Another Rockford Fosgate Punch 200ix repair

[cebby]

Originally Posted by seankane

Set your meter in ohms with the range on auto and measure the rsistance between the gate and source legs of all 4 power supply fets. That would be leg 1 and 3 looking at the fet from left to right, what do you get?

The board location of these fets is Q10,Q11,Q6,Q7

Next measure the gate drivers resistance the little smd resistors marked 510 what do you get? These are 51 ohm and should read somewhat close to that.

The board location of these resistors is R31,R36,R32,R37

Here are the values:

Q10 - 7.35 m ohm
Q6 - 7.34 m ohm
Q11 - 7.25 m ohm
Q7 - 7.24 m ohm

R31 - 51.1 ohm
R36 - 51.1 ohm
R32 - 51.0 ohm
R37 - 51.0 ohm

[cebby]

Originally Posted by Perry Babin

As a side note...

On this site (and others), if you type anything that would take more than 1 minute to re-type, highlight the text and copy it to the clipboard (ctrl-c or right-click and select copy) before clicking anything that will move you from the page where you typed it. It's happened to me so many times that I always do this for long posts.

Most sites (that I visit anyway) don't timeout that quick anymore - I've run a number of forums over the years and that value is one of the first things I change.

I just need to keep it short and sweet.

[seankane]

With the amp powered on what is the the DC voltage on the gate legs of the power supply fets, that leg being the first leg from left to right.

[cebby]

It's weird - these were fluctuating some, plus when I went through and remeasured, all of the values had dropped.

Q10 - .850 - dropped to .811
Q6 - .905 - dropped to .825
Q11 - .934- dropped to .832
Q7 - .955 - dropped to .833

[Perry Babin]

Most Rockford amps have a bit of voltage regulation for the rails. They quickly go to full duty cycle when driven into a load but at idle, the duty cycle of the drive signal is reduced. This will make the measured DC voltage relatively low at idle unless the DC input voltage is low.

If you have a regulated 12v power supply with a variable voltage, decrease the voltage. The gate voltage should increase as you decrease the 12v supply voltage.

If you do this, check the voltage on the gate resistors. There will be less of a chance of damage if the probes slip.

[cebby]

Ah OK - that makes perfect sense to me. Do those sound like acceptable numbers - and is that much of a disparity (over .1 volt) between Q10 and Q7 normal?

Let me see what I can find figure out on the power supply.

[Perry Babin]

I don't see any problems with the numbers you posted.

[seankane]

Do you have the means and part to replace the IN4003 and then to further test the amp?

[cebby]

I need to order the part - I'm comfortable replacing it.

I was hoping to place a bigger order through identifying more bad parts first. If it helps with the process, I'll order the part and get it swapped out for further testing.

[Perry Babin]

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