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Please help me recognize clamp-meter's cap ratings for replacement

Discussion in 'Repairing Electronics' started by BGAmodz, Sep 18, 2013.

  1. BGAmodz

    BGAmodz Member

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    ac and dc , and this meter also has OHM and diode test modes , if its for protection then it should be a varistor , i wonder why there would be a capacitor between positive input and the motherboard .

    Am really confused about this thing .
     
  2. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    Microwave serving is probably not at a level you should attempt, but here http://www.google.com/url?sa=t&rct=...ogvJnMtdgm-N2wg&bvm=bv.52288139,d.dmg&cad=rja is a service manual for a microwave.

    The real point to remember is that the magnatron is an electron tube with a 3000 VDC supply and a filament supply.
    Most high voltage tests can usually be performed with the oven off and the capacitor discharged. Discharing the capacitor can be a feat in itself, but most have a discharge resistor across the terminals. But what if the resistor is bad? High voltage capacitors have this odd property: When discharged, they don't stay discharged. Some HV caps have to be stored with a keeper ( or short) across their terminals. So, it may take multiple attempts to discharge the cap.
     
  3. BGAmodz

    BGAmodz Member

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    Thanks for the advices , actually the microwave is working fine now , but my meter is hanging , i don't know if that's a varistor or a capacitor , anyways here is some new pictures of it

    [​IMG] [​IMG]
     
  4. dave

    Dave New Member

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  5. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    It would be wise to perform the water test for microwave. I think its outlined in the manual I posted.

    Intermittent operation and poor heating is usually seen prior to magnetron failure. Typically, the magnetron thermal is first affected.
     
  6. BGAmodz

    BGAmodz Member

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    Thanks for the infos about the microwave but no offence lets just skip this and focus on the Clamp meter , i removed the component from the motherboard and i see PTC on the mobo and XP and last 2 numbers 02 on the black component .
     
  7. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    No biggie the microwave.

    PTC usullay means Positive Temperature Coefficient and usually refers to a thermister. This means a thermister whose resistance increases with temperature.

    You still haven't answered
    1. Is the unknown part in series or parallel with the binding jacks?
    1a. Any other easily identifyable components when you trace the input out.

    2. What is the function of the jacks. AC only, AMP, all other functions of the meter besides the clamp on ammeter?

    Here is the manual I found for the CM-600 http://www.google.com/url?sa=t&rct=...nSIx0N7-vOR0dTw&bvm=bv.52434380,d.dmg&cad=rja
    H
    If it's a ZNR, then it usually will be in parallel and the meter will work without it.

    If it's a capacitor, then possibly series, but only if being used for an AC function.

    If a PTC, then probably in series and a resistor would work temporarily, but it might not work for ohms.
     
  8. rumpfy

    rumpfy Active Member

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    Can I weigh in and say that the clamp meter is of a type generally used in power systems work. The google reference suggests the meter is protected to 660 VAC by means of a 'component' connected in parallel with the input terminals.
    My guess is that the 'component' is a Voltage Dependent Resistor and these are commonly used nowadays in all kinds of mains connected equipment.
    The meter is autoranging, so how the protective component is isolated from the measuring leads for ohms values above say 200,000 ohms is not clear.
    However, if the component is a protective device, then the meter should operate with it disconnected.
    Microwave ovens give pulsed power and it is not surprising that an oven would have a supply voltage seriously greater than 600 Volt AND a huge supply current which would destroy the protective component in no time.
    I would check the meter for operation as is,on ohms and volts and take it from there.
     
  9. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    No, they don't give pulsed power (other than on lower power settings - where they cycle ON and OFF on a ten second cycle), and as I've mentioned previously the supply is 3000V (and even higher until the mag fires up) at high current.
     
  10. BGAmodz

    BGAmodz Member

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    Hi guys , i sent the unit for waranty exchange , after more researsh i found out that the writing on the broken component is SYP 12102 "PTC" , any ideas on this ??
     
  11. BGAmodz

    BGAmodz Member

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    And another problem with this kind of tools is that the main processor is covered with a black material , is there a possibility to retrieve any information from that too ??
     
    Last edited: Sep 20, 2013
  12. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    No, it's called 'COB' (Chip On Board).

    However, blowing your meter up by doing something utterly stupid rather invalidates the warranty (as does disassembling it), so it'll be interesting to see if they exchange it OK.
     
  13. fezder

    fezder Well-Known Member

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    Luckily it was the meter that got shocked, not you!. not that shocks would be nice anywhere....but they are nice at correct places. But as i said, good thing it didn't bite you.
    Hopefully you'll get some sort of compensation of broken meter, but as nigel said, well, we'll see :).
     
  14. BGAmodz

    BGAmodz Member

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    I got a new one actually , if you dont believe it ill post pictures :D
     
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  15. BGAmodz

    BGAmodz Member

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    So these chips on board are made on demande for a specific unit , don't they use commercial ones ???
     
  16. fezder

    fezder Well-Known Member

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    wow, you got new, for free? cool, thumps up for ya :)

    as for those COBs (chip-on-board) if i'm not terribly wrong, they use those to ensure that no-one tries to service them, keep their own ''secrects''. There are some stories, which are true, like an example usb-hubs. There is COB, so there's gotta be something inside that black resin? wrong, turns out, some companies just like to put that black resin, just for cheating upon customers.....and please correct me if i'm wrong :).
    And COB's save space too at pcb. Google chip-on-board to see how much is pressed in tiny square :S...
     
    Last edited: Sep 20, 2013
  17. BGAmodz

    BGAmodz Member

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    i agree its usually for keeping the companies secrets .
     
  18. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    No I believe you, you were lucky they didn't check for customer damage to the original one :p
     
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  19. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    They might be commercial, they might be custom chips, they may even be programmable ones - but it's done for cost and size reasons (it's cheaper and smaller), not the suggested 'secretive' reasons. Often a circuit diagram is even included in the instruction manual.
     
  20. BGAmodz

    BGAmodz Member

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    And its damn hard to get service ' not user 'manuals for them
     
  21. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Why would you expect a service manual to be available? - people seem to want cheap products and then want expensive service provided for free on them.

    There's also the added 'problem' that as you aren't an authorised service centre they probably wouldn't supply you a manual (or parts) even if they were available.
     

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