Weller WES51 failed

Discussion in 'General Electronics Chat' started by Triden, May 10, 2011.

  1. Triden

    Thread Starter New Member

    May 10, 2011
    8
    0
    I have a Weller WES51 that stopped working in the middle of using it. It will no longer heat the iron, and the LED on the base will not light no matter what temp is selected.

    I followed the service manual and it appeared that the temp sensor in the handle was bad; so a new iron (PES51) was ordered. Plugged in the brand new iron, still will not heat and the LED stays off.

    The service manual says to test the transformer secondary side for 24 VAC +/- 10%. The secondary side measures 28.1 V rms using my Fluke 123. This voltage is outside of the range stated in the service manual. Should I replace the transformer or move on to replacing the PCB? The PCB is the last part the service manual says to replace.

    Anyone else have experience with Weller (or other brands) failures?

    Thanks.
     
  2. #12

    Expert

    Nov 30, 2010
    16,283
    6,795
    No. An unloaded transformer normally measures high by a few volts. Besides, the utility companies keep jacking up the power line voltage, year by year.

    I've never had a Weller fail, unless you count wearing out the tips. That's why I have 3 of them.
     
    Triden likes this.
  3. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
    363
    You could repair the PCB, but you'd need a soldering iron to do that.
     
  4. tom66

    Senior Member

    May 9, 2009
    2,613
    214
    Are there any fuses on the secondary, or on the PCB?
     
  5. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
    363
    Open it up and put up some good pictures.
     
  6. Triden

    Thread Starter New Member

    May 10, 2011
    8
    0
    Excellent, I was hoping I wouldn't have to replace the transformer as well.

    I have one but its a cheap freebie that starts to smoke from the handle after a while.

    No fuses that I can easily see.

    It is already open, I will post some pictures.
     
  7. Triden

    Thread Starter New Member

    May 10, 2011
    8
    0
    [​IMG]

    This is the front of the PCB. The wires at the bottom right go to the iron plug.



    [​IMG]

    Closeup of the front top of the PCB. Shows the MCU. Is there a way to test it?



    [​IMG]

    Closeup of the bottom front of the PCB.



    [​IMG]

    Back of the PCB. The wires on the bottom left go to the transformer secondary.
     
  8. tom66

    Senior Member

    May 9, 2009
    2,613
    214
    The microcontroller is probably fine. But if it is dead, then the program inside is lost, which would mean the iron could not be made to work again unless you replaced the program with one of your own.

    The device marked with LM78L05ACM could be fried; a 5V linear regulator. Can you probe pins #1 and #8 of the MCU and measure from 4.9V to 5.1V?
     
    Geniek6 likes this.
  9. radiohead

    Active Member

    May 28, 2009
    474
    31
    I have a Weller WD1. Readiing the service manual, it tells you how to reset it to factory defaults by pressing buttons in a sequential order. Read your manual and try it that way... or look for a fuse/circuit breaker inside the unit. All commercial electronics that run on AC voltage must have a fuse.
     
    Last edited: May 11, 2011
  10. Triden

    Thread Starter New Member

    May 10, 2011
    8
    0
    0 V measured. So that got me looking and I think I found the problem and possibly learned something new. There is a fuse on the back of the board (see attached image). The fuse measures open, so it must be blown. The markings on it say BUSS 4A 125V.

    I am assuming it is a MCRW4A axial lead fuse. I did not know fuses could have black plastic covers on them.

    Do you see any flaws in my logic?

    Also what could have caused the fuse to blow? A faulty heater element in the iron?

    Thanks.
     
  11. radiohead

    Active Member

    May 28, 2009
    474
    31
    It is a fuse. Over-current causes fuses to blow. Maybe the iron was plugged in with the power switch on, or there was a spike in the line. Replace the fuse and see if it blows. If it doesn't great. If it does, continue troubleshooting.

    MCRW4A Bussmann Subminiature Microtron Fuse
    See link to data sheet.

    http://www.datasheetarchive.com/Indexer/Datasheet-093/DSA0064199.html
     
    Last edited: May 11, 2011
  12. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
    363
  13. Triden

    Thread Starter New Member

    May 10, 2011
    8
    0
    Update: Repair successful. I replaced the fuse and tried to operate the device using the old iron, the fuse blew after a 30-40 seconds. So it looks like you were correct and the old iron has a intermittent short (or something like that).

    I replaced the fuse again and used the new iron--so far so good. I have used it for at least 2 hours now with no issue.

    Thanks to everyone for their help.
     
  14. Geniek6

    New Member

    Yesterday
    1
    0
    I am have the same problem the LM78L05ACM is only showing 2.5 volts at pin1 and 8. Is it bad?
     
  15. WBahn

    Moderator

    Mar 31, 2012
    17,743
    4,792
    Don't be too surprised if no one responds in a 5+ year old thread.
     
  16. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,032
    3,803

    Did you read the UPDATE in Post #13?

     
Loading...