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 fine 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 can 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.
RE: Philco Predicta Siesta picture over time getting dimmer - Platinumblonde36 - 11-22-2024
RE: Philco Predicta Siesta picture over time getting dimmer - Platinumblonde36 - 11-22-2024
RE: Philco Predicta Siesta picture over time getting dimmer - Platinumblonde36 - 11-22-2024
RE: Philco Predicta Siesta picture over time getting dimmer - Platinumblonde36 - 11-22-2024
RE: Philco Predicta Siesta picture over time getting dimmer - Platinumblonde36 - 11-22-2024
I found that the wire insulation was burnt.
The fly back needs corona dope!
Why would someone put that there?
RE: Philco Predicta Siesta picture over time getting dimmer - TV MAN - 12-14-2024
To me the picture looks "bloomed", as in low high voltage. You're probably using a set top box, which will cause the dark spaces at the top and bottom (normal), I'm also observing that it looks like most of the capacitors are originals. Those should be replaced, which is some work, but could be some are 'leaky', causing a drain on your power supply. I don't know what your abilities are concerning TV service, but you should have around 14kv on the anode of your CRT (picture tube). Some immediate causes would be a bad 1B3 high voltage tube. They tend to go to air and are readily available on different sites. You could look for a violet/blue glow from the HV tube,(inside the high voltage box) connecting to the flyback. If you see that, the 1B3, its bad. But that glow ON the glass (of other tubes) doesn't mean the tubes are bad, unless its inside the elements, which IS bad. Also, be very careful not to break the lead off that flyback transformer. It looks like the damper tube has some use on it. This could be causing your problem too. Usually you replace the horizontal output and damper as sets for good measure. This would probably solve the immediate problem. I doubt the picture tube is bad, those 17" usually last a long time. Mr Anderson has a lot of good videos on these and might jump in here too. (BAnderson tv on youtube) Also, IF you do try to test the picture tube, it is probably a 2v filament, so be careful.
RE: Philco Predicta Siesta picture over time getting dimmer - Platinumblonde36 - 12-14-2024
Hey thank you TV MAN!
I'm currently working on replacing the original caps, like the paper ones and black beauties and I found that some of the replacement caps currently on my board were not the right values!
I also removed those pods, I'm not sure what the purpose of them was but I shouldn't need them if I replace everything properly. Also do you know why a capacitor would be on the crt yolk connected to ground?
I just pulled the board and I'm going through and testing some resistors also before I order everything.
I did purchase a new 1b3gt just in case and I'm looking at getting a new damper tube now. I also noticed the damper is loose in its socket, do they make modern ceramic replacements for it?
My hope is that it is low high voltage like you suggested and once I replace the components with more reliable and in tolerance ones that it will function properly like it did!
RE: Philco Predicta Siesta picture over time getting dimmer - Platinumblonde36 - 12-14-2024
Hey MrFixr55!
It looks like my original reply didn't post for some reason back to you but I do think it's blooming until proven otherwise! Thank you for all the information!
RE: Philco Predicta Siesta picture over time getting dimmer - TV MAN - 12-15-2024
As far as that cap on the crt, without a schematic in front of me, my guess would be that they're either trying to use it as a HV filter or they've bypassed a bad cap on the board. The schematic would show if it's suppose to be there. I'd take a look at my Siesta, but it's buried. I have a 21 out and in pieces, so I'll take a look. Bob Anderson has some very good videos about restoring these on YouTube. There's also couplates available online. About 50 if I recall, probably be money well invested. They affect sync.
RE: Philco Predicta Siesta picture over time getting dimmer - morzh - 12-15-2024
From the photos, this TV is long due for....gentle maintenance. Starting from vacuuming and ending by...recap?
RE: Philco Predicta Siesta picture over time getting dimmer - Bob Andersen - 01-16-2025
They went for the low hanging fruit and replaced the paper caps they could get at from the top of the board. They left the vertically mounted paper caps installed. Looks like the vertical linearity pot burned out (a common problem) and they tacked in a pot and left in on top of the PCB.
I'd pull the main board and go over everything.
Yes, a little super corona dope on the flyback donut will do the trick.
RE: Philco Predicta Siesta picture over time getting dimmer - radiorich - 01-16-2025
Hello Guys,
Someone went the lazy way to recap this set and no way around it as bob said pull the board to do it right !
Sincerely Richard