kicker 1200.1

[timwebb]

ok back on this amp. i with the transistors in the 494 gets very hot. it only goes into protect when q05 is in the circuit. i check the transistors they read fine but look in bad shape. im going to replace them.could the 494 be damaged?

 

[Perry Babin]

With no power applied. What's the resistance between the collector and emitter of each of the individual driver transistors?

It's possible that the 494 is defective but if you had a clean drive signal on pins 9 and 10 with the drivers out, it's likely OK.

 

[timwebb]

with the resistance set to 200k it read 46.4

 

[Perry Babin]

Measure the resistance from the gate to the drain for all of the power supply FETs. Do they all read the same?

 

[timwebb]

one side reads 47.1 and the other 46.4

 

[Perry Babin]

ohms, k-ohms, M-ohms?

 

[timwebb]

oh sorry k-ohms

 

[Perry Babin]

Do you read...

0 ohms between pins 9 and 10 and their respective driver transistor bases?

100 ohms between the driver transistors and the gate legs of the FETs that they drive?

~235 ohms from pins 9 and 10 to ground?

 

[timwebb]

0 ohms between pins 9 and 10 and their respective driver transistor bases? yes

100 ohms between the driver transistors and the gate legs of the FETs that they drive? yes

235 ohms from pins 9 and 10 to ground yes

 

[Perry Babin]

I don't see anything wrong. Can you post a high resolution photo of the area around the drivers?

 

[timwebb]

.

 

[timwebb]

MMBTA56 are good replacements for the drivers?

 

[Perry Babin]

Those are the transistors I've always used as subs in these amps.

Did you power it up with the A56s out of the circuit (don't if you haven't done so already).

If so, did the amp draw excessive current?

 

[timwebb]

no there was no current draw. ok will the power supply transistors have to be in place when i try to power it up?

 

[Perry Babin]

Are they currently out of the amp?

 

[timwebb]

yes.

 

[Perry Babin]

Post a photo of the waveforms on both pins 9 and 10 of the 494. If you have two probes, post a photo of both waveforms displayed at the same time.

 

[timwebb]

.

 

[timwebb]

the amp is in protection.

 

[Perry Babin]

If that's taken from pins 9 and 10, the IC is defective.