MAG 3200 - Standby light, dead set no change when power is pressed

[Doc38343]

Another junk pile re-visit to try board level repair.

OK I have all the voltages correct from the power board with the exception of the 12v is reading 11.2v... all are stable not fluctuating. Also noted no voltages change or fluctuate when i press power.

On the main board I have the 3.3v going to the power on and found the pull down (is working) that returns from the power switch. (when i press the switch it pulls down from 3.3v to 0.01 as it should)
SO - I am trying to follow the path to find the component or short stopping the transistor from switching on.
Hopes of a schematic?? (i confess I have posted here first because of some time constraints but i will search also)
Was hoping someone had experience with this brand or model.

The blurry main board number is 200-107-JL321XA-DH Rev-D

[dskall]

Re: MAG 3200 - Standby light, dead set no change when power is pressed

What do you have on stb and 5vsb
Here's board pretty cheap https://www.tvrepairtips.org/board/200-107-jl321xa-dh

[budm]

Re: MAG 3200 - Standby light, dead set no change when power is pressed

Another junk pile re-visit to try board level repair.

OK I have all the voltages correct from the power board with the exception of the 12v is reading 11.2v... all are stable not fluctuating. Also noted no voltages change or fluctuate when i press power.

On the main board I have the 3.3v going to the power on and found the pull down (is working) that returns from the power switch. (when i press the switch it pulls down from 3.3v to 0.01 as it should)
SO - I am trying to follow the path to find the component or short stopping the transistor from switching on.
Hopes of a schematic?? (i confess I have posted here first because of some time constraints but i will search also)
Was hoping someone had experience with this brand or model.

The blurry main board number is 200-107-JL321XA-DH Rev-D

So are you really getting the 24Vdc? How about the command signals Voltage level, what do you have when TV is OFF and when power switch is activated? What dcv do you have between the two legs of the main filter cap?

[Doc38343]

Re: MAG 3200 - Standby light, dead set no change when power is pressed

What do you have on stb and 5vsb

5v on the top STB pin as well as the second.

12 v rail is reading 11.2
24v is 24.3v all voltages on the power supply are exact and stable with exception of the 12v rail being 11.2v

The original diagnosis was failed main board but i want to see if i can do a board level repair. I followed the voltage from the power board to the main and found the pins where the 3.3v goes to the IR and led power on/standby light and to the power vol channel menu buttons boards. they are also correct and working. Then i followed the 3.3v back to the main board to the pins where it actually pulls down to 0.01v to turn on the mosfet or transistor that should start the set. I lose the path at the two little transistors you can see in the close up photo. there are a couple of resistors where i see the pull down but nothing at the transistors changes on any of the 3 pins. I need a schematic but am stuck working so i have to hop in and out as i can here. jumping between tasks.. LOL I was going to try searching a schematic web site link i got as soon as i can because i have a feeling this will be a component failure i can find and fix. you input is appreciated also so thanks.

[budm]

Re: MAG 3200 - Standby light, dead set no change when power is pressed

Right now the STB (PS-ON) is high that is why you are getting the switched 24VDC at those red wires going to the inverter board. If the BL-ON and the Dimming command are present at this point then you should have backights. If the PS-ON should toggle between <1VDC and >2VDC when power switch is toggle.
Did you check all the Voltages of the regulator IC's on the main board?

[Doc38343]

Re: MAG 3200 - Standby light, dead set no change when power is pressed

So are you really getting the 24Vdc? How about the command signals Voltage level, what do you have when TV is OFF and when power switch is activated? What dcv do you have between the two legs of the main filter cap?

OK - it has the red standby light. All the voltages - ALL are there and VERY stable. When you press power NOTHING happens no fluxuation, no changes.

The 3.3V that runs the LED and power switch board is there. When I press the power button the return pin (pull down pin) does its job and pulls down.

I therefore have a component failure on the main board at the power on level.
I have not located the mosfet or transistor that the pulled down voltage is supposed to turn on, yet. It could be a shorted cap, an open resistor or simply a failed transistor. No apparent burns or anything visible. The 12v 5v and 3.3v rails are all there there on the main board but I need to trace them out but a schematic would make it easier to find.
This is an old tv and has been sitting in my shop for over 2 years. I am using it to learn on so i can get better at board level repairs. (gotta eventually try to pay for my "toys" as my wife calls them)

[budm]

Re: MAG 3200 - Standby light, dead set no change when power is pressed

You need to find out if BL-ON is also stuck low or not, if it is then it will be something that is command to the control signals which will be the micro controller is stuck or bad regulated Voltages. You have many Voltage regulator IC's on the main board that you need to test, that will be the next step.

[Doc38343]

Re: MAG 3200 - Standby light, dead set no change when power is pressed

Right now the STB (PS-ON) is high that is why you are getting the switched 24VDC at those red wires going to the inverter board. If the BL-ON and the Dimming command are present at this point then you should have backights. If the PS-ON should toggle between <1VDC and >2VDC when power switch is toggle.
Did you check all the Voltages of the regulator IC's on the main board?

Hey I looked up the two regulators they are LM1084 and the lower one has 3.3v output pin and 5.01v at the input pin the reference pin reads 2.1v That one appears correct. The higher up one has 5v on the input pin, 2.5v on the output pin and only 1.2v on the reference pin. Nothing even flickers at all when i press the power button. They are very stable. (more so than most of the other tv's i have checked)

Checking more..... gotta get out the old magnifier hood before i stick my nose into mains.. LOL

I don't think the power supply is doing 3.3v it is a very good looking piece of work and quite simple... They have a horrible design pin connector underneath the main board that connects the other lower parts (like the power switches and IR board) The T-con is from the wire you can see in the middle of the board. The cable that controls the backlights and all are off that pin connector, the main board is doing all the regulation and checking best i can tell. It is a weird design so I cant really take the plastic shroud off without removing the power supply/main board module. The connectors are connected to the plastic shroud. But after taking it apart I realized everything is controlled by the main board.

[budm]

Re: MAG 3200 - Standby light, dead set no change when power is pressed

The power supply board supplies 5V to the main board to run the logic circuits, that 5 is regulated down to lower Voltages.
I see three large regulator ICs and two small regulator ICs.
Output Voltage (+/-3% or so) of adjustable regulator (1117 series) is = 1.25Vref + Vadjust. Pin 1 = ADJ, pin 2 9or big tab on top) = Output, Pin 3 = Input.
You may have EEPROM problem.
http://www.shopjimmy.com/catalogsear...lt/?q=MAG+3200

[Doc38343]

Re: MAG 3200 - Standby light, dead set no change when power is pressed

Hey Budm,
Just to verify you are right I traced the 3.3v pulldown under the magnifier. It took me thru quite a trip but it goes strait to the IC in the photo.
Since it has the big old heat sink I'm going to try one of my computer board tricks just for the kicks and practice. I will pull the heat sink (if i can get it off) and re-flow that chip with my hot air station. Definitely made the right diagnosis 2 years ago when i first tried this one. I still don't think it is worth spending any money for a board. Thanks so far and i will let you know if it works. (even if it does work it will likely be only temporary fix)
Doc

[Doc38343]

Re: MAG 3200 - Standby light, dead set no change when power is pressed

OK I can add this one to the WHY oh WHY list.
The reflow didn't work which I really didn't expect it to.
The chips supply voltages are smack on it is just a DOA.
I did learn quite a bit getting here so not a loss in my book.
Anytime I'm learning i'm gaining value.
I will store it for a while longer there are a few compatible brands just like this one so perhaps one may wonder my way with a different problem.
Thanks for your help guys.
may even spring $20 for a board if it ever comes up.