[Solved] PVM monitor repair - Page 1
Forum section: electronics / repair

author: fabiodl
author_rank: Frequent Contributor
timestamp: September 13, 2021, 08:57:01 am
content: I have a sony PVM-204MIts service manual ishereAll of a sudden, I got the RED, GREEN & BLUE lines displaying on the top of the screen as shownI fully recapped it (155caps!) but the problem remains. Indeed, the ESR of every single cap was ok.I am worried connecting a faulty console to it may have damaged it.Video signals are still shown correctly, so let's say a faulty power brick let 110V through the console and through the video inputs. Wouldn't that have damaged the whole input section? However it's only the vertical position which shifted all of a sudden.What would be your next action?

author: perieanuo
author_rank: Frequent Contributor
timestamp: September 13, 2021, 02:16:32 pm
content: the menu shows up ok? if it shows, then yes you have popcorned your input stage

author: perieanuo
author_rank: Frequent Contributor
timestamp: September 13, 2021, 02:33:25 pm
content: on page 42 i see some input list, which one you used?

author: fabiodl
author_rank: Frequent Contributor
timestamp: September 13, 2021, 02:40:05 pm
content: All inputs still work (the image comes out fine), but it is vertically shifted down.The menu is shifted in the same way.

author: Ian.M
author_rank: Super Contributor
timestamp: September 13, 2021, 02:55:40 pm
content: Later model Sony CRT monitors and TVs have auto white balance, performed by measuring the individual R, G and B electron gun beam currents (to control for decreasing emission) on three scanlines during the vertical blanking interval. If the vertical timebase circuit is faulty, its not uncommon to see them on screen.It is *EXTREMELY* unlikely to be caused by damage from a possibly faulty console, and the only possible way that could happen and still leave it capable of showing a synced stable picture would be if the console used a frame rate right on the margin of what the monitor could accept, which could have over-stressed an already weak and failing vertical output stage. If it had input stage (or input selector) damage, it would have problems displaying one or more colors and/or if the sync inputs were damaged, the picture would either be unstable or blanked.

author: Runco990
author_rank: Frequent Contributor
timestamp: September 13, 2021, 03:16:03 pm
content: You need to go into the service menu and re-adjust the Vertical and Horizontal settings. Typical after a re-cap. I used to repair these by the pallet load back in the studio days before we switched to HD.Possibly also the vertical blanking on top, as this can cause the white balance lines to come down too far.

author: fabiodl
author_rank: Frequent Contributor
timestamp: September 13, 2021, 03:58:50 pm
content: I did the recap because if this problem. I did enter the service menu. By adjusting v-blanking I can move the lines up, but the even the maximum value is not sufficient to bring the image to the center

author: Ian.M
author_rank: Super Contributor
timestamp: September 13, 2021, 05:17:57 pm
content: Are there any geometry problems? Try displaying a grid of squares + diagonal lines and look for any vertical linearity defects. If found, go over the vertical output stage looking for low ohm resistors that have changed value, diodes that have gone open or short, and dry joints, especially on inductors.Also, did you use good, name brand 105 dec C caps in the vertical section?

author: fabiodl
author_rank: Frequent Contributor
timestamp: September 13, 2021, 10:10:06 pm
content: There are no other geometry problems. All the caps are Nichicon, 105degrees, long life.I tried wiggling the board / pushing it with a plastic stick while in operation, but I saw no difference.I checked the value of the resistors near the heatsinks (I checked only the through hole ones,though),but they were spot on.I will have a check at diodes, thank you.

author: Runco990
author_rank: Frequent Contributor
timestamp: September 13, 2021, 11:02:41 pm
content: Did you change any values in the Vertical circuit? In particular the 4.7 uF and maybe a 1uF or 2.2uF? Don't! I forgot the exact ones after so many years, but the set doesn't like it. One is usually orange in color, if I recall. Next to one of the vertical transistor heatsinks.

author: fabiodl
author_rank: Frequent Contributor
timestamp: September 14, 2021, 12:36:54 am
content: C-572 and C-584,isn't it.It's indeed the orange one, close to the heatsink. The board mounted a 1uF cap, but the service manual listed 2.2uF (according to the linked video, the change was published in a service bulletin from sony).I tried both values, but I got no change at all. I replaced the 4.7uF one with a 4.7uF.

author: perieanuo
author_rank: Frequent Contributor
timestamp: September 14, 2021, 09:53:53 am
content: the op says he had problems before recap, so maybe changed values isn't the thingV-blanking adjustment works? pages 28-29v-size adjustment works?

author: fabiodl
author_rank: Frequent Contributor
timestamp: September 14, 2021, 12:11:40 pm
content: Yes, the problem start before the recap.The service menu adjustments work in the sense that I see the image change on the screen, but even the maximum values are not enough to center the picture.

author: Kerlin
author_rank: Regular Contributor
timestamp: September 15, 2021, 12:06:58 am
content: Why would you replace all the caps?Some comments that follow are also really dubious.Take it to some one who has been trained and experienced to do such to do such work, it wont cost much.If the cost is too much then throw it out.When I was young and family or a friend had faulty electronics equipment my farther would show his knowledge of electronics by saying " Oh that will be a capacitor" sometimes just to balance it out he would say "Oh that will be a short".People thought he was smart and he felt smart.After I was trained, qualified and experienced I realized he knew nothing about electronics, he was a bus driver!!He couldn't describe the symptoms and even if some one gave him the reason for the problem he wouldn't understand it.

author: Ian.M
author_rank: Super Contributor
timestamp: September 15, 2021, 12:31:25 am
content: CRT TV and monitor repair is a dying trade, and has been for over a decade, so its getting harder and harder to find a repair shop that still handles them, and the few specialists that do wont be cheap.As CRT TVs and monitors are no longer in production, yet are still in demand by the gaming and retro-arcade communities, and Sony CRT monitors used to be known for their quality, even if its BER (which is unlikely given the symptoms described unless a unobtanium Sony chip is fried), it should still have some value as a parts donor, so please don't scrap it without trying to find someone who wants it.

author: pcwrangler
author_rank: Regular Contributor
timestamp: September 15, 2021, 12:57:23 am
content: Quote from: Kerlin on September 15, 2021, 12:06:58 amI'm not sure your post follows the spirit of this forum. Many here have saved electronics destined for a landfill, get this, without training or official education.I encourage the OP to do anything they can to save their equipment, safely. As another contributor just posted, please don't throw out a PVM monitor without trying to give away or at least sell it. Good luck!

author: sean0118
author_rank: Frequent Contributor
timestamp: September 15, 2021, 03:01:42 am
content: Replacing the caps wasn't a waste of time, once you get it fixed it will be less likely to fail again in the future, as electrolytics do have a finite life.

author: perieanuo
author_rank: Frequent Contributor
timestamp: September 15, 2021, 08:23:13 am
content: Quote from: fabiodl on September 14, 2021, 12:11:40 pmthat narrows to vertical deflection the fault, in page 41 you have the big pictureyou say you cannot center the V, but size it's ok?you gotta be more explicite to narrow down the defective area, tbo a scope would be gold for this job, verifying the V sync pulses (IC507 pins 22/20/19 they say) would eliminate half of the problem, my experience with tv's is that is almost always the power stages falls first, some capacitor or resistor in that area

author: fabiodl
author_rank: Frequent Contributor
timestamp: September 15, 2021, 09:56:00 am
content: I am now checking the parts' value (at the moment, only for the ones for which that can be done in circuit),and the continuity of the traces, starting from V+ V-.I have a question though. What is a reasonable value for the thermistor TH-500? I read 56 ohms at ambient temperature.Quote from: perieanuo on September 15, 2021, 08:23:13 amYes, the size looks ok.I have a scope,I'll check and report. As for pin 19 and 20, I believe the correct pulses are the one shown for test points 55 and 54 (page 71), respectively.What kind of signal would you you expect on pin 22?

author: fabiodl
author_rank: Frequent Contributor
timestamp: September 16, 2021, 06:06:41 am
content: I noticed one strange thing. The menu seems to be shifted, but the signal not so much.See the attached picture.The top pictures show the monoscope, and the menu, with underscan.The bottom pictures show the same things, without underscan.As you can see, the top of the image is replaced by the retracing lines.

author: perieanuo
author_rank: Frequent Contributor
timestamp: September 16, 2021, 10:16:23 am
content: in that manual, i see vertical/horz deflection brain at page 59-60 IC507, waveforms for H/V deflection are on page 61 (54, 55 and so on)we're watching different things

author: perieanuo
author_rank: Frequent Contributor
timestamp: September 16, 2021, 10:32:40 am
content: the bizarre part is vsync and hsync came from different parts (see ic503/502), not easy to track thisbut my intuition says the problem is before vsync (video v) attack ic507 on pin 22, in ic502-503 area or before this

author: fabiodl
author_rank: Frequent Contributor
timestamp: September 17, 2021, 03:43:14 am
content: 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

author: Runco990
author_rank: Frequent Contributor
timestamp: September 17, 2021, 03:50:59 am
content: 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.You are not doing a bonehead move like adjusting it in 16:9 like I did once?But I have seen these with every setting totally screwed up and it took a total setup to get everything balanced out again. I may be wrong, but I have never found these monitors to have any problems other than the 2 caps. They were absolute tanks.Now the 20M"4"U had crt problems, but the 20M2U is basically a PVM 1954Q at heart. They just ran forever.

author: james_s
author_rank: Super Contributor
timestamp: September 17, 2021, 04:06:41 am
content: Quote from: sean0118 on September 15, 2021, 03:01:42 amThat 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.

author: fabiodl
author_rank: Frequent Contributor
timestamp: September 17, 2021, 07:09:03 am
content: Quote from: james_s on September 17, 2021, 04:06:41 amQuote from: fabiodl on September 13, 2021, 10:10:06 pm

author: fabiodl
author_rank: Frequent Contributor
timestamp: September 17, 2021, 07:13:21 am
content: Quote from: Runco990 on September 17, 2021, 03:50:59 amI 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.Quote from: Runco990 on September 17, 2021, 03:50:59 amI am pretty sure of that. furthermore, if you see the monoscope, it's not switching to 16:9 by some hardware fault either.

author: perieanuo
author_rank: Frequent Contributor
timestamp: September 17, 2021, 07:18:41 am
content: Quote from: fabiodl on September 17, 2021, 03:43:14 amnot 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 havethe 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

author: perieanuo
author_rank: Frequent Contributor
timestamp: September 17, 2021, 07:21:50 am
content: 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 shiftedcheck all components in blanking area V-blk, see around pin 13 IC507, C561, Q510 (16:9 selection) ...

author: fabiodl
author_rank: Frequent Contributor
timestamp: September 17, 2021, 08:18:33 am
content: Thank you so much, this weekend I will check that area

author: Runco990
author_rank: Frequent Contributor
timestamp: September 17, 2021, 05:03:33 pm
content: Quote from: fabiodl on September 17, 2021, 07:13:21 amAhh.... 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.

author: fabiodl
author_rank: Frequent Contributor
timestamp: September 19, 2021, 08:04:07 am
content: Quote from: Runco990 on September 17, 2021, 05:03:33 pmAbout 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?)

author: Runco990
author_rank: Frequent Contributor
timestamp: September 20, 2021, 03:18:50 pm
content: 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.

author: fabiodl
author_rank: Frequent Contributor
timestamp: September 21, 2021, 05:51:34 am
content: Quote from: Runco990 on September 20, 2021, 03:18:50 pmWhen I was a kid your job was my dream jobQuote from: Runco990 on September 20, 2021, 03:18:50 pmActually 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.

author: fabiodl
author_rank: Frequent Contributor
timestamp: September 30, 2021, 09:55:59 am
content: 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.

author: fabiodl
author_rank: Frequent Contributor
timestamp: January 01, 2022, 07:31:50 am
content: 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 aservice manual.

author: fabiodl
author_rank: Frequent Contributor
timestamp: January 02, 2022, 11:29:24 am
content: Quote from: perieanuo on September 17, 2021, 07:21:50 amI took some measurements, I really do not understand what is wrong. See the attached PDF.

author: fabiodl
author_rank: Frequent Contributor
timestamp: January 04, 2022, 10:14:53 am
content: Problem found. R598 went open. Probably by resistor sulfuration.

author: Runco990
author_rank: Frequent Contributor
timestamp: January 04, 2022, 03:38:18 pm
content: 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....But that is an interesting one.

author: james_s
author_rank: Super Contributor
timestamp: January 10, 2022, 06:43:56 am
content: 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.

author: 10u
author_rank: Newbie
timestamp: June 26, 2022, 09:44:03 pm
content: 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!

author: fabiodl
author_rank: Frequent Contributor
timestamp: July 03, 2022, 10:08:20 am
content: Quote from: 10u on June 26, 2022, 09:44:03 pmHappy to hear this! It took me the whole Christmas holiday to spot that sucker!

author: deezdrama
author_rank: Contributor
timestamp: December 01, 2022, 06:27:48 am
content: Quote from: 10u on June 26, 2022, 09:44:03 pmQuote from: fabiodl on July 03, 2022, 10:08:20 amI 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!

author: zimbo1616
author_rank: Newbie
timestamp: January 25, 2024, 12:25:46 am
content: 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.

author: Runco990
author_rank: Frequent Contributor
timestamp: January 25, 2024, 07:13:51 pm
content: Quote from: deezdrama on December 01, 2022, 06:27:48 amSo 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.