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Thread: PCB Repair

  1. #1
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    Default PCB Repair

    Hi All.
    Would any members know of a electronics repair guy on the Northside of Brisbane who could repair Pcb out of a full body Vibe machine, backyarder or business i'm not fussy.
    It's blowning fuses and shows a smoke track from either the transformer or the biggest cap, should be a straight forward repair it has the same sort of running gear as a treadmill.
    I have tried an electrician and a computer tech in my street but it's beyond them both.

    Thanks
    Whitey

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  3. #2
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    I could probably do it, but I would need to take a look. Can you post a pic before I commit? If its easy I will do it, if its going to take me hours of fault finding forget it. I am just over the big bridge from you.

  4. #3
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    Quote Originally Posted by Pearo View Post
    I could probably do it, but I would need to take a look. Can you post a pic before I commit? If its easy I will do it, if its going to take me hours of fault finding forget it. I am just over the big bridge from you.
    Hi Pearo, Here are the photo's i cannot see any physical damage apart from the smoke track from the corner of the tranny to the biggest cap, it will blow the fuse immediately after the power is switched on.
    The original fuse was a pigtail solder in ceramic type i have piggybacked a wire type fuse for testing.

    The only abuse we have given the machine was to leave the power switched on for a day, it appears have a sleep function on the control screen but i'm not sure what happens at the PCB could still of had power there all day, it did work ok for 2 weeks after that.
    Thanks for any help.
    Attached Images Attached Images

  5. #4
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    Hard to say. Looking at the back I can tell the connection to the green transformer is intact, so if that is what is causing the fuse to blow then its probably a short circuit and a throwaway. I doubt however this is the case.

    The board has 2 separate things happening on that board, the side the green transformer is on has a linear regulator and control circuitry, the the side opposite is a switched mode power supply of some type, and I would hazard a guess that its used to control the speed/operation of a motor and that would be the part that is blowing the fuse. IF I was to take a stab in the dark, 2 likely things:

    a) That yellow capacitor has gone short circuit, this is rare, but given the proximity to the burnt track I would be suspicious and I have seen it before.

    b) the transistor on the heatsink is faulty. This is the most likely scenario, but what causes it is often downstream and that could mean a motor fault.

    You should be able to check both parts for short circuits in situ with a multimeter on the ohms range (would read 0 if part is faulty). If the yellow capacitor is indeed short, you can remove it and see if the fuse still blows. Just be very careful though, that circuit is rectifying the 240v to about 350 volts DC. That cap with the 220VAC sticker on top will hold that charge for some time after you disconnect power.

    I could take a look, but it wont be till next week and I cant give a day at this stage.

  6. #5
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    Thanks for the quick reply Pearo, i checked the yellow cap and it shows .5 ohm, the brown pillow cap next door is 8.13 and the large cap climbs to 200 ohms before the meter goes back to "ol" not sure why but happens on 2 multimeters i have here.

  7. #6
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    Just had a hunt around for the yellow cap, Jaycar have them in stock locally, 250v not 275v like the original though.
    A question about the fuse if you don't mind Pearo, It is a M205 and the original was a 3-15a ceramic i have replaced it with a 3-15a wire type , i cannot see any harm in this what do you think.
    I will PM you next week to see how you are traveling.

  8. #7
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    Quote Originally Posted by whitey56 View Post
    Just had a hunt around for the yellow cap, Jaycar have them in stock locally, 250v not 275v like the original though.
    A question about the fuse if you don't mind Pearo, It is a M205 and the original was a 3-15a ceramic i have replaced it with a 3-15a wire type , i cannot see any harm in this what do you think.
    I will PM you next week to see how you are traveling.
    If its reading 0.5 then there is a good chance the cap is faulty. You will probably find if you touch your meter leads together they will read 0.5, if they do looks like you may have found the problem.


    Ceramic fuses that size usually fail less spectacularly and are typically more rugged, thats about it. Its probably a slow-blow type as well.

    Re. the yellow cap, you have to make sure its an X1 or X2 rated cap, looking at jaycar website it looks like they have a mistake, because as far as I am aware they is only X1, X2 and X3 and they will all be 275V. Altronics at virginia also sell them. X rated caps are designed to take a spike down the mains and are self healing. If you have the technology to remove it you can double check before you buy one. Also, you can power up the board without the cap and if the cap is faulty the fuse should not blow with the cap out of the circuit.

    FWIW, I just ordered a new desoldering machine last week. The old one was no longer viable and was getting too hard to get parts for. Should arrive today hopefully. If you can't get the part out, I can do it next week, probably Tuesday or Wednesday at this stage.

  9. #8
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    Thanks mate, Yellow cap is a x2 if i can get one before the w/e i'll swap it out and let you know the results.

  10. #9
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    If you don't have any luck, PM me. I am in Brisbane.
    Cheers,
    Glenn.

  11. #10
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    Just a update the blue ceramic cap next to the large cyl. type failed, now waiting on a delivery from China as they are not listed anywhere in Oz.
    Hopefully it will be a long term fix.
    Thanks to the forum member who was very helpful with his time to check it over for me, much appreciated mate.

    Whitey

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