Quote:
Originally Posted by old_coot88
The CRT heater already has its own dedicated 'floating' winding in the power xfmr, designated 'Y and YZ', going to 'KIN' (for kinescope, the archaic term for CRT).
Try this- unplug the CRT from the socket and check for heater to cathode short with the ohmeter on highest range. It should read infinity (although a short might occur when the heater warms up).
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It reads infinity on the Megohm scale.
Quote:
Originally Posted by old_coot88
Also check DC resistance form the floating winding to ground. It should also read infinity, but double check the schematic to verify this, and that it's not connected to B+.
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It has a path to ground, but it's connected to B+
Quote:
Originally Posted by old_coot88
With the set on (and the CRT reconnected), measure the DC voltage between heater and ground, and see if it reads the same as the cathode (or not). Ideally, it should not if it's truly 'floating'.
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It reads a different voltage than the cathode. Heater reads +225V and cathode reads +195V, which I see is a little low so I took a measurement where it should read +425V and it only got +350V. It's right on the 20% mark but it looks like I'll be going resistor hunting at some point to address that.
Quote:
Originally Posted by old_coot88
Then try shunting the heater to ground with the 10mf cap, first from one side of the heater and then the other. And see if the bar remains.
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The bar wins this round.