|
Goal: Still trying to get the best focus moved to the center of the focus control range rather than just beyond fully CW. (Audio volume is marginally adequate.)
Correction: In my last post I thought there was something out of place on the 6V6 Vid Output pin 6 situation. Never mind. As some of you well know, Philco made it pretty “narrow and deep” in that area of the chassis and I somehow got disoriented on the tube sockets. All wiring is according to both Rider’s and Sam’s schematics.
Update: Going back to what Don said: “When you remove the 6AQ5 (audio output), the sound and picture should go out and the screen should go blank. If not, something is bleeding through to the 135 volt source.” I repeated that trick and I would describe the raster and video that remain as degraded but watchable – perhaps half the contrast as with the tube in. So where would I start to track down that possible short or low resistance? BTW, the 6AQ5 tests fine on my RCA WT-10A, but I don’t have any spares so I’ve ordered some new ones.
As to using another power source to run a higher current through the focus coil... I’m going slowly on this to make sure that I know what I’m doing. I don’t want to have to go shopping to replace an open coil. To make sure that I don’t burn out the coil, should I use a sort of dim bulb setup? (Not talking about me!) I previously measured 52-165 mA through the coil connected to the set’s B+ of 330VDC. So, do we not care what the voltage is so long as we keep the mA current, say, within 200 mA? What source would you use? Would a 13.8VDC source be okay and what would be best to limit the current? Would a 69 ohm resistor plus a pot be enough?
When I put the digital mA meter between the 5U4 output, pin 8 and the filter choke and caps, I read 0.11 A.
As to the audio: the electrolytics are new as is the .0068 and the output xmfr checks okay. The 2uf in the detector is new. I find 6V driving the 6AQ5 - but only about 1V on the volume control.
I continue to try to get schooled up on all fronts – including what it would take to make sure the permanent magnet is “saturated.” Just reading the Rider’s TV volumes 5 and 6 covering all brands is giving me a better feel for this. It's “Heavy” reading. Sorry, couldn’t resist.
Roger
|