Author Topic: Help with SMPS  (Read 495 times)

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Offline SashPlaneTopic starter

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Help with SMPS
« on: November 21, 2024, 06:12:20 pm »
Hello,

I'm looking for help with  what  TR5 and TR6 are doing. I'm not quite sure as what they do ??  The Problem is TR5  BF  487  has gone Obsolete and we can no longer get. 
I tried a MPSA44 but it does not work like the BF487.  When you use the MPSA44 , R41 Gets Supper Dupper HOT(Technical Term)  SMPS  works but  TR5 HOT
the BF487 had a gain of Aprox 50 ish  , the MPSA  gain of 1

Input voltage is  90 - 260 vac  ,   outputs: 5v and 12v

Thanks for any help :)

2442781-0

 

Offline Slh

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Re: Help with SMPS
« Reply #1 on: November 21, 2024, 06:24:34 pm »
Tr5 and tr6 are making a linear regulator to supply the controller IC. You should be able to substitute anything with similar voltage and power rating and gains. The current won't be very high.

 

Offline xavier60

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Re: Help with SMPS
« Reply #2 on: November 22, 2024, 06:24:52 am »
For an undamaged MPSA44 to have a current gain of 1, is likely due to E and C being swapped.
HP 54645A dso, Fluke 87V dmm,  Agilent U8002A psu,  FY6600 function gen,  Brymen BM857S, HAKKO FM-204, New! HAKKO FX-971.
 
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Offline SashPlaneTopic starter

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Re: Help with SMPS
« Reply #3 on: November 22, 2024, 12:01:31 pm »
OH Man......   you nailed it   |O
Now I feel like a Co-op again....lol

Thanks a bunch :)   :-+

2443429-0
 

Offline Harry_22

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Re: Help with SMPS
« Reply #4 on: November 24, 2024, 02:09:49 am »
Hi!
Let me be curious: who drew such a proper diagram with common bus wiring?
 

Offline SashPlaneTopic starter

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Re: Help with SMPS
« Reply #5 on: November 24, 2024, 02:57:30 am »
this drawing was done long before I took over this...
the original was Hand drawn on vellum and then later converted to PDF.
I still even have the Vellum PWB @ 4x F Size Artwork layout... of course i also have it converted to Gerber now also.
Tape layout with stick-on pads -  Good ole days of layout
 
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Offline Harry_22

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Re: Help with SMPS
« Reply #6 on: November 24, 2024, 04:45:33 am »
I have not yet seen that the current sense resistor at MOSFET source being bypassed by a capacitor.
Is it possible to obtain traces from the current sense resistor at maximum load with C28 capacitor and without it?

PS
Do you have any transformer data? Dimensions, core material, air gap?
« Last Edit: November 24, 2024, 01:14:20 pm by Harry_22 »
 


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