neotec nt-27e mid res chassis issue. no power

[GMZombie]

ok so i have 2 of these chassis with no power. first i thought i would replace the hot. did that and no luck still dosent power up. now i setup my station so i was able to take some readings while its hot and here is what i have. from ac power in i had a 55vac/60vac right at the ac in on the black and white ac in wires. followed power on each side till it hit a d101 which is a 4 pin what im assuming a diode and when jumping from 1 pin to the next it goes from 55vac to 1.4vac and the 60vac goes to 2.0vac. just to be sure i checked it in dc and there was no volts. i checked r117 and there is no volts on either side. please advise next route of action as im stumped

[ed12]

ok so i have 2 of these chassis with no power. first i thought i would replace the hot. did that and no luck still dosent power up. now i setup my station so i was able to take some readings while its hot and here is what i have. from ac power in i had a 55vac/60vac right at the ac in on the black and white ac in wires. followed power on each side till it hit a d101 which is a 4 pin what im assuming a diode and when jumping from 1 pin to the next it goes from 55vac to 1.4vac and the 60vac goes to 2.0vac. just to be sure i checked it in dc and there was no volts. i checked r117 and there is no volts on either side. please advise next route of action as im stumped

huh ?
120vac is not after the :bridge:
that should be 160vdc volt's dc
chk on the main filter cap,rem u are in :volt's-d-c: not volt's ac

ed

[GMZombie]

ok i have located a bad dioed in the board d106 but when i take it out it tests ok. i checked it with another board that i have of the same type and it tests good in the board? also dc volts is 170 to the t101

[ed12]

hi
ok now we are getting some where
170 vdc is a good sign
this means the powersupply front end is good :ie-input-filter:
but at 170 i would first look for bad solder joint's,blown fuse
that feed the hot circuit,could also be a dropping resistor
i will look up the schewmatic and get back to u

ed

[GMZombie]

http://www.vidiot.ca/manuals/Neotec_NT-2X.pdf
here is the service manual with schematics in it.

[grantspain]

check the high voltage poly cap on the HOT collector

[GMZombie]

i dont have a cap tester persay is there a way to check with the dmm.

[grantspain]

i dont have a cap tester persay is there a way to check with the dmm.

not really but last one of these chassis I fixed had a split on that cap which was quite obvious-like a small burn infact

[GMZombie]

ill take some pics a second

[ed12]

hi
if u are apt with a dmm
and have the chassic hooked up ?
turn it up-side down,carefull not to short anything
look for c425. there should be 125vdc there
now rem u are working with a smp style monitor
so the switch will switch up >tech term for starting<
if this happen's and u are not getting 125vdc there
then go to the :output: of the smps,there is a .47ohm resister at 2watt's
it act's like a fuse,it will be open..if so u have a hot problem >common<
u cannot read it in circuit..

ed

[GMZombie]

ok so i did some checking and on one of the 2 chassis's i cant read the hot but when i pull it out it reads fine. the second one i can read in circuit but when i do it reads voltage on both sides checking black from collector and then red to base then emitter. checking between emitter and base i get 0. of course i get no volts from c125  but then i get no volts at r117 either.

[ed12]

hi
ok when chking the hot
1 side of the meter is to go to common ground
the other side of the dmm is used to chk for b+ feed
the base will read small,the collector should read about 125vdc
the emitor is at 0
chk 1 side of l402
then the other that is your b+ feed
it then run's through the flyback to the hot transistor
u can tie the ground of the meter to ground side of
c116..
this should then tell u if u are getting b+
if not go back to the resister i asked u to look at

ed

[GMZombie]

what is the number for that resistor?

NM i believe your talking about r117 which is .47 2w correct

EDIT: checked all of these and when it is hooked up i get no voltage. resistor is in tact at .6 ohms..so im not getting b+

[ed12]

hi
right
and it is comman for them
chk the fet in the smp's
now u isolate the chassic as u are going to be on the hot side
of it :ie-117vac converted to 123vdc:
the fet is on the ac side after the bridge and input filter etc

ed

[GMZombie]

well from gate to drain on the fet i had 167vdc of course i sparked it trying to test gate to source which freaked me out. i stopped shut everything off and waited a second. retried voltage check from gate to drain and it is still 167vdc.

[ed12]

hi
your switch is not comming on
ic101
be sure it is getting it's voltage through r102
please rem u are on the hot side of it,:isolate:
if u are then your fet is south,there is no real test for a fet
in your case u sparked it
might be a good chance u blew it :open: and took the smps switch with it
ic101

ed

[GMZombie]

yea from the r102 i get 49vdc. at the pin where the trace goes to on the ic101 im getting about 45vdc so it deff has voltage. so would you agree that it woudl probably be the fet and the ic101?

[ed12]

hi
i just looked the spec for that ic +20vdc
+49 is a ?
also there is a soft start cap
c110 which is 1mf at 50vdc <problem child>replace
so 49 now becomes the magic problem
look into the fet
and prey the ic is not blown >not-un-comman<
but all hope is not lost as it will cross to a nte..

ed

[GMZombie]

i found a spot to get those ics only 3 dollars a piece so no big deal there. i did a voltage check from the pin on the ic that the resistor trace ends up going to, to the c110 and im getting 8.92vdc on that on each side. dont know if that helps. i can get the cap replaced and i do have a new fet. bought it when i bought the hot

[ed12]

hi
ya let's start there
also rem d105 and d103 are high speed switch diodes
and doing a chk on them is just about use less, if u can find them replace them,there again high speed switch diode's
Industry Number  : RGP10M
NTE Device Number: NTE558
RECTIFIER-SI,1500V,1A,DO-41
1500v/highspeed

ed

[lilshawn]

you can try the NTC parts to substitute the diodes, but i've never had much luck with replacing them with anything other than what was originally there.

my experience has been they either blow right away or fail within a few months.

also be warned these parts are high voltage, they may test okay with the low voltages used in the diode test on the voltmeter but still fail when subjected to the higher voltage of the operating circuit.

[GMZombie]

with the cap should i get a high temp high freq cap or just the high temp cap>?

[ed12]

hi
on the input side of the smps
i would use a low esr high temp cap's

ed

[GMZombie]

have some success on one board. got it fired up after replacing the ic101, fet, and that cap. only thing is the red dosent seem like its getting bright enough. could this be the tube?

second chassis not so much luck. figured since i already had the same parts as i bought 2 of each item to fix both chassis's i put them in as it was having the same issue with no power, i also changed the hot on this one as the old one was deff bad,  but at first i didnt have that cap in. when i turned it on it made a squeal so i turned it back off. i hoped i didnt blow the hot doing this..i found a new cap and after installing it the squeal went away but the system still dosent turn on. i tested 133vdc at cap 425 and on pin 2 of the flyback along with 133vdc at the middle pin of the hot. when checking for volts over the hot i get nothing on each side. but when i check the hot with diode check and off i get from base to emitter .417 and from base to collector .417 with collector to emitter a 0

[ed12]

hi
GMZombie
on the first chassic :no-red: i would want to do all the other test's
first,but if u have a rejuv handey or know a bud who dose chk the tube
it's 50-50 to say it's a bad gun in the tube without chking it's drive,etc

on the second 1
them reading's are all wrong
u should have full dc on 1 side and drive to the tranistor
.5,the emmiter should b at 0
i would just swap the hot transister out
and go from there

ed

[GMZombie]

its not no red...i just had to turn the drive up all the way to see some red. ill try the hot replacement. luckly i didnt have to change the hot in the other one so i have another one lying around. i assume if it squeals it is broke.

[ed12]

hi
that is :overdrive:
in the second 1

first 1
i may have read wrong
>have some success on one board. got it fired up after replacing the ic101, fet, and that cap. only thing is the red dosent seem like its getting bright enough. could this be the tube?<
u are right g2 could have been turned down

>
second chassis not so much luck. figured since i already had the same parts as i bought 2 of each item to fix both chassis's i put them in as it was having the same issue with no power, i also changed the hot on this one as the old one was deff bad,  but at first i didnt have that cap in. when i turned it on it made a squeal so i turned it back off. i hoped i didnt blow the hot doing this..i found a new cap and after installing it the squeal went away but the system still dosent turn on. i tested 133vdc at cap 425 and on pin 2 of the flyback along with 133vdc at the middle pin of the hot. when checking for volts over the hot i get nothing on each side. but when i check the hot with diode check and off i get from base to emitter .417 and from base to collector .417 with collector to emitter a 0<

u have a hot problem

ed

[GMZombie]

Switched out hot with another one still no power, did voltage testing again afterwards and now it seems as there is a alarm clock beep coming from the area around the Fet. tried putting the old one back in and still beeps.

[lilshawn]

that tweeting is the SMPS in overload...it tries to start up then shuts down because of an overload or a short in the B+. after a very short period it then tries to start back up again. over and over and over.

sometimes it sounds like a tick sound, sometimes a flub, others a preet sound

you have a bad HOT or a dead cap in the high voltage (B+) section.

[GMZombie]

so i figured out i switched out the wrong hot. i had 3 in my area but i only seen 2. the 2 were bad and now that i have the good one in it dosent beep anymore. it still dosent turn on but it dosent beep.

[GMZombie]

so did i stump some peeps with this cause it sure has been stumping me.

[lilshawn]

you can't just say it still isn't working, you have to give us a little more than that.


 if it's not beeping anymore you need to check your voltages coming out of the SMPS. is there any at all? is it dead now?

[GMZombie]

there is still volts going to the hot. 130vdc to be correct, its back to pre beep voltage levels. i switched the ic101 the FET, the Hot, and the c110 cap.

[lilshawn]

there is still volts going to the hot. 130vdc to be correct, its back to pre beep voltage levels. i switched the ic101 the FET, the Hot, and the c110 cap.

how about the 25 and 12 volt lines? You need all of them for it to work.

[GMZombie]

So my 25v is freaking out along with the b+ it starts at 125 and goes.up which.messes with.the 25.and the 12. I tried adjusting per the manual on r112 but.it.just made the volts higher

[lilshawn]

I tried adjusting per the manual on r112 but.it.just made the volts higher

of course, that's what that pot does. Don't go adjusting it all willy-nilly. You can blow a whole shitload of components by driving the B+ way up and having nothing working. if your B+ is stable set it to about 120 or you marked the original start point set it there.

So my 25v is freaking out along with the b+ it starts at 125 and goes.up which.messes with.the 25.and the 12.

tell me. hook up the meter to measure B+.... apply power.... second by second, what happens. something is screwed up.

does it - spike up to 136 then down to 120 then slowly over 10 seconds rise into 129

does it -  start at 93 after about 6 seconds it has climbed to 125.

does it - start at 125 and climb up to 130 after 4 seconds and then stay.

also measure the B+ on AC once it's stabilized....this will let you know how much a noise ripple is in the B+

[GMZombie]

So the good chassis that I fixed I hooked up today and after some adjustments I got the red working and everything was going great. Then after adjusting the horiz posi on the mobo the chassis did its watch beep. Did I just blow the hot. Seems like its overloading. I don't have any voltage measurements yet as I haven't been at my bench. Just need some thoughts. It looked great before this happened but it didn't last long.

EDIT: Found the problem i had the old hot in and not the new one. put the new one in adjusted the b+ to 113.5 as per manual and it is on. but im curious should i look for anything else that could be going out?

[lilshawn]

try changing c106 and see if it starts up properly.

you can also try and change it from a 100uf to a 220uf

this capacitor provides feedback regarding the B+ voltage. if it goes for crap sometimes it can keep the powersupply from starting up properly. upping the uf can give the power supply the little extra time it needs to startup before shutting down. It's quite common to change the value of the bypass cap on the pentranic chassis.

maybe try and shoot an e-mail to "support AT neotecgraphic DOT com" the guys there are usually pretty good about getting back to you.

[GMZombie]

quick question i got the first monitor working again but when i try to adjust the horizontal phase or width it does nothing and it seems like the width is just to far for the tube. adjustments dont work. im thinking the side board may have a problem and was going to swap it out with the other chassis that i have but would like to know where to start on that side board? nothing looks burnt.

[lilshawn]

If there is too much width it likely needs to be recapped.

no width control (turning width pot does little or nothing) is a sign the caps in the horizontal section are dry and need to be replaced.