service manual and next steps to repair a sony ssm-20n1u crt monitor - Page 1
Forum section: electronics / repair

author: oggie
author_rank: Contributor
timestamp: June 16, 2018, 05:42:01 pm
content: I have a sony ssm-20n1u and the screen now has an hourglass shape to it. I've attached a photo of it.https://photos.app.goo.gl/oTu6qogukhdXWxHd8What's the term for this distortion?I don't see much for adjustments inside after a quick inspection, so is this a monitor where a lot of adjustments are software based? I don't even know how to get into the service menu.Any recommendations on next steps? I have an electronics background, but I've never repaired a CRT before. I also dont have access to a scope or signal generator since my job doesn't call for that stuff and I've never needed one personally.Since it's from 1997, should I replace the caps and see if that inproves anything? Anything this old should have caps replaced by now anyway.I can't seem to find a service manual for it either.

author: helius
author_rank: Super Contributor
timestamp: June 16, 2018, 07:40:38 pm
content: Quote from: oggie on June 16, 2018, 05:42:01 pmPincushionQuoteSome Sony monitors have an internal serial port used for diagnostics, although this one looks to be a simpler model where the digital control may be minimal. In general, the adjustment pots in a CRT like this will be in 3 groups: (1) near the cathode amp board (in the back) for brightness and color balance; (2) on the side (HV) board for geometry; and (3) on the opposite side for convergence, especially on precision monitors with dynamic convergence. If the set uses digital control, there are fewer physical pots.QuoteLook on the left side shielding for a series of holes to access the pots on the high voltage board. There may be one labeled "PIN"You should only adjust them with a suitable insulated tool as high voltages are present.If adjustment doesn't have any effect on the screen, the pincushion circuit may be at fault:http://www.repairfaq.org/REPAIR/F_monfaq7.html#MONFAQ_007QuoteThere are a lot of electrolytics inside a CRT, and many expensive or specialized types. I would not replace them unless troubleshooting shows they are the cause of a problem.

author: PKTKS
author_rank: Super Contributor
timestamp: June 17, 2018, 10:59:09 am
content: The explanation is good ... if you have a PIN POT.If NOT ... try looking your vertical osc. sweepIt must be a flat linear RAMP which currently is not.It is deviating in the middle but returning at the endI would guess some eletrol. cap has gone wild or may be just a bad solder jointThis devices accumulate a lot of heat which given enough time cause cracksin particular associated with some "black" or dark areas in the pcb.Paul

author: oggie
author_rank: Contributor
timestamp: June 17, 2018, 05:52:20 pm
content: So started looking some more, and it seems there's no PIN pot to be found, and I don't know how to get into the service menu to see if it's adjustable there.Here's an album of some photos I took:https://photos.app.goo.gl/Yf7TRXnmGEdW3uf16On top of the tube, there's 2 rotaries that are glued in place and the red/blue wires go to a connector on the main board labeled HDY+.On the board attached to the tail end (cathode) of the tube, there's one pot labeled HSTAT and one labeled SCREENAnd on the mainboard there's a really large pot that has a wire going to the andode.Those are the only pots in there.There's another photo there that kind of shows that there's a few large microchips on the board under the crt, but they're hard to see. That makes me think there's a lot of software controls for tuning. If I could just find a manual or determine how to enter/navigate the service menu.I didn't see any caps that were leaking or bulging, and all boards look fine except for the solder side of the main board because I have not attempted to remove it yet.One question on the discharge of the CRT. Do I need to do anything different to discharge it since there's some chips on the main board? No chance of frying them with the old fashioned way of discharging?

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: June 17, 2018, 05:59:53 pm
content: Get a cooling spray, if a electrolytic is the culprit you'll know which after cooling one by one while watching the effect on the screen.

author: Rasz
author_rank: Super Contributor
timestamp: June 17, 2018, 06:32:35 pm
content: http://f6csx.free.fr/DOC/moniteur_Sony_PVM_14N2E.pdfthis one more helpfulhttp://diagramas.diagramasde.com/otros/SSM-20N5U_9976686010-00e.pdf

author: helius
author_rank: Super Contributor
timestamp: June 17, 2018, 06:34:33 pm
content: Quote from: oggie on June 17, 2018, 05:52:20 pmI believe those are magnetic chokes used to adjust the horizontal deflection linearity.QuoteSCREEN is the contrast control, it goes directly to the grid electrode in the CRT to control the beam current. HSTAT is a feature special to Trinitrons that controls both horizontal convergence and X-Ray protection. You shouldn't touch these.QuoteThat is the focus control. It doesn't look like focus is a problem.CN052 looks like a service port. I2C and 'AGING'.QuoteOnly discharge the anode to the metal frame whose fingers press on the CRT coating. If there is a plug between that and the circuit board, remove it first.Quote from: GeorgeOfTheJungle on June 17, 2018, 05:59:53 pmYou can also try poking the leaded components with a wooden stick to find cold solder joints, they are very common.

author: helius
author_rank: Super Contributor
timestamp: June 17, 2018, 07:47:38 pm
content: Quote from: Rasz on June 17, 2018, 06:32:35 pmIt shows H. PIN AMP as parameter #97 of the service menu.[But that appears to be a newer generation, N5 vs N1]

author: shakalnokturn
author_rank: Super Contributor
timestamp: June 17, 2018, 09:12:39 pm
content: Before looking to adjust anything look to find what has failed, you'll save yourself some time later.There are no trimpots to adjust pincussion in your monitor, it is software controlled, so the only way it needs readjusting is after a repair or if the EEPROM has failed, but in that case you'd have other symptoms.Look at the second link Rasz posted for the SIIA chassis it should be close enough although component positions (numbering) may not be the same, your chassis is SII.Check solders in the H deflection, beware of split blue ceramic disc caps.Check that glue has not come off inductors letting the ferrite slug loose.Check the equivalents on your model of: Q551, C553, R561, L551, C506, C501, C502, D501, D502.Also worth checking while you are in there: C509, C514.

author: oggie
author_rank: Contributor
timestamp: June 17, 2018, 11:27:57 pm
content: Quote from: helius on June 17, 2018, 07:47:38 pmYes, I saw that. But I can't seem to even enter the service mode as instructed in this manual..

author: oggie
author_rank: Contributor
timestamp: June 17, 2018, 11:29:40 pm
content: Quote from: shakalnokturn on June 17, 2018, 09:12:39 pmWhen you say 'check' , do you mean for any physical problems (splitting, bad solder joint etc), or do you mean check the actual values and for shorts?

author: shakalnokturn
author_rank: Super Contributor
timestamp: June 18, 2018, 01:03:01 am
content: Visual inspection of the lot for dry solders.Visual inspection of the blue disk ceramic capacitors for splits/burn marks.Visual inspection of large inductors for loose/missing slugs.Measurement of transistor, diodes, electrolytic capacitors, MKP/MKT capacitors.That's the way I usually go about things.Likely you'll find thins wrong on the solder side but then you may have to figure out what went wrong after that.If you must (most of the time it can be avoided) discharge the CRT as previously mentioned, when reassembling double check that the CRT graphite coating has been reconnected to the PCB ground before powering-up. Failure to ground the CRT usually ends in extra work...

author: oggie
author_rank: Contributor
timestamp: June 18, 2018, 11:59:37 am
content: Curious about your statement that you don't have to discharge the tube. I'd prefer to leave it alone, but I don't feel like taking the chance of a nice zap either.

author: shakalnokturn
author_rank: Super Contributor
timestamp: June 18, 2018, 09:37:30 pm
content: I feel I must clarifyIf you must disconnect the HV anode from the CRT, I insist that it is much wiser to discharge the CRT and even leave the ground strap in place until you reconnect.I was only trying to say that in many cases you can get away with leaving the HV connected while twisting/tilting the PCB round for maintenance.

author: oggie
author_rank: Contributor
timestamp: June 20, 2018, 11:26:53 am
content: Understood. I will probably have to disconnect the cable since the main board has to slide out of the slots to even look at the bottom.

author: Chris56000
author_rank: Frequent Contributor
timestamp: June 20, 2018, 04:44:24 pm
content: Hi!Unfortunately you won't find a Service Menu in Sony Monitors of that age, as they're electronically adjusted using a tool called Sony D.A.S. ("Digital Adjustment System!"), – I think it's called J40 but the server that hosted it disappeared years ago – Sony found about it and got it removed!I did have one version, but I could never get it to work, so I got rid of it – I don't know wether anyone still has a login/password for Sony's Technical Server, but you can try putting feelers out!Sorry I can't be of more assistance at the moment!Chris Williams

author: oggie
author_rank: Contributor
timestamp: June 20, 2018, 04:55:40 pm
content: are you sure? There's service menus in the 201n5u which is almost the same monitor

author: oggie
author_rank: Contributor
timestamp: June 20, 2018, 05:04:19 pm
content: I think the software you're referring to is windas. I think it stands for windows digital adjustment system?

author: oggie
author_rank: Contributor
timestamp: June 20, 2018, 06:47:44 pm
content: I found this:http://www.piclist.com/images/com/geocities/www/gregua/windas/

author: oggie
author_rank: Contributor
timestamp: June 21, 2018, 06:12:21 pm
content: Does this cap look a little puffy, or is it just me?https://photos.app.goo.gl/cCvmX9eWqpBA6HeL7It's on the source input board.

author: james_s
author_rank: Super Contributor
timestamp: June 24, 2018, 04:20:41 pm
content: Why do people always try to adjust things when something breaks? Monitors this "modern" don't drift like that, if the pincussion cannot be set properly with the user controls then it's not an adjustment, something has failed. Don't try to adjust anything, locate the fault and repair it. Over the years I have seen so much easily repairable equipment turned to scrap because something broke and someone opened it up and fiddled with every adjustment they could find.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: June 24, 2018, 05:48:17 pm
content: Hear! Hear!

author: oggie
author_rank: Contributor
timestamp: June 25, 2018, 12:26:56 am
content: Not trying to adjust anything at this point. I agree that the pincushion doesn't get that bad on it's own without something failing.Having said that, What about the thermistor thp601 for the degauss circuit? Is it possible that it's bad? I have no idea what the value of it is though. It has TDK 150M 7802 written on it, and it's a 3 pin PTC thermistor . It looks like this one:https://www.ebay.com/itm/sony-ptc-1-808-059-32-150m-tdk/263729650589?_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D2%26asc%3D52475%26meid%3D0ec0e57cbe8146bc8fdac3d1104505d2%26pid%3D100011%26rk%3D1%26rkt%3D1%26sd%3D271255653920%26itm%3D263729650589&_trksid=p2047675.c100011.m1850]https://www.ebay.com/itm/sony-ptc-1-808-059-32-150m-tdk/263729650589?_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D2%26asc%3D52475%26meid%3D0ec0e57cbe8146bc8fdac3d1104505d2%26pid%3D100011%26rk%3D1%26rkt%3D1%26sd%3D271255653920%26itm%3D263729650589&_trksid=p2047675.c100011.m1850]https://www.ebay.com/itm/sony-ptc-1-808-059-32-150m-tdk/263729650589?_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D2%26asc%3D52475%26meid%3D0ec0e57cbe8146bc8fdac3d1104505d2%26pid%3D100011%26rk%3D1%26rkt%3D1%26sd%3D271255653920%26itm%3D263729650589&_trksid=p2047675.c100011.m1850I can't find a datasheet for it at all.

author: helius
author_rank: Super Contributor
timestamp: June 25, 2018, 04:30:49 am
content: The degauss circuit is not related to the kind of geometry problem you have. It only has one job: removing residual magnetic flux on the face of the tube, that would cause color purity errors.

author: oggie
author_rank: Contributor
timestamp: January 24, 2019, 07:52:19 pm
content: so I finally got around to replacing all the elec caps on this monitor. And it didn't change a thing. The image is still the exact same. Very frustrating. Not having a manual where I could trace things makes it difficult. I do have access to a scope.

author: james_s
author_rank: Super Contributor
timestamp: January 25, 2019, 12:46:51 am
content: I wouldn't expect replacing the electrolytic caps to solve a pincushion problem. In general I'm not a fan of the shotgun approach because it's easy to introduce new problems. Track down how the pincushion circuit works, often there will be a pin coming out of the main controller IC with a voltage that varies based on the setting in the menu. If you can find this pin, follow it and look for a dead transistor.Many years ago I got a 14" SVGA monitor with a pincushion problem, the fault was a single bad small signal transistor.

author: oggie
author_rank: Contributor
timestamp: January 25, 2019, 01:18:42 am
content: I figured out how to get into the service menu, thanks to someone on this video:I only tried turning the 'pin amp' up and down from the original value to see if it would change at all, and of course it didn't.I see in the circuit diagram q551, 2s02394-ef PIN OUT. It's fed from pin 5 (E/W OUT) of IC301, VDP3108 DECODER IC.

author: james_s
author_rank: Super Contributor
timestamp: January 25, 2019, 01:24:42 am
content: Isn't there a pincushion adjustment in the user menu? It's rarely necessary to poke around in the service menu.

author: oggie
author_rank: Contributor
timestamp: January 25, 2019, 01:27:38 am
content: Nope. There's almost nothing in the user menu on this monitor.

author: fzabkar
author_rank: Super Contributor
timestamp: January 26, 2019, 12:00:05 am
content: Quote from: oggie on January 25, 2019, 01:18:42 amThat's where I would start looking. The East/West correction output from the IC should be a "vertical parabola". Its frequency will be the vertical scan rate. Somewhere there will be an amplified version of this signal which modulates the horizontal output circuit, usually via inductive coupling.

author: oggie
author_rank: Contributor
timestamp: January 26, 2019, 01:04:54 am
content: So I took a quick look at q551, and the numbers on it are of probably no use. It was hard to read, since the bar holding it to the heatsink wore the lettering down, but I think it said D2394 and e645. I can't find it in the service manual. But would it be a 2SD2394? They're not made any more, but what would be a good substitute?

author: fzabkar
author_rank: Super Contributor
timestamp: January 26, 2019, 02:25:36 am
content: Does the transistor test bad? Is there a fusible resistor in its collector circuit? Which component(s) does it drive?2SD2394, Rohm, NPN power transistor, Vcesat = 1.0V, 60V, 3A, hfe E=100-200, F=160-320, TO220-FN:http://www.kontest.ru/datasheet/rohm/2sd2394.pdf

author: oggie
author_rank: Contributor
timestamp: January 26, 2019, 06:14:25 pm
content: i've never tested a transistor in circuit, but my meter has a diode tester. It read .65v from b-c and from b-e while in cicruit. That means it's good, right?

author: james_s
author_rank: Super Contributor
timestamp: January 26, 2019, 06:41:33 pm
content: It can be tricky to test conclusively in circuit but what you measured is certainly reasonable for a good transistor.

author: oggie
author_rank: Contributor
timestamp: January 26, 2019, 06:47:26 pm
content: Well this is frustrating. I have this manual, but it's not a very good scan and is missing have the pages....https://drive.google.com/file/d/1vmd90qea4q2fH-xCmfY9CWoe8GN2kbLy/view?usp=sharingI could try to start testing the points mentioned in there with my scope. but I don't like testing live circuits when it comes to CRTs.

author: fzabkar
author_rank: Super Contributor
timestamp: January 26, 2019, 09:04:14 pm
content: Which page of the manual has the E/W section of the circuit?

author: oggie
author_rank: Contributor
timestamp: January 27, 2019, 12:46:03 am
content: page 27. although the poor scan has cut off part of the diagram.

author: fzabkar
author_rank: Super Contributor
timestamp: January 27, 2019, 12:56:54 am
content: The transistor is being driven by one half of the dual op amp. This op amp gets its supply from a rectified tap on the secondary side of the flyback transformer. Check the fusible resistor between the rectifier diode and the tap.

author: oggie
author_rank: Contributor
timestamp: January 27, 2019, 01:09:16 am
content: I assume you mean r511?

author: fzabkar
author_rank: Super Contributor
timestamp: January 27, 2019, 02:40:39 am
content: I can't make out much from the blurry diagram. However, all you need to do is to follow the Vcc pin of the IC (pin #8) back to the transformer. There will be an electrolytic filter capacitor, a rectifier diode, and a fusible (aka flameproof) resistor in the path. The resistor typically has a value of 1.0 - 2.2 ohms. The diode should be a fast rectifier.Edit: I managed to improve on the view. I now see that the op amp has a positive supply on pin #8 and a negative supply on pin #4. Each supply is generated by a separate tap on the flyback transformer. The components to check appear to be R510 and R511, D506 and D507 (RGP10G), and two 470uF, 25V capacitors.Edit #2: I now see that the abovementioned supplies are shared by the vertical output IC (IC551), so they must both be OK. Instead I would examine the fusible resistor (?) between the collector of Q551 and inductor L551.Direct download link to service manual:https://drive.google.com/uc?export=download&id=1vmd90qea4q2fH-xCmfY9CWoe8GN2kbLy

author: oggie
author_rank: Contributor
timestamp: January 30, 2019, 01:22:57 am
content: I checked, and the fusible resistors are fine. However, they appear to be just jumpers. Is that correct, or did they not bother using resistors?

author: fzabkar
author_rank: Super Contributor
timestamp: January 30, 2019, 01:40:32 am
content: It looks like Sony took a cheap approach to the fusible resistors.Another common problem is dry solder joints at the inductors, transformers, and the like. In fact many techs make it a practice to reflow the solder at all magnetics and power components such as ceramic resistors and power semis.

author: oggie
author_rank: Contributor
timestamp: January 30, 2019, 01:47:12 am
content: Yea. I may have to do that just to see if that's the problem.

author: oggie
author_rank: Contributor
timestamp: February 02, 2019, 01:28:06 am
content: So I went and reflowed a lot of the components, and still the same problem.I sure wish I had a better service manual so that I could start testing it live with a scope.