Switching Power Supply 24VDC 4.5ADC

Discussion in 'General Electronics Chat' started by minit, Apr 8, 2008.

  1. minit

    Thread Starter New Member

    Apr 8, 2008
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    Hi,
    If you can recognize this image, I need some info about it maybe the diagram and some voltages.
    You can observe here a Switching Power Supply 24VDC 4.5ADC with the model number 29201283 Rev-B B1 made in Taiwan ROC in '95.
    You can also observe the main IC, a hybrid one from Sanken the STR81145.
    Other main parts are two IRF840 and one double diode FEP16DT at the output, a SCR FOR3G and another hybrid this time mounted on a ceramic board SMT model,all painted in black with the inscription: PHCO2.
    The main voltage is 120VAC with a fast fuse protection of 4Amps.
    If you think you need some more information, please feel free to contact me. Thank you in advance.
     
  2. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    I highly doubt that anyone here will have that sort of information. Is there a particular reason that you wish to know the exact workings of the unit?

    Steve
     
  3. minit

    Thread Starter New Member

    Apr 8, 2008
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    I have a bunch of units like this not supported anymore by the manufacturer, so the only choice is to try to repair them.
    Thank you.

     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Power in on the left, out on the right - but you probably figured that one out already. Looks to me like those two big electrolytic caps in the middle are convex (bulging out), which is not a good sign. Due to their age, replacing ALL of the electrolytic caps would be a prudent first step (if you really need to save them). Several Asian electrolytic cap manufacturers used an electrolyte solution that was much too concentrated (to boost the cap's ratings) but which quickly ate them up due to corrosion. I won't name them here; do a search on Google if you want to find out more.

    Replacing all of the electrolytic caps can get mighty expensive. Unless there is a ready market for them, I would scrap them.

    Do any of them work per mfg's specs? If so, take some readings from them and compare to those which aren't working.
     
  5. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,157
    The datasheet for the STK 81145 is still available. I'm sure there will be data sheets on all the active devices you find.

    Is there any markings on the chassis, indicating a model number or something?
     
  6. minit

    Thread Starter New Member

    Apr 8, 2008
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    Interesting point of view. I have already desoldered all the parts on the board with one exception :the ceramic board SMT model,all painted in black with the inscription: PHCO2.
    I have measured all the parts with the exception of the STR 41185 who I know is a IC who double the voltage so after it I can measure 310 volts DC. The information you have provided lead me to verify again the two 330microFarad capacitors and also the others.
    If something is going to be wrong I'm going to inform you with the result.
    Thank you.

     
  7. minit

    Thread Starter New Member

    Apr 8, 2008
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    I already have the diagram for STR 41185. It is a IC who double the voltage so after it I can measure 310 volts DC.
    It will be some problems with the two IRF 840 in the chopper module on the middle of the board, because after measuring they are i good condition. I have also measured all the transformers and filter coils and they are fine.
    I have already desoldered all the parts on the board with one exception :the ceramic board SMT model,all painted in black with the inscription: PHCO2.
    For this, the only method I know is to measure the voltages and comparing with a good board.
    The model number is 29201283 Rev-B B1 made in Taiwan ROC in '95.
    Thank you.


     
  8. SgtWookie

    Expert

    Jul 17, 2007
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  9. minit

    Thread Starter New Member

    Apr 8, 2008
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    Very interesting, I have already registered the site, and I'm going to work until I will repair at least 5 of the modules.
    I'm going to announce you all with any news.
    Thank you.

     
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