37pd5200e smps

[zx81]

Re: 37pd5200e smps

Also did my peanut sized brain interpret 10% of whats going on in the circuit as per my post no:4 ?

[zx81]

Re: 37pd5200e smps

Yes Paul I can definitely confirm r003 is open circuit r005 is reading 10ohms it lasted a few seconds i heard the relays click followed by a hiss of power. I thought it was going to be okay but r003 went went open again.

I had it working for about 3 seconds

[paulstef]

Re: 37pd5200e smps

page 7 of the diagram I posted shows the AC input circuitry. The relay RL002 should short the inrush current limiting resistors once the main caps are charged.

In your first post you said Resistor r003 failed again after the relay clicked once. Do you mean RLY001?

Without the signals PFCGO,VCEGO, VSAGO there shouldn't be excessive current draw initially.
Disconnect from AC, (always make sure main caps are discharged!)
Q003 and Q004, make a diode check from drain to source (middle and right pin). should read open. Then inverse the probes, should read a diode drop.

Is the board disconnected from everything else apart AC mains?

[zx81]

Re: 37pd5200e smps

I should have mentioned I could just go and replace parts by taking them out of circuit and testing for faults. But I am a Knowledge Seeker and would like to learn as much as I can about the circuits I'm working on. Hopefully in the distant future I may try and build my own circuits just for fun.

zx81

[zx81]

Re:Hitachi 37pd5200e smps

Does this diagram make sense?

Hi Paul,

Thank you for your reply.

Yes it makes sort of sense its a kind of block diagram of the stages of the SMPS.

I'm pretty much a beginner in electronics and I can kind of follow it through.

This is what I understand and please feel free to correct me if i'm wrong.

On the left of the diagram I see the AC comes in IC202 needs to see STB 5v
also checks if the PFC is ok along with other voltage checks. If all is okay then the AC detect stage turns on the relays RL002 and RL001 very confused on this section

The bridge rectifier does a full sine wave rectification of the AC.
Then we move to PFC section which I think is the power factor correction stage which involves IC001, transistors Q003/4/005.
I don't totally understand how the PFC section works but it involves AC100v,320v AC200v,370v not 100% sure what this all is but I understand it is used to make the power output more efficient and reduces power consumption.

The large capacitors C201 and C016 filter the DC power and send DC via diode D020 and D021 to Capacitor C101 which in turn goes to STB transformer T101. IC101 then somehow goes on to provide STB 5v and a regulator is also used off T101 to have a regulated stepped down STB 3.3v

T201 is for 30v, 12v,10v and 5.1v IC201 as I understand it is the driver which controls the on off state and time for Mosfet Q201 (this is the section I am not sure how to test without scopes and knowing the pin outs. I'm worried that if there is a short here I might not be able to fix it. I suspect Q201 may be faulty but will have to remove it and test. Could Q201 have been damaged by a fault IC201?

Then there is T301 Va (60v) and Transformer T501 Vs (80v)
I'm not sure what IC391 does. I think its somehow involved with the HV output section. But I can see the chopper is somehow involved with IC391 and the HV output section.

I hope you'll forgive my noob interpretation of these things. I only started learning about SMPS yesterday and as you can see I have a lot to learn

zx81.

[paulstef]

Re: 37pd5200e smps

Does this diagram make sense?

[zx81]

Re: 37pd5200e smps

Sorry Guys,

I should have put in the manufacture name in the title of the thread along with model number. Tried editing my thread but wasn't able update the title to show on the top page.

Cheeers,

zx81

[zx81]

Hi Guys,

I wonder if you could assist me repairing a SMPS ?

I have attached some pictures of the board which is from a Hitachi 37PD5200E.

I replaced r003 and r005 both where open circuit but r003 failed again after the relays clicked for just a second. Main fuse before the supply board was and still is fine.

I'm thinking that the Mosfets pictured may be the cause but I'm worried about damaging the surge protection resistor again.

The main problem is I am not sure if the daughter board and what I think is the driver IC201 could also be short? My dilemma is I don't know how to test this IC for shorts or other faults and it has loads of SMD components on it.

I may have also jumped the gun a bit in assuming that the main filter caps and bridge rectifier where fine as the main fuse looked ok.
Caps looked fine visually too. No bulging or oozing electrolyte.

I will be removing the Mosfets, large filter capacitors, bridge rectifier from the board and test out of circuit.

Just not sure what to do to test the driver ic201 without access to an oscilloscope ?

Could I use a 100watt bulb across the fuse holder (with the fuse removed) after I have replaced any parts that are found to be faulty? Will this protect the board and the surge protection resistors and any other components from damage ?