# Maxent MX 42VM10 Plasma Need help



## OhioBob

I have a Maxent MX-42VM10 plasma EDTV that is totally inop. No turn on, no LED light. Seems this brand is low cost. Very little useful information about it can be found. I would like to find a free download of the service manual/diagrams. I will start at the power supply. I learned from some googling searches that the power supply board is an LJ44-00051A.
Another place shows this board also used in the following units. AKAI PDP4294 and PDP42298ED, ESA PDP4294LV, ILO P42BSMT, MAXENT P4202YD04, Phillips 42FD9935/17, SAMSUNG SPN4235, SANYO DP42746. Any one have information on this power supply? Diagram and information will be appreciated.
Bob


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## lcaillo

Bad caps in the power supply of cheap LCD units is a common problem. Look for shorted semiconductors, swollen caps, high esr caps, i.e. the typical power supply problems.


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## OhioBob

Thanks. That will be my first step. Also, will keep looking for schematics.
Bob


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## OhioBob

OK. I opened this one up. Found that all the PCB's, display, etc are marked Samsung.
Here are the PC board info. All marked Samsung.
LJ44-00051A Model B4K-50 Rev 02
S.D. 1 LJ41-0214A rev 1 
LJ92-00998A
LJ41-01194A
LJ41-02142A Rev R1

Anyone recognize these boards--and maybe have schematics, service manual, etc.
The TV's control voltage comes up. Turning it ON, closes the power relay. Looks like most of the voltages are there on the main power board. But, there is a little SM LED on the middle board that is flashing constantly. Doesn't appear to be any code indicated--just continuous blinking.

I found a fuse blown on the PCB LJ41-02142A. Replaced it--and it blew immediately.

Pulled board and applied 5.00VDV to VCC IN with a new fuse. It did not blow. But there is another input shown on the PCB as VDD IN. Haven't figured out what that voltage is supposed to be.

There are also connector pins for VS, VSET, and VSCAN. These do not show "IN" like the other two.
Would these be outputs?

By the way, the 5.00 volts does not show up on the ceramic fuse that blew. Makes me suspect the problem may be with the VDD IN----or maybe one of the three others, IF they are inputs.

Then again, if they are outputs--the problem could be back on the board preceeding this one.

This board has gobs of heat sink mounted Full Wave Rectifiers and Transistors mounted in groups of 4 or 5. And a lot of larger capacitors. It has four main output connectors labled Out H and Out L.

Any suggestions--or references to a similar Samsung Plasma TV. 

Thanks, Bob


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## OhioBob

*Re: Maxent MX 42VM10 Plasma Need help (Samsung)*

Quick follow-up.

I suspect the VS is an AC input, as I found that it goes to the two legs of a Full Wave Rectifier. And the output of that rectifier DOES go through the Ceramic Fuse that blew. Then through a choke and a bank of 8 each 100uf 160volt Caps. The bank measures 760 uf--not too much lower than the 800 installed. And the bank's ESR is 1 ohm or less.


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## lcaillo

VS is d.c. from the power supply and is usually around 200V. There should be a lable on the panel identifying several voltages.

It sounds like the V-Sus board that you are describing. I can tell you that it can be very dificult to sort out whether failures on these are simply local to that board or due to a bad buffer or bad panel. If you are not familiar with troubleshooting these panels I would refer the problem to a professional. It may be difficult to get information on it, however, and you may not be able to find someone who is qualified, but I would check around.

Vcc is usually a voltage supply to a device and Vdd is usually voltage drain, ground, or reference. It is unlikely that the 5v line is your problem. I would not apply voltages without knowing exactly what you are doing, as you may cause further damage.


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## OhioBob

Thanks, Icaillo.
Yes, I found the board listed as the "Y Sustain Board" or "Y Main Board". I see there is an "X-SUSTAIN" board listed also. I'll have to go over to my Daughter's house to look at that one. Maybe they will be enough similar, that I can compare some of the metering results looking for problems.

The VS goes to a full wave rectifier. If this is DC, why would it need rectification. I am new on these SMPS's--just getting my feet wet. Is it possible part of the SMPS--the high voltage generator circuit--is on the Main Power board, with its rectification and smoothing on this PCB?

The VDD is not grounded. It goes through a micro-fuse, a tiny inductor, and has a small El Cap. But, I cannot find continuity to anything else on the PCB. But, this appears to be a sandwich PCB, and I cannot see the inner tracings. I am assuming it goes through some Surface Mounted semiconductors on the board that is blocking my continuity searchs. I need a schematic badly. LOL

Can you help me with definitions for the following? Or steer me to a source?

VS, VSET, VDD, VCC, VSCAN

I agree, the problem could be further down stream from this board--as it connects to several others.
I was hoping that since the fuse that blew was on this PCB, that the fault might be on it. Wishful thinking I guess. But, one has to start someplace.

These PCB sets are common with Samsung Model SPN4235, Sanyo Model DP42746, Phillips Model 42FD9935/17, and Akai Models PDP4294 and PDP4298ED. Would help if someone has a service manual or schematics for one one these.

Again, thanks for the help. I'll keep at it.

Bob


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