#16
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See U tube for discharge vids.
You set is solid state. On turn off MOST of them bleed off in a few seconds. It will not kill you, just teach respect. In fact in theory if you have an irregular heart beat ( afibs) it may cure you ! Same thing as they do in the hospital. ( cardioversion) I got bit at least once a week for 40 yrs and I am still here The dangerous part of anything is where the AC comes in. BTW I will take the weed thing with humor But I came from South Acton, the beer side of town The pot heads came from West Acton or Acton Center. 73 Zeno LFOD ! |
#17
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Well mine died the instant I'd touched the knob. If that's really the case, something is very wrong.
Quote:
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ALSO it'd be nice to have the Sams' for this model. |
#18
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About the measurement... yes, this one requires the system functioning. Is good to measure "in a hurry", with the + lead of the multimeter attached to the point (negative from multimeter will be to circuit ground, like the channel selector shield or some easy point), and then powering up the TV, watching as fast you can the measured voltage (before damage). Just when you are able to read the stable measurement, turn off the TV.
Then you can repeat for the HOT PSU, to take note. Same fast principle. Is interesting both measurements, tyo see if one or both deviates from normal, to try to find soem culprit. Another possible test, and more challenging, to check the PSU, is to remove the HOT and uses a resistor to emulate the HOT current, to independent test the PSU, before HOT eating. Some old PSU reacts bad to no load, hence the need for some load: some linear PSU rises the output voltage without load, making no-load measurement useless; and some older SMPS explodes without load. A small lamp for emulating load... it depends, some PSU can be damaged by the filament in-rush current.
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So many projects, so little time... |
#19
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With all this going on I'm wondering about the horizontal efficiency capacitors, I've had many issues with these in older JVC production monitors over the years.
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#20
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To expand on that a cheap thing can be done. Follow the wire from L351 to the main chassis. On that line is a @4.7 mfd @350V. I can almost guarantee it is bad & may be the problem. It can cause a lot of different symptoms on ALL brands, its in the top ten of common fails. Also there is a SCREEN control on the CRT board. If to high it gives too bright a pix & poor focus. Looking at the screen shots I see too bright a pix & poor focus. Too much bright will draw too much current & stress the HOT. Build a dim bulb tester. It will cost < $10 and will be very useful. ( socket, 2 alligator clips, some wire & a real bulb ). enuf fer now Zeno |
Audiokarma |
#21
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#22
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#23
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#24
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#25
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I resoldered the pads for the FBT, driver transformer, and the HOT leads on the main PCB. I replaced the safety capacitor & HOT. I turned screen & bright all the way down. I did NOT use a lightbulb in place of the +B fuse. I didn't measure +B either. But I did catch the HOT death on camera, sadly. https://youtu.be/3RQW40rBP8s
Here is a frame-by-frame analysis of the HOT breaking down. I only have one HOT left. One chance to fix everything... the +B adjustment knob is left on one extremity. so turning it the other way will either decrease +B voltage or send it through the roof. |
Audiokarma |
#26
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The horizontal bands on the video were caused by me turning up the brightness. I turned it back down.
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#27
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I installed another HOT. When I removed the old one which blew last night, there was goopy electrical tape around the transistor base. Maybe there was an arc.
This time around I tested +B. the TV had it set to 133VDC but turning the adjustment knob all the way to the right will bring it up to 140V. I tested by setting the multimeter to 500VDC range and putting one lead on ground and the other lead on the +B fuse. |
#28
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I should really replace the 4.7μF cap before doing anything else, no?
Could low +B voltage be causing a problem? You said it should be around 180VDC. ...yeah, I think a total recap is the way to go Last edited by luRaichu; 04-06-2024 at 03:38 PM. |
#29
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Should I drop the lightbulb in place of the line fuse, or the +B fuse?
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#30
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There is quite a pulse on that transistor case, you can't use layers of tape to replace the original mica insulator.
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Audiokarma |
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