Emerson hdtv troubleshooting

[martino]

Re: Emerson hdtv troubleshooting

you can solder that diode back in place,it's not the bad guy we are after...
I send budm a inbox,asking for help,hope he chimes in...
There's a few diodes in the Q600,Q601 circuit I would be interested in to test.
Mainly D605 as it's directly on the source of Q601,Q601 drives Q600 and in turn Q600 is responsible for the proper drive of T600 that gives you your 5 and 24 volt etc...Seeing 2.43 volts on the source of Q600 makes me think Q600 is not driven correctly(brings us to Q601 circuit)
So,D605 and also D613,D604 and D610 we should test.
Do you have a diode scale on your meter?(has a diode symbol,remotely looking like ->l- )

[ddarn]

Re: Emerson hdtv troubleshooting

it has a diode setting but its on the same one as ohms..

[martino]

Re: Emerson hdtv troubleshooting

Ok. Power unplugged ! Put meter on diode scale.
Red probe on one leg of diode, black probe on the other leg
Note reading, reverse red and black probe and note reading.
One way should read something like 0.540(approx) and reversed should read OL.
If you find one that reads lets say 0.4 BOTH ways, then unsolder one leg of that diode and re measure.(cause there could be a resistor etc in parallel )
Plz measure diodes named in previous post. And while at it,any other diode you find in that area of the board.
Can you post the readings? I'm looking for a diode that's halve failed and dragging down the circuit.

[selldoor]

Re: Emerson hdtv troubleshooting

Martino - dont know if you have seen it but there is another BIG thread on this board
https://www.badcaps.net/forum/showth...t=36180&page=1

[martino]

Re: Emerson hdtv troubleshooting

No I didn't see that threat.
Interesting read,I'm pleased with myself that they are talking about pretty much the same diodes etc,as we are here(I'm pretty new to the game,so a little conformation here and there that I'm somewhat thinking correctly is nice haha)
Showed my friend this threat yesterday and told em I'm frustrated with it being a fairly simple setup,but yet how complex it can seem to be...then ad the fact,the board is not in front of you and it's all through messages back and forth...
I'm not sure what ddarn has in mind as in how extended he wants to make this,he should definitely read that threat,and see if he's game to try
thx selldoor for that threat,I was having a bit of a hard time understanding how the circuit made the T600 oscillate,good explanation in that threat...

[ddarn]

Re: Emerson hdtv troubleshooting

readings I got: D605(4.99kohms/4.99kohms)....D613 33.5kohms/33.5kohms....D604 0L/0L
D610.....0.4 ohms/0.4ohms......2 of the diodes I guess are in the board,and no legs are visible(D 604 and D 605 I believe) so I had to measure from the bottom points on the board.

[martino]

Re: Emerson hdtv troubleshooting

D610 could make sense as it's parallel with R608,a 0.18ohm resistor,impossible to measure without lifting a leg..
D605 should almost be able to measure in circuit,same with D613...
You are getting weird readings,this was on the diode setting? and with POWER OFF AND UNPLUGGED?

[ddarn]

Re: Emerson hdtv troubleshooting

yes the power was off and unplugged

[martino]

Re: Emerson hdtv troubleshooting

Here's a video that explains a little long drawn but very clear how to test a diode and also a transistor,skip to the 5 minute mark...
I looked for one that also shows transistor checking,as we probably have to test Q600 and Q601..

http://www.youtube.com/watch?v=_3G8t-cV1d8

plz watch this to double check method of measuring.
This is not to insult your ability,more to make sure measurements are correctly done.

After that recheck diodes,ANY weird readings that don't make sense like 33kohm both ways,unsolder one leg of diode and test again.
Some diodes don't have legs(underside board),same thing,weird readings,desolder and test again.

[ddarn]

Re: Emerson hdtv troubleshooting

I used a different meter(fluke with automatic selection)...D 613,D 605, and D604 read 0L....D 610 was .5 with leads both ways..the craftsman meter still has the same readings as in above post.

[martino]

Re: Emerson hdtv troubleshooting

If D613,D605 and D604 read OL in both directions,even when out of circuit then those are bad for sure.D610 will have to be measured out of circuit,as their is a resistor parallel with it
Trying to puzzle out how the psu can still produce voltage with those diodes defective.
I would strongly suggest to remove the diodes and measure them out of circuit,as that might shed some light on true measurement and them being bad for sure.

[ddarn]

Re: Emerson hdtv troubleshooting

how do you remove the two that are in the board?

[martino]

Re: Emerson hdtv troubleshooting

mark the direction,ad little bit of solder on both sides,place solder iron in length with diode,it will melt both sides and you can easily flip them off the board,there is no legs on these.

[Caleb]

Re: Emerson hdtv troubleshooting

Not sure if you've checked d640 on backside of board, is a common failure and will keep voltages low

[ddarn]

Re: Emerson hdtv troubleshooting

Ok..I went ahead and bought a multimeter,an innova 3320 with the diode setting.I remeasured all 5 diodes mentioned in previous posts and the readings seemed more realistic.I also checked out the video you posted on here,Martino,and adjusted my readings..the first reading is forward bias,the second is reverse bias:

D 604 -(.665V/0L
D 605 -(.667V/.890V)
D 610 -(0V/0V)
D 613 -(.468V/0L)
D 640 -(.214V/0L)~~~Measured on the 2 solder points on either side of black component
on bottom of board

also,D604,D605 are in the board and my leads were too big to fit in the holes on the front side of board so I had to measure on bottom.If I have to remove one of them diodes that are in the board,would you happen to have a video showing how to do this?

Thanks!

[martino]

Re: Emerson hdtv troubleshooting

D605 and D640 and D610(altho probably ok,due to resistor parallel to it will have to be measured out of circuit) you will have to desolder of the board and test out of circuit.
I will look for a little video for how to remove them.
Rest of diodes look ok.
D605 is high suspect,as it should almost have read correctly in circuit.

[martino]

Re: Emerson hdtv troubleshooting

Just look at first part ,forget the tweezers etc...

http://www.youtube.com/watch?v=8JM4oCpWnjU

[ddarn]

Re: Emerson hdtv troubleshooting

I made the measurements of d604 and d605 on the bottom of the board,but if you look at the bottom of the board,the only things you can pop off of the board are labeled d604a and d605a..I'm assuming these are the actual components ,d604 and d605.Should I have measured around d604a and d605a instead? Also, if you look at the bottom of the board,it looks like q600 has a burn spot? I just wanted to check to make sure before I pull anything off the board..thanks!

[martino]

Re: Emerson hdtv troubleshooting

Could you take a close up picture of that?

[ddarn]

Re: Emerson hdtv troubleshooting

I've attached the pic of the bottom portion of the board..notice the brown spot by q600 and off to the side is d605 ,d605a and d605b