Intermittent bread machine controller board

Discussion in 'Electronics Resources' started by steve2004, Jul 23, 2011.

  1. steve2004

    Thread Starter New Member

    Jul 23, 2011
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    :)Hi everybody, I am new to this forum. I've a West Bend bread machine that works perfectly 60% of the time. That is, it make 3 perfect bread/ dough then make 2 bad batches. I'd attached a pic of the said controller board (please see attachment). I've access to a multimeter, logic probe, an oscilloscope and a soldering station. I just don't know where to start probing. Any suggestion is appreciated.
     
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    In your user manual there is a sequence describing how the machine kneads and bakes and how long each step takes. When it does not function properly, what does it not do?
    Also, what exact model do you have? (I guess they have several models, right)
     
  3. steve2004

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    Jul 23, 2011
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    Sorry about that. The machine is a West Bend Homestyle plus bread machine. It is supposed to stop for 32 minutes after a 23 minutes kneading cycle (see attachment under 1 1/2 lb). Like I said previously, 3 times in a row it performed flawlessly, then the 4th and 5th time it won't pause (it just keeps churning and kneading). I'm just scratchinng my head to the question why sometimes it works perfectly and other times it fails?
     
  4. praondevou

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    That's difficult without a schematic. Is there something written on the other side of the PCB to identify it?

    Have a look on the PCB and wiring if there are bad contacts, loose/corroded wires etc.

    If you can provide a PCB number maybe one can find something on the net...
     
  5. steve2004

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    Jul 23, 2011
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    Sorry, there's nothing printed on the other side. I can't find the schematics for it anywhere! Thanks.
     
  6. KJ6EAD

    Senior Member

    Apr 30, 2011
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    That PCB has some condition issues that should be addressed first. There's some solder draw through that indicates a less than stellar solder job. One end of R8 looks like it may be a cold joint or blow hole on the other side. You need to inspect all joints and reflow any suspect ones. Defluxing would make it easier to inspect.

    It would be good to see the solder side of the board. I know it's partially covered by the display.
     
  7. steve2004

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    Jul 23, 2011
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    I took another look at the PCB, the solder joints side had nothing printed on it. The side I photographed had P33-173 rev 6 The West Bend Company JR34 1996 on it (this got chopped off when I took the pic). I plugged these into Google and nothing shows up.
     
  8. praondevou

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    How old is this thing? You said it worked three times ok then it failed 2 times. And after that? Did you stop trying or is it always this sequence 3-ok, 2-bad?

    I'm asking myself for what an equipment like this needs a battery? To continue the program in case of a power interruption maybe? Is this battery ok?
     
  9. KJ6EAD

    Senior Member

    Apr 30, 2011
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    There's no battery. If you're referring to BZ1, it's a vertical mount piezo buzzer. I'll repeat my previous advice. This PCB has some condition issues that should be addressed first. You need to inspect all solder joints and reflow any suspect ones.
     
  10. praondevou

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    Ok thanks for the hint. BZ also makes more sens for BuZzer. :)
     
  11. steve2004

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    Jul 23, 2011
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    This thing is about 15 yr. old. I got it from my parents. They haven't used it for a while. At first it worked everytime. Then it started acting up. 3 times good and 2 times bad. The solder joints looked shiny. I found that a connector is lose on the board. I may have caused it by pulling the connector plug off the board in order to remove the PCB from the machine. I'll epoxy it tight back on the board.
     
  12. steve2004

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    Jul 23, 2011
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    This thing is about 15 yr. old. I got it from my parents. They haven't used it for a while. at first it worked everytime, then it acted up. good-bad cycles are cyclical. The solder joints looked shiny. There's no sign of burnt resistor, cap, diode etc. Sometimes when it acts up the motor keeps turning for an hr. or more (non-stop). Other times it totally stops, and goes back to the beginning. If I hit start, it'll start the kneading cycle again. Most of the time it works perfectly and finish with a baked loaf of bread. Go figure!
     
  13. KJ6EAD

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    It would be really helpful to see the solder side of the PCB.
     
  14. steve2004

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    Jul 23, 2011
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    This thing is about 15 yr. old. I got it from my parents. They haven't used it for a while. At first it worked every time. Then it acted up doing 3 good 2 bad cycles in a cyclical fashion (duh!). The solder joints looked shiny. All the resistors, caps, diodes etc. doesn't look burn. By pulling the connectors wires off and putting it back; one of the connector came lose from the board. I'd since epoxyed it back and the tracing repaired (running a jumper). All said and done it still behaves the same 3 and 2 cycles.
     
  15. BMorse

    Senior Member

    Sep 26, 2009
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    The TMP47C222N is a 4 Bit CMOS Microcontroller (Big chip on bottom of picture).... if this "issue" you are having can be duplicated every time you use the appliance, this could be an indication of corrupt data in the uC..... if this problem is repeatable, (i.e. it always does 3 good and next 2 are bad..) then corrupt data in the uC is most likely the culprit.....
     
  16. steve2004

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    Jul 23, 2011
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    How do I go about verifying that this CMOS is the culprit? West Bend is of no help in supplying the chip or the controller board! I can't seem to locate this chip (TMP47C222N-JR34) anywhere. Any suggestion is appreciated.
     
    Last edited: Jul 26, 2011
  17. praondevou

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    Jul 9, 2011
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    If corrupt data in the program memory is the problem, then either you find the same machine somewhere (maybe on ebay?) swap the chip or the board and hope it works.
    I didn't read the whole datasheet but I guess it's an OTP (one time programable), so if the data is corrupt then there is no way of repairing it.
    Even if it was a flash memory you wouldn't know where to get the data to repair it.

    If it's really always the same sequence then BMorse is right. To verify that you'd have to draw the circuits diagram, find out what pins of the uC controls what and then see if the uC gives always the "right" commands or not.

    Is this the only board in your machine?
     
  18. steve2004

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    Jul 23, 2011
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    Yes, that's the only board on the machine. I couldn't find the same model on eBay. The TMP47c222 does have some rom space on it. The JR34 probably has some proprietary data for the bread macnine. I do have an eprom programmer that can fit a 40 pin eprom, but not the 42 pin TMP47C222. It seems to me the data probably repeats 5 times. The first 3 times no error, then the last 2 times have errors. If that's the case I can find where the first bit of data starts and ends and copy the correct 1x data to the start of the 4th and 5th cycle. Its always easy on paper, lol. Now I've to modify my eprom reader/writer to fit the 42 pin chip and see if I can read it.
     
  19. praondevou

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    Sorry I couldn't be of more help. Good luck with the memory reading. If I were you I would check first if this memory can be rewritten or if it's OTP...
     
    steve2004 likes this.
  20. Markd77

    Senior Member

    Sep 7, 2009
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    If you unplug it after the third cycle will it still do 2 bad cycles or is the sequence reset? Worth a try.
     
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