Quote:
Originally Posted by CaryLee
I didn't think changing out ONE mica cap would cause such a problem. I had a stable, if slightly dim, picture before. Now I can't get the picture to stabilize for more than a few minutes at a time. . . . .
First picture, before the change of the cap.
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Cary, if that first picture is not a composite picture with the CRT image and the cabinet from two different exposures, that is a good picture tube. Back when this set was made, most people watched TV in a semi darkened room! Most 19AP4's had a gray faceplate that absorbed a bunch of light to allow the set to produce a darker black in a lighted room and hide reflections. Even when new, that tube would not be nearly as bright as a modern tube.
I'm using factory numbers for the R113 and I am confused as to what your are talking about. Did you change C-245 the 270 µµf mica capacitor that goes between pin 4 of the 6SN7 and pin F of the horizontal transformer Z-210?
If so, C-245 will affect horizontal sync, but I don't see any way this capacitor could affect vertical retrace in your picture or the brightness (provided it did not change the width of the image.)
Have you replaced the 6SN7 that changed the picture when thumped? This usually is the sign of a shorted tube. If it now is in the sync circuit, it could well be the cause of our problem.
If C-245 is the part that you changed, you need to recheck all your changes for a wiring error, wrong value component or an over heated pin on the transformer while soldering, or a cold soldered joint.
Once you get the set back to working, for either retrace or lack of brightness on a set without traditional sweep blanking, the first thing I would check is the DC restorer.
My first check in the DC restoration circuit would be to measure the 1 meg resistor on cathode and check the voltages on that tube and also try a substitute 6AL5.
Where your retrace only shows at the top of the screen, usually this is caused by a wave shape error on the vertical sweep spike, although I've seen a gassy CRT do this. (The spike is the part of the sweep where the beam moves back to the top and if it slows down near the top, it often will be visible.)
Jas.