Help! Repairing water damaged PCB from Massage chair.

[dorke]

Hi Jonatan,
There seems to be a problem with the " forum alerts",I didn't see any.so I checked the thread directly.

To our board...

1. There is another pair of resistors with suspicious values,near the MOCs.
The Photo is not completely clear(see below),
what I see is 120K [brown (violet?),red,yellow],that is way too high!
What is the actual value ?

2. The purpose of checking the voltage on the 1K (10k) resistors was to determine the value of the BTA12(8) gate-current.
Calculating by dividing the voltage(AC) reading by the resistor value.
That is how we found out that the resistor values are too high.

3. from #240
"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"

Not completely clear:
Which diode is 120V and which isn't ?
By "LED" you mean the MOC's?

4. Did you mange to clean the socket well?
no corrosion in the inner contacts?

5. I don't understand the bottom right red arrow on your last Post.

 

[Jonawald]

Do the resistors have to be exact? I don't have 330 but I do have 224 and 470

 

[dorke]

If you have 220 and 100 use them in series instead of the 330.
Is that the value of item 1 resistors in #241 ?

 

[Jonawald]

If you have 220 and 100 use them and series instead of the 330.
Is that the value of item 1 resistors in #241 ?

Yup. That was the problem. I found some 330Ω resistors and replaced the. Somehow I had substituted 120k resistors for all for 330Ω by the MOCs. oops. Now when I jump Pin 6 to ground I get 108V at Leg up/Down and Pin 4 gets me 108V at Back up/down. I still get 79V without the MOCs on.

Next question is. What about those 79V. Should they be there? The only thing remaining that can allow that is the blue round things. Rectifiers?

 

[dorke]

Now it is time to check the DC voltages on CN13 and CN14 directly.

1. You should get 0V on both regardless of the 4,6 jumper in or out
Is that so? (Carful ! there is voltage on the pins but the difference is 0)

2. Now use jumper 4,
Add to it a jumper (to 5v) to click the corresponding UP relay (you should have two jumpers in the socket)
Note the voltage and polarity.
What do we get?

4. Repeat steps 2 and 3 above for jumper 6 and corresponding UP/Down relays.
What do we get?

 

[dorke]

Another pair of resistors that needs checking-near the white TLP251s.

 

[Jonawald]

Now it is time to check the DC voltages on CN13 and CN14 directly.

1. You should get 0V on both regardless of the 4,6 jumper in or out
Is that so? (Carful ! there is voltage on the pins but the difference is 0)

2. Now use jumper 4,
Add to it a jumper (to 5v) to click the corresponding UP relay (you should have two jumpers in the socket)
Note the voltage and polarity.
What do we get?

4. Repeat steps 2 and 3 above for jumper 6 and corresponding UP/Down relays.
What do we get?

1. Right
2. GND-4 jumper and +5v-7 gets me 120 Change the +5v to 8 and polarity swaps.
Same thing happens when I move GND-6 and jump 9 and 10. I think that circuit is fine now.

I replaced resistors in #246 at the same time as I replaced the 330 Ohms. They are now at 470 ohm.

 

[dorke]

That is very good news.

1. Time to connect the motors to CN13,CN14 and verify they are working(no IC ,same as you did in #246).

The only thing to watch for is:
Working with no functional IC ,no limit switch has any effect.
So,take care not to drive the motors beyond the limits, if there are any for those motors.
i.e.
Drive a motor for a short time and then switch it's direction movement for a short time.

2. After that, it would be time to re-check the AC motor .
First thing would be checking all resistors values near the other 4 MOCs.

 

[Jonawald]

I already went through all the resistors and compared their values the the print underneath. I only found the four 330Ω and the 470Ω by the TLP251s.

The AC Motor is my next area of concern. It has 101V even without the IC in.

I had the IC checked out. It is unreadable because four pins are bad. This includes one of the pins needed for programming so it cannot be read. I have to wait a bit to get it back because the friend who has it is not nearby. But when we do get it back, I expect it should work to try out some of the circuits of this chair because RX and TX are fine it can still preform some of it's functions.

Jonathan

 

[dorke]

We can go on testing without the IC.

Please note on the pic the values of the resistors marked,
and check they are the correct values.
Just to be clear,Did you replace the ones with "green arrows" to 330 ohm?

What is written on the IC in the 2nd pic ?

 

[73's de Edd]

.
.

Sir Jonathan . . . . . .


You're certainly lucky that the presence of board symbolization let you CORRECT your self on the erroneously high values of resistors that were being there on the
gate drive line to the triacs as well as the input sides of the MOC O.I.'s.

Your LEG up/dn and BACK up/dn DC motor drive lines are at connectors C14 and CN13.
BTW . . . . a commonly used DC motor specification is 90VDC.
You are now worried by some voltage presence at CN13-14 when the TRIACS are turned off.
That might be a "phantom" static leak thru voltage.

How about trying this dynamic test:

Get a common AC table lamp and have a 100 watt bulb in it. Turn it on to confirm it works and then unplug.
Then use 2 clip leads to connect the separate blades of its AC plug to CN 14 LEG up/dn connector.
Now I haven't read back all 250 pages . . . . but are you to the degree of operational capability that you can
get a microprocessor command signal to activate the LEG up/dn MOC and thereby activate the gate of the TRIAC to get power to that section ?
If so the lamp should light up.
If not I guess that you have been relying upon a jumper resistor to perform that turn on.

If that works on lighting the lamp for the LEG up/dn, then move the lamp to the BACK up/dn CN 13 connector and see if it functions, if being activated in the same manner.
ALSO in reading across the CN 13 or CN14 terminals, that mystery voltage should have disappeared, when you have a load across that associated CN connector.

A final test would being to see that the four relays are operating properly in their switching actions / purpose of reversing the polarity of DC voltage at the CN14 nd CN 13
connectors, which you will have to monitor with a DVM across the lamp load.
That would be easy to do at the test lead connectors, already clipped on at the lamp plugs blades.

Use the same procedure of finding a valid microprocessor signal at CN16 or use the same jumper resistor method to activate the relay driver transistors, if it can't be
done with the microprocessor..

That test lamp load would be a precursory test , somewhat less than the full load that the connecting of the motors would then receive.
But you can certainly see that you are now switching some power.


73's de Edd


.

 

[Jonawald]

.
.

Sir Jonathan . . . . . .


You're certainly lucky that the presence of board symbolization let you CORRECT your self on the erroneously high values of resistors that were being there on the
gate drive line to the triacs as well as the input sides of the MOC O.I.'s.

Your LEG up/dn and BACK up/dn DC motor drive lines are at connectors C14 and CN13.
BTW . . . . a commonly used DC motor specification is 90VDC.
You are now worried by some voltage presence at CN13-14 when the TRIACS are turned off.
That might be a "phantom" static leak thru voltage.

How about trying this dynamic test:

Get a common AC table lamp and have a 100 watt bulb in it. Turn it on to confirm it works and then unplug.
Then use 2 clip leads to connect the separate blades of its AC plug to CN 14 LEG up/dn connector.
Now I haven't read back all 250 pages . . . . but are you to the degree of operational capability that you can
get a microprocessor command signal to activate the LEG up/dn MOC and thereby activate the gate of the TRIAC to get power to that section ?
If so the lamp should light up.
If not I guess that you have been relying upon a jumper resistor to perform that turn on.

If that works on lighting the lamp for the LEG up/dn, then move the lamp to the BACK up/dn CN 13 connector and see if it functions, if being activated in the same manner.
ALSO in reading across the CN 13 or CN14 terminals, that mystery voltage should have disappeared, when you have a load across that associated CN connector.

A final test would being to see that the four relays are operating properly in their switching actions / purpose of reversing the polarity of DC voltage at the CN14 nd CN 13
connectors, which you will have to monitor with a DVM across the lamp load.
That would be easy to do at the test lead connectors, already clipped on at the lamp plugs blades.

Use the same procedure of finding a valid microprocessor signal at CN16 or use the same jumper resistor method to activate the relay driver transistors, if it can't be
done with the microprocessor..

That test lamp load would be a precursory test , somewhat less than the full load that the connecting of the motors would then receive.
But you can certainly see that you are now switching some power.


73's de Edd


.

Thank You Edd. On your first comment. I think if I had looked at this board and not seen the correct values and models of all the components I would not have started the project in the first place. I knew I had a fighting chance with all the values there. Even with that, I am not sure how I managed to mess up with the resistors' values. I guess I will write it down to rookie mistake.

I will do the light bulb test next time I have enough time to sit down and do some proper work on this board. There are a few resistors I need to replace and one I found that is completely disconnected inside somehow. I will work on my own to double check and replace all resistors needing replacement and get back here when I run into major problems or major success.

Thank you for your input Edd.


Dorke
the printing on that IC is
HD74LS00P 7E46

 

[dorke]

Time to check the AC motor.
I think there is a good chance to have it working after the repairs we did on it so far.

1. We should connect the main and controller boards with CN28.

2. On the main board connect CN1,CN2.

3. On the control board connect CN35 and MgDetect (the opto circuits).

4. In order to activate and set direction of the AC motor.
Use a short wire in the IC socket pins 28,29 to 5v
(one at a time! see pic below)

5. Start by blocking both limit optos(up and down) simultaneously.
No movement should occur with a short in the IC socket at either pin 28 or 29.

6. Now remove the block from both optos.
We should get movement with the shorts(one at a time) in both directions up and down.
At this stage don't get to the limit points yet, just check both directions of movement.

7. If stage 6 is o.k,
Test that the opto limits indeed stop the movement when reached (on both up and down).
"Long " operation in one direction.
Take care, and remove the short jumper immediately ,
if while testing you see it doesn't stop- so no damage will occur.




Side note:
The control circuit of the AC motor is more complicated than what we have seen so far:
it includes the IC, the 74LS00 chip, some diodes "gate"', and the opto limit circuit.

About What Ed wrote:
We are already beyond the need for any further tests like "lamps" etc.
The CN13,CN14 circuit on the main board is fully functional!
The only thing missing is connecting the motors to CN13,CN14 and testing with them (as per #248).

 

[Jonawald]

Time to check the AC motor.
I think there is a good chance to have it working after the repairs we did on it so far.

1. We should connect the main and controller boards with CN28.

2. On the main board connect CN1,CN2.

3. On the control board connect CN35 and MgDetect (the opto circuits).

4. In order to activate and set direction of the AC motor.
Use a short wire in the IC socket pins 28,29 to 5v
(one at a time! see pic below)

5. Start by blocking both limit optos(up and down) simultaneously.
No movement should occur with a short in the IC socket at either pin 28 or 29.

6. Now remove the block from both optos.
We should get movement with the shorts(one at a time) in both directions up and down.
At this stage don't get to the limit points yet, just check both directions of movement.

7. If stage 6 is o.k,
Test that the opto limits indeed stop the movement when reached (on both up and down).
"Long " operation in one direction.
Take care, and remove the short jumper immediately ,
if while testing you see it doesn't stop- so no damage will occur.




Side note:
The control circuit of the AC motor is more complicated than what we have seen so far:
it includes the IC, the 74LS00 chip, some diodes "gate"', and the opto limit circuit.

About What Ed wrote:
We are already beyond the need for any further tests like "lamps" etc.
The CN13,CN14 circuit on the main board is fully functional!
The only thing missing is connecting the motors to CN13,CN14 and testing with them (as per #248).

View attachment 24551

IView attachment 24673

t seems my life has settled back into the familiar routine of way to busy and way to busy. I got a bit of a chance to play with this board today. I am stuck at CN1. It has 5 pins. Three are used. One is AC one is Down the other is Up. The problem I have with this connector is that if I set my DMM to ACV and put the black probe to AC I get 120V from both UP and Down pins. I am not plugging anything in with that situation. I have replaced both BTA12 with BTA08 because the BTW12 were shorted out. The MOCs for these two pins are not getting voltage so they aren't turning on the power. The resistors have all been checked and corrected to right value. But I still get the voltage.

The only difference I can find between this circuit and the working AC Pump circuit beside it is the resistance between posts on the BTA08 I substituted and the BTA12 in original. When I do a diode test I get the same measurements on the BTA12 and the BTA08. When I do an ohms test I find a difference as indicated in the picture uploaded.

 

[73's de Edd]

.


Sir Jonawald . . . . . . . . . . . . .


Consider the possibility of that AC voltage that you are now reading across those terminals as being a weak phantom / sneak path / static AC voltage.

Your meter can READ presence of a voltage but not actually be able to differentiate on the POWER drive behind that voltage.

And not a true DYNAMIC AC voltage, which you then could truly worry about.
Trying my earlier mentioned AC lamp test would confirm that, while you are additionally AC metering across the same terrminals.
Even if a lamp is not at hand, a simple temporary tack in soldering of a 10 K 2w resistor across the terminals and taking a reading of the AC voltage across it should find that voltage dissappearing.


e.g. . . . .

Little Johnny Golightly's experiment:

One day Little Johnny was piddling around with some lemons, dimes and pennies and he had stacked a penny, a lemon juice saturated blotter paper spacer and then a dime.
A metered voltage test from penney to dime revealed that there was one volt.
WOW I have made a battery !
Then another electrolytic spacer and a penny produced twice the voltage, Gee Oh Gosh Oh Golly, Batman . . . . He's on a roll !
Multiplying the effect eventually resulted in 12 volts.
Now 12 volts . . . . . thats a VERY-VERY familiar voltage figure, and in a streak, he is heading for the garage to see if he can jump start his dad's Harley .
One wire connected to the starter motor and another was used to touch to its other terminal . . . .contact . . .ACTION ! . . . . . but with no action coming forth, seems like just as soon as contact is made, the metered battery voltage drops to zero.

Soooooo, starting at a very early age, Young Johnny has initially fathomed between a Static and a DYNAMIC voltage , the latter of which, has some real power punch behind it.




73's de Edd

.

 

[dorke]

Hi Jonatan,

1. Your attachment doesn't open.
2. In what way were the Triacs shorted?
3. Please measure the AC motor resistances(between all 3 wires).
4. What were the resistors you replaced, and to what value?
5. I wouldn't worry about that voltage, like Ed said it could be a phantom voltage.

 

[Jonawald]

Hi Jonatan,

1. Your attachment doesn't open.
2. In what way were the Triacs shorted?
3. Please measure the AC motor resistances(between all 3 wires).
4. What were the resistors you replaced, and to what value?
5. I wouldn't worry about that voltage, like Ed said it could be a phantom voltage.

.


Sir Jonawald . . . . . . . . . . . . .


Consider the possibility of that AC voltage that you are now reading across those terminals as being a weak phantom / sneak path / static AC voltage.

Your meter can READ presence of a voltage but not actually be able to differentiate on the POWER drive behind that voltage.

And not a true DYNAMIC AC voltage, which you then could truly worry about.
Trying my earlier mentioned AC lamp test would confirm that, while you are additionally AC metering across the same terrminals.
Even if a lamp is not at hand, a simple temporary tack in soldering of a 10 K 2w resistor across the terminals and taking a reading of the AC voltage across it should find that voltage dissappearing.


e.g. . . . .

Little Johnny Golightly's experiment:

One day Little Johnny was piddling around with some lemons, dimes and pennies and he had stacked a penny, a lemon juice saturated blotter paper spacer and then a dime.
A metered voltage test from penney to dime revealed that there was one volt.
WOW I have made a battery !
Then another electrolytic spacer and a penny produced twice the voltage, Gee Oh Gosh Oh Golly, Batman . . . . He's on a roll !
Multiplying the effect eventually resulted in 12 volts.
Now 12 volts . . . . . thats a VERY-VERY familiar voltage figure, and in a streak, he is heading for the garage to see if he can jump start his dad's Harley .
One wire connected to the starter motor and another was used to touch to its other terminal . . . .contact . . .ACTION ! . . . . . but with no action coming forth, seems like just as soon as contact is made, the metered battery voltage drops to zero.

Soooooo, starting at a very early age, Young Johnny has initially fathomed between a Static and a DYNAMIC voltage , the latter of which, has some real power punch behind it.




73's de Edd

.

Thanks both of you. I guess I should check on that phantom voltage. The reason I am concerned is because previously whenever I plugged in that motor it would start humming and weakly try to move the carriage down. When I read 120V across both up and down portions, I thought I had found out why. But perhaps it is different now that I have replaced the BTAs

1. The attachment is a phantom attachment.
I made the post, then I realized I hadn't tapped the button to make attachment full size. Then I went back to edit my attachment, made it full size and saved my changes. It looks like whenever I do that. I get a ghost attachment that does not lead anywhere. You do see the full size image right?

2. When I used diode test with black in the middle lead I got a beep from both other pegs. This didn't happen when I tried the triac on the working PUMP circuit.

3.I started by putting black probe on outside leg. The AC pin on the connector. and touched the other two. On the middle on I got 19Ω On the Up peg I got 20Ω..Then I checked between UP and Down and got 37Ω. I was sort of expecting nothing between those two.

4. I replaced some 2K with 1K and I think there was a 10KΩ in there instead of a 100Ω. Order of magnitude stuff on both cases. I've learned to back up my reading the colours with reading with the meter.

5. See opening comment. I will check next time I have a bit of time to look at it.

Thanks again.
Jonathan

 

[dorke]

Had some time to look into that "phantom voltage" on the AC motor terminals.
The reason you measue it is the fact that there is a snubber circuit(R-C network R=100,C=0.1uF?) between the Triacs A1 an A2 terminals.
Since you use a DMM with 10M-ohm input resistance you would measure the line voltage even in the case the Triacs are off.
But with the motor(low resistance) connected it will not be there.

Please fill in the values of the parts(assuming all 3 sections are the same) in the pic

 

[Jonawald]

Here is a more up-to date image of that corner.

 

[dorke]

And the value of the "Red-orange" Capacitor ?