1084S-P LOPT+HOT replace

[roy_bates]

check it with a multimeter not a screwdriver mains tester please.

[e278c0ffbca5f4a6caaa599fa]

i have 128,26,17 volts readings in the pins of the power supply

---------- Post added 20th February 2014 at 00:49 ---------- Previous post was 19th February 2014 at 23:44 ----------

12.41pm in Athens Greece a beautifull night with 18 degrees Celcius...............my monitor is working again

it was a nusty... welding on a capasitor left of the flyback.
i want to thank you all of you with your help.Harry

[jcarvalho]

Great job!!! Another 1084s saved!!

[chromium]

Looks like I am going to have to learn how to fix these. I now have 2 dead 1084S-P1 monitors

I have no idea what I'm doing, so I guess my first step is to learn how to discharge the tube properly and then identify my LOPT and HOT, then start looking for replacements. Pretty sure these are the problem, both monitors make a squealing noise when I turn them on. The power light comes on, but no picture.

One only died last night while I was using it. A bright light came on the screen and then a horizontal line appeared on the screen. I turned it off and then back on and then the squealing noise started.

I'd appreciate any help from you guys Also if anyone is in Melbourne, Australia that can fix these it would be even better. I'll pay!!

[e5frog]

So... similar problem, power supply squeeks when I turn power on and sounds like a bomb falling in a video game when turning power off. Disconnecting the power out cable connector renders it quiet, unplugging the purity coils makes no difference - so I guess those aren't shorted. No glow in the tube and when discharging I get no spark (nor sound).
https://www.youtube.com/watch?v=ZgMGm2elDUw

Desoldered the "HOT", it's a D1577 (2SD1577) on this 1084S-P, flyback is marked E39144, AT2079, 30102 TY PHILIPS (tiny at the bottom edge) and the manufacturing year and month stamped on the small label placed in an annoying place where it was hard to get a good picture or a good look. The HR 7506 should be a suitable replacement at about €32 with tax and shipping to Sweden...

D1577 seemed to measure OK, base to collector and base to emitter measured 0.50 and 0.56 with diode test, no other reactions with all pin combinations on diode test. So it behaves (with no load) as it's supposed to.
I assume the flyback could be shorted anyway, unless there's some other problem or that the "HOT" is bad although it measures fine. Any advise welcome, I have an ESR meter so I hope I don't have to randomly swap capacitors.

Also resoldered parts on the power board as well as the flyback and hi power parts around it - didn't help.

I might have a spare monitor I could borrow parts from, is it advisable to desolder flyback and "HOT", mount these and see if there's a difference? Should I look for other problems first?

[roy_bates]

that is the right lopt for that monitor...its a philips chassis.

you can remove the lopt completely ,then measure the 125 volt rail when its on to see if its stable.
check the other rails as well.
also check the input voltage after the rectifiers to see if its getting dc,its a switchmode supply.

[e5frog]

I measured the voltages from the power board and got 127.1V, 25.8V, 16.9V with no load. When trying it in a 1081 monitor it worked just fine.

Removing the orange wire (127.1V) from the connector I also didn't get the whistling sound from the power board - so problem is probably there and probably in the flyback. Going to desolder it and check.

Is the recommendation to swap the "HOT" at the same time? Even if it seems to measure OK?

[e5frog]

Desoldered the flyback and measured it.



1-2 0.07 Ohm
6-5 0.13 Ohm
6-2 0.30 Ohm
5-2 0.22 Ohm
9-10 1.0 Ohm

7, didn't get any thing to any pin

However I had about 18 Ohm when measuring from 9 or 10 to 2,6 or 5. Those shouldn't be connected, right?

With the flyback desoldered, no screech sounds from the power board when powering on.

The three diodes showing in the image above (right side), are these internal? Should it measure something between pin 7 and one of the wires going out?
Measuring in the right direction between 7 and 11 that should give some measurement, right?

[e5frog]

Measuring voltages at the power board with the flyback removed:
126V
22.6V
13.5V

Don't know if it's OK, have nothing to compare with, this power board powered the 1081 fine though.

Swapping flyback and the HOT (I read the BU508AF should be fine for replacing the D1577) seems like the right way to go...?

[roy_bates]

Desoldered the flyback and measured it.



1-2 0.07 Ohm
6-5 0.13 Ohm
6-2 0.30 Ohm
5-2 0.22 Ohm
9-10 1.0 Ohm

7, didn't get any thing to any pin

However I had about 18 Ohm when measuring from 9 or 10 to 2,6 or 5. Those shouldn't be connected, right?

With the flyback desoldered, no screech sounds from the power board when powering on.

The three diodes showing in the image above (right side), are these internal? Should it measure something between pin 7 and one of the wires going out?
Measuring in the right direction between 7 and 11 that should give some measurement, right?

yes the diodes are internal,there the tripler

as for a measurement across 7 and 11,not necessarily


you could still get resistance across some windings,even when bad

- - - Updated - - -

Measuring voltages at the power board with the flyback removed:
126V
22.6V
13.5V

Don't know if it's OK, have nothing to compare with, this power board powered the 1081 fine though.

Swapping flyback and the HOT (I read the BU508AF should be fine for replacing the D1577) seems like the right way to go...?

yes.for the transistor

and...looks like the flyback is bad