Kenwood KAC-X201T will not turn on

[spooney]

pin 35 4.83 volts
pin 36 4.83 volts
pin 37 .017 volts

These all stayed constant. I rechecked the other pins using the ground of the processor and the results did not change for those pins.they would still start out low jump up and then go back down.

 

[Perry Babin]

37 needs to be high.

Post the voltages on Q406, Q407 and Q408.

 

[spooney]

can you give me an approximate location on those devices Perry? I think I've found them but none of the SMD parts have any designations next to them to let me know what is what and i have no schematic.Does the remote turn on signal run into this trio of transistors through a resistor and two diodes?

 

[Perry Babin]

See attached.

 

[spooney]

cool turns out I found the right ones.The voltages are listed as follows assuming the single lead is the top of the transistor:
bottom left,top middle,bottom right

Q406 1.908,.019,.002
Q407 .002, 1.908, .002
Q408 .002 on all legs

 

[Perry Babin]

Q408 may be shorted. Check it with your meter set to ohms.

If it's not shorted, post the voltage across D303 and R73 (on the other board near the remote/p.con terminal).

 

[spooney]

if q 408 is shorted its not completely shorted.Reading about 3 k ohms from top lead to either bottom lead with it in circuit. D 303 with meter leads on either side of it is at 12.6 volts and R73 with leads on either side of it reads nothing.

 

[Perry Babin]

D303 is a 7.5v Zener. If it has 12+ volts across it, it's open. If you jump the zener out (solder a wire across it), the amp may power up.

There is a 3.3k resistor from the top terminal to the right terminal (collector to emitter) of Q408 so 3.3k is normal. Check to make sure the bottom two terminals are not shorted together. If they are, remove the transistor from the circuit.

 

[spooney]

d 302 is seeing 12 plus volts so should i replace that as well or is that diode a different voltage rating?Is it safe to try to power it up with wire soldered in place of those diodes as long as i make sure nothing gets shorted(like a power wire or something).I have some 6 volt zeners lying around will those work or do i need the 7.2?

 

[Perry Babin]

D302 is a 15v zener and is used to shut the amp down when the voltage goes above ~16v.

D303 prevents the amp from turning on when the remote voltage is less than ~8v.

A 6vZ will work but you should replace it with the correct part before the amp is put back into service.

 

[spooney]

i'm ordering a few things from mouser anyways so i might as well stop being cheap and get the right parts.

 

[Perry Babin]

Use the 6v to see if you can get it to power up. If you find you need other parts, you can order them when you order the correct zeners.

 

[spooney]

well i soldered in the 6.2 volt zener in today and i'm happy to say that the amp finally works.This is by far the most troubleshooting I've ever had to do or I should say that Perry had to do for me I'd given up on this thing so many times.It feels good to finally get it going.All i need is that 7.5 volt zener and some terminal screws and i'll be able to finally put this thing to bed.

 

[spooney]

The 7.5 volt zener is in and so far all seems well.I've got this amps bigger brother on the way and with any luck i'll get that one going as well and have a nice pair of amps for my car.