Philco Predicta Siesta picture over time getting dimmer - Printable Version
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Philco Predicta Siesta picture over time getting dimmer - Platinumblonde36 - 11-14-2024
Hey I'm not sure what to look for but my Predicta's picture has been getting dimmer and fuzzy. What should I look for and what tests should I do? Ill include a photo
RE: Philco Predicta Siesta picture over time getting dimmer - MrFixr55 - 11-17-2024
There could be several issues going on here. If you darken the room and turn down the brightness, does the focus get better? When you crank up the brightness, does the picture get a litter bigger as it gets fuzzy (blooming)?
The following are possible issues:
- Low high voltage or poor regulation of high voltage- This should be a relatively easy fix if limited to the HV rectifier, but this can also be caused by a weak horizontal output tube, especially if the width shrinks as the brightness is turned up.
- Poor video amp circuit- This could be due to a bad video amp tube.
- "Soft" (low emission) CRT. Obviously, this is the worst scenario.
Start with the following:
- Remove a Video IF tube (if this is a parallel filament set) or try to hold the tuner between stations. Adjust focus for good raster (the lines that make up the picture. You should be able to get a sharp raster. The focus should not change as you change the brightness. If you can't get a sharp raster, then focus, high voltage or the CRT is at issue. You can try a "brightener", but these may shorten the life of a CRT that may be near the end of its life anyway.
- Once you get a raster, allow for a picture either by reinserting the video IF tube removed or setting the tuner to a channel. Adjust finr tuning for sharpest image. Set brightness and contrast for sharpest image. If the raster is good but the picture is blurry, then you have a video IF or video amp issue.
If the pic starts out sharp but gets fuzzy as the set heats up, you can use "freeze spray" to cool down individual components (especially capacitors in the Video IF, detector or video amp circuits. If you can't get "freeze spray, turn a cane of "air duster" upside down. the "air" (actually a refrigerant" will now come out as a liquid, evaporating when contacting the suspect component, causing it to freeze as the liquid refrigerant boils off. Be careful to not spray a tube, because it will likely crack.
Hope this helps.
RE: Philco Predicta Siesta picture over time getting dimmer - Radioroslyn - 11-18-2024
The Siesta has a full on power supply w/a transformer. And if I recall the crt has a 2.5v heater not 6.3v.