rockford fosgate bd15001

mike49504 · 2009-12-21 3:56 am

When you hook power up to this amp the light blinks and u can hear the torriod hissing loudly. I checked the fets and outputs all test good. I tryed twisting the torriod it quiets it a lil til u let go and then hiss's loud again

Wondering what i should check next?

Perry Babin · 2009-12-21 4:04 am

I'm not sure which amp this is. Can you post a photo of the guts?

mike49504 · 2009-12-21 4:11 am

heres the photo of the inside of amp

Perry Babin · 2009-12-21 4:15 am

Is it drawing excessive current?

Does it have any DC on the speaker terminals?

What DC voltage do you have on pin 6 of U21?

lumanauw · 2009-12-21 4:22 am

One time I can reduce the noise by painting transformer glue (something like elastic nail polish) to the toroid (to bond the wires) and deflecting that black/red cable (next to the toroid) away from the toroid.

mike49504 · 2009-12-21 4:26 am

when powerd up it doesnt draw excessive current.

no dc voltage on speaker outs

u21 pin 6= 8.19

Perry Babin · 2009-12-21 4:31 am

Does the amp produce audio and the only problem is the hissing?

mike49504 · 2009-12-21 4:39 am

No output amp doesnt produce audio

Perry Babin · 2009-12-21 4:42 am

When driving the amp with a strong preamp signal (~1v) and the gains set to at least 1/2, do you have any audio on pin 1 of U4?

What is the DC voltage measured directly across the red and black wires? Be careful not to allow the probes to short to anything when measuring the voltage.

mike49504 · 2009-12-21 5:02 am

red and black twisted wires no voltage across them

Perry Babin · 2009-12-21 5:06 am

What's the DC voltage on the gates of the power supply FETs?

Place the black meter probe on chassis ground.

I'm assuming that you've had the amp powered up (including remote) during the testing procedure.

mike49504 · 2009-12-21 5:14 am

I had the amp powerd up when tesing the twisted wires.

Gates of the power supply fets are the same for the 6215's and the 3415's
they read 9.87

mike49504 · 2009-12-21 5:17 am

on the power supply fets i tested all 3 legs
gate leg=9.87
middle leg=0
3rd leg=0

Perry Babin · 2009-12-21 5:19 am

Look at the gate signals of the power supply FETs. Do you see a square wave (that goes to ground) or is it straight DC (or a square wave that doesn't go anywhere near ground)?

Perry Babin · 2009-12-21 5:21 am

Middle leg 0v? Are you sure?

The middle leg comes from the power supply transformer windings which are connected directly to the B+ terminal. To have 0v, you would have to have broken transformer windings, a burned trace or no 12v on the B+ terminal.

mike49504 · 2009-12-21 5:23 am

yes 100% positive middle leg reads 0 volts

Ill check for open traces

mike49504 · 2009-12-21 5:31 am

My bad i was looking at the outputs

The power supply fet are mtp75n05hd

gate leg=7.72

middle leg=13.89

3rd leg=0

Perry Babin · 2009-12-21 5:32 am

Look at the gate signals of the power supply FETs. Do you see a square wave (that goes to ground) or is it straight DC (or a square wave that doesn't go anywhere near ground)?

mike49504 · 2009-12-21 5:42 am

ok im stupid wondering what do i need to do to test this with my scope

what should my scope setting be

time/div-
volts or millivolss

and my probe 1x ref 10 x?

Perry Babin · 2009-12-21 5:49 am

timebase set to 10uS

vertical amp set to 5v/div

coupling set to DC

touch the probe to the B+ terminal of the amp and confirm that the trace deflects to ~2.5 divisions. Set the probe so that the scope produces this deflection.

Touch the probe to the gates of the power supply FETs. You should see something that looks like the attached image.

rockford fosgate bd15001

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