Rockford 500a2

[Frycztech]

It's unlikely that all are defective. Slide them off to one pad and remeasure.

It's far more likely that a transistor is leaky or shorted.

Perry,

It looks like R255 is bad. Its reading way over 1k. Is this a good replacement?
CRCW08051K00JNEAC Vishay / Dale | Mouser

Also R253 are bad. are these a good replacement?

CRCW080510K0JNEAC Vishay / Dale | Mouser

 

[Perry Babin]

It's almost impossible for the 10k to be damaged. Is it cracked?

Those look OK.

Lift Q217 and Q218 and check for leakage and open junctions.

 

[Frycztech]

I lifted Q218 and it was within range. I replaced Q218 and now it is good. I will have to order the replacement for R255. Wen testing Q218 is the leg that is by itself the gate?

 

[Perry Babin]

Look up the datasheet.

There is no gate on a bipolar transistor.

 

[Frycztech]

Ok so I would be checking from the base to the emitter in both directions?

 

[Perry Babin]

Use the link on the following page and send a screen-cap after filling in the form.
Basic Amplifier Repair - Transistor Test Applet Link

 

[Frycztech]

Look up the datasheet.

There is no gate on a bipolar transistor.

Perry,

I replace the last resistor and tested the audio and now it is clear. Should I now set the Bias on both channels?

 

[Perry Babin]

After you have all of the old heatsink compound removed and the replaced, all of the transistors clamped to the heatsink, yes, set the bias. This is how I set it:
http://www.bcae1.com/temp/ausettingbias.swf

 

[Frycztech]

After you have all of the old heatsink compound removed and the replaced, all of the transistors clamped to the heatsink, yes, set the bias. This is how I set it:
http://www.bcae1.com/temp/ausettingbias.swf

Perry,

I know that you told me before to set them while measuring across the dummy load on the power wire. How much voltage change is ok for each bias? 0.10vdc ?

 

[Perry Babin]

As long as you see a slight increase, that's likely OK. You just need to get the output transistors to begin to conduct (pass current).

 

[Frycztech]

Perry,

Thank you the amp is together and is working! Your the man.