Sony PVM 14N1U repairs

[roboblaster]

Hi all. I recently had a chance to pick up a PVM! Great, except it's currently in quite a sorry state

My goal with this set is to bring it back to life if possible, and learn a lot along the way about PVMs. Hopefully I can tap into the brain trust here, and document some info for future readers.

So this is what it looks like now, the "before" picture:



https://imgur.com/a/3Zy0EzM

The case was open when I bought it. I did get the cover as well, but no screws. The previous owner wouldn't tell me much, just that "it turned on and made a bad electronic smell but i couldnt figure out what was wrong".
I haven't connected it to power yet, just discharged the tube and had a look at the board. I can see that an RGB mod of some description has been added to it, uknown if it work (the quality of the work looks pretty sus!).

Before i go further with it I wanted to ask if there are any signs I should look for that would immediately mark it as a write off. Like if the tube neck is broken, where do you look for signs of that?

Next step is to blow it off with compressed air and inspect what mods the previous owner has done to this poor thing ...

[Hoagtech]

I wouldn’t assume the tube is broken unless there’s chipped glass on the neck connector.

Check the connection to the neck PCB first

[kamiboy]

If the vacuum inside the tube has been broken you usually can see the effect on the phosphors on the front of the tube. There are usually spots where they have been blown off, it should be pretty obvious with the tube off, when you look at the front it should have inconsistent large patches, and some times you can look all the way into the inside of the tube.

I doubt that is the problem. The smell suggests a short or failing component somewhere. If you are lucky it is something passive, like a resistor, which usually will be obviously charred, or perhaps a diode. A popular culprit of failure is bad caps, usually visible as bulging or leaking brown fish smelling liquid.

There might also be cold solder joints at play, especially around the flyback transformer legs. Except for broken neck the, which is game over, a fixable worst case scenario might be a broken flyback transformer. They might not be easy to source a replacement for.

[roboblaster]

Thanks for the tips guys. I'll check for any obvious damage on the tube.

I'm hoping it might be something simple, but I'm not in a rush, I can take time to troubleshoot it as needed. Just waiting on delivery of a ESR meter though, so might be a week or so before i can start checking components.

Also need to do some research on rgb mods for this model to see if i can reverse engineer what prev owner has done. If any components were removed or modified that could be relevant!

[roboblaster]

Took the chassis outside today and blew the dust off it with compressed air and wiped down the external case. It's already looking a lot better

while I'm tinkering, I'm looking for replacement screws. The prev owner pulled it apart and presumably lost the originals. The service manual is quite helpful, on the exterior I'll need:
4x “claw screw M4 x 8”
4x “BVTP 4 x 16” (??)
1x "3 x 12"


https://imgur.com/a/HHiIXTA

The BVTP screw is a weird one. looks like a sony thing. I'll dig up some M4 self tapping screws, see if that works. hmm no idea what the thread pitch is supposed to be. Hopefully it will Just Work (tm).

Searching online yielded a thread with info about RGB modding this model: https://www.reddit.com/r/crtgaming/comm ... _pvm_14n1/
Some good info there to compare whats been done to mine. It might not be exactly the same process they used but it's a start to look for any missing or added components

[roboblaster]

Had a chance to have more of a look at what's going on

Before doing anything else I pulled out the main board and had a look for modifications. I'm not sure why these would be added (are black wires likely from factory?), but the the green wire and cap seems a bit suspicious. The cap is across C307/C454. Green wire running from pin 38(TBC) to C415 (TBC).

https://imgur.com/a/uY8N1R6

The set had been tested by previous owner so I figured I'd try connecting the headers back on main board and turning it on. There are signs of life - it sounds like its powering up, and a horizontal blue line comes up.

https://imgur.com/a/ghHEL1O

Sooo.. any thoughts on what could cause it? Issue with vertical deflection IC maybe?

[roboblaster]

Thought I might try replacing the caps in the vertical deflection area, so I pulled out C551, C555, C556, C671.
Tested all of them out of circuit (atlas esr70) and they seem fine:

C551: 100.7, 0.9o
C555: 10.14 uf, 1.85o
C556: 8.9 uf, 2.3o
C671: 10.38 uf, 1.41o

Since I had them out I figured I might as well put in new ones, but after reassembly still same issue. damnit...

[tongshadow]

Disconnect the daughter board (S-Board) and the connectors from the video/input board, just to rule out issues there.
You should be able to see at least the OSD menu.

[roboblaster]

Disconnect the daughter board (S-Board) and the connectors from the video/input board, just to rule out issues there.
You should be able to see at least the OSD menu.

hey - I just tried that. still same behavior unfortunately, just the horizontal line near the bottom of the screen..

I've been thinking about how to tackle this. I think at this stage I'll just work through each section and check or replace components. If I'm lucky I might stumble on the issue. Unless anyone has any better ideas I'll start with H and V deflection areas

[tongshadow]

This is going to be a difficult repair, just going by "it turned on and made a bad electronic smell but i couldnt figure out what was wrong" makes me think the previous made a mistake.
Do you have an Oscilloscope and a high voltage x100 probe? I would start by measuring the waveforms of the horizontal and vertical deflection.

[roboblaster]

This is going to be a difficult repair, just going by "it turned on and made a bad electronic smell but i couldnt figure out what was wrong" makes me think the previous made a mistake.
Do you have an Oscilloscope and a high voltage x100 probe? I would start by measuring the waveforms of the horizontal and vertical deflection.

Yeah i am quite suspicious of prev owner.. but what can you do.. at the very least I am learning a lot already.

i dont have an Oscilloscope no.. (not yet anyway ). Is it a fairly common failure mode having the V or H IC's fail? Replacing both components would only run about $10 for the parts. I'm not sure how else i could check them