Rockford punch 250a2 dead

[mbates14]

Having a power supply issue on this. it had blown channel along with both 50N06s shorted/blown. replaced all of that, and checked the driver transistors off the TL494 and they are good.

However i get NO action from the TL494 at all. checked all the voltages, and i have my 12V VCC sitting at the TL494, but no drive output. changed the TL494 and no change. Everything appears to be ok voltage wise, i had the reference 5V present at the IC. both error amplifiers and feedback pin are in the "false" meaning the IC should start up and run just fine without an error condition. I even scoped the oscillator, and had a clean 66khz ramp.

only thing that is odd, is the DTC is pinned kinda high. around 4V. maybe higher, i cant remember the exact value. but it seems high, as the fosgate 1200 i worked on, the DTC was near 0.

any ideas?

[Perry Babin]

Pin 4 must be near 0v. Post the voltages on the LM339.

IC#
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:

[mbates14]

I swapped the LM339 as a potential failure point. But i will do the readings monday when i get back to the shop. I will have to repair a couple burned traces and replace a mosfet becuase my meter lead is too fat. it slipped and shorted 7/8 together momentarily which resulted in smoke, flames and heavily loaded 12v power supply. lol.

[mbates14]

I fixed it. rockford sent me the 250a2 schematic.

But i found a shorted thermistor. of ALL THINGs. the thermistor was shorted 0ohms. removed it, replaced it with another one from a scrapped amp. it fired right up. go figure. it worked fine though.