Help! Repairing water damaged PCB from Massage chair.

[Jonawald]

They are all supposed to be 2K resisters. They all measure 1.9K close enough I guess.

 

[Jonawald]

Here is an overlay of the other board. Also a shout out for GIMP.org. Graphic Image Manipulator.

 

[dorke]

o.k so on the main board (with the controller board disconnected) we get
1= 7.5KΩ
2= 3.8KΩ
3= 3.99KΩ
4= 3.99KΩ

2-4 are fine (2x2k=4k).
1 is wrong ! needs checking of resistors values near 1 with the ommeter.

What do you get if you measure the same points on the Controller board(cable between boards disconnected) ?

 

[Jonawald]

o.k so on the main board (with the controller board disconnected) we get
1= 7.5KΩ
2= 3.8KΩ
3= 3.99KΩ
4= 3.99KΩ

2-4 are fine (2x2k=4k).
1 is wrong ! needs checking of resistors values near 1 with the ommeter.

What do you get if you measure the same points on the Controller board(cable between boards disconnected) ?

Relay 1, 31KΩ
Relay 2, 94KΩ
Relay 3, 3.6 MΩ
Relay 4. 0Ω

I am sure I already posted this but I cannot find it now. Relay 4 seems to have a problem here.

 

[Jonawald]

o.k so on the main board (with the controller board disconnected) we get
1= 7.5KΩ
2= 3.8KΩ
3= 3.99KΩ
4= 3.99KΩ

2-4 are fine (2x2k=4k).
1 is wrong ! needs checking of resistors values near 1 with the ommeter.

What do you get if you measure the same points on the Controller board(cable between boards disconnected) ?

Relay 1 Measurement was wrong there. I re-measured that was a typo that I missed. Sorry. They are all essentially the same.

 

[dorke]

Relay 1, 31KΩ
Relay 2, 94KΩ
Relay 3, 3.6 MΩ
Relay 4. 0Ω

Well the spread is too large to make sense.
but # 4 =0 is a short to GND and that is wrong.(Are you sure it is number 4 and not 1?)

 

[Jonawald]

I am sure of all those measurements. Have done them a few times now. Yes that is Relay 4. all those traces go straight to the IC

 

[dorke]

I am sure of all those measurements. Have done them a few times now. Yes that is Relay 4. all those traces go straight to the IC

Like the pic below related to GND?

 

[Jonawald]

I am not sure what is in that circle. Is that referring to the trace on the outside of the board? 12V or is it circling a word I cannot see? I was using the GND pin on that connector.

 

[dorke]

I am not sure what is in that circle. Is that referring to the trace on the outside of the board? 12V or is it circling a word I cannot see? I was using the GND pin on that connector.

Yes the GND pin on the connector,and the relays order on the IC pins.

 

[Jonawald]

 

[dorke]

O.k so #4 is shorted to GND.
Do you know how to remove the IC from it's socket (have you ever done such a thing?).

 

[Jonawald]

I have not. I have been thinking about trying it but not daring because I might break it. I can try with some instructions. I can look up how to do it safely, but don't think I have tools other then a spudger.

 

[Jonawald]

I might have a tool in a box of stuff at school. Would have to check. It's only a 5 minute walk from here. Could be back in 15 minutes.

 

[Jonawald]

In the mean time. Working very slowly and careful with a spudger from both ends, I managed to slowly take it out. Pins are all fine. What now? I guess I should be looking for shorts.

 

[Jonawald]

The board underneath is a mess.

 

[dorke]

Just repeat the Ohm test with the Ic out.

 

[Bluejets]

An OHM test between the res points and ground shows 0 ohms. No connection between them.

Jonathan,
When using your meter on ohms and you get a reading O.L , that is not zero ohms, it means "Open Loop" or open circuit ...no circuit.
You were partly correct in the latter part of your statement by saying "no connection between them" but as shown in Dorkes reply in #110, he took the first part of your statement and wrongly assumed you had a short.
See how confusing it can be when you give inaccurate replies.
Understand you are learning but it's a point you need to look at and remember.

A simple task....get you meter on ohms, look at the scale with the leads apart......O.L ....open circuit
Then join your leads together ........ usually about 0.2 ohms ......meaning a closed circuit.
Your meter will never read zero ohms on ohms scale.

 

[Jonawald]

Jonathan,
When using your meter on ohms and you get a reading O.L , that is not zero ohms, it means "Open Loop" or open circuit ...no circuit.
You were partly correct in the latter part of your statement by saying "no connection between them" but as shown in Dorkes reply in #110, he took the first part of your statement and wrongly assumed you had a short.
See how confusing it can be when you give inaccurate replies.
Understand you are learning but it's a point you need to look at and remember.

A simple task....get you meter on ohms, look at the scale with the leads apart......O.L ....open circuit
Then join your leads together ........ usually about 0.2 ohms ......meaning a closed circuit.
Your meter will never read zero ohms on ohms scale.

Thanks BlueJets. I knew there was something I was missing in that. I already repeated the test. It reads O.L. Open circuit for all points. now. Here is the IC for your inspection. If your display is as nice as mine it should be pretty crisp.

 

[dorke]

Thanks BlueJets. I knew there was something I was missing in that. I already repeated the test. It reads O.L. Open circuit for all points. now. Here is the IC for your inspection. If your display is as nice as mine it should be pretty crisp.
View attachment 24081View attachment 24082

Well,
Bluejets has a very good point.
So, without the Ic your are getting O.L(open circuit) on all 4 points?
You cleaned The IC but it's legs are very corroded.
Clean the socket and under it as well.

Please check the following points on the IC itself to GND (ohm test),as on the pic
what do you get?