Hyundai l50s - dead

[tmcw]

I've had this monitor for several years, used several times a month at most. I was using it a few days ago, and left it on, came back 30 mins later, and it was dead, no light (green or orange) showing on the LED.

Power board has the following markings:

Frontek PL1542C02-V3 (on circuit board)
FLF1542-02A FA040130C VER 2.0 (on a sticker)

Voltages on CN101 are as follows (7 is the pin nearest the edge of the board):

1 0
2 0.35
3 0.35
4 0
5 0
6 0.22
7 0.35

The fuse F101 near the power connector is ok.

The thermistor TH101 has continuity through it.

I've replaced the capacitors C110 and C121 with new Panasonic and Nichicon (PW(M)) caps (though the original Sam Youngs tested ok on ESR meter). Monitor is still dead after changing the caps.

I'm getting around 120V at the big blue cap. It seems to retain it's charge when power is removed.

The bridge rectifier tested as expected in circuit, so I didn't remove to test.

D102 tests ok too in circuit (open one direction, 0.505 the other way).

D104 tested ok too out of circuit. I haven't changed the caps down that area yet, as when I tested for voltage on the downstream side of the transformer, I didn't see any voltage on any of it's 5 pins there.

What to try next?

EDIT: File upload isn't working for me, I'll try it later.

[selldoor]

Re: Hyundai l50s - dead

Thats a nice dinky little board can you post a picture of the other side.
and some of the main board

Is your meter ok and new battery - you should get around 350vDC on the BIG Cap - Did you test on VDC

What is under the white blob in the middle

Did you have the boards connected it may not start without a signal from the main

[tmcw]

Re: Hyundai l50s - dead

Had trouble with uploading images earlier, here's the other side.

Have uploaded a pic of the mainboard, nothing on the other side, other than tru-hole soldering and traces, no components.

Meter does have good batteries, actually changed them this morning, I can double-check with another meter.

Tested the big cap on AC and DC. The values quoted were at AC, but I don't think the values were as high as 350 on DC, maybe around 220. What;s the correct way to measure the voltage of the big cap? I'm a bit cautious of it, as it gave me a buzz the first time.

Under the white blob here is another blue capacitor (C111) and a resistor (R112).

Power board and main board were connected while testing.

[selldoor]

Re: Hyundai l50s - dead

Ok the caps you replaced - you got the same uf and voltage? and put them in the right way round? what values were they V & uf

Working on a non conductive surface?

Big cap - you only need the power board connected to the mains - I usually suggest via an RCD socket/adapter. Meter on 600vDC and just test across the legs - keep in position for 5-10 seconds to see if it is stable. Use aligater clips on your probes if you have them.

[tmcw]

Re: Hyundai l50s - dead

There seems to be issues with the server for uploading images, I'm getting "internal server 500" messages.

I'll upload the picture of the main board when it works.

EDIT: Finally got the pic of the mainboard up, nothing on the other side, other than tru-hole soldering and traces, no components.

[selldoor]

Re: Hyundai l50s - dead

No rush for them retest the big cap

[tmcw]

Re: Hyundai l50s - dead

Ok the caps you replaced - you got the same uf and voltage? and put them in the right way round? what values were they V & uf

Working on a non conductive surface?

Big cap - you only need the power board connected to the mains - I usually suggest via an RCD socket/adapter. Meter on 600vDC and just test across the legs - keep in position for 5-10 seconds to see if it is stable. Use aligater clips on your probes if you have them.

Thanks for the info.

I've tested the big cap, and it's giving 323V, pretty steady too, only around 0.5V fluctuations.

I've been putting the boards back into the monitor chassis when appying power.

The 2 caps I replaced with the same voltage and uF, one was 1uF/50V, the other 47uF/50V. Both were Sam Young, but I think they were ok, capacitance is fairly close to stated, and ESR similar to the Nichicon and Panasonic I put in. In the correct way too, the component side is silk-screened with the polarity, so difficult to get wrong.

Edited a post above to add the mainboard picture.

[selldoor]

Re: Hyundai l50s - dead

What is the part number on the ic between the two caps you replaced

[stj]

Re: Hyundai l50s - dead

check the fet on the heatsink and tell us what caused the flashover under the main cap!

[tmcw]

Re: Hyundai l50s - dead

It's a ICE2AS01

I get around -120V on pin 6 of that IC, supply should be around 8.5-21V according to datasheet. Could that be right? I checked with both AC and DC and it was roughly the same 110 and 120V.

[tmcw]

Re: Hyundai l50s - dead

check the fet on the heatsink and tell us what caused the flashover under the main cap!

I got zapped first time by the cap , so I've been discharging it with a screwdriver everytime I disconnect the board from power.

How do I check the fet, do I need to take it off?

[selldoor]

Re: Hyundai l50s - dead

Can you measure the resistor under the white blob what should it be - what colour are the
stripes

[tmcw]

Re: Hyundai l50s - dead

Can you measure the resistor under the white blob what should it be - what colour are the
stripes

Seems to be Brown, Black, Yellow, Gold, Red

which is 10.4 Ohms 2% accoring to the calc on Digikey

http://www.digikey.ie/en/resources/c...or-code-5-band

It's reading 98.2k Ohms though!

I probably need to measure out of circuit?

[selldoor]

Re: Hyundai l50s - dead

Also if look on the back I think that pin 6 is connected to the transformer via
two resistors R135 and another of the same value under a stain - can you clean the stain off - any idea what it is?

I think that striped resistor is not the one I wanted - its the ones on the back.

Its best to use a large resistor to discharge the big cap or just wait a bit then test it with meter.

[selldoor]

Re: Hyundai l50s - dead

How do I check the fet, do I need to take it off?

Lots of tests in here https://www.badcaps.net/forum/showthread.php?t=10419
start at post 19 - for now just scroll down to mosfets in post19

[tmcw]

Re: Hyundai l50s - dead

The 2 resistors are R135 and R134.

They both have "124" on them. One is reading 116.2K ohms, the other 120.5K ohms.

[tmcw]

Re: Hyundai l50s - dead

Lots of tests in here https://www.badcaps.net/forum/showthread.php?t=10419
start at post 19 - for now just scroll down to mosfets in post19

Thanks for the direction.

Using that test on the 3 pin fet, I get:

1-2 3.3M
1-3 2.2K
2-3 2.2M

Seems to be ok?

[selldoor]

Re: Hyundai l50s - dead

Well it isnt shorted which is a good start.

Resistors look within spec as well - I was looking at them as being the resistor shown in the
IC datasheet.

Damn fall for that every time !!! You have to test pin 6 using the negative leg of the big cap for ground - that is the case when testing components on th eprimary side.

[tmcw]

Re: Hyundai l50s - dead

Well it isnt shorted which is a good start.

Resistors look within spec as well - I was looking at them as being the resistor shown in the
IC datasheet.

Damn fall for that every time !!! You have to test pin 6 using the negative leg of the big cap for ground - that is the case when testing components on th eprimary side.

I presume that is DC voltage?

I'm seeing between 9.5-13 V DC between the neg of the cap and pin 6 of the IC.

[stj]

Re: Hyundai l50s - dead

solder a 1m, 2m2 or 4m7 resistor across the cap pins.
preferably a gray high voltage one.