Elo 1525L power board ptb-1218

[BlkSmth]

Re: Elo 1525L power board ptb-1218

This is really outside my area of expertise, and I get a queasy feeling whenever I suggest substituting parts. I was hoping someone more knowledgeable would have jumped in here.

The rated voltage and current of your proposed replacement are better than the original. The only area that might be a problem is input capacitance. The proposed replacement has a capacitance 4 time greater than the original. I really can't predict how that will affect performance.

PlainBill

any other takers on this mosfet swap? I dont want to destroy the board
the OEM # was 4N60B, this one is p10nk70zfp

[PlainBill]

Re: Elo 1525L power board ptb-1218

Readings just in

Fet removed as request. 538 /8 /1925 / 1925 / 9/ 534

what are the rules with fet for replacement as far as voltage etc.
For example I have a p10nk70zfp from another board that I believe is good.

Data Sheet: http://pdf1.alldatasheet.com/datashe...K70ZFP_07.html

This is really outside my area of expertise, and I get a queasy feeling whenever I suggest substituting parts. I was hoping someone more knowledgeable would have jumped in here.

The rated voltage and current of your proposed replacement are better than the original. The only area that might be a problem is input capacitance. The proposed replacement has a capacitance 4 time greater than the original. I really can't predict how that will affect performance.

PlainBill

[BlkSmth]

Re: Elo 1525L power board ptb-1218

Readings just in

Fet removed as request. 538 /8 /1925 / 1925 / 9/ 534

what are the rules with fet for replacement as far as voltage etc.
For example I have a p10nk70zfp from another board that I believe is good.

Data Sheet: http://pdf1.alldatasheet.com/datashe...K70ZFP_07.html

[PlainBill]

Re: Elo 1525L power board ptb-1218

got them readings. sorry it took o long guys... got a bit busy.
here they are: 512 / 8 /1920+ / 1921+ / 8 / 524
still not understanding why that diode on D806 reads both ways (317) on diode mode.

looks like the acer al502 and the nec 1550me are based on this similar design.. I've scoured the web looking for this Now all I might need is a walk thru to make sure I'm learning to follow these schematics correctly, and get sufficient tools as needed.

links to docs I found:



and especially this one:


note page 40, 88- *, then especially page 130

Don't worry about delays. My wife is on vacation for the summer, so my time is no longer under my control.

Thanks for the links for the schematics; that will make it easier to explain things.

Those numbers suggest something is seriously wrong with the FET. I'd suggest removing it from the board and testing it out of circuit; I've been wrong before. Here's the datasheet.

PlainBill

[BlkSmth]

Re: Elo 1525L power board ptb-1218

Those values indicate the diodes are fine. At this point I'm going back and re-examining my conclusions. Let's try this - use the diode test function to make readings across the leads of Q803.

Alldatasheet.com is having database problems, so we'll have to wing it. Number the pins in any order and measure 1-2 1-3 2-3 2-1 3-1 3-2 (the red probe goes on the first number of each pair).

PlainBill

got them readings. sorry it took o long guys... got a bit busy.
here they are: 512 / 8 /1920+ / 1921+ / 8 / 524
still not understanding why that diode on D806 reads both ways (317) on diode mode.

looks like the acer al502 and the nec 1550me are based on this similar design.. I've scoured the web looking for this Now all I might need is a walk thru to make sure I'm learning to follow these schematics correctly, and get sufficient tools as needed.

links to docs I found:



and especially this one:


note page 40, 88- *, then especially page 130

[PlainBill]

Re: Elo 1525L power board ptb-1218

Removed them again to get actual postable readings out of circuit:

D809 = SF34 Diode and reads on Diode Mode: 441 Black probe on Cathode stripe side... nothing reverse... and nothing either direction on 200, 2k, 200k

D810 = SR360 Diode and reads on Diode Mode: 192 Black probe on Cathode stripe side... nothing reverse... and nothing either direction on 200, 2k, 200k

Are these the values we needed, or did I set the DMM wrong?

Thanks again

nothing meant just a "1" or "l"

Those values indicate the diodes are fine. At this point I'm going back and re-examining my conclusions. Let's try this - use the diode test function to make readings across the leads of Q803.

Alldatasheet.com is having database problems, so we'll have to wing it. Number the pins in any order and measure 1-2 1-3 2-3 2-1 3-1 3-2 (the red probe goes on the first number of each pair).

PlainBill

[retiredcaps]

Re: Elo 1525L power board ptb-1218

nothing meant just a "1" or "l"

A multimeter ALWAYS gives a reading. "1" IS a reading. "1" on the left hand side of the multimeter means it is out of range for the chosen range. So if your multimeter is set to 200 ohms, it means the reading is greater than 200 ohms.

[BlkSmth]

Re: Elo 1525L power board ptb-1218

Removed them again to get actual postable readings out of circuit:

D809 = SF34 Diode and reads on Diode Mode: 441 Black probe on Cathode stripe side... nothing reverse... and nothing either direction on 200, 2k, 200k

D810 = SR360 Diode and reads on Diode Mode: 192 Black probe on Cathode stripe side... nothing reverse... and nothing either direction on 200, 2k, 200k

Are these the values we needed, or did I set the DMM wrong?

Thanks again

nothing meant just a "1" or "l"

[PlainBill]

Re: Elo 1525L power board ptb-1218

Shall I remove D809 get value from label and replace your thinking?

I had assumed you had checked them out of circuit. If you haven't, do so and also check D810. They should both read open in the reverse direction for both resistance and on the diode test.

PlainBill

[BlkSmth]

Re: Elo 1525L power board ptb-1218

Shall I remove D809 get value from label and replace your thinking?

[PlainBill]

Re: Elo 1525L power board ptb-1218

Update on the Resistor.... Brown/Red/Gold/Gold see image.
The D809 has no value either way on 200 (ohm range), on Diode Mode reading of 423 black probe on stripe side (873 backwards) Then the D810 has on 200 mode 159.7 then with Diode Mode 187 (1700+ backwards) Are these supposed to work backwards on Diode Mode?

OK, so it's a 0.12 ohm resistor. Allowing for lead resistance, it's good.

Meters vary. On the diode test range mine applies 1 ma at a maximum of 2.5 volts across the leads. I'd have to look it up, but it uses less than .2 volts for resistance measurements. I'd say that those diodes should read about .2 volts forward and open in the reverse direction when tested out of circuit. I don't have a board on hand that I care to strip, but I verified that in circuit.

Judging by the board, D809 did get uncomfortably warm. Note that these are high speed Schottky diodes. You can't use a 1N5400 diode and expect it to work.

PlainBill

[BlkSmth]

Re: Elo 1525L power board ptb-1218

Update on the Resistor.... Brown/Red/Gold/Gold see image.
The D809 has no value either way on 200 (ohm range), on Diode Mode reading of 423 black probe on stripe side (873 backwards) Then the D810 has on 200 mode 159.7 then with Diode Mode 187 (1700+ backwards) Are these supposed to work backwards on Diode Mode?

[BlkSmth]

Re: Elo 1525L power board ptb-1218

Those aren't standard colors!! Let's agree that .22 ohms indicates the fuse is good.

PlainBill

Amen to that brother :P

my first guess would be red/orange/gold/gold...just uncertain...
however if they are that color senario, you'd be correct from what i understand

I'll be checking that diode D809 out of circuit later tonight. I really appreciate all the help here. I have one of them Dynex LCD32 thats on this forum also, to play with next... except mine looked like the .1 ohm 1w fuse burnt (out of production got 6 coming from malaysia heheh) Thats my next tackle!

updates will be later tonight or tomorrow friends! ...Thanks again!

[PlainBill]

Re: Elo 1525L power board ptb-1218

Burgundy/Redish - Redish/Orange - Gold -Gold

Those aren't standard colors!! Let's agree that .22 ohms indicates the fuse is good.

PlainBill

[BlkSmth]

Re: Elo 1525L power board ptb-1218

Burgundy/Redish - Redish/Orange - Gold -Gold

[PlainBill]

Re: Elo 1525L power board ptb-1218

R811 showed .224-.225 on DMM , should I remove this component and test it? also what would be preferred setting on DMM for this?

C807 was replaced before incident. D809 may be shorted (both directions) on the DMM diode test. D810 seems ok. (posting from work, I forget what that reading was one direction). Interesting to me seems if I choose ground on the chassis of the monitor (not on power supply) and test lower half it's all 80.4-.80.5v on most components, nothing on the top half. But when I ground to the large cap like I did for the test of I801, the upper half tests power at 80.4-80.5v and nothing on the bottom? Why is this... I'm doing something wrong here.....

What is the color code on R811? It's in shadow in the pictures. Typically it is a .22 ohm resistor

Check D809 out of circuit.

This is a common question. To understand what is happening, several facts are important.

1. The nominal input voltage is 125 VAC. There are three wires coming to the monitor - live, neutral, and ground. Neutral and ground are tied together at the breaker (or fuse) box.

2. The live line swings from roughly +170 volts to - 170 volts (and back) 60 times a second. Thus half the time the live wire is at a higher instantaneous voltage than the neutral wire and the other half the time it is at lower voltage.

3. There is a bridge rectifier before the main cap. This ties the + side of the
large cap to whichever line is at a higher voltage, and the - side of the cap to whichever line is at the lower voltage.

4. this means that half the time the - side of the cap is at 0 volts and the other half of the time it is going toward or returning from -170 volts. The + side swings from 0 volts to + 170 volts.

5. Since the chassis is tied to ground, and ground is tied to neutral, the + side of the main filter cap is at an average of 85 volts DC with respect to ground.

PlainBill

[BlkSmth]

Re: Elo 1525L power board ptb-1218

R811 showed .224-.225 on DMM , should I remove this component and test it? also what would be preferred setting on DMM for this?

C807 was replaced before incident. D809 may be shorted (both directions) on the DMM diode test. D810 seems ok. (posting from work, I forget what that reading was one direction). Interesting to me seems if I choose ground on the chassis of the monitor (not on power supply) and test lower half it's all 80.4-.80.5v on most components, nothing on the top half. But when I ground to the large cap like I did for the test of I801, the upper half tests power at 80.4-80.5v and nothing on the bottom? Why is this... I'm doing something wrong here.....

[PlainBill]

Re: Elo 1525L power board ptb-1218

here we are with those results

nothing held steady for some reason... voltage all over the place....
taken measurements with black probe on negative side of large cap (stripe side)

1 = .00-.72 DMM set on 20
2 = .00-.09
3 = .64-.70
4 = .03-.35
5 = .01-.03
6 = .00-.01
7 = 11.91-13.96
8 = .12-.69

again the voltage was all over the DMM.... Large cap was 168.8-168.9

Interesting. Check the value of R811. That senses the current through the primary of the transformer. If you haven't already done so, replace C807. Both I801 and Q803 could have been damaged, but the readings don't really support either being bad.

If you haven't already done so after the accident, check both D809 and D810. If either was shorted, it could account for the readings.

PlainBill

[BlkSmth]

Re: Elo 1525L power board ptb-1218

here we are with those results

nothing held steady for some reason... voltage all over the place....
taken measurements with black probe on negative side of large cap (stripe side)

1 = .00-.72 DMM set on 20
2 = .00-.09
3 = .64-.70
4 = .03-.35
5 = .01-.03
6 = .00-.01
7 = 11.91-13.96
8 = .12-.69


again the voltage was all over the DMM.... Large cap was 168.8-168.9

[PlainBill]

Re: Elo 1525L power board ptb-1218

Believe it or not, that is good news - sorta.

Now you get to take voltage readings on I801. I'd like the voltage on each pin. Use the negative lead of the large cap (C805?) as the ground point. And try not to short anything out this time.

If you want to get more information on what is going on here, the ON Semiconductor datasheet for this IC contains a typical application schematic (Figure 34). It's not identical, but it should be close enough.

PlainBill