power acoustik ps1-5500d

[bdgf2004]

would anyone happen to know the value of R101? the amp will pop and distort whenever something comes in contact with it (only while the rca's were connected). so i opened it up and i found R101 behind the rca's burnt.

[Perry Babin]

220 ohms if it's one of the clone amps. They burn when the transformer shorts primary to secondary and when the positive speaker wire shorts to chassis ground.

[bdgf2004]

thanks i just looked at a planet audio i have laying around and it uses a 220 ohm.

thanks perry that was super fast

[bdgf2004]

does anyone know where the muting transistor is located

[Perry Babin]

There is no muting transistor. Watch the voltage on pin 6 of the driver board (counting from the RCA end of the amp). When it is near rail voltage, the amp will be muted. When it is very near 0v, the amp should produce a rail-rail square wave on its output transistors.

[bdgf2004]

ok, i will hook it up and watch the voltage.

several weeks ago i replaced R101 and everything appeared ok. now the guy said he had a part for his car laying around that was bumping the amp and at high volume he noticed it was audible through the subwoofers.

when he showed it to me it was fairly difficult for him to demonstrate the problem as it only does it at full tilt and he used a cigarette lighter to tap the amp. i heard it but it was nowhere near as loud as it was before i replaced R101.

before he left he mentioned a turn-on pop but i didn't hear that.

i will check C101 but it has no visual damage as R101 did.

just probing around i noticed the jumper wire grounding the circuit board to the heatsink is not connected to the power ground terminal but i haven't pulled the board to follow the traces yet.

[Perry Babin]

Try twisting the transformers. If one is intermittently shorted, it could cause all of the symptoms that you mentioned.

[bdgf2004]

you're right!! but no big surprise, you're always right.

with no rcs'a hooked up just power and a speaker i started playing with the 2 transformers and one of them definately has an intermediate short that is audible through the speaker.

i will locate the exact spot and seperate it.