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Ranger built cobra 148F GTL
- Thread starter skybolt58
- Start date
Well I just took the final out 2sc1969 and tested it with a DMM on diode test, between the base and collector and emitter tested one way had current and the other way didn't, that is good, but between the collector and emitter there should not be current either way and there is, so the final is bad? now for the fun part in finding a real c1969 in this world?
Gee am I testing these transistors right?
Here is how I do it, I set the DMM on Diode test,
I probe the collector and base both ways and it tests like a diode, then I test the base and emitter both ways and it also tests like a diode?
then I test the collector and emitter both ways and it is NOT suppose to have a reading both way's? it should read OL, both ways. RIGHT? because all the finals I have when testing the collector and emitter it tests like a diode, to my understanding, then that transistor is bad?
Now it this correct?>
Yeah I saw that, Wow I guess every 1969 and 2166 I have even 2 new ones are bad, since I get a reading one way between emitter and collector!
OK fine.
Put the DMM on diode check. Have the transistor with the print side facing you. Attach the red lead to the pin on the left. Then use the black lead to touch the middle pin. Should have a reading. Then, test the pin on the right with the black lead. Should have a reading.
The other test is a resistance test, but the above test should be fairly conclusive. That should work for the 2166 and the 1969.
Put the DMM on diode check. Have the transistor with the print side facing you. Attach the red lead to the pin on the left. Then use the black lead to touch the middle pin. Should have a reading. Then, test the pin on the right with the black lead. Should have a reading.
The other test is a resistance test, but the above test should be fairly conclusive. That should work for the 2166 and the 1969.
So what you are saying, that the Video you posted where it says that there should be no reading between the collector and emitter , that it don't matter if there is a reading? one way
Just like two diodes tied together with the anode in common, they should conduct only one way from the base.
Perhaps you might want to watch some more videos and perhaps practice on known working transistors a few times to get the hang of it.
Perhaps you might want to watch some more videos and perhaps practice on known working transistors a few times to get the hang of it.
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Yes I know the Base -Collector conduct one way and the base - emitter only conduct one way, BUT what about the emitter and collector, I under stand for a good transistor, they should not conduct either way? right?
your transistors are not necessarily bad.
some transistors have whats called "damper diodes" built in to them across the C to E junction causing this junction to test like a diode.
the 2SC1969 is one such transistor.
LC
here is a quote from a site about testing transistors:
"Note: some power transistors have built in damper diodes connected across C-E and resistors connected across B-E which will confuse these readings. Also, a few small signal transistors have built-in resistors in series with the base or other leads, making this simple test method useless. Darlington transistors can also show unusual voltage drops and resistances. When testing a transistor of this type you will need to compare with a known good transistor or check the specifications to be sure."
some transistors have whats called "damper diodes" built in to them across the C to E junction causing this junction to test like a diode.
the 2SC1969 is one such transistor.
LC
here is a quote from a site about testing transistors:
"Note: some power transistors have built in damper diodes connected across C-E and resistors connected across B-E which will confuse these readings. Also, a few small signal transistors have built-in resistors in series with the base or other leads, making this simple test method useless. Darlington transistors can also show unusual voltage drops and resistances. When testing a transistor of this type you will need to compare with a known good transistor or check the specifications to be sure."
Ok then, My transistors all are good, I get the same on the 2166. tests like a diode between C-E,
I was getting the info from that video you posted, he stated that C-E should not have any current either way.
Now I still have to find out why I cant adjust the Bias on the driver and I only get 6-7 watts out of the Radio?
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most transistors do show "open line" between the C and E junction, and the test in that video is correct.
its just that the 1969 happens to be one of the weird ones.
i sometimes wonder how many good 1969's have been junked over the years due to this.
if you are getting 7 watts out of the radio, then the final is good.
the driver cannot produce this much power on its own.
low power problems can be a real bear to track down, so the very first thing you want to do is completely eliminate any outside possibilities like the power supply.
hook a voltmeter to the power jack on the back of the radio, note the voltage (should be between 13 and 14 volts give or take), then key the radio and look for any voltage drop.
then hook a current meter in line with the positive lead into the radio and again key the radio up.
you should notice the amp draw go from a few hundred milliamps to almost 2 amps depending on where your deadkey is set.
of these two tests go well, then you can look inside the radio.
if they dont, its time to switch power supplies or check in the radio for old leaky electrolytics that attach to PC board ground.
if the power supply checks out, first find R187, and connect a DC voltmeter to the end of it that is opposite VR9.
key the radio and check that you have 8 volts on this line.
if it is lower than that, you'll have to start checking components that are in parallel with this line.
if that goes ok, try pulling VR9 completely from the board and make sure that it makes a smooth resistance change across its range like it should.
if it acts funky, try replacing it. ive seen them go bad before.
other things to check are C191, R187 itself, D50 (the bias diode), and C156.
this is just a few that popped out at me.
all this is assuming that you can adjust bias on the final like normal.
if you cant, then there is more to it.
after all this, you might just have a crappy 2166 that is just very weak but still tests good.
the pre-driver (2SC1973 or 2314 usually) could also be crappy.
its not very common, but it does happen.
good luck,
LC
its just that the 1969 happens to be one of the weird ones.
i sometimes wonder how many good 1969's have been junked over the years due to this.
if you are getting 7 watts out of the radio, then the final is good.
the driver cannot produce this much power on its own.
low power problems can be a real bear to track down, so the very first thing you want to do is completely eliminate any outside possibilities like the power supply.
hook a voltmeter to the power jack on the back of the radio, note the voltage (should be between 13 and 14 volts give or take), then key the radio and look for any voltage drop.
then hook a current meter in line with the positive lead into the radio and again key the radio up.
you should notice the amp draw go from a few hundred milliamps to almost 2 amps depending on where your deadkey is set.
of these two tests go well, then you can look inside the radio.
if they dont, its time to switch power supplies or check in the radio for old leaky electrolytics that attach to PC board ground.
if the power supply checks out, first find R187, and connect a DC voltmeter to the end of it that is opposite VR9.
key the radio and check that you have 8 volts on this line.
if it is lower than that, you'll have to start checking components that are in parallel with this line.
if that goes ok, try pulling VR9 completely from the board and make sure that it makes a smooth resistance change across its range like it should.
if it acts funky, try replacing it. ive seen them go bad before.
other things to check are C191, R187 itself, D50 (the bias diode), and C156.
this is just a few that popped out at me.
all this is assuming that you can adjust bias on the final like normal.
if you cant, then there is more to it.
after all this, you might just have a crappy 2166 that is just very weak but still tests good.
the pre-driver (2SC1973 or 2314 usually) could also be crappy.
its not very common, but it does happen.
good luck,
LC
Hey loosecannon
Is this info you are giving me here based on the EPT014811z board, because that is what I have? Cant find r187 anywhere by vr9
I cant set the bias for the driver, BUT when I turn VR8 the wattage does go up? a little,
There is no problem in setting the bias for the driver, But I have a new 2166 here I just may try it for shits and grins!
Also do you know if a SD1446 is like the 2sc1969. you get a reading like a diode between the E-C?
Is this info you are giving me here based on the EPT014811z board, because that is what I have? Cant find r187 anywhere by vr9
I cant set the bias for the driver, BUT when I turn VR8 the wattage does go up? a little,
There is no problem in setting the bias for the driver, But I have a new 2166 here I just may try it for shits and grins!
Also do you know if a SD1446 is like the 2sc1969. you get a reading like a diode between the E-C?
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