another performance teknique

[timwebb]

ok i have another one of these amps and ive changed the output transistors but when i turn the volume up and down the sub pull and pushes out?

 

[bob91343]

What amplifier is this? If it's direct coupled you may be introducing some dc at its input.

 

[timwebb]

performance teknique 1200w 2ch

 

[Perry Babin]

Changing the volume on the head unit causes the woofer to pulse?

 

[timwebb]

no just when i adjust the gain it pushes and pulls the sub.

 

[Perry Babin]

Does it do this with the crossover set to full range, high pass and low pass?

 

[timwebb]

low pass

 

[Perry Babin]

Can you post a photo of the inside of the amp (showing the entire end of the board near the RCA jacks)?

 

[timwebb]

here they go

 

[Perry Babin]

Those look like 9 pin op-amps. Do any have more than a fraction of a volt of DC on pin 2 or 8?

 

[timwebb]

it reads

 

[Perry Babin]

Are you saying that no pin (2 or 8) reads more than 0.06v DC (amp powered up)?

 

[timwebb]

thats what they read. i tried with a little input and i got like 2v or a little less

 

[Perry Babin]

Generally, this sort of problem is due to an op-amp with excessive DC on its output. Did you check all of the op-amps in that area?

Does it do this without a signal source connected to the amp?

 

[timwebb]

it reads 0.6 while its on but no input with input it jumps up.all are doing the same thing

 

[Perry Babin]

Does the speaker pulse in/out when you turn the gain control with no signal source connected?

 

[timwebb]

yes it does

 

[Perry Babin]

What's the resistance from the RCA shield to either of the non-bridging speaker terminals (no RCAs plugged in)?

Set you meter to the lowest resistance range.

 

[timwebb]

its showing no resistance

 

[Perry Babin]

No resistance, 0 ohms? If so, that's OK.