circuit board testing ?

[cwb]

Afraid there's no diode test on it

I get the same reading with the leads reversed.

 

[KJ6EAD]

Some of your meter readings don't make sense to me. Are you using the lowest Ohms scale?

 

[cwb]

Some of your meter readings don't make sense to me. Are you using the lowest Ohms scale?

I've tried it on different settings, maybe it's faulty .

Only thing I can do is try and borrow another one over the weekend.

 

[cwb]

Just been and borrowed a meter, don't know if this helps

From Left @ 20k setting

1 & 3 = 0.00 - reversed 0.00
1 & 2 = no reading - reversed 9.45
2 & 3 = 9.45 reversed- no reading

1 & 3 = no reading - reversed no reading
1 & 2 = no reading - reversed 8.41
2 & 3 = no reading - reversed no reading

1 & 3 = 0.15 - reversed 0.15
1 & 2 = no reading - reversed no reading
2 & 3 = no reading - reversed no reading

 

[KJ6EAD]

Are you referencing left to right with the components inverted as shown in the last photo? When you say 'no reading' is the meter indicating 0L or what?

 

[cwb]

I'm reading left to right as in pic

By " no reading " , when the meter is turned on it reads 1 on all settings ( with leads not touching ) and when testing across contacts it still reads the same .

 

[KJ6EAD]

You're getting too many open leads or infinite resistance readings. Can you tell me what meter you're using? Maybe we can find a better test setup.

 

[cwb]

I had to return the meter I borrowed so the only one I've got now is made by HILKA, it's a few years old.

 

[KJ6EAD]

The meter has a diode test feature. It's at the left end of the resistance scales and has a diode symbol and a musical note symbol. This feature will apply a voltage to the leads a little higher than the regular resistance settings and it will display the voltage drop through the component junction under test. If the voltage drop is 0 or very near 0, it will beep indicating a short. Make sure you have good batteries in the meter and use the diode test setting to reread those three components. It would be nice if you could read them left to right with the components right side up (SCR -> IGBT -> rectifier).

While you're at it, do the same test on pins 4 & 6 of the optocoupler. The pinout is on the first page of the data sheet.

 

[cwb]

Right here we go again, new battery in meter

SCR pins pointing down, left to right
1&3 =202 R 202
2&3 =nr R nr
1&2 =nr R nr
IGBT
1&3 = 1220 R 1655
2&3 = 379 R nr
1&2 = nr R 1918
REC
1&3 =buzz R buzz
2&3 = 380 R nr
1&2 = nr R 379

No reading from 4 & 6 pins of optocoupler

 

[KJ6EAD]

Can you desolder the rectifier and test it again out of circuit?

 

[cwb]

Can you desolder the rectifier and test it again out of circuit?

1&3 = nr R nr
2&3 = 384 R nr
1&2 = nr R 384

On a seperate note, my son's tried changing the keyboard on his laptop and managed to break the plastic clip that holds the ribbon cable in the socket

Any idea where to start looking for one or is there a way round it ?

 

[(*steve*)]

You're getting too many open leads or infinite resistance readings.

I'm not overly surprised.

You have a triac, an IGBT, and a double diode. Those readings are what I would expect if they were out of circuit.

It is kinda curious that we're not seeing in-circuit effects.

Or have they been removed...? (The components from the board)

 

[KJ6EAD]

While most tests were done with the parts on the board, they're isolated by the optocoupler and the motor is disconnected.

 

[KJ6EAD]

Cwb, can you test the bridge rectifier with your diode test? It's the big square thing with four leads mounted vertically next to the - side of the large capacitor. It's marked BR3510L on the top of it's case.

http://www.google.com/url?sa=t&sour...5IimCg&usg=AFQjCNFLELHASD4ks79A0R52eU5k99_yUQ

 

[cwb]

Bridge Rectifier, pins at front, facing down.

1&2 = 480
1&3 = 479
1&4 = 888
2&3 = nr
2&4 = 485
3&4 = 483

No readings on any with leads reversed.

 

[KJ6EAD]

So far we've tested most of the likely suspects and found nothing out of the ordinary, certainly nothing that would be able to immediately trip an 8A breaker. There are several power diodes on the board that are worth testing. I can't see them well enough to tell you where they are or their designations. A much clearer picture of the board would help if it can be had.

 

[cwb]

Don't know if this helps

http://s1244.photobucket.com/albums/gg580/cwb7/

 

[KJ6EAD]

That was frustrating. Lot's of almost clear enough pictures. The key to good pictures is lots of indirect light, no flash and the correct lens and distance.

 

[cwb]

I've added a few more taken outside, they maybe a little better but I'll try again tomorrow as the lights gone now.