Happ MTG-2601 HV shutdown

[ragtime4]

Ohmerone, what do you mean by 'secondary voltages' at C818 or C811 or R818, and how do I check for secondary voltage?
?
How do I check Q801 and D801?

Heres the Schematic MTG-1901

http://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_schematic.pdf

If you don't have any secondary voltages at, C818 or C811 or R818 then

I would check Q801 and d802,fuse and the others in that same area.

The str I802 would be a suspect as well does the heat sink get warm after its

on for a few minutes if no then it maybe dead replace it.

From my experience Q801 and around it were an issue when you don't have B+

The B+ diode can be an issue it does fail, not always shorted.

sometimes you may hear a whine and then it stops and then works it because d810 RU3

The resistors around Q801 look overheated for me so check them as well

When you have secondary shorts you may hear ticking, confirm

theres no shorts on all three test points.


If there is a short, using your ohm meter, remove the part and see if the short is gone.

Like the HOT on the 123v B+ line

and the vertical ic, and remote board on the 24v line

now the 12v supply at R818

So caps first then check for shorts on all the supply voltages.

Before you order caps and you can add more parts to your list if needed.

Resolder the standup large watt resistors in the power supply too.

Let us know what you find..

 

[Ohmerone]

You should look up how to test a transistor and resistor

on your downtime so your ready for trouble shooting a chassis

filled with them.


You need to measure the Plus side of c818 and C811 and R818

using the ground side of C818 as a common cold ground or the large

heat sink ground in most cases is part of common ground around the board.

looking at the schematic t801 is the switch mode power supply.

the left side is the primary side and the right of the transformer is the secondary

side of the SMPS.. This transformers supply's regulated voltages

and isolates the hot side from the cold side. Can you see the ground symbols

on the schematic they don't look the same because they are not the same.

You don't measure voltage on the hot side using your cold common ground

or your voltages wont be correct just move your ground lead to the neg-side

of c808 the filter cap.

when testing voltages on the hot side..

Caps do fail in the chassis, you need to restore the caps for best results.

On any chassis so the dc level is good enough for the circuits to work properly

then check off the parts listed bad in a previous repair.

 

[beerbarrel]

This is the HV diagram from the manual. You need to lift zener diode D361.

Here is my malfunctioning board...



Here is the diode on the component side of the board...



here is the solder side....



Here is a pic of that diode lifted....just desolder one side and lift it up from the board.

 

[beerbarrel]

Btw, mine works as advertised with the diode lifted. On to some troubleshooting...

 

[ragtime4]

My monitor is back up and running. During the cap kit installation i noticed that many caps near the main RGB input were very wet on top. When i powered on the first time after the cap kit, i had no red. I noticed the connector was actually dirty with spilled soda! After some cleaning she powers off and on just fine. Millipede is back up and running.

I learned a ton in this thread about basic techniques. Thanks a ton.

Very interested in the secondary voltages. I dont quite grasp it yet. Why is the voltage considered secondary and why is secondary voltage important?

Heres the Schematic MTG-1901

http://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_schematic.pdf

If you don't have any secondary voltages at, C818 or C811 or R818 then

I would check Q801 and d802,fuse and the others in that same area.

The str I802 would be a suspect as well does the heat sink get warm after its

on for a few minutes if no then it maybe dead replace it.

From my experience Q801 and around it were an issue when you don't have B+

The B+ diode can be an issue it does fail, not always shorted.

sometimes you may hear a whine and then it stops and then works it because d810 RU3

The resistors around Q801 look overheated for me so check them as well

When you have secondary shorts you may hear ticking, confirm

theres no shorts on all three test points.


If there is a short, using your ohm meter, remove the part and see if the short is gone.

Like the HOT on the 123v B+ line

and the vertical ic, and remote board on the 24v line

now the 12v supply at R818

So caps first then check for shorts on all the supply voltages.

Before you order caps and you can add more parts to your list if needed.

Resolder the standup large watt resistors in the power supply too.

Let us know what you find..

 

[Ohmerone]

My monitor is back up and running. During the cap kit installation i noticed that many caps near the main RGB input were very wet on top. When i powered on the first time after the cap kit, i had no red. I noticed the connector was actually dirty with spilled soda! After some cleaning she powers off and on just fine. Millipede is back up and running.

I learned a ton in this thread about basic techniques. Thanks a ton.

Very interested in the secondary voltages. I dont quite grasp it yet. Why is the voltage considered secondary and why is secondary voltage important?

Appartently the caps were the only major issue with your chassis.

Thats why we should get the caps and replace them first

and then test chassis again..

instead of trying to trouble shoot it and no obvious shorts.


I find the secondary to need alot of capacitance and if its low

in the secondary the chassis won't start..

If the cap have been replaced less then a couple of yrs then

i would suspect other parts not caps again.

The Primary and Secondary are used with transformer's

Here's a website, you can get a better idea of how it works.

http://www.etcai.com/

The SMPS is a complex circuit alot different on how it works

With the conversion of AC to DC to AC signal or Electromagnetic Energy.

transfered to the secondary windings as a ac signal and then gets rectified

though the Diodes at each supply.

Good Luck!