Problem with Kicker Kx 500.2 Amp

tireman406

Member
2009-08-08 3:40 am
So i am having a similar problem to what desaf had with the same amp. Have rca input running but no sound output. +15v pin reads 14.60, -15v reads 9.18. Nothing appears to be burnt or disconnected. Negavie line from board to cooling fan does not work. Not sure if problem is related or not. Any info from you perry would be much appreciated.

Update pulled board off of amp underside of Q15and Q16 were burnt. Resoldered but still get same voltage out of +/-15v prongs. And no sound output. Also resoldered ground under fan to no avail.
 

tireman406

Member
2009-08-08 3:40 am
I am sorry to say that I do not have a scope. How exactly would I check the rail voltage on the output transistors?

I attempted to find the solution on your bcae1 site but could not locate that information. I am sorry I would still consider myself novice as far as amp repair goes.
 

tireman406

Member
2009-08-08 3:40 am
Ok Perry after more reading I believe I have tested the transistors properly. I used my dmm with the black attatched to the negative input on the amp, and touched the positive to each leg of each transistor. My results were as follows:

All readings left to right with power supply side of the amp on my left.

Far side
Q211
-10.89
43.2
-14.06
Q211
-10.91
42.8
-14.20
Q215
-11.29
-42.8
-14.69
Q212
-11.76
-42.6
-15.33

Near side
Q115
-.185
-43.2
-.515
Q112
-.185
-43.2
-.515
Q114
-.186
43.2
-.515
Q111
-.186
43.1
-.515

also my voltages at the +/-15v pins on the audio board have remained the same. +14.45 -9.16
 

tireman406

Member
2009-08-08 3:40 am
I have a quick question. I'm thinking i should test voltage on Q15 & Q16 before removing Q212. Is that correct?

Also is it going to be ok to have all the transistors removed from the heat sink to test voltage on Q15 & Q 16?
I am at a point where i can accomplish both tasks just need to know the correct order to complete.
 
Readings left to right as usual.
Q16
.922
43.8
-15.29
Q15
14.99
25.51
15.56
Q212 Out of amp
leg 1-2) 1.69 ohms
leg 1-3) 2.233 ohms
leg 2-3) reads 28.14 ohms before dmm goes blank like it is reading but cant show reading if that makes sense.

The points of Q16 and Q15 under the board were touchy as to where they would give a reading.

If new parts are needed I am close to a radio shack. Would they sell the needed parts for replacement?
 
Rechecked the legs of Q16 and no it was .922 volts dc. Ran out of time at the end of the day as far as reassembly and sound test. Will do it first thing in the morning and give you an update.

What does that low voltage on Q16 tell you? I also heated the solder around all the legs of Q15 & Q16again to ensure solid connection to the board.
 
I will post all the original part numbers in the morning. I am working on the amp during the day at the tire shop i work for. I have all the bench power and dmm stuff there not at home. Just wanted to thank you again for helping. You dont know how much i appreciate it. I wouldnt have known the first place to start without your assistance.
 
I'd recommend that you use a 2N6488 and 2N6491 as replacements and install clip-on heatsinks as shown below.

I'd also suggest that you replace all 4 output transistors in the blown channel.

Digi-key
2N6491GOS-ND
2N6488GOS-ND
HS333-ND order 2
TIP35CGOS-ND order 2
TIP36CGOS-ND order 2

You'll also need heatsink compound.
345-1006-ND order 2
 

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