Sony Trinitron E450 bad contrast 15-20 minutes after turning on

[R_J]

Re: Sony Trinitron E450 bad contrast 15-20 minutes after turning on

The heater cap is likely 100µf/16v, If you give location numbers of the cap, that would help. Where is this 4.7µf/400v cap?

[Xan03]

Re: Sony Trinitron E450 bad contrast 15-20 minutes after turning on

Yes I misread while skimming back through the posts here, this should be for C572.

[R_J]

Re: Sony Trinitron E450 bad contrast 15-20 minutes after turning on

Yes I misread while skimming back through the posts here, this should be for C572.

That cap is likely ok, If it was bad you would probably have a width problem. Replace that heater cap C641

[momaka]

Re: Sony Trinitron E450 bad contrast 15-20 minutes after turning on

So while I got the caps for this in a while back, for one of them I had to get a Panasonic NHG (4.7uF/400V, that heater cap apparently), and that one doesn't measure too great on the ESR60 - 4.32uF and 4.8 ohms ESR. Now since that is at 100khz maybe the ESR is normal but capacitance is a bit low for a supposedly brand new cap.

Capacitance is still well in spec there. But the ESR seems a bit high for a cap of that size, even though it is a GP cap.

Since this is not a bi-polar cap (NHG series aren't, at least), you should be able to use a 4.7 uF 400-630V metal film (polypropylene). In fact, for a lot of the HV caps under 5 uF, you can substitute them with metal film caps. Just note that the metal film caps will be quite a bit larger (so space must not be an issue.)

Also, for any Bi-polar electrolytic caps of similar voltage and capacity, you may not be able to use film caps as easily, because those Bi-polar electrolytics are usually rated for very high ripple current. So to get the same kind of RC with film caps, you'll probably have to use higher voltage film caps (to get a bigger cap, which will have higher RC capability.)

The heater cap is likely 100µf/16v

That seems kind of small for the heater cap only.
Again, on most of these Sony CRTs, either the PSU board or the flyback will generate a "raw" voltage rail for the heater, followed by a regulator and a smaller cap. So perhaps that cap you mention might be on the output on the regulator? But I expected there to be a much bigger cap on the input of the heater voltage reg... and I also don't expect it to be bad, but worth checking anyways.

The magnets are there from the factory to improve purity, there position and orientation are important, leave them alone.

+1

A lot of my Trinitrons have them too (though not all.) Since every tube is sort of "unique" from the factory, each one needs custom adjustments made to it.... which is why we'll probably never see CRTs mass-produced ever again - too much (skilled) manual human labor. LCDs, on the other hand, are assembled by robots for the most part.

It is a soldering station actually, just a really crappy one - a ZD-937 (don't know if that thing is sold under that model number worldwide). The 48W number might be just on paper anyway as I've rather had the issue of not enough heat being transfered despite setting it to 370°C, especially on newer PCBs with lots of layers and ground planes.

Looks like a station that uses 900M -style soldering tips (or just one where the tip slides on top of the heating element.) If that's the case, that's probably why you may be having issues with "not enough power". Technically speaking, even 45-50 Watts is actually plenty. The problem with 900M -style tips (especially the cheap ones) is poor thermal transfer from heating element to tip, poor thermal mass (especially the really cheap Chinese tips with high-steel content in the tip), and poor temperature sensing of the tip, due to tip design. I did a write-up on this a while back:
https://www.badcaps.net/forum/showthread.php?t=46338
^ In my case, I have a very cheap station that uses 900M tips, so mine performed really badly. It can just about solder on single-layer boards with normal (not big) traces. The genuine Hakko 900M tips are much better of course... but even those can't compare to T12 tips. When I switched to a T12 station, it was a night and day difference. I can now easily solder/desolder even on lead-free motherboards with thick copper planes with temperature set at 310-320C and not struggle at all. So it's just down to tip design, really.