Rockford Fosgate T40001bd

RockfordFIx

Member
2012-12-03 11:56 am
Perry

Sorry for the delay in getting back with you. Turns out after replacing the FETs and replacing all the components of the 4 drive circuits it powered up and played perfectly. Thanks for all your help...Now, for the next one.. I have another T40001BD that someone else repaired and they're work is somewhat questionable. I first opened the unit up and diode check the outputs and the powersupply chips. Everything seems fine. So i powered up the amp and everything is fine. No protect light until about 10 seconds. Amp meter on powersupply is around 1-3 amps and then jumps to 10amps. Nervously, i power down and check for hotspots. Nothing obvious, I power up again and check output voltages. I read 110v on half the outputs and then the unit goes into protect. I remove power and remove the +hv, gnd, -hv from the output board and power up. Unit stays out of protect mode now but i seem to have higher voltages from the previous amp. I am reading 184v from +hv and -hv. Does this seem normal or high? I was expecting around 120 or 110V.
 

RockfordFIx

Member
2012-12-03 11:56 am
Perry,

While i had D11 lifted I powered up the output board and all the outputs seemed to be working. It actually produced clean power. Although the voltage on the outputs were a little lower than expected. Half of them around 34V and the rest around 30V. I did notice the amp draw increased from 3amps to about 8.5amps with no load.
next, i powered down and soldered D11 back down and now i am getting the correct rail voltage. ~112vdc. My only concern is the amp draw with no load.
 
sorry maybe i was unclear. the 2 to 3 amp draw was with the hv cables disconnected from the output board. When the HV cables are connected to the output board it holds at 8 amps. tried pressing on certain areas and no change. kinda weird. Do you think replacing all the outputs would on the out put board would help with the current draw at idle. i tested all the outputs prior to the sound test. I know no two amps are the same. i Will replace Q12 and check it again in the morning
 
All amps get burned in. The burn-in type depends on what was repaired in the amp.

I use both subs and dummy loads. For higher power, long term testing, I use the dummy loads. If an amp had a noise or some intermittent problem, I'll listen to it with speakers or a sub.

I use multiple 100 watt tubular ceramic wire-wound resistors for testing. With a lot of air flowing over them, they can easily handle much more than their rated power.

I use multiple paralleled 12v power supplies generally for power but I also have a battery that I can switch in for large amps or amps that easily go into protection (JLs are the most sensitive).

All amps get run to hard clipping for at least 5 minutes. After that, I generally let them run at moderate power for about 3 hours.
 
I use two 2 ohm resistors in series and parallel the series'd pairs to get to the load that I want.

You can use higher power resistors. These are what I purchased when amps weren't so powerful and since I haven't been able to burn them out, that's what I continue to use.

Bear in mind that I test with music up to and sometimes into clipping for long term testing (hours). I also avoid really large amps. The largest amps that I normally have to bench are the ones rated at 5500 watts (power acoustic ratings). If you are going to test amplifiers that can really produce thousands of watts and are going to do long term testing with a sine wave (tougher than with music), you'll need resistors rated to handle the true power output of the amp.

Another problem that you run into is supplying power to the amp. It's very difficult to supply 12v to an amp that's capable of more than about 3000 watts for long term testing. Batteries will drop in voltage quickly and standard wall outlets are not capable of supplying more than about 1500 watts. To get more power, you have to use multiple mains circuits and multiple power supplies or a 220v supply.
 
currently i have a 52amp pyramid powersupply that i purchased on ebay for around $100. It was producing 14 but the voltage has dropped to 11.5 in the last few days and the voltage adjustment knob goes from 12 to 15, has no effect on output. I am building a setup with 2 car batteries with the powersupply so i sustain and adequate current draw.