Author Topic: service manual and next steps to repair a sony ssm-20n1u crt monitor  (Read 676 times)

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Offline oggie

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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/oTu6qogukhdXWxHd8 What'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. 
 

Offline helius

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #1 on: June 17, 2018, 05:40:38 am »
What's the term for this distortion?
Pincushion

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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.
Some 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.

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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.
Look 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_007

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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.
There 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.
 

Offline PKTKS

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #2 on: June 17, 2018, 08:59:09 pm »
The explanation is good ... if you have a PIN POT.

If NOT ... try looking your vertical osc. sweep

It must be a flat linear RAMP which currently is not.
It is deviating in the middle but returning at the end

I would guess some eletrol. cap has gone wild or may be just a bad solder joint
This devices accumulate a lot of heat which given enough time cause cracks
in particular associated with some "black" or dark areas in the pcb.

Paul
« Last Edit: June 17, 2018, 09:01:40 pm by PKTKS »
 

Offline oggie

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #3 on: June 18, 2018, 03:52:20 am »
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/Yf7TRXnmGEdW3uf16

On 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 SCREEN
And 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?
« Last Edit: June 18, 2018, 04:01:30 am by oggie »
 

Online GeorgeOfTheJungle

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #4 on: June 18, 2018, 03:59:53 am »
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.
« Last Edit: July 26, 2018, 07:40:02 am by GeorgeOfTheJungle »
 

Offline Rasz

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Offline helius

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #6 on: June 18, 2018, 04:34:33 am »
On 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+.
I believe those are magnetic chokes used to adjust the horizontal deflection linearity.

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On the board attached to the tail end (cathode) of the tube, there's one pot labeled HSTAT and one labeled SCREEN
SCREEN 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.

Quote
And on the mainboard there's a really large pot that has a wire going to the andode.
That is the focus control. It doesn't look like focus is a problem.

CN052 looks like a service port. I2C and 'AGING'.

Quote
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?
Only 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.

Buy 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.
You can also try poking the leaded components with a wooden stick to find cold solder joints, they are very common.
 

Offline helius

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #7 on: June 18, 2018, 05:47:38 am »
this one more helpful
http://diagramas.diagramasde.com/otros/SSM-20N5U_9976686010-00e.pdf

It shows H. PIN AMP as parameter #97 of the service menu.
[But that appears to be a newer generation, N5 vs N1]
« Last Edit: June 18, 2018, 06:00:55 am by helius »
 

Offline shakalnokturn

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #8 on: June 18, 2018, 07:12:39 am »
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.
 

Offline oggie

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #9 on: June 18, 2018, 09:27:57 am »
this one more helpful
http://diagramas.diagramasde.com/otros/SSM-20N5U_9976686010-00e.pdf

It shows H. PIN AMP as parameter #97 of the service menu.
[But that appears to be a newer generation, N5 vs N1]

Yes, I saw that. But I can't seem to even enter the service mode as instructed in this manual..   :-//
 

Offline oggie

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #10 on: June 18, 2018, 09:29:40 am »
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.

When 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?
 

Offline shakalnokturn

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #11 on: June 18, 2018, 11:03:01 am »
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...
 

Offline oggie

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #12 on: June 18, 2018, 09:59:37 pm »
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.
 

Offline shakalnokturn

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #13 on: June 19, 2018, 07:37:30 am »
I feel I must clarify  :o

If 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.
 

Offline oggie

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #14 on: June 20, 2018, 09:26:53 pm »
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.
 

Offline Chris56000

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #15 on: June 21, 2018, 02:44:24 am »
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
It's an enigma that's what it is!! This thing's not fixed because it doesn't want to be fixed!!
 

Offline oggie

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #16 on: June 21, 2018, 02:55:40 am »
are you sure? There's service menus in the 201n5u which is almost the same monitor
 

Offline oggie

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #17 on: June 21, 2018, 03:04:19 am »
I think the software you're referring to is windas.  I think it stands for windows digital adjustment system?
 

Offline oggie

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Offline oggie

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #19 on: June 22, 2018, 04:12:21 am »
Does this cap look a little puffy, or is it just me?

https://photos.app.goo.gl/cCvmX9eWqpBA6HeL7

It's on the source input board.
 

Online james_s

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #20 on: June 25, 2018, 02:20:41 am »
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.  :palm:
 

Online GeorgeOfTheJungle

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #21 on: June 25, 2018, 03:48:17 am »
Hear! Hear!
 


Offline helius

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Re: service manual and next steps to repair a sony ssm-20n1u crt monitor
« Reply #23 on: June 25, 2018, 02:30:49 pm »
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.
 


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