Quote:
Originally Posted by Electronic M
You may need to walk the IF.... Basically tune the IF for max volume, shift fine tuning closer to best picture tune the IF for volume again till best sound and pix are in the same place.
The distortion could be ratio detector adjustment.
Definitely recap (and maybe check resistances) before playing with audio alignment.
Early post WWII TV stations used stronger sound carriers so TV and sets were not designed to have the same sound IF gain as 50s sets....It may end up like my Stromberg Carlson Dumont RA-103 clone where TV sound is adaquate with volume at max and FM radio is far beyond adaquate at a lower setting.
You got the affliction bad.... Just be glad it's TVs and not that other affliction going around.
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A bad audio IF tube and weak output improved things, and I walked the audio IF as you suggested. Sound is very good but not all that loud - sounds like the way you described your SC..
Here's what's weird: when I put the TV/FM switch in the FM position, the screen of course goes dark but the TV sound gets considerably louder. I would be thrilled if the audio level was that loud when it's in the TV position. Note to those who are not familiar with this TV: the TV/FM function switch is NOT a bandswitch. This uses an infinitely variable Mallory "inductuner" (not a 12 position incremental type), so it tunes the FM continuously between VHF low and VHF high.
The TV/FM switch does several things: it lowers the B+, it disables the sweep by ungrounding the 6CD6 cathode, and turns off the filaments to the video section and CRT. It looks like it's supposed to also ground the -11V source at the bottom of the main bypass caps but that doesn't seem to happen, but then there are also a couple of changes made in my version than the SAMS I have for it.
All I did so far was disconnect the part of the switch that lowers B+ and the sound didn't improve, although the picture certainly deteriorated with the low B+.
I don't see how it could be the shutdown of the filaments because the increase of sound is immediate when put in the FM mode, and decreases immediately when it's put back in TV mode.
I'll play some more with it tomorrow.
Kramden66 was certainly right: this TV has a very good picture, better than I hoped actually.
The video IF definitely is a little off. When tuning from one extreme to the other, the picture is sharp on either side of center, but differently sharp (hard to describe it). One side has a bit of ring on vertical edges, the other a bit of noise. The center is free of artifacts but it has much less detail.
I mean, it's very good, but not optimal. When I'm finished done recapping and verifying the resistors, I'll do an alignment.
John