OT: various electronics questions by "newone"

newone · Post by **newone** » Wed Dec 21, 2005 11:50 am

how to know the transistor is npn or pnp

pleasw whith full detail

newone · Post by **newone** » Wed Dec 21, 2005 11:52 am

how to check 400v capacitor whith analog meter is breakdown or not

zaphod7501 · Post by **zaphod7501** » Wed Dec 21, 2005 9:30 pm

newone wrote:how to check 400v capacitor whith analog meter is breakdown or not

Most meter tests will be one-way tests. You can test for a failed part but you can't test for a good part. In other words, if a test says it's bad then it's probably bad. If a test says it's good then you don't know anything.

The voltage of a capacitor is irrelevant for testing purposes and cannot be tested without destroying the part. (exceeding the voltage rating will usually damage the part) The capacitance (uf or microfarads) can be tested with special testers and not with a VOM. You can test for a short (0-100 ohms) and a large power supply filter will show a temporary short which goes away as the filter charges. An analog meter cannot test capacitors unless it has a built-in testing function.

zaphod7501 · Post by **zaphod7501** » Wed Dec 21, 2005 9:51 pm

newone wrote:how to know the transistor is npn or pnp

If the part has markings they might tell you. Axxx or Bxxx are usually PNP (example A701 stands for 2SA701 which stands for a PNP). Cxxx and Dxxx are NPN (D2588 = 2SD2588 which is an NPN). Kxxx are FET's. If you are going to search (Google?) for a number, you need to include the '2S' prefix which is not actually on the part but is part of the type number.

If you know the leads (base, collector, emitter) then you can figure out the type by measuring accross the base - emitter junction. positive on base and negative on emitter will conduct slightly (x100 range) with an NPN but not a PNP.

There is a more complicated series of meter tests for transistors but I'd have to dig back through years of old literature. This should get you started

newone · Post by **newone** » Wed Dec 21, 2005 11:50 pm

how to check the regulator ic is short or open or lekage

THE IS INFORMATION IS

LM317T
CC01P VW
MAR 507

THE IC IS IN MOST DIGITAL RECIEVERSE

PLEASE TELL ME WHERE TO PUT RED AND BLACK PROBES OF METER IN IC TO CHECK VOLTAGE IAM NEW IN THIS FIELD

underquark · Post by **underquark** » Thu Dec 22, 2005 5:58 am

newone wrote:how to know the transistor is npn or pnp

Click on the pictures for further info.:

zaphod7501 · Post by **zaphod7501** » Thu Dec 22, 2005 8:21 am

newone wrote:how to check the regulator ic is short LM317T

Well, since I responded before, I will do it one more time; but:
You need to find a basic electronics forum or read some library books.
If you are trying to fix something JP1 related, then someone might be better able to help.
If you had done a basic Google search, you would have found that a LM317 is a variable regulator and a simple test will not tell you anything. You need technical info on the product that you are trying to fix.

Basic diagnosis: troubleshoot the product not the individual parts.

newone · Post by **newone** » Thu Dec 22, 2005 10:38 am

how to know the transistor is fet and how to check it whith analog or digital meter

the transistor is short or damaged. and what is the best procedure to check it powerup or poweroff

newone · Post by **newone** » Thu Dec 22, 2005 5:55 pm

how to know the zenor diode how much watt and how much voltage

zaphod7501 · Post by **zaphod7501** » Thu Dec 22, 2005 6:53 pm

newone wrote:how to know the transistor is fet and how to check it whith analog or digital meter

the transistor is short or damaged. and what is the best procedure to check it powerup or poweroff

Here ( http://www.eio.com/repairfaq/REPAIR/F_semitest.html ) is a discussion of meter testing of semiconductors. About half way down the page it gets into simple testing methods.

newone · Post by **newone** » Fri Dec 23, 2005 6:00 pm

the best procedure to check ultra fast diode by analogmeter

what is the best procedure?

how to know whith analog meter the diode is short or leckage

newone · Post by **newone** » Fri Jan 20, 2006 2:46 am

400 volt capacitor how to know its leckage or damaged

one day my own digital satellite reciver not working

itry but not fix

i went to technican and he only change the 400 volt capacitor

my capacitor was like new one

my question is how to know its leckage

i have analog and digital meter

which is best for capacitor

zaphod7501 · Post by **zaphod7501** » Fri Jan 20, 2006 7:26 am

First of all, the voltage of a capacitor is not very important, the capacitance value is. (like 4.7 uf or 3300pf or 332j, etc) The voltage just has to be higher than any voltage present in the circuit. Many digital meters have a capacitor checking feature but usually only low values. (2.2uf but not 1000uf; uf = microfarads)

Capacitor checking is usually done with an oscilloscope, in circuit, by viewing the signals present on it, and determining if it is doing it's job correctly. Most likely the tech replaced it based upon past history or manufacturers reccomendation, not by testing it.

newone · Post by **newone** » Fri Apr 21, 2006 6:28 pm

What is replace of this diode here 208

electronics_field · Post by **electronics_field** » Fri Oct 06, 2006 9:35 pm

HOW TO KNOW THE RESISTOR IS SHORT

BY ANALOG METER

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