NT-2701 HORIZONTAL Collapse (SOLVED)

[smartbomb2084]

Hey all,

Got one of these NEOTEC NT-2701 monitors in which the HOT and Flyback were replaced a little over two years ago and suddenly, the other day, it developed the dreaded Tick Tick Tick.

I check the HOT and sure enough it is blown. I replace the HOT and check the board over and can't find anything else wrong. I fire up the monitor and it now has Horizontal collapse...


As far as I can tell IC 401, IC 501, Q 501, and the yoke are all good.

I am missing something here... What is it?

Thanks

[Ken Layton]

Check the width coil. Look for cold solder joints.

[JBARAHONA55]

check horizontal yoke resistance
if yoke is ok call jbmonitorrepair.com

check horizontal yoke resistance
if yoke is ok
check this link jbmonitorrepair.com ask for jose b

[smartbomb2084]

I checked the width coil (L401) and it seems good.

I don't know if it is the right value but I do know that it is not 'open' and that it has continuity within the circuit.

I solderd the Hell out of everything in sight.    I still have the same condition...

Could Q501 be bad even though it tests good out of circuit?

Any chance of IC301 causing this?

[grantspain]

should you not be looking at the horizontal yoke circuit,there are a couple of diodes,a resistor plus the hot(looks like a bu25xx) can't see if its q401 as the schem is poor

[smartbomb2084]

Well... back to square one.

Blew the replacement HOT today... I knew it wouldn't last.

I'm feeling the pain.

 

[lilshawn]

i dont have a schematic handy for the 2701 but there is a chip that sends out the horizontal pulses for the HOT. they often go.


i think it's like a LM7823 or 7830 or some TDA like a 8172... something like that.

[MKFan4Life]

Had these from a while back I took when working on mine in the Gauntlet Legends cab.  Maybe they'll help?

(Click below pics if too small to see.)



http://i368.photobucket.com/albums/oo124/TorreyG/NT-2701%20Schematics/DSCN7359small.jpg



http://i368.photobucket.com/albums/oo124/TorreyG/NT-2701%20Schematics/DSCN7455small.jpg



http://i368.photobucket.com/albums/oo124/TorreyG/NT-2701%20Schematics/DSCN7450small.jpg

 

[grantspain]

if the hot is blowing constantly and the high voltage caps on the collector are reading fine then i suggest you remove and check the yoke for burning internally
i have had 2 x d9200 monitors in last few weeks with failing yokes,they read fine but when operation they short and destroy the horizontal deflection circuit

[smartbomb2084]

Thank you gentlemen for the replies.

I have had to shelve this monitor temporarily until I get some more HOTs.

The Horizontal control IC is IC401 an LA7851 which has been replaced.

The above drawings from MKFan4Life are the original series and the monitor I have is the later series from 2004. I need to upload these drawings as they seem to be impossible to find on the web for download.

I am not sure how horizontal collapse is even possible.  If I have horizontal collapse doesn't that indicate that the HOT is good and switching and that the flyback is good too?

How can I check the yoke for internal shorts?  I checked the yoke on a known good WG 27D9200 and I got the same resistance reading of .05 Ohms.

[grantspain]

no horizontal deflection but HOT ok could be missing voltage,i.e a safety resistor blown

can't read faulty yokes as such,read fine when off but short when power applied-well thats the case with 6 x d9200 i have had in last 2 months

[ed12]

i know them bugger's are famous for
a short in the foucs circuit of the high voltage divder control's
ie foucs and screen
u will note  it on the side of the hot
right betwenn the control's and or right beside it
the will arc to ground
now i have trided to contact the mfg but there phone's no longer work
and i have not been able to source out a flyback
maybe ken could help as i have 4 of them the same way

ed

[grantspain]

is this the flyback?
http://hr-shop.es/index.php?command=viewProduct&id=7961

and here

MRCFT252
http://www.arcadecup.com/

[MKFan4Life]

The above drawings from MKFan4Life are the original series and the monitor I have is the later series from 2004. I need to upload these drawings as they seem to be impossible to find on the web for download.

Oh, sorry about that.  This manual came with my monitor in the Gauntlet Legends cab when I got it.  Seems like users on here told me my chassis itself was odd, 'cause I showed pics of it where the neckboard has the NT-2701 designation on the attached cardboard, but on a metal plate on the chassis it showed NT-27E.  Schematics in the manual seems to match well though.  Lol. 

[smartbomb2084]

No need to be sorry, I appreciate the gesture in providing information.

I tried to do the PDF scan of the later manual but can only seem to get one page at a time without having to 'subscribe' to the Adobe system of 'online' PDF creation.  Looks like its the JPEG route for me next.

I have ordered some HOTs (BU2532AL) and they are in transit.

I am suspecting that C423 (924J / 400V) is bad but can't find one anywhere.

Flyback MRCFT-252 is the same one I have used too.
 

[smartbomb2084]

FINALLY got back to working on this recently...

Turns out C423 IS bad, OPEN actually.  Couldn't find a film cap rated at .92 mF so I ended up with a 1.0 mF film cap instead.

Picture is nice and wide now and still has plenty of Horizontal width adjustment.

THANKS, as always, to those who helped out.

 

[MKFan4Life]

FINALLY got back to working on this recently...

Turns out C423 IS bad, OPEN actually.  Couldn't find a film cap rated at .92 mF so I ended up with a 1.0 mF film cap instead.

Picture is nice and wide now and still has plenty of Horizontal width adjustment.

THANKS, as always, to those who helped out.

 

Glad you got it working man.