Sounds like the rectifier is dead. The question is why the second one is dead. If there is a short in the regulator, and you hooked up the new one then the short killed it too.
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Dead DX2517
- Thread starter TruckerKevin
- Start date
I really appreciate everyones patience with me. I feel like a cat in a dog pen, trying to learn electronics. As you can tell, I am fairly new to this.
For today I have to give up, I am a midnight truck driver and I have to get some rest. Believe me, I am a much better truck driver than I am an electronics person. But if anyone has anything to say, ill be back on late tonight
For today I have to give up, I am a midnight truck driver and I have to get some rest. Believe me, I am a much better truck driver than I am an electronics person. But if anyone has anything to say, ill be back on late tonight
Good luck on your quest, if you get the same results with the new rectifier, go through this thread and soak in some of what has been shared already, the portion before the regulator board is really straightforward. Line level A/C gets transformed into a much lower voltage, the lowered A/C gets rectified (becomes D/C) and moves onto the regulator board.
I'm surprised you are familiar enough with the 'scope but cannot work through the basics of this power supply, I'm not faulting you but it seems to me that you have a grasp of what is going on here, you've even shared the schematic with us!
A few more things to consider, does your volt meter have a range selection option? Perhaps you are attempting to read a voltage higher than what the meter is set to read. Also, please be careful not to probe voltage rails while on the Ohm setting, this can damage some multi-meters.
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did you ever check the rectifier with a meter to see if it is bad. so simple to do. just put the meter on diode check and you can see if the rectifier is bad. I know I read a few post back that being mentioned to you.
Be sure when you are checking for the dc voltage out of the rectifier, that the 10,000uf electrolytic capacitor is not connected .....
http://www.cbtricks.com/cgi-bin/database/galaxy_db.cgi?
If TR602 is not a 2SD2531 (better or equivalent) now is the time to update the radio as per Galaxy Tech Support, standard operating procedure.
If TR602 is not a 2SD2531 (better or equivalent) now is the time to update the radio as per Galaxy Tech Support, standard operating procedure.
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i realize this has probably been mentioned in the thread before, but have you tested the bridge rectifier without it being connected to anything else besides the transformer?
(including the two ceramic disc caps that are soldered to it. remove those also)
If something connected to the DC portion of the rectifier is shorted, then you will not read any voltage here.
so, remove the bridge rectifier from the radio completely. no wires connected to it.
connect the wires from the output of the transformer to the AC terminals on the bridge rectifier.
now measure the DC voltage on the other two terminals of the rectifier.
If you get 0 volts out of the rectifier when it's not connected to anything inside the radio, then your only possibilities are a bad rectifier or a bad volt meter.
If you do get voltage out of the rectifier like this, (you should get around 22 volts DC)
then your next steps are to find the short downstream from it.
test C606 and C607 (the ceramic disc caps on the rectifier itself) using the ohms function of your multimeter. they should read open circuit IE: no connection.
if they don't, replace them. if they do read correctly, then put them back on the rectifier, they need to be there.
next place to look for a short would be the two wires that would get soldered to the DC output of the rectifier (they should still be disconnected from it for this test).
with the meter in ohms function, measure the two wires.
you should read open connection here also, but because of the large value of C605, you may read a short initially that gradually fades to an open connection.
this is the cap charging and is normal. however, if you read a short across these wires that doesn't go away in a few seconds, then you have a problem and need to test C605 and the transistors on the power supply board.
LC
(including the two ceramic disc caps that are soldered to it. remove those also)
If something connected to the DC portion of the rectifier is shorted, then you will not read any voltage here.
so, remove the bridge rectifier from the radio completely. no wires connected to it.
connect the wires from the output of the transformer to the AC terminals on the bridge rectifier.
now measure the DC voltage on the other two terminals of the rectifier.
If you get 0 volts out of the rectifier when it's not connected to anything inside the radio, then your only possibilities are a bad rectifier or a bad volt meter.
If you do get voltage out of the rectifier like this, (you should get around 22 volts DC)
then your next steps are to find the short downstream from it.
test C606 and C607 (the ceramic disc caps on the rectifier itself) using the ohms function of your multimeter. they should read open circuit IE: no connection.
if they don't, replace them. if they do read correctly, then put them back on the rectifier, they need to be there.
next place to look for a short would be the two wires that would get soldered to the DC output of the rectifier (they should still be disconnected from it for this test).
with the meter in ohms function, measure the two wires.
you should read open connection here also, but because of the large value of C605, you may read a short initially that gradually fades to an open connection.
this is the cap charging and is normal. however, if you read a short across these wires that doesn't go away in a few seconds, then you have a problem and need to test C605 and the transistors on the power supply board.
LC
That is some pretty good trouble shooting information, I will try that Saturday morning as soon as I get back in the town buddy. I appreciate it
Yep, what loosecannon said above. That is exactly what I was trying to convey ....
I might have possibly found my problem.
I think I have a bad power transistor (the one that screws onto the back of the radio under the shield) and connects to the power supply. The base, emitter and collector wires run directly to the PS board.
It is a Toshiba 2N3771 0320 transistor.
I do not have another one to use in its place, but according to what I am reading, it is an NPN type.
It is not passing the npn tests
I am not getting a reading at all on base to emiter when I should be getting a reading
I think I have a bad power transistor (the one that screws onto the back of the radio under the shield) and connects to the power supply. The base, emitter and collector wires run directly to the PS board.
It is a Toshiba 2N3771 0320 transistor.
I do not have another one to use in its place, but according to what I am reading, it is an NPN type.
It is not passing the npn tests
I am not getting a reading at all on base to emiter when I should be getting a reading
oh come on man, you're not even going to tell us whether or not the bridge rectifier was bad?LOL
seriously though, yes, it's an NPN transistor and with your meter set to the diode test, positive lead on the base, and negative on the emitter, you should see a reading of around .5-.7 volts.
if it's open, that would be your problem, BUT! don't just buy one replacement transistor if you aren't going to try to discover the cause of its failure.
If you are just going to replace it and cross your fingers that the radio works, you should buy 2 or 3 of them in case the new one blows too.
Many times a semiconductor that works hard will just give up the ghost on its own, but in many cases, there is another component at fault, like a shorted capacitor or open resistor, or even another blown semiconductor.
With your level of experience, my suggestion would be to just try a new one since they are not expensive, and hope for the best.
hoewever, if you sent the radio to me, i would be testing components on the power supply board and probably suggesting a new filter cap to the owner.
LC
seriously though, yes, it's an NPN transistor and with your meter set to the diode test, positive lead on the base, and negative on the emitter, you should see a reading of around .5-.7 volts.
if it's open, that would be your problem, BUT! don't just buy one replacement transistor if you aren't going to try to discover the cause of its failure.
If you are just going to replace it and cross your fingers that the radio works, you should buy 2 or 3 of them in case the new one blows too.
Many times a semiconductor that works hard will just give up the ghost on its own, but in many cases, there is another component at fault, like a shorted capacitor or open resistor, or even another blown semiconductor.
With your level of experience, my suggestion would be to just try a new one since they are not expensive, and hope for the best.
hoewever, if you sent the radio to me, i would be testing components on the power supply board and probably suggesting a new filter cap to the owner.
LC
I agree with LC; did the diode bridge show voltage out on the two bridge pins ?
Could be a bad zener diode (there are two showing in the schematic), or a shorted cap, or a bad regulator too . . .
Could be a bad zener diode (there are two showing in the schematic), or a shorted cap, or a bad regulator too . . .
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