HV does not come on for Daytek 1731-D monitor?

[[email protected]]

I don't think the HV is coming on. No static sound as it fires up and
screen stays black.

Just hear a soft ...tic, ...tic, ...tic, two a second
my guess is the circuit trying to 'kick start' the HV oscillator

Anyone have experience with this monitor?
Or, what is likely culprit?
Or knows what usually goes wrong?
The MOSFET that drives the HV transformer?

Schematic is VERY difficult to read, too

This monitor has the best red phosphor I've seen and would like to get
it up and running again.

Help.please

- Robert -

 

[nucleus]

my experience is that this happens when the HV transformer is shorting
internally or to ground; the HV never reaches full potential, thus is a
black screen. the tic is when the HV tries to build and reaches a
value high enough that leakage occurs. try dark room to see if you
can see visible arc outside of tranny; if not, the leakage is internal.

 

[[email protected]]

my experience is that this happens when the HV transformer is shorting
internally or to ground; the HV never reaches full potential, thus is a
black screen. the tic is when the HV tries to build and reaches a
value high enough that leakage occurs. try dark room to see if you
can see visible arc outside of tranny; if not, the leakage is internal.

Afraid you may be right.

ticking is now up to 4 times a second.

Neglected to mention that recently now and then the monitor would make
a sound, zzziiiitttt and tthe image would get small and pull way to the
right, then another sound and return to normal. Not often, just once
in a while. Thought that was topical contamination buildup, so I
disassembled, cleaned as possible, reassembled and hasn't done that for
some time, but has done it again.

Confusing the issue is the intermittent pot controlling the blue gun.
One of 3 of those really really cheap pots on the PCB on the neck seems
to go open and loses the blue gun. Tap slightly and it comes back.

Very difficult to remove that board, it's glued on, and soldered into
the RF Shielding.

Will do that dark room test. May be imagination, but swear the unit
has been running hotter than originally. Does that relate?

Robert

 

[[email protected]]

Afraid you may be right.

ticking is now up to 4 times a second.

Neglected to mention that recently now and then the monitor would make
a sound, zzziiiitttt and tthe image would get small and pull way to the
right, then another sound and return to normal. Not often, just once
in a while. Thought that was topical contamination buildup, so I
disassembled, cleaned as possible, reassembled and hasn't done that for
some time, but has done it again.

Confusing the issue is the intermittent pot controlling the blue gun.
One of 3 of those really really cheap pots on the PCB on the neck seems
to go open and loses the blue gun. Tap slightly and it comes back.

Very difficult to remove that board, it's glued on, and soldered into
the RF Shielding.

Will do that dark room test. May be imagination, but swear the unit
has been running hotter than originally. Does that relate?

I have seen a lot of these Daytek 17 inch monitors. All dead, and all
with the
same problem.

 

[[email protected]]

I have seen a lot of these Daytek 17 inch monitors. All dead, and all
with the
same problem.

....and that problem is?

I tried the dark room to 'see' the arcing if any and did not see any.

I did note the HV transformer has a cracked mounting tube, no idea when
that occurred. The crack appears to be completely mechanical and not
even have voltage around it, just looks like a poor choice of plastic.


Listening closely to the tic this time, the tic sounds more mechanical,
like a relay, than arcing

Seriously, what is the same problem?

- Robert -

 

[[email protected]]

...and that problem is?

I tried the dark room to 'see' the arcing if any and did not see any.

I did note the HV transformer has a cracked mounting tube, no idea when
that occurred. The crack appears to be completely mechanical and not
even have voltage around it, just looks like a poor choice of plastic.


Listening closely to the tic this time, the tic sounds more mechanical,
like a relay, than arcing

Seriously, what is the same problem?

The same as your problem. HV does not come up. I did not find parts
or a service manual at the time, so I did not investigate further.
Looks like the service manual has popped up on the net since then.