Working on a Zenith 25MC33 color roundie chassis and would like some troubleshooting advice. I have gone through and replaced any resistors over 20% which was only 4, weak tubes were swapped with good tested tubes, replaced the electrolytic capacitors, and like others had to replace the horizontal linearity coil as the plastic form had fallen apart.
The set powered up but I can not get full vertical deflection, it appears to be folding over short from the top. I can fill the screen by adjusting the vertical size and vertical linearity but then can not get the vertical hold to lock.
- 117v line voltage
- adjusted high voltage to 25kv
- 230ma HOT current (a bit high, 110v line voltage brings it down to 210ma)
- 4:3 ratio DVD player feeding composite video/audio into RF converter outputting to ch3
- quick and dirty first pass on color & convergence
Troubleshooting so far:
- I have tried substituting both vertical tubes (V7 & V10) but get the same results.
- Knowing that the vertical output transformers are subject to fail I went in and replaced the film capacitors and resistors in the vertical circuit.
- I also tried replacing K1 & K2 with a homemade circuit, thought they might be the problem and swapped the originals back in (same performance)
- I took pictures and now have rechecked and retested each component to ensure I didn't make a mistake
Here is what I get:
Highlighted parts replaced:
