NEC V920 monitor broken -- please help!

A

Alex

Guest
Hi,

I have a NEC V920 19" monitor which seems to have a faulty flyback.

It was occasionally (once every couple of weeks) arcing internally
somewhere - a quick, short arcing sound could be heard, and the screen
would noticably dim for a short time.

Late last week it became quite frequent (a few times a minute), and
finally a long arcing sound, and then the screen went blank.

The monitor seems to make all the normal sounds when turned on (you
can hear the relays clicking), and the power light under the switch
turns on (the power supply seems to be working), but there is no EHT
being produced by the flyback (tested by placing an earthed
screwdriver near the EHT connection on the side of the tube, under the
rubber boot. No discharge. In fact, the screndriver can touch the
metal connection, and no discharge is observed).

I've measured the voltages on the PCB connections to the FBT (T302),
and there are five connections at ~120VAC, five with 0V on them, and
one connection with 24VAC present. Without a schematic, I can only
assume that this indicates that the FBT is being supplied with the
correct voltage, and it has become open circuit internally.

Is the flyback a common fault in these monitors?

Are there any other tests I should perform before replacing the
flyback?

Is it economically viable to replace the flyback in this monitor? (Or
cheaper to buy a new one?)

Where is the best place in Australia (Perth) to buy a replacement
flyback?

The flyback has the following codes on an attached sticker:
H0003931
F94056A F-801
MERITRON
CT-8733 00806A

Thanks,
Alex.
Alex.
 
On Mon, 06 Sep 2004 13:06:53 +0800, Alex
<lisalexernie@bertiinet.net.au> wrote:

|Hi,
|
|I have a NEC V920 19" monitor which seems to have a faulty flyback.
|
|It was occasionally (once every couple of weeks) arcing internally
|somewhere - a quick, short arcing sound could be heard, and the screen
|would noticably dim for a short time.
|
|Late last week it became quite frequent (a few times a minute), and
|finally a long arcing sound, and then the screen went blank.
|
|The monitor seems to make all the normal sounds when turned on (you
|can hear the relays clicking), and the power light under the switch
|turns on (the power supply seems to be working), but there is no EHT
|being produced by the flyback (tested by placing an earthed
|screwdriver near the EHT connection on the side of the tube, under the
|rubber boot. No discharge. In fact, the screndriver can touch the
|metal connection, and no discharge is observed).
|
|I've measured the voltages on the PCB connections to the FBT (T302),
|and there are five connections at ~120VAC, five with 0V on them, and
|one connection with 24VAC present. Without a schematic, I can only
|assume that this indicates that the FBT is being supplied with the
|correct voltage, and it has become open circuit internally.
|
|Is the flyback a common fault in these monitors?
|
|Are there any other tests I should perform before replacing the
|flyback?
|
|Is it economically viable to replace the flyback in this monitor? (Or
|cheaper to buy a new one?)
|
|Where is the best place in Australia (Perth) to buy a replacement
|flyback?
|
|The flyback has the following codes on an attached sticker:
|H0003931
|F94056A F-801
|MERITRON
|CT-8733 00806A
|
|Thanks,
|Alex.
|Alex.


You obviously didn't notice any charred components while measuring
voltages in the set but the simplest way to find out if your FBT has
carked it is to do a ring test on it. For this you need a ring tester
such as Bob Parker's http://members.ozemail.com.au/~bobpar/fbt.htm

Also a search for this set came up with;

QUESTION NO. P100202-7: NEC V920 Monitor. Need Flyback VCC resistor
value (R31A) color not recognizable looks like 0.--?? ohms 1 watt
fusible, silver middle code only readable.
ANSWER: R31A is 0.33 ohms fusible (flameproof) 1 watt. Also replace
caps and resistors on FBT supply back to secondary p/s especially 0.22
ohms 2w will be partially open.
In NEC chassis# N9902, R31A is 0.33 ohm.
 
On Mon, 06 Sep 2004 13:06:53 +0800, Alex
<lisalexernie@bertiinet.net.au> wrote:

Hi,

I have a NEC V920 19" monitor which seems to have a faulty flyback.

It was occasionally (once every couple of weeks) arcing internally
somewhere - a quick, short arcing sound could be heard, and the screen
would noticably dim for a short time.

Late last week it became quite frequent (a few times a minute), and
finally a long arcing sound, and then the screen went blank.

The monitor seems to make all the normal sounds when turned on (you
can hear the relays clicking), and the power light under the switch
turns on (the power supply seems to be working), but there is no EHT
being produced by the flyback (tested by placing an earthed
screwdriver near the EHT connection on the side of the tube, under the
rubber boot. No discharge. In fact, the screndriver can touch the
metal connection, and no discharge is observed).

I've measured the voltages on the PCB connections to the FBT (T302),
and there are five connections at ~120VAC, five with 0V on them, and
one connection with 24VAC present. Without a schematic, I can only
assume that this indicates that the FBT is being supplied with the
correct voltage, and it has become open circuit internally.

Is the flyback a common fault in these monitors?

Are there any other tests I should perform before replacing the
flyback?

Is it economically viable to replace the flyback in this monitor? (Or
cheaper to buy a new one?)

Where is the best place in Australia (Perth) to buy a replacement
flyback?

The flyback has the following codes on an attached sticker:
H0003931
F94056A F-801
MERITRON
CT-8733 00806A

Thanks,
Alex.
Alex.
Click to expand...
Page on FBT testing here
http://www.noahtec.com/fbtest.htm

Wayne
 
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