Help! Repairing water damaged PCB from Massage chair.

[dorke]

While the TRiacs are pulled out,the correct reading is 107V on both diodes with the short wire in and no voltage with it out.
Your marking in red is not correct ,
you marked a short(red)between legs 2 and 3.
The blue one is between legs1 and 2 and the blue circles are the lifted resistors legs.
So,which way did you short?




About reading the Triacs parameters:

The manufacture is ST-micro
It reads BTA12-600B .
That is 12A, 600V,B is standard(50ma gate current).

The BTA8-600B you have is 8A,600V,standard(50ma gate current).

So,
Apart from the current they match.
In general,we should replace a bad part with one that has same current or higher(other parameters being the same).
For testing only, you can replace the Triacs with the BTA8s.
We need to know the current of the motors the Triacs are driving under full load to be able to decide if the 8A is o.k.
That isn't easy without full identification of the motors.

The BTA12's look badly corroded and need replacement anyways.
The one that "produces" 77v is definitely bad.
The other one, most probably bad as well,
since there should be no voltage on the diode without the "control board activation" .

So
1. Please take out the short wire in the Triacs location.
Insert and solder the BTA8 Triacs(leave the resistors legs pulled for now) .
measure the voltage on the diodes-you should get non.

2. Now re-solder the resistors legs ,
measure the voltage on the diodes-you should get non.

3. "Activate" the voltage by inserting a short wire in the IC socket(as per #211)
measure the voltage on the diodes:
you should get voltage with the wire connected and no voltage otherwise.

What do we get?

 

[Jonawald]

While the TRiacs are pulled out,the correct reading is 107V on both diodes with the short wire in and no voltage with it out.
Your marking in red is not correct ,
you marked a short(red)between legs 2 and 3.
The blue one is between legs1 and 2 and the blue circles are the lifted resistors legs.
So,which way did you short?

View attachment 24413


About reading the Triacs parameters:

The manufacture is ST-micro
It reads BTA12-600B .
That is 12A, 600V,B is standard(50ma gate current).

The BTA8-600B you have is 8A,600V,standard(50ma gate current).

So,
Apart from the current they match.
In general,we should replace a bad part with one that has same current or higher(other parameters being the same).
For testing only, you can replace the Triacs with the BTA8s.
We need to know the current of the motors the Triacs are driving under full load to be able to decide if the 8A is o.k.
That isn't easy without full identification of the motors.

The BTA12's look badly corroded and need replacement anyways.
The one that "produces" 77v is definitely bad.
The other one, most probably bad as well,
since there should be no voltage on the diode without the "control board activation" .

So
1. Please take out the short wire in the Triacs location.
Insert and solder the BTA8 Triacs(leave the resistors legs pulled for now) .
measure the voltage on the diodes-you should get non.

2. Now re-solder the resistors legs ,
measure the voltage on the diodes-you should get non.

3. "Activate" the voltage by inserting a short wire in the IC socket(as per #211)
measure the voltage on the diodes:
you should get voltage with the wire connected and no voltage otherwise.

What do we get?

Ok. Looks like did the triac short test wrong. I had the triac in when I did that btw. I guess I shouldn't have left them in. Now looking at it I understand what you were trying to do. I can repeat that test sometime today when I have more time.

I put in the BTA08 following the procedure you described. In with the BTA08s measure voltage. Down with resistor measure voltage. Then short and measure voltage again. Something is amis. I get 77V on both diodes for all three tests. Triacs only, resistor in and with a jumper from 31 to 4 and 6 respectively. I know those triacs are supposed to block full wave but they seem to be blocking half wave only. What's up with that?

jonathan

Ok I went ahead and quickly did the deed. I pulled the triacs and one leg of the resistors. I still get 77V on both diodes. I am guessing it's gonna be those two capacitor things. I attached a picture of them.

 

[dorke]

I'm trying to understand.

After the replacement of the Triacs to BTA8 and with resistors connected ,without "Triack shorts"
i.e the normal connection:
Does the " IC sockets shorting" have the effect of on/off on the voltages of the diodes?Or do you still get the voltages all the time(no effect)?

No need to repeat the tests without the Triacs yet.

 

[Jonawald]

I'm trying to understand.

After the replacement of the Triacs to BTA8 and with resistors connected ,without "Triack shorts"
i.e the normal connection:
Does the " IC sockets shorting" have the effect of on/off on the voltages of the diodes?Or do you still get the voltages all the time(no effect)?

No need to repeat the tests without the Triacs yet.

The jumping at the socket did not affect the voltage at all. see above. I edited the post.

 

[dorke]

With everything in it's place.
Please check the AC voltage on the resistors with/without a short in the IC sockets.
and at the same time the DC voltage on pins 1 and 2 of the opto-Triacks MOC3020.

A total of 4 AC readings and 4 DC readings.
See pic below

 

[Jonawald]

 

[dorke]

#226 is without jumpers in the IC socket?
What are the diode voltages in this case?

Need to use jumpers in the IC socket and re-measure as well.

 

[Jonawald]

#226 is without jumpers in the IC socket?
What are the diode voltages in this case?

Need to use jumpers in the IC socket and re-measure as well.

Test was done with jumpers out. Voltage on diodes was 80V on both.

Ok I redid the other test too with jumpers.
JP4 is with 4 jumped to 31 jp6 is with 6 jumped to 31.
No time to explore why they are do different right now.

 

[dorke]

As always we are taking our time.

Assuming both results are with the Jumpers in the IC socket
The "top" MOC measurement is not as expected.
The "bottom" one is o.k.

Did you measure the AC voltages on the resistors?
They are not as expected.
So we always get 0V on them?

Please measure the voltage on pin 1 and 2 of the opto MOCs this time relative to GND(you have it on CN16) .
With and without Jumpers in the IC socket.

 

[Jonawald]

As always we are taking our time.

Assuming both results are with the Jumpers in the IC socket
The "top" MOC measurement is not as expected.
The "bottom" one is o.k.

Did you measure the AC voltages on the resistors?
They are not as expected.
So we always get 0V on them?

Please measure the voltage on pin 1 and 2 of the opto MOCs this time relative to GND(you have it on CN16) .
With and without Jumpers in the IC socket.

View attachment 24431

No wonder they say haste makes waste. I had forgotten that I was supposed to do the resistor test on AC. Now they read 2.4 mV each without jumper.

When I test the MOC and use GND I get 4.9V without jumpers in. The top has 0.9V with jumper in 6. The bottom has 0.9V with the jumper in 4.

The jumpers still don't effect the voltage at the diodes which stays at around 77V.

 

[Jonawald]

I got an email from iRest today requesting a serial number, pictures of the part I need and pictures of the chair. There's life out there.

 

[Jonawald]

I think I know why my answers to these questions have been inconsistent. I just spent a lot of time doing measurements over and over again. I got a solid 9V AC at those resistors. Then I came back a few minutes later and got nothing. A few MV. I played around for a while trying to find out what went wrong repeating my measurements and doing everything to see what happened. Then I turned off the power and did a resistance check on the resistors. It was 10kohms Ok that's fine so I powered it back up and checked voltage and got 49V which quickly dropped to 19V. Then a check a few minutes later got me 16V on those resistors.

Could there be a capacitor somewhere that is affecting the voltage?

Ok. Looks like I found what was causing this. When I turn power on with jumpers in, I get Voltage across those resistors. If I pull one leg of the jumper to move it, the voltage across those resistors drops to milivolts. It stays at MV till I power cycle with the jumpers in then it's back up to 19V.... After re-checking that I can't repeat that. Now I get a few milivolts even when I turn on the power with the jumpers in. Something is crazy inconsistent. I will have to keep experimenting to see if I can get a pattern here.

 

[dorke]

Let's see :
With no jumpers in the IC socket we get
1. DCV between pin 1 and 2 of the MOC about 0V.
2. ACV on the resistors of about 0v


With the jumpers in the IC socket we get
3. DCV between pin 1 and 2 of the MOC about 1.6V.
4. ACV on the resistors of about 9V to 49V.

5. At all times(regardless of the jumpers in the IC socket) you get DCV of about 80V on the diodes

6. You are using the BTA08 instead of the BTA12.

7. please post 2 new(current) clear pics of the areas in question, including the MOCs the Triacs the 8 rectifier diodes till the board edge.
one for CS the other for PS (no overlay).

8. Have you changed the resistors? 10K sounds too high for me.
What is the full writing on the MOCs?

9. What values are the resistors connected to pin 1 of the MOCs.

10. Good news about iRESET

please confirm items 1-6 and provide info for 7-9

 

[Jonawald]

Let's see :
With no jumpers in the IC socket we get
1. DCV between pin 1 and 2 of the MOC about 0V.
2. ACV on the resistors of about 0v


With the jumpers in the IC socket we get
3. DCV between pin 1 and 2 of the MOC about 1.6V.
4. ACV on the resistors of about 9V to 49V.

5. At all times(regardless of the jumpers in the IC socket) you get DCV of about 80V on the diodes

6. You are using the BTA08 instead of the BTA12.

7. please post 2 new(current) clear pics of the areas in question, including the MOCs the Triacs the 8 rectifier diodes till the board edge.
one for CS the other for PS (no overlay).

8. Have you changed the resistors? 10K sounds too high for me.
What is the full writing on the MOCs?

9. What values are the resistors connected to pin 1 of the MOCs.

10. Good news about iRESET

please confirm items 1-6 and provide info for 7-9

1-6 Yes as far as I can determine that is all right.

7. See attachments.
8. I don't remember changing those resistors but you are right. The writing underneath them is 1K and the resistors are 10k I will change them out and report back.
9. The writing underneath says 230. They test at 218. Again, I will take a look at what happened there.
10. Agreed.

 

[Jonawald]

iRest came back to me. They say the part is 11USD with shipping coming in at $60USD. Total 77. Considering I would be paying in Canadian $ that would make it $110. More than I want to pay before I know I can get everything else working. I asked her if she can put it on the slow boat or ask her boss if she couldn't send the file for me to burn my own.

Jonathan

 

[Jonawald]

And yes I know the solder on the triacs looks bad from the top. It does make good contact though. It's just that I have had them out and back in a few times today already and haven't taken the time to wrap a wire around and tie it into the trace as I do with these areas where some of the pad around things is gone.

I replaced the 10K resistors with 1K resistors. (Found a box of 10k in my 1K bin wonder why.)

Nothing changed. At first I thought I had fixed it because I got nine volts AC at the resistors and I was able to switch the MOCs from 5Vdc to .9Vv with jumpers at the IC socket. Then when I switched the jumper from 4 to 6 the voltage on both of those resistors dissapeared again and I have not been able to make it come back. Power cycling with jumper in 4,6 or out nothing. I even completely unplugged everything form the mains board let it sit for a few seconds then plugged in and re-tried NO volts. Since it is getting late, I will shut it down and leave it overnight see if anything changes. And yes I am looking for AC volts. I am convinced that this is exactly what happened before. I always begin with checking pin 4 then moving up to pin 6 because it's easier to find pin 4 quickly.

 

[Jonawald]

 

[Jonawald]

So I checked for AC voltage again at the resistors this morning. I get nothing. Just a handful of mV. Is it possible that I have been getting mV all along and just didn't see the little m? I am sure I looked and double checked, but now I'm beginning to doubt again because I cannot make it happen again.

 

[Jonawald]

So it turns out I am not going crazy after all. My Multimeter is. With it switched to ACV when I only touch one probe to those resistors I get voltage. So if one probe is making good contact and the other isn't then I get voltage. Depending on which probe is in contact, I get different voltages. The red one shows about 9V, the black one shows about 6V. That explains why it was harder for me to get voltages to show with the replacement resistors. They have more bare wire and it is harder for one probe to not have contact.

 

[Jonawald]

Ok. I spent the afternoon playing with this thing. By now I am quite sure I have been measuring the voltage at the resistors wrong. I have been doing it at the resistors as your instructions indicated I should but it's just wrong. Why would there be potential at the opposite ends of a resistor? I propose I should have checked for voltage at the MOC as indicated with arrows in the circle. Voltage should mean off no voltage should mean on. Exactly the same as on the opposite side of that MOC. If the potential is low it is on. Potential high off.

When I short Pin 4--6 on the MOC I get 120V at the diodes. But turning the LED on on the other side does not have that effect. I swapped a MOC from the other end of that board in to see if I can make a difference I could not. As I read it, those MOCs are not working as they should. Somebody either confirm this or explain why I am wrong.

I got suspicious of the IC socket so I took it completely out, cleaned it and soldered it back in. My best looking soldering job so yet BTW.