#31
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1000 pf (mmf) (uuf) = 1 nf = 0.001 uf (mf). 1000 nf = 1 uf (mf). Most ceramic caps are less than 1 uf (mf). Even film caps seldom are more than 10 uf (mf) and they are very large in that value. Mica are commonly in values 1 pf (mmf) (uuf) to 1000 pf (mmf) (uuf). The reason for the most part for using electrolytic caps is that they are smaller and less expensive that other types for the same capacitance. |
#32
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I believe modern tantalums will sub fine for lytics, but haven't tried those in tube gear to be sure. Ceramic dielectric caps are usually disc caps and typically aren't seen in values above 0.1uF. The old school ones that look like 30s era dog bone resistors are typically pF (aka mmf in old speak). Paper caps shouldn't be replaced by ceramic dielectric caps as ceramics are not temperature stable and exhibit piezo electric dimensional changes in dielectric thickness and thus capacitance as voltage is applied so in some applications where they get high voltage AC waveforms they will pass them in a non-linear fashion.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#33
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Tantalum caps can be useful for their small size, BUT they degrade permanently and fail if they are EVER reverse biased. So, typically used only for bypassing power to ground, not as interstage coupling or waveform generating components, where the voltages on either end can rise at different rates during turn on.
Safest thing in restoring old gear is to replace electrolytics with electrolytics. |
#34
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I just pulled this capacitor out of the tv and I am not sure what type it is. It is definitely not an electrolytic. I can not identify it but it resembles the "black beauty" or "black cat" capacitors. Can anyone identify it?
https://imgur.com/a/KWQtDRu |
#35
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That is a Motorola brand cap and I don't know whether it is paper of plastic film. It is a molded plastic case.
There were some caps by Sprague that looked similar. The ones with white printing were paper, the ones with red printing were plastic film. That was a situation that was not very common where it was hard to tell from the general look. Those could actually be made by Sprague but branded by Motorola, that kind of thing happened many times. If you have a capacitance leakage tester that tested using hundreds of volts it would tell if the capacitor is good. I'm pretty sure someone else may know how they are constructed. I have cut similar caps apart but it can be hard to tell, the paper can be extremely thin and look transparent like plastic. They also can be very tightly wound. Also from the time the TV is from they could be either one. Sometimes the SAMS parts list states if it is paper or plastic. SAMS also lists electrolytic caps separately. With out knowing for sure, I would not replace those unless they were suspected to cause a problem. Last edited by Notimetolooz; 08-30-2022 at 09:45 AM. |
Audiokarma |
#36
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__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#37
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Where was this in the circuit? |
#38
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The capacitor was physically on the top part of the chassis near the high voltage box. As far as the schematic goes it looks to be in the general area where the vertical output tube is and the other stuff related to the vertical.
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#39
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Electronic M has a point. I could go either way with this.
However if you are a newbie to this kind of stuff (and you sound like you are) you may create more problems than solve them. Not only do you have to get the type, value and voltage rating right but you must not make a mistake connecting to the right points. With electrolytic caps you also get the polarity right. It takes a level of concentration that someone that has done a lot of can take for granted. I have come to this conclusion after helping many newbies. I would definitely replace the electrolytic caps, those almost always have a metal case even if that is covered with a plastic film or cardboard. You really should get the service info on the set, that may clear up some facts like the type of capacitors and where they are in the circuit. |
#40
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Audiokarma |
#41
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I think it would be good to slow down and identify a part in the schematic before you replace it or ask questions. Then you can get better opinions on your options.
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#42
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Will do. The biggest concern I have at this point is not the recapping. I am pretty confident in getting that taken care of correctly. I just know that the CRT is very high hour. I don't have the equipment to test it but I can tell its is going to be probably a bit dim, since the color drivers are turned all the way up. Someone mentioned about replacing it with a superior newer RCA picture tube which I am all for doing if it is compatible.
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#43
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If you are chasing a specific problem you can tack in a cap
of the same value & voltage as a test. If not leave it be for now. If you are recapping the set just do a few at a time & recheck as you go. Its always best to get the PS running first the Hoz/HV then vert. In other words one stage at a time. Mass recapping very often leads to a broken set thats MUCH harder to fix. 73 Zeno LFOD ! |
#44
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#45
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If you are sure that the problem is the CRT and you think you can find a replacement tube, I suppose as a last resort they are OK.
There have been cases where a previous person put a brightner on because they didn't correct the real problem with the set. Brightners age the gun cathodes faster than normal so whatever life is left in the CRT is used up fast. The proper use for them was so that a TV owner could have a brighter image while the repair shop was waiting for a replacement CRT to arrive. Today replacement CRTs are much harder to find. Typically on a color tube one gun wears out first making the color balance impossible to achieve. If you say all the drive controls are set near one end it suggests there is another problem that is common to all colors. |
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