Author Topic: neotec nt-27e mid res chassis issue. no power (Read 14069 times)

GMZombie · « **Reply #40 on:** August 11, 2012, 06:04:15 pm »

im getting in order to buy the caps for this horizontal board but the cap list is different in the schematics than it is on the board? should i just go with what is on the board. it dosent look like they have been changed before.

lilshawn · « **Reply #41 on:** August 12, 2012, 01:20:51 pm »

go with what's IN the board. there are lot's of little tweaks and changes to parts throughout the lifecycle of electronic parts.

if they haven't been changed before, stick with those. if someone has messed with them previously, check against the schematic.

GMZombie · « **Reply #42 on:** September 15, 2012, 04:42:49 pm »

i changed the caps on the horizontal board and the damn chassis went back to beeping again..grr i hate these chassis

GMZombie · « **Reply #43 on:** September 25, 2012, 09:26:41 pm »

ok after i blew the first board already by changing those caps i figured now should be the time to put that one aside and work on the other one so i dont destroy it. after looking at the voltage on the 25v and the 12.5v im getting short spirts of that voltage but it dosent stay. i tracked it back to d107 which it is fluctuating at. that goes to the transformer and from there it looks like it goes to c113 and c112 but what should i be getting at that point? at c112 should i be getting the whole 170v or should it be less>? this chassis's b+ is at 130 at the hot and stays pretty much around there within a few vdc.

lilshawn · « **Reply #44 on:** September 25, 2012, 10:38:53 pm »

do you have a schematic for this monitor...if not i can get you a copy.

you have to realize what you are looking at is an SMPS power supply.

basically they rectify the AC to a rough DC and then pulse it at high frequency with a MOSFET through a transformer.

this creates a weird half wave DC wave on the output side of the transformer...after you run this through a diode and a cap or 2 you end up with a relatively high amperage and high voltage DC power that can be used for various things. several taps on the out side of this small transformer will provide your B+ (130 or some volts) 5 volts, 12 volts 50 volts etc etc etc.

the main switching MOSFET has overload protection built into it...if the currant load on it is too high, the MOSFET will stop conducting for a short time before trying again. Tick tick tick tick...this is the sound of the MOSFET in overload. sometimes you can hear it sometimes not.

NOW, if the MOSFET is in protection, you need to determine the source of the overload and correct it. the output diodes are a good place to disconnect your various voltages to narrow down the section.

i recommend having the monitor out on a bench where you can get at it.

lift out one side of the output diode on one of the voltages. (leave the B+ section hooked up) and hook everything up and power on the monitor.

is it coming on? can you hear the "whine"?? YES?? good! pull the plug because that is your faulty section. don't leave it on long...it can be damaged. should only take 2-3 seconds TOPS.

is it still dead? YES?? okay not our problem area...try a different one.

TRIED THEM ALL? your B+ has a fault.

GMZombie · « **Reply #45 on:** September 26, 2012, 12:09:44 am »

heh yea i do have the service manual/schematics for this chassis. so i should lift one of the output diodes which should be d107 which is directly after the t101 and that controls the 26v and 12.5v correct? if this is correct i will pull this tomorrow and test out what you said.

On a different chassis but same model i have power and video but it seems when i adjust the fly-back brightness if i push a little bit on the dial some of the color will go away. Also cant seem to lock on vertical hold. it holds for a little bit then scrolls? Also i seem to be getting some over-scan lines but the fly-back is turned down low. does this seem to indicate a faulty fly-back? sorry for all the questions as i have 3 of these damn chassis to fix.

These chassis's seem to want to be the death of me.

lilshawn · « **Reply #46 on:** September 26, 2012, 12:18:50 am »

yeah just after the transformer. that will kill power to some of the sub systems (vertical deflection etc.)

there is a chip that handles the vertical deflection...sometimes a dry cap will cause the chip to act funny...sometimes the chip can partially fail and cause all sorts of wierdness. I would check the voltage going into the chip and see if it's low.

I'm not sure of the location or number. (I thinkn it's a "TDAxxxx or an la7835) I'll check the schematic at the shop tomorrow and let you know what one i'm talking about.

ed12 · « **Reply #47 on:** September 26, 2012, 12:37:33 am »

hi
to start with the line's u are refing to are called retrace
if the flyback is turned down,replace all of the neck bard cap's + any 160v or better cap
they dry out and become bad

tda-xxx or la-xxx is the vert ic lilshawn
nailed it
do your self a favour and do not diode test the diode's,they are high speed high current
and u will not get .5v foward drop..more like .3 or less
they can not be tested the normal way
i have even seen what looked like perfect diode's fail under load

ed

lilshawn · « **Reply #48 on:** September 26, 2012, 11:30:44 am »

okay. lift D107 and see if it will power up. if it does you have an issue with something in that system. If not, it's something in your B+ (113v)

if it is something in your 25/12 volt system (vert deflection or sync chip sub systems) it's easy enough to start narrowing it down.

GMZombie · « **Reply #49 on:** September 26, 2012, 06:10:26 pm »

ok i lifted it and one time i could hear the system click but it would not start up. it sounded like that before though. so something within the b+ part of the system

lilshawn · « **Reply #50 on:** September 26, 2012, 06:43:29 pm »

while it's powered can you hear anything from the chassis? if the SMPS is in overload it usually makes a noise. it's constant while it's powered. tick,tick,tick,tick... or zzzt,zzzt,zzzt.... sometimes it will sound like a constant sound that will slow down to several seperate clicks that slow down to nothing after the power is removed.

trying to onomonopia is hard $:-\$

if the SMPS isn't starting there could be something there going on.

hook your meter to L102 and power on the monitor. are you getting a massivly flucuating reading or is it steady? (adjust your meter to read 200 volts)

if it's flucuating, leave d107 disconnected and disconnect L102 on the side that connects to C116. hook your volt meter up to the leg you pulled out. this will tap your B+ and kill everything running off it.

it should read around 120 volts... and it still doesn't start up (still flucuating all over) you probably got an issue with the SMPS (bad controller chip IC101 or MOSFET Q101)

if it comes on connect D107 and repeat the test.

GMZombie · « **Reply #51 on:** September 26, 2012, 07:01:13 pm »

ok with d107 leg disconnected testing voltage at l102 gives me a reading of 148 and then it goes up a bit but i didnt let it go long as you said not to run it for more than 2-3 seconds with that out. it didnt make a noise at all no buzz or tick or anything. before i tried this i was looking at the b+ adjustment where it was and i dialed it back a bit to see if the voltage would go down since it should be around 113 at d106 am i correct? well it didnt work it didnt adjust it at all. so i just put it back to where it was.i have replaced the q101 before and the ic101 and c110 and the hot. testing voltage there is no voltage from the collector of the hot to either the base or emitter should that be?

GMZombie · « **Reply #52 on:** September 26, 2012, 07:12:55 pm »

also l102 reading with the one leg off going to c116 and still d107 off 155 and goes up but only checked for 2-3 seconds

lilshawn · « **Reply #53 on:** September 26, 2012, 10:23:15 pm »

The B+ can really only be reliably checked under full operating conditions.

under load the voltage will flucuate. with no-load the B+ will just run wide open.

if you connect L102 and D107 back in circuit and test the voltage at L102 it comes up but goes down to nothing correct?

if yes sounds like a bad HOT or bad flyback. a faulty flyback/yoke/B+ can take out a HOT in miliseconds.

ed12 · « **Reply #54 on:** September 26, 2012, 11:40:23 pm »

hi
insert a 100 watt 117vac light in line with the choke and diode
it will tell u the trick of the tail
and yes the yoke will suck up hot's in a heart beat

ed

GMZombie · « **Reply #55 on:** September 29, 2012, 12:12:59 pm »

Quote from: lilshawn on September 26, 2012, 10:23:15 pm

The B+ can really only be reliably checked under full operating conditions.

under load the voltage will flucuate. with no-load the B+ will just run wide open.

if you connect L102 and D107 back in circuit and test the voltage at L102 it comes up but goes down to nothing correct?

if yes sounds like a bad HOT or bad flyback. a faulty flyback/yoke/B+ can take out a HOT in miliseconds.

yup it went up for a bit but then kept going down. i didnt wait till it went all the way down but it went down into the 80's before i took it off. it spiked at like 130 then went down. I can take out the hot and do a diode test on it would that indicate anything or is there a surefire test for the flyback?

ed12 · « **Reply #56 on:** September 29, 2012, 11:26:14 pm »

hi
yes to the flyback
if u can sweep it ?
no to the hot..as it has a diode in it
the yoke is the same way..u need to sweep it...

ed

GMZombie · « **Reply #57 on:** September 30, 2012, 10:51:46 am »

so the flyback sounds suspect how do i do this sweep test?

lilshawn · « **Reply #58 on:** September 30, 2012, 12:13:19 pm »

I'm still not conviced the SMPS is operating properly.

can we disconnect D107 and the output leg of L102. Hook a lightbulb (around 75 watts) to the output and to ground and see if it lights up nice and bright.

don't worry about running it longer this way. the supply will be properly loaded down. and the rest of the chassis wil be disconnected.

GMZombie · « **Reply #59 on:** October 02, 2012, 09:33:41 pm »

I did hook up a 60w light which is all I had and it lights up bright

edit:

On the other chassis that i originally fixed but then it went out again i replaced the hot in it and it worked although i couldnt get the horizontal hold and frequency right. it ended up blowing the hot again. any ideas. i replaced caps on the side board except fore one cap which i couldnt find a replacement for. it was a big 4.7uf@50v cap at the top left on the side board

edit2:
would these Hots work for this chassis. i know the nte replacement as ive blown those and the original but when i was looking up a spec sheet it had the line 2sc4542 and the info and to the right of it it also had this 2sc4924 which here is the spec sheet

http://www.alldatasheet.com/datasheet-pdf/pdf/39085/SANYO/2SC4924.html
here is the original spec sheet
http://pdf1.alldatasheet.com/datasheet-pdf/view/439593/ISC/2SC4542.html
and of course the nte replacement
http://pdf1.alldatasheet.com/datasheet-pdf/view/9972/NTE/NTE2354.html

GMZombie · « **Reply #60 on:** October 07, 2012, 04:59:43 pm »

so would that replacement ic work for the hot?

lilshawn · « **Reply #61 on:** October 07, 2012, 05:15:15 pm »

NTE is sometimes a crap shoot if it will work properly or not.

most of the time it's fine, but you can get it to work sometimes and it fails within hours/days/weeks.

if cost/availability is making obtaining originally specified parts impractical then go NTE, otherwise stick with OEM specified parts.

GMZombie · « **Reply #62 on:** October 09, 2012, 11:23:40 pm »

so i did your lightbulb test and the light was bright and did not dim down. what is the next course of action?

ed12 · « **Reply #63 on:** October 10, 2012, 01:02:50 am »

hi
the light is bright ??
no load....
u need a load
ie the sweep circuit is not working,the light should >dim<...but but not go out
rember ohm's law

ed

lilshawn · « **Reply #64 on:** October 10, 2012, 01:51:45 am »

how about with D107 connected...does the lightbulb still come on bright?

don't run this way more than necessary... it's bad for the vertical.

if it's way dim now or pulses/surges you have an issue with the vertical deflection.

if it's still bright, you have an issue with the horizontal deflection/high voltage.

GMZombie · « **Reply #65 on:** October 14, 2012, 06:56:02 pm »

its still bright. so its a problem with horizontal deflection or high voltage

GMZombie · « **Reply #66 on:** October 23, 2012, 11:12:00 pm »

im thinking about just pricing out replacing almost all the components on the power supply side that i an get reasonable. sound like a good idea? Also thinking it might be time for a cap kit too.

lilshawn · « **Reply #67 on:** October 24, 2012, 12:40:41 pm »

if it still runs with the B+ disconnected and the B+ loaded with a bulb, your problem is with the horizontal deflection or the flyback.

check c415 for dark spots on the sides. check C421 and C420 as well.

you'll have to pick up another transistor Q402 "2SC4542" if you still have no luck after replacing that your flyback might be toasted.

if it'

i've never had much luck with NTE parts

GMZombie · « **Reply #68 on:** October 24, 2012, 08:22:26 pm »

ok checked those parts didnt have a c420 it was not there on all 3 of the chassis so i looked at the 2 and they look good. no dark spots. would the ic301 or ic401 be the culprit for the horizontal deflection or neither? i know they are both deflection ics

lilshawn · « **Reply #69 on:** October 24, 2012, 09:35:04 pm »

ic301 is vertical deflation. if you had good horizontal but no vertical deflection you would have a flat line left to right.

if you had no horizontal deflection but you had vertical you would have a line on the screen up and down.

if you have neither horizontal or vertical you would just have an intensely bright dot in the middle.

Quote

didnt have a c420

it's okay, they might have just doubled up on c421.

IC401 does supply sync timing signals to both IC301 and the HOT. There could be something up with that.,

ed12 · « **Reply #70 on:** October 24, 2012, 09:58:51 pm »

hi
ok i am confused
do u have the nessary b+ off of the smp's ?
ie 125/25/12 ?
if not look no more expect to that area..did u replace the fet ?
did u replace the slow start part of that circuit ? ic101? and it's slow start cap ?
if so and u did a non chassic load test as we both told u to do?,if so what did u get ?
ic401 is the horz drive ic301 is the vert drive ic
both circuit's use bi-polar output's,so they are predriver's

ed

GMZombie · « **Reply #71 on:** October 26, 2012, 05:31:37 pm »

i did replace the fet, c110 ic101 and the hot. at d107 and d106 my readings fluctuate d107doesnt get above 16v drops when you hear the chirp or click, d106 at first goes up past 150v then goes down to as far as i watched it to 85. i noticed when it goes below 120 is when the hot starts clicking

ed12 · « **Reply #72 on:** October 26, 2012, 07:14:55 pm »

hi
well if it is not the flyback
u will need a yoke :it will do the same thing: with a tad different systom's

ed

GMZombie · « **Reply #73 on:** October 26, 2012, 09:06:11 pm »

i dont believe it is the yoke and here is why. ive been fixing 3 of these nt27e chassis's. i have one right now that i have starts up but the horizontal isnt syncing and i believe it may be cause i need a cap kit which im waiting on but ive had working chassis on that yoke before.

ed12 · « **Reply #74 on:** October 26, 2012, 09:28:52 pm »

hi
fair enough
i have seen u went through this full chassic
it olny come's to 2 conculison's
or u missed a point,the light load is the master of all tail's
it tell's u the trick

ed

lilshawn · « **Reply #75 on:** October 26, 2012, 10:09:36 pm »

the L102 i had you disconnect powers the HOT/flyback.

if you connected the light bulb (load) to the tail end of the disconnected L102 and the power supply fires up and is nice and stable, your problem lies someplace in the horizontal deflection or the flyback.

if the problem was somewhere else (vertical deflection, electronic subsystems...etc, etc, etc...) and you connected the light bulb (load) to the tail end of the disconnected L102... the power supply would still not come on line and would still be pulsing. See what i'm getting at?

I know you replaced the HOT, but if you have/had a shorted cap in the horizontal deflection or even a bad flyback, it would take it out as soon as you powered up. (since the flyback is powered from the pulses generated by the HOT)

It's going to be one stupid tiny little thing and when you find it you're going to kick yourself right in the butt.

<beginrelatedstory>
was working last week on a 500dx (the 27e's brother) in a 2 player head-to-head cabinet... would come on for about 3 seconds...vertical would fold over squash down and blip off. figured the vertical deflection chip (ic301) went bad and replaced it. tested overnight on a 500dx tube we have in shop <thumbsup> drag the chassis out to the game...lasts 10 SECONDS and it's cooked. the stink of burnt components fills the air. get PO and rip the monitor out tube and all and drag the thing back to the shop. replace the 301 again...fried. Yoke must be toast. pulled it off..stinks like dust and dirt but nothing like electrical. put in a third vert deflection chip and used our shop tube no problems. sent it out. tossed the original tube. I'll have none of that. Lesson here...never underestimate the sneaky nature of electronics. even if you think it's okay...you never know.
<endrelatedstory>

ed12 · « **Reply #76 on:** October 26, 2012, 10:52:27 pm »

hi
lilshawn
thank-u

ed

GMZombie · « **Reply #77 on:** October 28, 2012, 09:42:41 pm »

fair enough i will go back and try the light load again. is it ok to leave it on for a little bit then. i believe then it will probably dim after it drops below a certain voltage b ut i didnt know if i could properly leave this running for a minute. also would like to pre thank you guys for helping me get this far. im fairly good with electronics but these chassis have driven me crazy..

lilshawn · « **Reply #78 on:** October 29, 2012, 09:37:25 am »

it would be best not to run it too long.

hook up a voltmeter to the B+ too as well. that way you can visually see it's working, and also get a reading of if it's stable or not since an incandescent bulb may appear on solid but could be varying by 20 or 30 volts and you can't see it cause it's so bright.

GMZombie · « **Reply #79 on:** October 30, 2012, 05:53:27 pm »

as soon as i get back home im going to try this out again. i just got those cap kits in last night and capped one board already..damn there is alot of caps on this board.


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