Hello diyaudio,
Kicker ZX750.1 No Audio, Relay turns on, red led turns on for about .5 second then off and stays off. FETS seem to be Ok nothing shorted out and getting expected rail voltages along with +- 15V from regulators. Speaker pops just a bit on turn on. Found Q250 in mute circuit shorted between pins on same side of transistor, can't find replacement? Removed Q250 didn't help resolve issue not sure where to go from here without a schematic. Was able to trace audio signal to U11 pin 3 with a scope but not sure what I should see from there? Any help greatly appreciated!
Kicker ZX750.1 No Audio, Relay turns on, red led turns on for about .5 second then off and stays off. FETS seem to be Ok nothing shorted out and getting expected rail voltages along with +- 15V from regulators. Speaker pops just a bit on turn on. Found Q250 in mute circuit shorted between pins on same side of transistor, can't find replacement? Removed Q250 didn't help resolve issue not sure where to go from here without a schematic. Was able to trace audio signal to U11 pin 3 with a scope but not sure what I should see from there? Any help greatly appreciated!
Someone with a diagram should help but did you look up the markings on the transistor to confirm that it wasn't a JFET?
https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/697/PMBFJ108,109,110.pdf
page 2, item #4. ~10 ohms between the adjacent terminals would be normal.
page 2, item #4. ~10 ohms between the adjacent terminals would be normal.
Thanks, How did you look that up, I tried the 39W and got nothing? It has 7.5 ohms so it's good?
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There are several versions of this amp. Do you see a date stamp on the PCB? If the serial number is legible take a pic. A pic of the PCB would be helpful also.
Replace Q250-J109 and Monitor the DC voltage at the junction of R248-10Kohm & Q250-gate, during Turn on and soft start. It should settle at -20Vdc.
Apply a test tone 50hz will do. With a scope or AC volt meter, trace signal through C249 and C250.Post results.
Apply a test tone 50hz will do. With a scope or AC volt meter, trace signal through C249 and C250.Post results.
I have a triangle wave from pin 1out, should I have it on pin 4 vcc- I have no wave form on pin 4. Not sure I follow where to and from to measure the rail to rail switching?
Post #6:
There are multiple sites that give codes but looking up the code isn't all you need. The fact that the two adjacent terminals were shorted was a clue that it was simply a JFET. I'd bet that it would be a close competition between the number of perfectly good caps replaced and perfectly good JFETs replaced. Virtually no one knows what they are or how they read when being tested.
Knowing it was a JFET and finding a listing for 39P that was a JFET and knowing that the manufacturer was NXP which uses both a P and a W production code...
This site was most useful here (and one of my favorites).
http://www.marsport.org.uk/smd/mainframe.htm
This is another good site:
https://www.s-manuals.com/smd
This site is sometimes overwhelming but has more codes than any other site I've found.
https://smd.yooneed.one/
There are multiple sites that give codes but looking up the code isn't all you need. The fact that the two adjacent terminals were shorted was a clue that it was simply a JFET. I'd bet that it would be a close competition between the number of perfectly good caps replaced and perfectly good JFETs replaced. Virtually no one knows what they are or how they read when being tested.
Knowing it was a JFET and finding a listing for 39P that was a JFET and knowing that the manufacturer was NXP which uses both a P and a W production code...
This site was most useful here (and one of my favorites).
http://www.marsport.org.uk/smd/mainframe.htm
This is another good site:
https://www.s-manuals.com/smd
This site is sometimes overwhelming but has more codes than any other site I've found.
https://smd.yooneed.one/
I was mistaken. Scope U14-LM361-Pins 3,4 and 13 and post screenshots.
Check Vdc on U14-Pin 8 & Pin 10 and post results.
Scope L105 & L106 and post screenshots.
Check Vdc on U14-Pin 8 & Pin 10 and post results.
Scope L105 & L106 and post screenshots.
U14
pin 3
Pin4
Pin10
I think L105 and L106 are the large inductors do I need to scope between them or ground to each?
Thanks
pin 3
Pin4
Pin10
I think L105 and L106 are the large inductors do I need to scope between them or ground to each?
Thanks
U14
Pin 8 3.2 vdc
Pin 10 -1.85
Pin13
Still not sure how it where to scope L105 or L106.
Pin 8 3.2 vdc
Pin 10 -1.85
Pin13
Still not sure how it where to scope L105 or L106.
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