over the course of working on my computer a transistor (at least that's what i think it is) came loose from my graphics card. unfortunately the transistor is no longer viable but fortunately the break was clean. i think given that i can find a replacement transistor i am relatively sure that this can be soldered back on. my question is who has tried this before and how effective is it. and secondly where can i find the a replacement transistor.

my graphics card is an ati 8500dv 64 meg while the only information on the transistor itself appears to be:

470
AFK
1QN

written on the top.

thanks for the input

I just got a sound card two days ago with five diodes loose in the box! Due to a dull color it was possible to determine exactly where they belonged. Next, these where two leads with a black mark on one side Thus determining the current flow through the diode as it can only go one way. Thankfully on the curcuit board there was a little white marking located near each location indicating direction of current. All five diodes were marked identiclally with #168 on them, therefore it didn't matter which went where. Due to my eyesight, I had to hold the curcuit board in my teeth and solder with one hand and hold the diode with the other. On second test after one resolder it works perfect. Now if they have three or more leads they are transistors or on up to multi IC chips. Two legs are diodes or resistors often they are one but doing the job as the other ie diodes have resistance. Do the leads come off same end/side or opposite. Plastic or metal, color of stripes, etc determine interchangability. I have thousands but that ain't even close to whats out there. Last month I rebuilt a fractured motherboard that had twelve broken tiny very close foil runners. By soldering telephone stranded(not solid)wire to the runners lands. 24 intricate solder jobs later and it's the computer I'm on at this moment. I have one only ATI Mach 64 graphics card and it has no transistors, just diodes and many resistors and six IC chips. I'll try to break down that manufacturer's coding. Like I said, I've got thousands in stock and supply catalogs galore. On these a picture is worth a million words. really need to know color, and legs.

Crunch

Due to my eyesight, I had to hold the curcuit board in my teeth and solder with one hand and hold the diode with the other.

You are the king in solder.I don't need a picture but, I will always have one.

Thanks for the moment crunch.LOL

Was that just a heart warming tale, or were there (secret) instructions embedded within?

So much for 'short curcuits' - more than a few diodes loose I fear

We've heard that a million monkeys at a million keyboards could produce the complete works of Shakespeare; now, thanks to the Internet, we know that is not true

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i have soldered components back on successfully but it is difficult.
you need to have very steady hand, good eyesight and a very fine tipped soldering iron, I ground the tip on mine on a bench grinder to make it finer.

haha thank you for sharing your experiences crunch they are very amusing and encouraging. i managed to find this pi cture of my graphics card and i highlited the missing component. if anyone can direct to where i can find it i would be much obliged

http://img306.imageshack.us/my.php?image=01c20000000522578ev.jpg

again the markings on it read:
470
AFK
1QN

There are two ways I might suggest.

1. Contact ATI, and tell them which xistor it is (Q2 OR Q3 or whatever - should be printed on the pcboard) and see if they can give you a part number, and or supply one.

2. Contact a local tv repair shop...look for an old fart like me running it. Take the xistor with you, and see if the guy has the usual ECG cross reference book, and look it up by the numbers that are printed on it. That book usually can help.

And finally...while you're there...if he wasn't been able to cross reference it...do what old time techs would do: Buy an ECG128 transistor from the guy (trust me, he'll have it) and try it in the board and see what happens. You're not out much money...it can't do much damage...and it might solve your problem. ECG128 is a NPN preamp that works well in many cases Good luck.

I wonder what'll happen if I do this ?

http://www.ixbt.com/video2/images/over-2003/r9100-64.jpg

http://www.mouser.com/ has all kinds of Surface Mount aluminum chip caps available on their webpage. They should be able to sort you out.

In the mean time, try all the generic computer shop in your local, you may be lucky.

thanks for the input so far guys but i've encountered an interesting situation. without this resistor i still get a video signal on my monitor. thus i assume even if i attach a wholly incorrect part i should still get a signal. how would i know when this is done properly?

I think that's a capacitor. How many leads (wires) does it have?

daveincaps it has two

Yeah, it looks like it's probably a polarized electrolytic capacitor. The 470 is a common value but you can't be certain if it's uF, nF or whatever. The manufacturers often had their own coding but a google search may indicate the exact value. I'll check later on.

hmm i don't have much knowledge of eletrical components so i will try to contact ATI for the exact component specs. that's for the input dave

That capacitor breaking off appears to be a common problem:

http://rage3d.net/board/showthread.php?t=33795372

In that posting, replacing it with a 470 uF (micro farad) electrolytic of at least 16v seemed to work OK.

As long as you get one that fits with those specs it wouldn't have to be an exact replacement. Pay attention to the polarity (+ and - sides).

When removing the old solder I usually use desoldering braid. Wherever you get the capacitor will also have the braid.

I guess it's a surface mount capacitor, meaning it's only soldered on the component side. So you'd need another surface mount to replace it.

wow daveincaps you are a miracle worker. i don't know how you found that topic but it was immensely helpful. thank you and everyone who contributed to this discussion very very much.

You're welcome. I hope you get it fixed.

Hi, Very ingenious holding the board in your mouth while soldering. I had a buddy that held the solder in his teeth while soldering. I use a THIRD HAND or a small plastic vise. Third hand is a stand with alligator clips on flexible arms. Jim

Hello DAVEINCAPS, how do you know so much about electronic components? I would like to get into that myself but don't know where to start.

Recognizing components is pretty much experience through trial and error. It's good to have a parts manual from a major manufacturer--ECG/Phillips or RCA for example. They'll have cross references for other brands as well as drawings and specs for the parts. Electronic parts stores usually sell the manuals for a few dollars or give them away.

The basic parts--resistors, capacitors, inductors (coils)--will have various shapes for different uses and often look very similar. If they're on circuit boards you may need to look for reference info printed on the board in order to identify them. One shown as 'R203' would be a resistor while 'C203' would be a capacitor. In this case the '203' is just a schematic label number and doesn't indicate a value. Fuses start with F and I believe inductors start with L.

Their values and tolerances (the amount they can vary from ideal) are often determined by colored bands on the part. These 'color codes' can be found in basic electronic manuals and no doubt on the internet. Googling something like resistor "color code" will probably show quite a few hits.

They'll also have maximum ratings for the electrical properties they control. Resistors will be rated by watts, capacitors by voltage and inductors by current. If those maximums are exceeded the part may be damaged.

If you want to get into the math you're probably better off with a basic electronics book you can find in a library or bookstore. Or at most a vo-tech book. Electrical engineering books go into quite a bit of theory that will require a familiarity with calculus. But you can pick up a lot from books that don't expect you to know calculus.

That's what you can do on your own. If you're still in school and are interested in electrical engineering take all the math you can. The more you take the easier it is because engineering is all math.

Thanks alot DAVEINCAPS. That was a big help.

You're welcome. Good luck with your future.