PPI PC225 blowing fuses

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This amp had a smoked IRFZ44N and a bad resistor. I replaced Q1 (it was cracked but not blown), Q2 (melted), R6 (out of tolerance) and R7 which was completely burned up. Verified that all solder connections are good.

When I place a 10amp fuse in line (gain all the way off) everything is fine until I turn on the radio. It blows a fuse right away.

What to check next?

Thanks in advance.
 
Initially, when an amp is pulling excessive current (only after remote voltage is applied), you check to see if the output transistors are shorted. Whey they short, they generally read very low resistance between the legs. They should not read anything near 0 ohms between the legs of any individual transistor. If none are shorted, you have to do a bit more troubleshooting. For now, see if any are shorted.
 
I pulled the transistor 2N6488 in location Q28 as it was connected to the R206 that initially read as .3-4 ohms but when I removed it from the circuit it reads fine.

All the legs on the 6488 read 0.000v no matter what config I use with DVM set to diode.

Thanks for your help Perry. :)
 
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Hmmmm, I tried to power it back up with the 6488 in Q28 removed. Clamped the cover back on. The 47ohm resistor in R106 burned up after power turned on for like 5 sec. Did it just burn up because of the transistor being removed or is this a sign of something bigger? The 10amp fuse didn't blow this time. Just burned up the resistor till I removed the fuse.
 
Perhaps you can set the resolution on your camera lower, or open the photo with paint and resave it as a bmp, or gif you can lower the resolution, and you can still generally see the circuit board designations.

pretty sure this is like the busted pc250 I have, so I am following along intently.
 
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Awesome!!! Pulled Q30 and replaced the resistor I smoked earlier and I now have clean signal from the left channel. Powers up, all is good... now I just need to order some of these 2N6488 & 2N6491 transistors and hopefully that`ll be all.

Thanks again Perry... you sir are the man. ... and I learned some things too. ;)
 
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