Kenwood 9102

[mike49504]

Im working on a kenwood 9102d i checked the outputs and 2 were bad i took them out . The problem is the amp wont power on its completly dead wondering what i should check at this point since all the power supply fets test good

 

[Perry Babin]

With the amp powered up, what's the voltage on the 3 pins of Q3?

Q3
Pin 1:
Pin 2:
Pin 3:

 

[mike49504]

Perry ,

Didnt see Q3 i saw Q403 is that what u mean ?? if so

Pin 1= 0
Pin 2- 5.97
pin 3= 5.97

 

[Perry Babin]

See attached.

 

[mike49504]

Ok on Q3
Pin1= 13.90
Pin2= 4.72
Pin3= 13.30

 

[Perry Babin]

It's likely defective. If you have any TO-220 PNP transistor (2N6491, 2SAxxxx, 2SBxxxx...), you can use it to allow further testing. You'll have to install it facing the opposite direction because the pin configuration is reversed. The base goes to the nearest edge of the board.

 

[mike49504]

ok i replaced it with a 2n6491 and reversed it so now it reads

pin1=13.80

pin2= 8.18

pin3= 13.35


wondering what do i check neck since the amp is still dead i appericate the help perry without you id be lost

 

[Perry Babin]

The 13.35 is on leg 1 of the 6491 (ignoring the numbering of the other transistor), correct?

If so... is the 6491 getting hot?

 

[mike49504]

ignoring the pin order of the old transistor pin 1= 13.35

the 2n6491 is not getting hot at all amp has been powerd up for 10 mins

 

[Perry Babin]

What's the DC voltage on the 3 pins of Q2 (SMD under board - see attached for pin numbers)?

What's the DC voltage measured directly across R6?

 

[mike49504]

ok i must be stupid or something tonight
where do i find q2 and r6 on this amp i know u said yunder the board is it labled or no?

 

[Perry Babin]

It's at the lower left of the orange oval on the board layout I previously posted.

Email me if you need/want the service manual.

babin_perry@yahoo.com

 

[mike49504]

Perry i tested Q2 and R6


Q2:
Pin1-6.47
Pin2- 5.90
pin3- 12.99

R6- voltage directly across it is 0.36

 

[Perry Babin]

The emitter of Q2 should be at ground. If you were using the chassis ground terminal for the reference (black meter probe), look for an open ground trace.

 

[mike49504]

Ok i found a broken ground trace and repaired it. Amp powers up now the led is red wondering if it is suppose to be red or blue? and 2 of the outputs were bad wondering whats a good sub to put back in there or do i need the same part number that was in it

 

[Perry Babin]

As always, I'd recommend using the original part number. Mouser has them:
511-STW34NB20

I don't know the color of the LED. If the LED is triangular, I'd think it's likely supposed to be red. If there's only one LED, it's almost certainly supposed to be red. I've never seen a dual color LED that was red and blue (but I haven't looked for any either .

Edit:
You can probably reinstall the original Q3. It appeared that it had low gain but that was due to insufficient base drive current (due to the open ground). The transistor was conducting but wasn't saturated.

 

[mike49504]

Ok thank you perry i have 1 other question Q3 i put the orginal part back in its labled B1241 and now the amp doesnt wanna power up again wondering if u have a part number for that so i can order one of thoose also thanks

 

[Perry Babin]

2SB1241

Give me the voltages on Q2 again.

 

[mike49504]

Here we go again i put in a 2n6491 in q3 spot reversed it and the readings im getting are

Pin1= 13.90
Pin2= 13.88'
Pin3= 13.28

Amp is dead wont power up at all any help would greatly be appericated

 

[Perry Babin]

Are you sure you had a good ground?

If so, post the voltage on the pins of the 494.


Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16: