Another treadmill problem

[KrisBlueNZ]

OK. I've just discovered that I've missed something important - the big white relay marked JQX-105F-1. This relay is controlled by Q2 and possibly another transistor next to it (it's covered with white goop so I can't tell), and these transistor(s) are controlled by the daughter board.

So don't worry about the MOSFET and diode measurements at the moment. Also, those devices that detect voltage on a wire by touching the insulation will not tell us much.

I think I will need to follow the circuit of the power supply as far as the daughter board. I need to see a good, well-illuminated picture of both sides of the main board, covering the area shown in dark contrast in the following picture.

For these pictures, please use a fairly high resolution setting, with the camera facing directly downwards on the board. The board needs to be illuminated, but not with a single light source, because that causes reflections in certain areas of the board. Ideally, a bright overcast day, using outdoor lighting, is perfect, but you could get the same effect by reflecting a light source off a light-coloured, rough surface so that the light is dispersed.

I need to be able to read markings and colours on the components, and clearly distinguish the copper tracks on the underside.

Also I'm going to need you to make some more voltage measurements. The rest of the treadmill isn't needed - not initially, anyway, so if you can get AC mains onto the mains input connectors on the board, you can test it stand-alone. You need to be extremely careful doing this, to make sure the board can't move or fall off the table and short out on anything or make contact with anyone, and that the mains connections can't become disconnected and touch onto anything or anyone.

The main reason here is to avoid back-and-forth and disturbing your father-in-law. I know it would be easier if you could do your work by yourself.

 

[loungedebaldy]

Yes, thanks for that advice. I have a few wood screw clamps that would work well, are insulated and gentle enough to hold the board without damage and can clamp them or it down with another. Should be secure. I have a GFI but wonder about grounding the board. Does the board have to be grounded? Will the GFI work without ground and if not how do I set this up. Thanks much.

 

[KrisBlueNZ]

That sounds good. Yes, definitely use the GFI. Don't ground anything on the board! Use a battery-powered multimeter! Yes, the GFI will work without a ground connection.

 

[loungedebaldy]

OK, I'M Back. I have to figure how to send these html pics so please bear with me.

 

[loungedebaldy]

Let's try this.

 

[loungedebaldy]

OK, I will try this. Note, I took some of the goop off the board so we could see better.

http://imgur.com/IxLTwfL
http://imgur.com/wGF7ZOD
http://imgur.com/r02KrS6
http://imgur.com/DEHmESj

http://imgur.com/cEfpQyt
http://imgur.com/K9hUELX
http://imgur.comK9hUELX

 

[loungedebaldy]

Here is a few more. Hope this works for you.

http://imgur.com/5SnwmmE
http://imgur.com/K3w7KzE
http://imgur.com/LTVysXd
http://imgur.com/BkSXhlY

 

[KrisBlueNZ]

OK, that's good.

The fourth image in post #26 doesn't work. (Also, the fifth and sixth images are the same.)

Can you please post the markings on the two black plastic devices (three-terminal regulators, I think they are) marked A and B in this photo.

Also, can you please take a close-up, in-focus picture of the track side of the daughter board, including all of the connector that connects it to the main board, and several pictures of the component side of the daughter board from a few different angles.

The best lighting is outdoors on a bright but overcast day. Avoid direct sunlight.

Thanks!

 

[loungedebaldy]

The numbers on the transistors that you asked for are A=ST(manf)L78L12 GE 752
B=CJ 78L05 011
I tested the diode and it was 367 and 0
Here are a few more pics for you.
http://imgur.com/YpbKP7C

http://imgur.com/VoSDhET
http://imgur.com/okmxVWz
http://imgur.com/JfiMgK7

*** Moderator's comment: the right way to include a URL in your post is to put a (URL) tag (with square brackets instead of parentheses), then the URL without double-quotes, then a (/URL) tag (again with square brackets instead of parentheses).
If the URL starts with http colon slash slash, the forum software will automatically detect it anyway; you don't need the (URL) and (/URL) tags around it.
-- KrisBlueNZ

 

[loungedebaldy]

One more pic that was missed the other night. Also please check #4 in #26. It should be a good one for tracing the runs in the circuits.
http://imgur.com/SKa6BPd

 

[KrisBlueNZ]

The second link in post #29 gives a "file not found" error.

Thanks for those pics. Now I need you to measure the two supply voltage rails that feed into the daughter board. You'll have to apply mains power to the main board. Use your GFI!

EDIT 2013-12-14: THE ABOVE DIAGRAM HAS +12V AND +5V EXCHANGED.

With the main board held firmly, can you please measure two DC voltages with your multimeter.

1. Negative probe to "0V", positive probe to "+12V". Should measure around 12V (duh!)
2. Negative probe to "0V", positive probe to "+5V".

These measurement points ARE half-live. You must use a battery-powered multimeter. Do not touch ANYTHING on EITHER of the boards!

 

[loungedebaldy]

Yes, I did get those measurements and hopefully I did everything right. It measured 1.46 where you have the 12 and 11.98 where you have the 5 marked on the board above.
I hope the pics are clear enough. I have trouble getting an in focus shot with this camera. No manual focus and on close ups the focus doesn't know what to do. I did try a few shots outside yesterday but at -30C it didn't take long to go back inside. lol

 

[KrisBlueNZ]

Ah yep, you're right. I had the +12V and +5V points backwards.

So there's 12V there, but the 5V rail is only 1.46V.

This means that either there's something wrong with the 78L05 regulator (that looks like a transistor) on the main board, or something is loading down the 5V rail. That something is most likely to be on the daughter board.

A good test would be to disconnect the +5V pin from the daughter board and measure the regulator output. You'll need to do this on the underside of the main board.

Desolder the +5V pin on the daughter board. This is the second from the end pin, the one that's marked +12V on the picture in post #31. The best way is to use a solder sucker (http://www.radioshack.com/product/index.jsp?productId=17241906) or perhaps a solder blower (http://www.radioshack.com/product/index.jsp?productId=2062742) to remove the solder around the pin on the underside of the main board.

Edit: I mean desolder the pin that comes from the daughter board, where it is soldered onto the main board.

You could try to disconnect the pin on the daughter board, but it's a double-sided board (copper on both sides) and will have through-plated holes (the holes have a little cylinder of metal inside them) which will probably make it harder.

When you've separated the pin from the pad, grab the end of it with pliers and jiggle it round in a circle to push away any solder fragments, and centre the pin in the hole.

With the board firmly clamped upside down, and the multimeter set to DC volts, apply mains, and extremely carefully, touch the negative test lead onto the third pin (that connects through to the one marked "0V" on the daughter board), and measure voltage on the pad that surrounds the disconnected pin.

As a check that you've disconnected the pin properly, measure the voltage on the pin end that's poking through the hole; if the pin is properly disconnected, it will be 0V or nearly.

Let me know what voltage you measured on the pad.

If it's roughly 5V, the regulator is probably OK and the fault is probably somewhere on the daughter board. If not, the regulator is almost certainly faulty.

 

[loungedebaldy]

Kris. Thanks for the de soldering hints. I don't have either a blower or a sucker but used a portable air tank from the shop and got the solder out that way. I will have to pick something up in the future.
Ok. I did this test a number of times. The first number of times I got the same readings all the time. From third pin OV to unsoldered pin was 5.47. From unsoldered pin to its unsoldered pad was 5.47 and from OV to unsoldered pad was 0.
Now I read your instructions again and went back and wiggled the unsoldered pin again and centered it again the readings were different but stayed consistent. They were 0 on all the tests as above. I tested from OV to where I got 11.98 before and got 10.8 instead. I will test again and see if something changes and will post if any.

 

[KrisBlueNZ]

I think you may have made a mistake.

The pin you need to desolder is the second from the end. You need to desolder it on the main board, and make sure the metal pin from the daughter board is not making contact with the surrounding pad on the main board.

The third pin is 0V ("zero volts"). Connect your negative multimeter lead to this pin for the voltage measurements.

With the second pin unsoldered at the main board, and the main board powered up, you should measure:

1. The fourth pin - should measure about 12V.
2. The second pin - measured at the metal pin from the daughter board, not the surrounding pad on the main board - should measure close to 0V
3. The second pin - measured at the surrounding pad on the main board, not the metal pin from the daughter board - this is the voltage I'm interested in.

 

[loungedebaldy]

Sorry, I put way too much info in my last post. It is good to keep tabs on me because I am learning and subject to making mistakes.
Ok, having said that I checked and do have the 2nd pin desoldered and have just taken the measurements again. The reading you are asking for is 0.

 

[KrisBlueNZ]

That doesn't make sense either. When you desolder pin 2 of the daughter board connector from the pad on the main board, you are removing the load on the 78L05 regulator. The surrounding pad on the main board is powered from that regulator. So I would expect one of two possibilities.

1. Around 5V on the pad - this would mean that the regulator is probably OK and that the daughter board was dragging the voltage down, and there is probably a fault on the daughter board, or

2. Significantly less than 5V - for example, the 1.46V that you measured on that pin in post #32. That would indicate that even with the daughter board disconnected, the 78L05 regulator is only putting out 1.46V, so it is probably faulty.

I would not expect to see 0V on the pad surrounding pin 2 from the daughter board.

Can you measure again.

1. Check that pin 2 from the daughter board is desoldered from the surrounding pad on the main board.
2. Grab pin 2 from the daughter board and wiggle it round, to make sure there is no connection to the surrounding pad. Centre it in the hole.
3. With the main board upside down, mount it so it cannot move.
4. Apply AC mains supply to the main board.
5. Measure DC voltage, with negative lead to pin 3 (0V) and positive lead to pin 4. This should be around 12V. Is it correct?
6. Measure DC voltage, with negative lead to pin 3 (0V) and positive lead touching pin 2 from the daughter board (touch the end that is poking through the main board but is not soldered to the pad). Should be close to 0V. Is it correct?
7. Measure DC voltage, with negative lead to pin 3 (0V) and positive lead touching the pad on the main board that surrounds pin 2 from the daughter board. Don't touch the probe to the pin; just touch the surrounding pad. What is the voltage?

 

[loungedebaldy]

OK, I have re-wiggled the ds(desoldered) and taken some dc voltage tests. I know you are going to wonder but here goes.
Note: It is the 2nd pin from the end that is ds.
4th pin to ds pin reads about 5.2
4th pin to ds pad reads 10.85
4th pin to 3rd pin reads 10.85
3rd pin to ds pin reads 5.47
3rd pin to ds pad reads 0 This is the one that you wanted
ds pin to ds pad reads 0
Hope this helps

 

[KrisBlueNZ]

I'm only interested in DC voltage measurements taken with the negative (black) multimeter lead on pad 3. These pads are counted starting from the end closest to the corner with the three connectors (for the display board and the signals from the motor assemblies).

3rd pin to ds pin reads 5.47
3rd pin to ds pad reads 0 This is the one that you wanted

That sounds exactly backwards. Have you desoldered the pin from the pad on the daughter board? That would explain it. I asked you to desolder the pin from its pad on the main board, because that should be easier, but if you've desoldered it from its pad on the daughter board, that's OK. Just confirm that that's what you did.

ds pin to ds pad reads 0

That doesn't make sense at all, but if the other numbers are right and you've desoldered pin 2 from its pad on the daughter board, then that's OK. In that case, there is probably a fault on the daughter board and it's loading down the 5V rail.

In that case, I really need a better view of the component side of the daughter board. Do you think you can remove it? The best way would be to desolder all the pins where they connect to pads on the main board. If you can do that, can you take photos of the component side of the daughter board, looking directly down on it, and with the camera angled slightly towards the pins, and slightly in the other direction.

I think the most likely fault is the PIC16F684 microcontroller. If that's the case, you're screwed, because the device contains firmware, so you can't just replace it with a new one, and the chances of the manufacturer sending you a new one are roughly zero. But we need to confirm that it's faulty. It's possible the fault is elsewhere.

Edit: You might be able to get a good photo looking straight at the component side of the daughter board without removing it, using a mirror.

 

[loungedebaldy]

Gee! This is turning into a puzzle after all. This pic is just a quickie of the main board showing the pin that I desoldered. Hopefully it is the right one.
I have not been able to duplicate the 1.46v that I posted in 32.
I do get about 5.5v from ds pin to ds pad and also from pin 3 to ds pin.
I get OV from pin 3 to ds pad 2 and also OV if I short out ds pin 2 and ds pad 2 to pin 3. I don`t understand this. Hope you do.
Edit: Forgot to say that I will take that pic of the daughter board and follow your direction., I just wanted to make sure I got the test voltages right and that I have taken them in the right place before I continue. Thanks much.

http://imgur.com/Z7g35oG