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Old 06-01-2013, 07:06 PM   #21
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Default Re: Questions about FETs

Moved from TV/Video sources.

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Old 06-01-2013, 11:47 PM   #22
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Default Re: Questions about FETs

Originally Posted by pk7tanner View Post
Well we had company stay over and I had been using the living room as my work space. That meant everything has been put up, but now that they've left, I'm free to resume my crash course in electronics.
Your previous two posts used acronyms and other terms I'm unfamiliar with, and therefor, don't know how one would test them.
  • SC Board
  • Vce sat
  • peak pulsed current rating
  • case construction (it varies?)

I'm also still confused about the reason why all of the N-channel fet's that I have removed, test OL on all the pin combos. But attached to a board, most measure correctly? It'd be one thing if they all came from one tv, but I'm taking parts from two other tvs and from an extra zsus board. Plus in the LG guide it lists the fet's by the num/letters printed on the front, but some also have a subset that I don't understand? For example fet RF2001 has D301-306, D311 & D312. What do the D___ mean?
They test differently because they're in circuit and have diodes across them generally speaking, no shorts is good. Out of cct you need to switch the gate on with a charge and go back and test the collector/Emitter .

This video helped me

I only started working with IGBTs on sustain boards about 12months ago and I'm pretty sure I threw out a good IGBT thinking it was open cct until Tom pointed out to me they needed to be switched on.

I thought I had already touched on this. "D" locations are diodes, "Q" are transistors, "ZD" zener diodes

The RF2001 you refer to is only a partial number,but what comes after that is important. RF2001 is a ROHM 20A fast recovery diode, the suffix will tell you what voltage and configuration eg single or double diode etc etc
[*]SC Board = Panasonic SC = YSUS, YMAIN, Panasonic SS = XSUS, ZSUS [*]Vce sat- to be honest I take it as the voltage for it to be switched on fully but I'm not too sure. I assume you'd want a value =< what the original was. [*]peak pulsed current rating - short burst current rating usually quoted in microseconds. There's a continuous current rating and pulsed.
From what I've seen so far the IGBTs on the sustain boards have around the 200A pulse rating. [*]case construction (it varies?) the type and size of casing it's housed in. You can get TO-220 as a full plastic case or with a metal backing or tab which is usually connected to the center pin. With the metal backed you'd have to use an insulator if mounting to a metal heatsink so it does not create a short. The full plastic would not need an insulator. the FETs your chasing are plastic but it's possible a sub exists in a metal back in which case an insulator would be needed to use it.

A TO-247 transistor may do the job but it's much larger and the pin positions also may differ and would not fit.

I'm sure someone will explain it all better, best I can do for now.
Attached Files
File Type: pdf rf2001t3d.pdf (201.4 KB, 27 views)
File Type: pdf rf2001t4s.pdf (277.4 KB, 16 views)

Last edited by tw2005; 06-01-2013 at 11:50 PM..
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