NANAO MS9-29T help needed

[caius]

Hi all,
finally I got my first cab and it's an Astro City equipped with TOSHIBA A68KJU96X MS9-29S CRT and NANAO MS9-29T chassis.
When I first powered it up it showed vertical geomery issue, screen was crushed vertically.So I decided to do a partial recap changing also the vertical deflection IC LA7837 but this didn't improve situation.So I've done a whole recap (found one with bad ESR @C513) but now I can't get any image on screen though I can hear (sometimes, not always) the click of the flyback transformer.
I'm wondering what happened.I resoldered critical points on main and CRT PCB, checked other components ( diodes and resistors), all seems fine.I also measured  the yokes resistance, they are 1 Ohm for H.DY and 6.9 Ohm for DY.Is it possible that I had not properly connected the anode cap into the CRT(the two prongs are inside it but loose)?Sorry for these stupid questions but I have a lot of experience with digital electronics of arcade PCB but very few with monitor since, as I said, this is my first cab.
I hope some one can drive me in right direction.Thanks in advance

P.S.
I noticed that one terminal of the V-SIZE pot (which I can't adjust since it's blocked in the underside) on remote board has a resistor tied to GND.-Besides replaced LA7837 had a 100nF by-pass capacitor which I removed when I installed the new part.Are these factory fixes?

P.P.S.
I'm struggling to find a readable schematics of this MS-29T chassis.Is it really impossible to source it?

 

[caius]

---deleted---

[grantspain]

you will not find a good quality shematic for this chassis anywhere-not even the original manual had one

i have never had to change every cap on these chassis and i must have repaired a fair few hundred of them

i would suggest checking your b+ by using a dummy load,check the polarity of all the caps you installed-if your b+ checks out fine(around 75v) then i would suggest replacing the la7837 again as there are loads of fakes on the market

[caius]

you will not find a good quality shematic for this chassis anywhere-not even the original manual had one

Thanks for reply.Yes, sadly also schematics from Sega Touring Cars are hardly readable.

 

i would suggest checking your b+ by using a dummy load,

I have to use a resistor or a lamp in series?Please, explain me.

check the polarity of all the caps you installed

Polarity and values are correct, I double-checked.Do caps must be low ESR?

if your b+ checks out fine(around 75v)

Which is the test point on this chassis?
Could the flyback be faulty?

then i would suggest replacing the la7837 again as there are loads of fakes on the market

Yes, I was aware of this, the problem is to know a reliable source.Big electronics components distributor don't have it in stock.
Anyway, I reverted all the changes  installing again the old LA7837 and original capacitors  and still get nothing of screen.I can't hear anymore the cracking sounds that a monitor makes when powered up ( I presume it's the tube that is charging up).
 

[caius]

Some updates.
I just checked the +B with CN503 installed and without any signal.VDC starts from 110V and decrease to zero with power ON.When reached zero I can hear a click inside and if I power OFF and ON , it starts again decreasing from 100V.I don't know, this maybe I used no load?
Anyway, I suspect the flyback... 

[grantspain]

never had a flyback in 20 years faulty on a ms9 chassis

dummy load will be a mains lightbulb across ground and b+ pin of flyback-with flyback pin isolated from circuit

[caius]

never had a flyback in 20 years faulty on a ms9 chassis

dummy load will be a mains lightbulb across ground and b+ pin of flyback-with flyback pin isolated from circuit

I forgot.I'm testing the chassis into the cabinet with the anode cap connected to CRT button so I presume there is a load.
If the flyback is good, what can I further check ?

[grantspain]

you are missing the point about dummy loads

nothing else you can check tbh,maybe worth sending it for repair somewhere

[caius]

you are missing the point about dummy loads

Please, if you can, explain me in details how to put a dummy load.Thanks.

nothing else you can check tbh,maybe worth sending it for repair somewhere

I think  I can do myself, I repair electronics (digital ones) since many years.

[grantspain]

ok,
desolder pin 2 of the flyback so that it is completely isolated from the circuit board
put a mains lightbulb across ground and the track of flyback pin 2
power on and the lightbulb should power on,then meter the voltage at the lightbulb and it should be about 75 volts

if that is good then the most likely issue is on the deflection circuit or a break on one the tracks

[caius]

ok,
desolder pin 2 of the flyback so that it is completely isolated from the circuit board
put a mains lightbulb across ground and the track of flyback pin 2
power on and the lightbulb should power on,then meter the voltage at the lightbulb and it should be about 75 volts

if that is good then the most likely issue is on the deflection circuit or a break on one the tracks

Pins of the flyback are not numbered.
How many Watt the lightbulb must be?
I have to do this test with the anode cap disconnected from CRT?
For ground do you mean the chassis ground?
Sorry for all these questions

[grantspain]

post up a photo of the solder side of the chassis and i will mark pin 2 and the points to attach the load

you do not need the chassis connected to the monitor to test the b+

40watt lightbulb will suffice-make sure its not an energy saving type

[caius]

post up a photo of the solder side of the chassis and i will mark pin 2 and the points to attach the load

OK, thanks for your patience.I'm going to take a picture

you do not need the chassis connected to the monitor to test the b+

Yes, sure, bulb will act as a load like the chassis was connected to the tube

40watt lightbulb will suffice-make sure its not an energy saving type

Yes, I know this, I need a incandescent bulb

Anyway, it seems I found a suspicious diode @ D955 in  the secondary part.It's marked 'B83004 69', I can measure a voltage drop of 160 mV, too few also for a Schottky diode I presume.What do you think about?
Damn, a schemtics is what I'd need to troubleshoot this beast...


 

[grantspain]

also check the solder joints on the small transformers

[grantspain]

for some reason i can't attach a file

pm me with your email address and i will send it that way

[grantspain]

its bloody well done it now

[caius]

for some reason i can't attach a file

pm me with your email address and i will send it that way

Thanks for picture
So, recapping, I have to desolder pin2 of the flyback (I will cut the track to it) and connect a bulb to this track and the chassis GROUND  and then measure +B putting one probe of the meter on cathode of C515 and other to any of the three terminals of Q506 horizontal deflection IC (2SC4962).Is it right?

[grantspain]

for some reason i can't attach a file

pm me with your email address and i will send it that way

Thanks for picture
So, recapping, I have to desolder pin2 of the flyback (I will cut the track to it) and connect a bulb to this track and the chassis GROUND  and then measure +B putting one probe of the meter on cathode of C515 and other to any of the three terminals of Q506 horizontal deflection IC (2SC4962).Is it right?

NO
just desolder pin 2 from the pad-just make sure it is isolated

correct to bulb on that track-use the capacitor ground of c515 for the bulb ground

meter the b+ at positive of c515

i only asked you to read c506 using a diode test to check it is not shorted-do not meter this with the chassis power on at all

[caius]

NO
just desolder pin 2 from the pad-just make sure it is isolated

I will cut the track, it's more easy than desolder the whole flyback to isolate pin2

correct to bulb on that track-use the capacitor ground of c515 for the bulb ground

meter the b+ at positive of c515

Is a 60W bulb good the same?
 

i only asked you to read c506 using a diode test to check it is not shorted-do not meter this with the chassis power on at all

Yes, I tested the 2SC4962 'Q506' some days ago and found that base and emitter are shorted when component is in circuit.If out-of-circuit, it's OK.The short is between two points (primary?) of the T501 transformer (see picture attached) even if I remove the 33 Ohm SMT resistor.Is this normal or transformer is bad?

[grantspain]

just desolder one pin-easy
60w ok
and yes the base/emitter legs will read short on circuit

i done 4 of these chassis this morning,i always check the b+ like this before powering on

[caius]

just desolder one pin-easy

Yes, but if you want to lift only pin2 you have to desolder the whole flyback

60w ok

OK

and yes the base/emitter legs will read short on circuit

OK, just for precaution today I bought a BU2727DX (well, the actual equivalent of  2SC4962 should be a BU2727DF but it's the same)

i done 4 of these chassis this morning,i always check the b+ like this before powering on

Four in a day?Which were the issue and the fixes?It would useful if you could post your repair logs here.

[caius]

Just a thought.You said to use capacitor C515 ground for the bulb ground but, as you know, alternate current is not polarized.Did you mean phase and neutral perhaps?So, at this point , flyback pin2 track or capacitor ground is the same.
I will use a 50W 230V bulb and power the chassis with 100V.I will disconnect CN902 connector as well.

[grantspain]

you just desolder the pin,as long as it not touching the track pad its isolated-the voltage will not arc over

the b+ is dc not ac-the lightbulb will work believe me

[caius]

you just desolder the pin,as long as it not touching the track pad its isolated-the voltage will not arc over

Yes, it's like I have done.

the b+ is dc not ac-the lightbulb will work believe me

I'm wondering how a 230VAC bulb will work with a 75VDC..sure 75VDC is more or less 150VAC...
Anyway I have prepared all and I'm going to do this test.

P.S.
I'm looking for a Sega TouringCar Championship sheet service  manual, it has a full NANAO MS-29S schematics.The PDF on the net is good for knowing the exact parts type but sadly the schematics are not readable.I will contact also directly the Sega Enterprise.

[caius]

Just done the test.The 50W light bulb went on although dimly and I could measure 75.2 VDC across the anode and cathode of C515.At this point the problem is elsewhere, powering circuit is good (and also flyback, I presume).This complicates the thing.
Before doing this test I desoldered the 2SC4962 horizontal IC and tested it out-of-circuit and I found some discrepancies with datasheet and equivalent BU2727DX/DF
In the meanwhile, many many thanks for you advices and tips, I will treasure this!

[s3phy]

Hello,

I'm bumping this few months old thread, I hope this isn't considered rude here!
I just registered here to say: Thank you grantspain!

I was fixing a Nanao MS9-29S and some Google searches led me to this thread.

I had already replaced the HOT and C513 (HOT was shorted and C513 had leaked) and I couldn't find what was still wrong with my monitor... I was told to do the "lamp test" but without being given proper instructions, I followed yours, and also payed attention to this comment:

also check the solder joints on the small transformers

I couldn't possibly have missed some dry solders right near the spot where I had already replaced a capacitor and the 2SC4692... could I?
...Of course I could! They where right in front of my face and I couldn't see them! Two dry solders on T501!

I re-soldered them both, mounted a 60W 230V bulb following your instructions, and powered the chassis... the bulb lit up and I measured a steady +75.2VDC on its legs. I then re-soldered pin 2 of the flyback, put everything back together and it (finally) works!

Thank you so much!

[segasonicfan1]

Great info here, and rather than start another thread I though it would be wise to share my problem with this same useful info collected here.

I am working on a MS9-29T (from an Egret II) which I was told was working after being returned from a repair shop.  It was given to me to install a cap kit and after the cap install I get nothing on the screen.  The kit was bought off ebay and I've installed these before, I have also triple checked all polarity and values and am really scratching my head.
I plugged in into my friends cab myself and there is the sound of the monitor being energized, but no image whatsoever beyond that.

D502 and HOT tests fine (had to pull it out of circuit since there's a 33ohm resistor between collector and emitter) HOWEVER, T501 (the transformer that leads to the HOT) measures ZERO ohms on the output side.  Not 0.1 even, I mean zero ohms.  I get a 0.5ohm reading which is just the leads of my meter.  This would appear to be a dead transformer but maybe I'm wrong?  Could someone measure theirs and tell me?  It's easy to access the spots without removing the plastic holder.  I attached a pic to show where the measurement is.

Any help greatly appreciated!  I feel terrible for recapping my friends board and now it doesn't work 

[ed12]

remove the transformer and test it
r5111 the small chip resistor tied betwen the 2 pins is thowing u off.
do not worry it is "keyed"
2 pins on 1 side 3 on the other

ed

[segasonicfan1]

Thanks for the reply Ed.  I did remove the transformer completely before measuring it.  It measures a direct short between the two pins on the output side.

[princess prin prin]

When testing coils/windings you should measure inductance not resistance. The coil you pointed out measures about 100uH, the other one a much bigger value, 15mH. It's normal that for such a short winding you measure 0ohms or so.

[segasonicfan1]

ahh okay, I tested out for inductance and it does pass.  I learn something new every day.

I have yet to do the lightbulb test (kind of afraid to power this up on my workbench since it isn't mine) though I can't find anything wrong.  I've triple checked all the caps I installed and they are correct.  I also reflowed everything on the board when I replaced the caps and all the solder joints look great.  The vertical deflection circuit had some leaky caps (I could smell the electrolyte) but otherwise was fine, and I reflowed solder joints around it.'

The only minor issue I had was one small pad got damaged on a small cap.  It traces out fine now, and I went over it in the schematics (goes to pin 4 of the large IC near the op amp).  Can't find any problem with it but here is a pic just in case.

Anything else I could check?  Diodes all test out fine in circuit.  Would a bad vertical deflection IC result in no image whatsoever?

[caius]

  Would a bad vertical deflection IC result in no image whatsoever?

Sure!