Sub COMPOUND TRANSISTOR with NPN.

[capwizard]

I have A redo on LC-26DV24U, after had changed Q413, original problem is white screen, now indeed needs to change Q419, is A COMPOUND TRANSISTOR, I used npn Tr (2sc1399 found it on junk PCB near by me) + two 2.7k (should be 10k) resistors , finished the redo. ..........

Reference:
Thanks to nuala "REPLACED Q419 (NTE2414) & Q413 (2SA1020) ALONG WITH R418 100 ohm"
https://www.badcaps.net/forum/showthread.php?t=31316 #6
Q419 is A COMPOUND TRANSISTOR

Can someone ID this Transistor ? Offer Equivalent part ?
https://www.electronicspoint.com/thr...t-part.274343/
Its from a SHARP TV LED. Model: LC-26DV24U. Specfically its Q419 on the Power board. Thanks in Advance.

NTE2414
https://cdn.badcaps-static.com/pdfs/...f2755dd7e9.pdf

KRC101S~KRC106S

[petehall347]

Re: Sub COMPOUND TRANSISTOR with NPN.

Krc102srtk
TNAAB05003

manual here ...

[Longbow]

Re: Sub COMPOUND TRANSISTOR with NPN.

I think you guys have to stock a few of these parts. I call them digital transistors, but what's in a name? They are switches, designed to accept logic voltage as input. Thus with an NPN style, emitter on ground, the logic high on the base would be +5. You can't "make" one using an analog style transistor with resistors. It has to be a switch. Otherwise the home-made substitute will get hot and fail again.

[capwizard]

Re: Sub COMPOUND TRANSISTOR with NPN.

For experiment, I put only NPN Tr with no resistor TV works, I put resistors is for better characteristics, this Tr is for switching 12v panel voltage.
To stock compound Trs or digital transistors is not easy, so many types of variation are there, Seems Panasonic, Sharp and Sony love to use those parts?

This Sharp LC-26DV24U which I almost let go, will update if redo again!!

[stj]

Re: Sub COMPOUND TRANSISTOR with NPN.

they are called "digital transistors" or "pre-biased transistors"
and they arent hard to get.

[budm]

Re: Sub COMPOUND TRANSISTOR with NPN.

Digital Transistor

[capwizard]

Re: Sub COMPOUND TRANSISTOR with NPN.

Thanks for the information, pic1 circuit is as same as Sharp LC-26DV24U TV's Q419 ( COMPOUND TRANSISTOR, driver for another PNP switch Tr Q413).

[capwizard]

Re: Sub COMPOUND TRANSISTOR with NPN.

One question is why Q413 after 10 years and failed? aging transistor decline??

Transistor aging:
http://spectrum.ieee.org/semiconduct...ansistor-aging

PIC1: the different physical mechanisms of transistor aging. Semiconductor engineers measure those aging effects primarily by examining transistors one at a time, using microscopic electrodes to probe a silicon wafer.

Circuit Aging: A New Phenomenon For SoC
http://electronicdesign.com/products...on-soc-designs

[budm]

Re: Sub COMPOUND TRANSISTOR with NPN.

How much current and inrush current does the T-CON board require?
Same failure also happen in the 32"version.
10 Years is not that bad if the part is used at max spec.

[capwizard]

Re: Sub COMPOUND TRANSISTOR with NPN.

Semiconductor is better than vacuum tube, and never get aging! So I am wrong and I always believe that old semiconductors is good as new one!!..............

[Longbow]

Re: Sub COMPOUND TRANSISTOR with NPN.

Digital transistors fail for the same reason that any other type of transistor will fail - heat and overvoltage/overcurrent. Certain transistor types are especially made to operate as switches instead of amplifiers. The object is to minimize the transition time between off and on. In other words, you do not want the transistor to linger in the linear region (I know, some academics refer to this state as "saturated" but they are incorrect). If the transistor is operating in linear mode, even for a short time, it is a resistor and will dissipate heat in the form of I2R loss, where R is some number other than ZERO or INFINITY. I forget if digital transistsors are available in various current capacities. But if there is a known failure in many TV's, I would certainly look into installing a larger one if available. That way, you won't have to fix the TV again in a couple of years.

[capwizard]

Re: Sub COMPOUND TRANSISTOR with NPN.

Thank you to Longbow: It is never too late to learn: a resistor and will dissipate heat with P = I 2 · R (is some number other than ZERO or INFINITY)/