines is the common return that runs around the chassis as an insulated wire, probably black, brown or bare.

If the power input has been "creatively" rewired with a polarized plug and the switch location altered, well....

YMMV
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