How to test a transistor (final) in a cb radio.
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- Опубликовано: 5 окт 2024
- Had some time and thought I would make this quick video to show how I test a transistor that is mounted to the chassis and the circuit board without taking it completely out. The transistor is a 2sc2078 NPN.
BTW, the blinking light on the component tester indicates the emitter. You normally have three legs (base, emitter and collector). The component tester will show you the base and emitter. The other leg is obviously the collector.
Please "Like" this video if it was helpful. :-)
73's
Jumpy
All Finals, All non Mos Fets/ TO TEST and save time: Just use your DVM (digital volt meter) in comp test mode (diode test) with the NEGATIVE probe on the base ALWAYS for any NPN transistor. PNP - use the RED probe on the base obviously. A) Lift the emitter from board always. B) Test from: Base to Collector, Test from: Base to Emitter, and C) for leakage on any level TEST FROM Collector to Emitter by swapping test lead direction. If XSTR is good you'll only get a quick beep, and a reading under 800, in circuit, no removal necessary. This takes all of 10 seconds. I mention in circuit since usually you will not have a resistor low enough between base and emitter to give a false. Sometimes you will and the beep on your meter will be solid with a reading of maybe 220 +/- but that's only if there's a resistor in circuit between base and emitter by design for impedance matching in SOME radios. Great time saver, always accurate and no transistor tester clip leads or component removal needed to test your semi's. PS Works for all diodes in question as well. My webcam is not available at the moment, or this would have been a quick demo. Try this, try it on all your bad semiconductors that I know you have in a box and you'll see my point. I miss the CB repair world. Good luck guys, 73's
Great info Jeff. Thank you Sir!
73s
Ken
Ken Graham Glad to help out- I'm wondering if you've tried it out yet. -It only takes a few times to get used to how your DVM responds while testing a semiconductor. (The quick beep, and the reading you get on DVM's display) simultaneously during testing. Just to let you know, it doesn't matter at all how old or inexpensive your DVM may be, if your DVM has the diode test feature , you're good to go. Feel free to contact me if you have electronic repair issues.
Thanks DS Graham. Always teaching me something. D5/46 1999
i personally have never used a desoldering pump but i have found that desoldering braid does a better job in comparison to a desoldering pump. the desoldering braid is cheap, and if you use an inch to remove a single part all well, side cutters to cut off what has sucked up the solder, and your already good to go. IMO next time, try to just use desoldering braid without the desolder pump. cleaner and faster depending on solder type
Justin. I use the pump to get the large solder points then clean up with the braid. For each his own. Good luck and 73s.
Rick, final was good to go after putting it back in. I've always done it that way. Self taught. No training. Anyway are you suggesting I not keep the solder iron on the contacts as long? Thanks for your comment.
Ken Graham:. Thanks for posting!!
I'm always learning thanks to great
video posters like you!! Question:
I've got a 1978(I believe)
RCA Co-Pilot 14T302 SSB radio.
Can I just swap out my stock
mosfet for another? If so,
how can I tell which one to use?
Should I also swap out
the audio chip & pll as well?
My goal is some extra power.
Thanks for answering, Norman.
Norman, thank you for your post. Sorry I'm just now getting back to you. I don't remember getting a notification. Anyway, to answer your question, yes you can absolutely swap out the stock final transistor for another as long as the transistor is an equivalent. Search CBtricks.com for some mods to increase power. My recommendation is to leave it stock and buy a cobra. Cobra's tend to have many types of mods for power modulation increase. Best of luck to you and 73's.
v/r Ken
thanks for the video btw
good info and show how its done. But you could have replaced the mosfet with a High Power Mosfet Conversion Mod.Kit and pump a lot more watts than just five. they sell them on ebay. I have heard guys talk about how good they work. It would be nice in an emergency to be able to talk further dont you think.
shartne you are correct and I have done a few of my own that way. for this video I was showing a friend only because he was interested in knowing how to test a transistor.
shartne & Ken Graham:
how do you know which
mod.kit will work for your CB? I've
got a 1978(I believe)
RCA Co-Pilot 14T302 SSB radio.
Can I just swap out my stock
mosfet for another? If so, again,
how can I tell which one to use?
Thanks for answering, Norman.
Can a transistor be checked in the board without removing solder
If you have solder-wick, you don't need a solder-sucker (and vise-versa). If that final wasn't cooked before, I'd say (with all that heat) it is now...
Rick Via thanks for that and your right. I made this vid for a friend and wanted to show him two techniques. Guess I should have explained.
I got hooked on solder wick back in the 70s, but recently bought a bulb solder sucker. It does OK. Good presentation, anyway Ken.
The other lead that i failed to mention is the emitter. On the back of the tester you can see the instructions.
Daniel. Check out this link ---> cbradiomagazine.com/March%202007/Cobra%2029%20LTD%20Super%20Modulation%20Modification.htm
Don't need pump pull
How muvh is the cost tu replace the final in a radio shack base station ? ghznks
Couple of dollars probably no more than $8 if you include shipping cost. Check out RFparts.com for replacement final transistors.
@@baltimore_amp_repair Thanks for the reply.
Why would u waste the time to unsolder the leads instead of just touching the alligator clips to them while they were still bent over and soldered?
good question Rzy. I always thought you needed to isolate the leads. Otherwise the transistor checker might end up checking or sensing another transistor somewhere else on the circuit board. But, I will look into this. Thanks.
Rzy Bzy I didn't know you could do it that way. I thought you had to isolate the legs. Learn something everyday. Thank you!
Ken Graham your correct leaving it connected to the circuit will affect the reading it's best to do it the way u did it
I can show u how to do it why it in the radio
Wrong tools for job sir ....
lol he said toshiba 2078 LOLOLOLOLOL
correction Sanyo makes the 2sc2078. Thanks.