PVM-20M2U Update.... New Sync Chip and Sync Caps....
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- Опубліковано 26 лис 2022
- This is a followup to the last video on the 20m2u, After fixing no power/protection state, faulty front panel board, and an arcing tube I lost vertical sync.... Ive had the sync seperator IC chip in hand for a while but wasnt confident that was the issue untill reading about sync seperator chip being faulty could cause horizontal distortion along with rolling.....both issues I was experiencing so went ahead and replaced the sync chip along with surrounding capacitors. so now the whole deflection side of the board has new caps.
Still didnt correct the issue. OSD bounces and still have horizontal distortion and vertical rolling.
back to the drawing board. Guess ill try vertical IC's next. Probably just a film cap or something stupid that I have no idea how to find. - Ігри
This is a followup to the last video on the 20m2u
ua-cam.com/video/cUFdCbEcRZQ/v-deo.html
After fixing no power/protection state, faulty front panel board, and an arcing tube I lost vertical sync.... Ive had the sync seperator IC chip in hand for a while but wasnt confident that was the issue untill reading about sync seperator chip being faulty could cause horizontal distortion along with rolling.....both issues I was experiencing so went ahead and replaced the sync chip along with surrounding capacitors. so now the whole deflection side of the board has new caps.
Still didnt correct the issue. OSD bounces and still have horizontal distortion and vertical rolling.
back to the drawing board. Guess ill try vertical IC's next. Probably just a film cap or something stupid that I have no idea how to find.
Was that bridging between one of the IC legs and R568 intentional/from the factory? --- Maybe you could ask Shangoo66, 12voltvids or savonpat about the sync issue ...
Yup, several of the sync chips vias had direct surface trace pads to nearby surface mounted resistors.
Ive posted this issue on multiple platforms and forums so ill have to wait and see. Starting to think its something like a bad film cap or diode
You can do it
Tell me what to do 🤣
Have you checked resistors etc or diodes around the sync chip or any of the bigger resistors around that area? Have you done a prod test around the board to see if it affects the problem at all? Might have been a cracked solder that gave way. Have you checked that the right voltages are getting to the sync chip? It definitely looks like something in the video processing section. Are any of the chips hot to touch? A failed vertical output IC would likely give a flat horizontal line. One that is bad can give shakiness in the picture but I wouldn't have thought constant scrolling like that. You could always solder some wires to test points and make sure you're getting the right voltages that way.
I did check the larger resistors that they werent open, and probed the diodes looking for diode voltage drops.
Havnt figured out a good way to test for voltages live because all the wiring is so short but need to figure it out and probably study the service manual some more lol
Depending on how many test points there are you could solder wires to the test points on the board and wire them out to choc blocks for safer testing.
I have a large consumer set which would lose high voltage and switch itself off. I replaced capacitors around the flyback, checked resistors, did all sorts. Someone suggested a dry solder joint may be the problem but I'd resoldered all the connections on the hot side of the board and tapped around all that section. Then when I was taking the scart connector out one day I noticed that it was affecting the picture.
It turned out to be a dry solder joint on the other side of the board. You might want to touch all those solder points up on the through hole stuff to rule it out.
@@Gubalicious Next time I have the board out ill check the other side for bad solder joints instead of just focusing on the deflection side. Good idea with the terminal blocks for testing voltages, also I cant remember if I tried swapping input boards so may need to try that as well.
@@Gubalicious
I forgot to update, i checked all caps esr again, reflowed entire deflection/sync side of the board , tiny surface components and all, checked all sync ic pin voltages, and recapped around vhold IC.... Same issue
www.eevblog.com/forum/repair/pvm-20m2u-vertical-deflection-issue/msg4558444/#msg4558444
@@LameGaming So it's not a dry solder joint. It's not a failed cap because you've replaced all of those, Plus it's not time dependant. Its a problem that is there indefinitely. Pointing towards a failed component.
It's not a sync issue because you've replaced the sync IC and checked all the components around it, the other thing to look out for on that is a high pitched whine, that's usually a sound you hear when the monitor is searching for a sync. Plus it looks like the picture is synced but just rolling, a missing sync usually looks more garbled than that.
The menu is still stable which suggests it's not a problem with the actual picture output to the tube. It's an imaging processing problem. I would say the wobbling of the menu is normal as my BVM does that on an unstable image.
On page 68 of the service manual there is a "hold amp". It appears again on the bottom of page 42. Not sure whether the hold is referring to the vertical hold. Might be worth having a look round there. There are some other youtube videos which show a rolling picture to be in the vertical output section. But where that is in the service manual... There are some good block diagrams to follow in that manual also.
Damn bro……
Yeah.... Bwa bwa bwaaaaaaa 😖
@@LameGaming hey bro. You made the attempt. That’s half the battle
@@Undar8ed03 Yeah, at least I know it isnt the sync IC now i guess.
Ready to pay someone to fix at this point lol
@@LameGaming you gave it a helluva fight bro. Don’t look at it as a defeat.
Need to know the title of that repair guide, please.
Homer L Davidson published a few tv repair books in the crt era. Some are for beginners, some more advanced. I cant recall which book I referenced but just look on ebay, i think i got mine from an ebay goodwill seller for a few bucks ea
@@LameGaming Thanks a lot dude, I' m just a beginner and I want to get inside, really in love for the old electronics. I hope you will have success with that PVM, it' s a damn good beauty. I saw you swapped the IC and replaced the caps, probably at this point it may be some bad resistor.
get the scope out and take some measurements
I want to buy one but would have to figure out what Im doing with it first lol