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Parker Probe Handheld Magnetic Particle Yokes Repaired

By on January 23, 2015









A customer brought this piece of equipment… This is called an AC/DC Magnetic particle Yoke. The purpose of this equipment is to test welding joint for cracks and fractures in the industry. The complaint was that they plug it into an onsite generator and it started to smoke. The below picture is the equipment… it is made by Parker Probe. Here is a link to the probe.

parker probe repair

There are 5 screw and nuts to be remove before you can open the probe.


Inside there is only one circuit board with a large heat sink.

 parker probe repairs

From the picture below you can see burnt marks on the board

parker probe repairing

On the other side you can see the damage component. It is burnt beyond recognition.

 parker probe repairings

Luckily I have another Yoke just like and I was able to get the part No. This was a Triac part No. MAC224A8 which is a 40 amp, 200 thru 800 Volt.  I replace the damage component and check the other components and found the SCR on the other was also blown Part No. 2N2508


Some of the circuit trace was damage and I had to make new trace using wire. I forgot to take a shot of the trace.


After I replaced the bad components the equipment came back to life. I tested the AC side and then the DC side and it work perfectly. Mission accomplish.

I am lifting a 14” Pipe wrench with the switch is on the AC side and then DC side:


This article was prepared for you by Andre Gopee from Calitech Limited Trinidad West Indies.

Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.

By the way if you have any good repair article that you want me to publish in this blog please do contact me HERE.




  1. Waleed Rishmawi

    January 23, 2015 at 9:55 am

    a job well done. good thing you have a machine just like it other wise, it will be put in the trash. keep up the good work

    • Andre Gopee

      January 23, 2015 at 9:07 pm

      Thanks Waleed.

  2. Gerald

    January 23, 2015 at 10:29 am

    Hello Andre,

    Very interesting, thanks for sharing. I never heard about this instrument before so I did some research and found an interesting link:

    I put it here for the ones like me who never came across this technology. We learn every day and the Internet is such a great tool.


    • Jestine Yong

      January 23, 2015 at 11:40 am

      Hi Gerald,

      In fact this is also my first time seeing such instrument. Thanks for the link and yes we learn every day.


      • M.Jais

        October 27, 2017 at 11:04 pm

        This equipment part of inspection... Non Destructive check any crack on surface and subsurface (+- 3mm) weldment of welding. I working as NDT tech 20 years ago...

    • Andre Gopee

      January 23, 2015 at 9:08 pm

      Thanks Gerald... I also put a link at the top for those who do not know this equipment.

  3. Yogesh Panchal

    January 23, 2015 at 1:14 pm

    Thanks for sharing your experience.

    • Andre Gopee

      January 23, 2015 at 9:09 pm

      Your Welcome.

  4. Mark

    January 23, 2015 at 3:54 pm

    Hey Andre,

    Thanks for your article. It's good news that you had another probe. Unless you had a schematic, it would have been a guessing game with that triac!

    • Andre Gopee

      January 23, 2015 at 9:11 pm

      Thanks Mark... Yes it was a good thing that I had... I made a Schematic drawing of the equipment so next time I will know what to look for.

  5. Krishna

    January 23, 2015 at 8:37 pm

    Good job Andre, I also work with contractors using these Instrument and always wonder how they work and what the circuitry looks like.

  6. Humberto

    January 24, 2015 at 12:40 am

    Hi Andre Gopee, I really confess it's an interesting repair.

  7. Merlin Marquardt

    January 24, 2015 at 12:46 am


  8. Robert Calk

    January 24, 2015 at 3:25 pm

    Good job Andre. Thanks for the article.

  9. Dominic

    January 24, 2015 at 8:26 pm

    Hi there. I think this instrument does the same thing as 'Magnafluxing' which is used a lot in certain industries to check for cracks in metal.I used to work for an airline company once & I know they used it there to check for cracks in metal parts of airplane.The Triac in the yoke probably reduces the amount of AC current which is then converted to DC to make the yoke magnetic.(AC cannot magnetize-it can only De-magnetize).

  10. mullugeta h/mariam

    January 25, 2015 at 3:55 pm

    mr.jestin,it is my first time to visit your website.but I have got much more lesson.I will be your follower for the next comming days,weeks,months,years... thank you!

    • Jestine Yong

      January 26, 2015 at 9:30 am

      HI Mullugeta,

      Thanks for the support!


  11. Tito

    January 26, 2015 at 9:32 pm

    Hie Andre,it's my first time to see such an instrument. Thanks for sharing.

  12. peter

    February 10, 2015 at 5:41 am

    Competent repair by a confident repairer.
    Yes having a duplicate certainly helped ID the faulty component.
    I wonder if the maker was contactable & if they would have provided a schematic or other info to help with the repair?
    Perhaps this should have been investigated so that the successful repair was not dependent on good luck (having a duplicate handy)
    Thanks & well done!

  13. samad

    May 24, 2018 at 6:01 pm

    tanks for comment
    my board is full damage .do you have compelet picture for this board?


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