Author Topic: [Solved] PVM monitor repair  (Read 7215 times)

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Offline fabiodlTopic starter

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Re: PVM monitor repair
« Reply #25 on: September 17, 2021, 07:09:03 am »
[That depends on whether they were replaced with good quality caps and the work was done properly. Multiple times I've had people bring me stuff to fix that they had either replaced good quality caps with the cheapest random no-name junk they could find, or bungled the job and done damage that wasn't there before. IMO it's best to fix the problem *before* shotgun replacing capacitors.

All the caps are Nichicon, 105degrees, long life.
 

Offline fabiodlTopic starter

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Re: PVM monitor repair
« Reply #26 on: September 17, 2021, 07:13:21 am »
This doesn't make sense to me.... seems like someone may have played around in the service menu and messed everything up.  The menu position is also adjustable, btw.
I can assure you this was not the case. I am the only user. I switched it on, it was ok, switched it off, switched it on again 5 mins later and it was bad.

You are not doing a bonehead move like adjusting it in 16:9 like I did once?
I am pretty sure of that. furthermore, if you see the monoscope, it's not switching to 16:9 by some hardware fault either.
 

Offline perieanuo

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Re: PVM monitor repair
« Reply #27 on: September 17, 2021, 07:18:41 am »
Yes, I think you are correct, but one thing puzzles me. Why does the menu get shifted, but the picture does not? if vsync was delayed, I would expect the image to shift down as well
not really, vsync and hsync are 'decrypted' differently in sync separator IC, so one sync signal, in this case V, came out delayed, that's my guess. you see for yourself, Hsync is entering IC507 separately, but i didn't read ic507 datasheet to affirm this for sure (that Vsync and Hsync decoding are totally separate from each other)
i think a 2 channel scope can point this delay, your case is somehow more complicate than tv's i repaired with V deflection issues because of all that delay logic you have
the menus should not be a real problem, some reset may exist so giving a reset should arrange the software parametrisation doubts, some people think this may be a problem, i don't. anyway, a reset won't hurt
 
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Offline perieanuo

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Re: PVM monitor repair
« Reply #28 on: September 17, 2021, 07:21:50 am »
yep, just downloaded that upc1377c datasheet, V and H sync separators are independent, so this is normal, if wrong delay on V or h sync, your image is shifted
check all components in blanking area V-blk, see around pin 13 IC507, C561, Q510 (16:9 selection) ...
« Last Edit: September 17, 2021, 07:30:08 am by perieanuo »
 
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Offline fabiodlTopic starter

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Re: PVM monitor repair
« Reply #29 on: September 17, 2021, 08:18:33 am »
Thank you so much, this weekend I will check that area
 

Offline Runco990

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Re: PVM monitor repair
« Reply #30 on: September 17, 2021, 05:03:33 pm »
This doesn't make sense to me.... seems like someone may have played around in the service menu and messed everything up.  The menu position is also adjustable, btw.
I can assure you this was not the case. I am the only user. I switched it on, it was ok, switched it off, switched it on again 5 mins later and it was bad.


Ahh.... a SUDDEN failure...  well, that would generally rule out Caps and point more toward a semiconductor problem.  Although, it IS possible that the NVram is corrupt and needs a total reset.  Unlikely, but we did see this on some TV's.  Unfortunately it took a laptop with service software and a clip to re-write the NVram.  Another possibility is a cracked solder connection on one of the surface mount components, seen that a few times, as well as a NON-soldered connection that somehow passed QC and ran for 15 years before it decided to NOT touch the pad.  Odd one... 

I am very curious as to the cause if you find it.... in this case I have never had the exact same failure, so no additional info to draw from except what has already been done and suggested.  These monitors are generally very reliable and tend to have the exact recurring failures only.
 
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Offline fabiodlTopic starter

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Re: PVM monitor repair
« Reply #31 on: September 19, 2021, 08:04:07 am »
[Although, it IS possible that the NVram is corrupt and needs a total reset.  Unlikely, but we did see this on some TV's.  Unfortunately it took a laptop with service software and a clip to re-write the NVram.  Another possibility is a cracked solder connection on one of the surface mount components, seen that a few times, as well as a NON-soldered connection that somehow passed QC and ran for 15 years before it decided to NOT touch the pad.  Odd one... 
About the NVram, do you mean the values shown by the service menu, or is there something else?
I compared the values in the service menu with the one listed on the service manual, they are not far from their default value, but where slightly tuned at some point (factory? previous user 5+ years ago?)
 

Offline Runco990

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Re: PVM monitor repair
« Reply #32 on: September 20, 2021, 03:18:50 pm »
Not everything is shown in the service menu.  But we don't have the tools to get into it.  I was trained by Sony for Broadcast gear repair in the mid 80's.  However, I no longer have the tools or professional database access.  Abandoned Monitor repair about 15 years ago.

Sure wish I could look at this in person...  I suck at trying to figure this stuff out remotely.

If all the values seem close... maybe the DAC?

I know this is unrelated, but I have see DACS "almost work".  In particular with Studer Gear... ONE function would be screwy.  It's a stab....

Sorry I cannot be more helpful... I have forgotten a lot since those days.
 

Offline fabiodlTopic starter

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Re: PVM monitor repair
« Reply #33 on: September 21, 2021, 05:51:34 am »
Not everything is shown in the service menu.  But we don't have the tools to get into it.  I was trained by Sony for Broadcast gear repair in the mid 80's.  However, I no longer have the tools or professional database access.  Abandoned Monitor repair about 15 years ago.
When I was a kid your job was my dream job :)

Sure wish I could look at this in person...  I suck at trying to figure this stuff out remotely.
If all the values seem close... maybe the DAC?
I know this is unrelated, but I have see DACS "almost work".  In particular with Studer Gear... ONE function would be screwy.  It's a stab....
Sorry I cannot be more helpful... I have forgotten a lot since those days.

Actually that would totally explain/fix the problem, because increasing the vsync value I can get it "better but not good enough". I actually thought about hacking a pair of resistors there to bring up the voltage, but that will be my last resort. I want first to try to understand the actual problem.
 

Offline ArcadeTV

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Re: PVM monitor repair
« Reply #34 on: September 28, 2021, 05:53:31 am »
 

Offline fabiodlTopic starter

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Re: PVM monitor repair
« Reply #35 on: September 30, 2021, 09:55:59 am »
Thank you. As I wrote in my first post, that was my first action, but it did not fix the issue.
I then replaced all the caps, and that did not solve it either.
 

Offline fabiodlTopic starter

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Re: PVM monitor repair
« Reply #36 on: January 01, 2022, 07:31:50 am »
I found out that the 24V rail (see the anode of D530, for instance) is actually 30V.
That rail seem to come out of the flyback transformer.
Who is actually responsible for the voltage regulation on that rail? IC500?
Here is a service manual.
 

Offline fabiodlTopic starter

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Re: PVM monitor repair
« Reply #37 on: January 02, 2022, 11:29:24 am »
yep, just downloaded that upc1377c datasheet, V and H sync separators are independent, so this is normal, if wrong delay on V or h sync, your image is shifted
check all components in blanking area V-blk, see around pin 13 IC507, C561, Q510 (16:9 selection) ...

I took some measurements, I really do not understand what is wrong. See the attached PDF.
 

Offline fabiodlTopic starter

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Re: PVM monitor repair
« Reply #38 on: January 04, 2022, 10:14:53 am »
Problem found. R598 went open. Probably by resistor sulfuration.
 
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Offline Runco990

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Re: [Solved] PVM monitor repair
« Reply #39 on: January 04, 2022, 03:38:18 pm »
WOW.... thanks for the update.  There is something you don't expect to see in these sets.

If that resistor failed in your set, don't be surprised if the same one fails in another set.  Sony's tend to be like that.  I used to repair them by the pallet load, always the identical problems.  At some point you build up a database for this stuff.  Or in many cases just fix them blindfolded....  ;D

But that is an interesting one.  :-+
 
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Offline james_s

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Re: [Solved] PVM monitor repair
« Reply #40 on: January 10, 2022, 06:43:56 am »
I remember seeing resistors failing open in quite a few CRT displays. I'm not sure why that is, in other devices they very rarely fail, at least not without being obviously burned out.
 

Offline 10u

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Re: [Solved] PVM monitor repair
« Reply #41 on: June 26, 2022, 09:44:03 pm »
Had the same issue present on my PVM-14M2U. Checked R598 and it had failed open as well. Thanks for the detailed post and follow-up on resolution, fabiodl. Saved me a lot of time!
 

Offline fabiodlTopic starter

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Re: [Solved] PVM monitor repair
« Reply #42 on: July 03, 2022, 10:08:20 am »
Had the same issue present on my PVM-14M2U. Checked R598 and it had failed open as well. Thanks for the detailed post and follow-up on resolution, fabiodl. Saved me a lot of time!
Happy to hear this! It took me the whole Christmas holiday to spot that sucker!
 

Offline deezdrama

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Re: [Solved] PVM monitor repair
« Reply #43 on: December 01, 2022, 06:27:48 am »
Had the same issue present on my PVM-14M2U. Checked R598 and it had failed open as well. Thanks for the detailed post and follow-up on resolution, fabiodl. Saved me a lot of time!


Had the same issue present on my PVM-14M2U. Checked R598 and it had failed open as well. Thanks for the detailed post and follow-up on resolution, fabiodl. Saved me a lot of time!
Happy to hear this! It took me the whole Christmas holiday to spot that sucker!

I have a 20m2u that was stuck in protection mode, I brought it back to life with a deflection recap but after 30min of the pvm being on I watched the image stretch/distort horizontaly on the bottom of the raster, then the image vibrated and jumped around vertically for a minute or so then went into a full vertical roll.
V hold has no affect other than slowing the rolling.
Rechecked all the caps I installed. Ive recapped dozens of crt's and consoles and confident its not the recap job.

I suspected I lost vertical sync and so replaced the sync seperator IC chip. Same problem.
I have vertical rolling with all input sources and even the menu isnt stable now.

Im wondering if its in the V oscillation circuit now but seen this post and figured id check out R598 but cant find it. Service manual shows its near q517 which is for h-v phase lock but couldnt spot it either.
Is R598 a surface resistor? Top or bottom of the board?

Any other ideas? I dont have a scope yet and grasping at straws. After the recap I dialed in geometry,focus, and picture and it looked fantastic untill the component failure, I hope to save this monitor .... The tube was bright and vibrant.

Any help is appreciated!
 

Offline zimbo1616

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Re: [Solved] PVM monitor repair
« Reply #44 on: January 25, 2024, 12:25:46 am »
Just posting this here because I struggled to find that damn resistor as well. Pictures show it's location on the top side of the board.
Hope this helps others.
 

Offline Runco990

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Re: [Solved] PVM monitor repair
« Reply #45 on: January 25, 2024, 07:13:51 pm »

I have a 20m2u that was stuck in protection mode, I brought it back to life with a deflection recap but after 30min of the pvm being on I watched the image stretch/distort horizontaly on the bottom of the raster, then the image vibrated and jumped around vertically for a minute or so then went into a full vertical roll.
V hold has no affect other than slowing the rolling.
Rechecked all the caps I installed. Ive recapped dozens of crt's and consoles and confident its not the recap job.

I suspected I lost vertical sync and so replaced the sync seperator IC chip. Same problem.
I have vertical rolling with all input sources and even the menu isnt stable now.

Im wondering if its in the V oscillation circuit now but seen this post and figured id check out R598 but cant find it. Service manual shows its near q517 which is for h-v phase lock but couldnt spot it either.
Is R598 a surface resistor? Top or bottom of the board?

Any other ideas? I dont have a scope yet and grasping at straws. After the recap I dialed in geometry,focus, and picture and it looked fantastic untill the component failure, I hope to save this monitor .... The tube was bright and vibrant.

Any help is appreciated!

So my thoughts on this:  There is at least ONE cap in the Vertical circuit that is special.  It should be a very high ripple tolerant type.  If you replaced it and used a "modern SMALLER cap" that may be your issue, as these cannot dissipate the energy going through it.  I had this problem back in the CRT projector days.  There were 2 special made capacitors in the vertical yoke circuit that were GIGANTIC for being 33uF.  The entire vertical deflection drive passed through them.  There were NO replacements and they were so big to dissipate the HEAT this generated.

Maybe look at the schematic again.  I used to repair these monitors 20 years ago, so don't recall many details, but I didn't mess with certain caps, as THEN it was not needed.

Food for thought, as your monitor worked and then slowly died.  Seems like an overloaded cap issue, so maybe check more closely.
 


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