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Damage testing

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giftiger_wunsch

New Member
Hi,

Very simple question: what's a definitive way of testing if I've heat-damaged these components through poor desoldering technique?

I removed 3 inductors from a VCR board and tested the resistance between the leads: showed 0.08Ω for two of them (brown marking on side) and 118.3Ω for the third (orange marking on side). I'm guessing that since it's just a coil of wire that this means they're not damaged; is the coloured marking indicative of its inductance?

I (accidentally :eek:) removed a PNP STS733 transistor (data sheet) from the same VCR board, and tested the impedance between collector-base to be ~4.1MΩ and between emitter-base to be ~3.7MΩ. These seem unusually high to me, and when I tried the same test with a store-bought transistor before, I seem to remember the value fluctuated, whereas it's remaining constant with this one. Have I burned out the transistor?

By the way, in case anyone's wondering how I "accidentally" desoldered a transistor, I was soldering two inductors from nearby and I picked the wrong solder joints; desoldered half of each inductor and 2/3 of the transistor :eek:. The extra time spent trying to clear the specks of solder I thought were still holding the inductors on probably made it even more likely that I damaged the transistor.

Thanks.
 
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Hero999

Banned
It depends on the voltage used by your DVM to test resistors, of it's 500mV then it's hardly surprising it reads about 4M.

Use the diode test, if your meter doesn't have a transistor tester.
 

audioguru

Well-Known Member
Most Helpful Member
It takes only one second for a solder-sucker (the kind with a spring driven piston) to remove solder from a solder joint.
If your soldering iron is temperature-controlled then the components will not get too hot.
 

giftiger_wunsch

New Member
I'm still getting used to it, so it usually takes 4-5 attempts for me to remove the solder completely. I'm using a desoldering pump with a spring driven piston, but as hero told me, my 'temperature-controlled' soldering iron is really just an iron with a dimmer to vary the power.

I'd never noticed the diode tester on my multimeter before :rolleyes:
 
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giftiger_wunsch

New Member
When I use the diode tester, it beeps and gives the value 0.672 (though I've never used the diode tester before so I don't know what the units are or what that indicates). My guess is that's the voltage drop and it's telling me that it's functioning as a diode, but feel free to call me a fool and tell me otherwise :p
 
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Hero999

Banned
Yes you're right, it's indicating the voltage drop and that the diodes work.

Try measuring the open circuit voltage of your meter set to resistance, with another meter and you'll probably find that the test voltage is under 0.6V. This is done deliberately so you can measure resistors which are connected to transistors.
 
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giftiger_wunsch

New Member
The only other meter I have is very inaccurate, it's mainly just meant to be used to check for dangerous voltages. I'll take your word for it that that will be the case.

So according to this check, the transistor wasn't damaged? I feel slightly better knowing that I didn't damage them even though I took longer than I would normally do. I read that the danger of damaging transistors is fairly low unless you're especially slow to solder them, but I figured I would be in that category :D
 
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Hero999

Banned
From what you've said, the transistor is fine.
 

giftiger_wunsch

New Member
I removed some more transistors from the board, but I can't find data sheets for these (other than the two more STS 733s); I've tried searching for the text on the transistors and for combinations of various portions, not knowing what part refers to the part number, but haven't had any success.

One transistor was marked with R2001 C217, and another couple were marked with K 214 C2303 Y. Didn't find any data sheet results using datasheetarchive.com or google.


Also, is there any simple way of testing if an infra-red IC is functional?
 
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Hero999

Banned
Sorry this isn't much help but it's pretty common not to be able to find datasheets for components found inside consumer electronics, especially transistors.

You'll need a 'scope and a remote control to test an IR IC. When the IC receives the IR pulse bursts it should output a stream of pulses which you'll be able to see on an oscilloscope.
 

giftiger_wunsch

New Member
Will any signal from a remote control cause this response? I believe the actual recognition of specific signals would be handled by a microcontroller connected to the IR IC, correct?

I don't have an oscilloscope, would I be able to see some sort of indication of a response with a DMM, or will an oscilloscope be necessary to determine if there is a response at all?


Hero999 said:
Sorry this isn't much help but it's pretty common not to be able to find datasheets for components found inside consumer electronics, especially transistors.
Well, at least I got 3 PNP transistors for which I have a data sheet; and maybe someone else will have an idea on how to find data sheets for the others.
 

Hero999

Banned
You need a 'scope, a DVM might miss the pulses because it's designed for 50/60Hz. You'll get a semi-functional 'scope next weekend.:D

Remote control carrier frequencies vary but the most common is 38kHz so there's a good chance it'll work with most remotes. The control codes may be specific to the device but the remote control IC will be fairly standard.
 
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giftiger_wunsch

New Member
Remote control carrier frequencies vary but the most common is 38kHz so there's a good chance it'll work with most remotes.
I have a good range of remotes to try it with, so I'm sure one will do the trick. I'm going to attempt to build an RS232 IR receiver to use with my media server - having to get up and press buttons on the keyboard everytime to operate MPlayer is getting tedious. MPlayer has integrated LIRC support so all I need is to build a homebrew device which works with LIRC. Most of the schematics involve PICs which complicates matters for me as I've never used them, but I found one which is remarkably simple. I wonder if it'll actually work?
 

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mneary

New Member
One transistor was marked with R2001 C217, and another couple were marked with K 214 C2303 Y. Didn't find any data sheet results using datasheetarchive.com or google.
See if 2SC217 and 2SC2303 make sense in context. It's typical to leave off the "2S". A second method to verify your guess would be a Good Thing. Package type, PNP/NPN, voltage of the circuit, manufacturer, application, etc.
 

giftiger_wunsch

New Member
2SC217 seems to be correct for one of them as it's from a toshiba VCR, and one of the "data sheets" which included this part was a toshiba manual. Unfortunately the best I could find was a table from "The Japanese Transistor Manual", so I don't know if the case-style matches, whether it's NPN or PNP, etc.

Same story for 2SC2303. One of the two available "data sheets" was a table listing manufacturers who use various parts, the other was the japanese transistor manual again.
 
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