Rockford Fosgate T30001

seankane · 2012-10-20 4:36 am

Does anyone know the function of U401 and why it is so hot it is burning my fingers upon touching it?

I think it is emitting the pulsing chirping squeeling noise. Maybe there is something in line with it that is causing this? T401 is sure loose and flopping around whatever that thing does. It looks like a transformer maybe????

The board number is PC-4760-A

Perry Babin · 2012-10-20 7:27 pm

U401 is a driver IC. It drives the transformer T401. If the solder connections are bad, you need to resolder them. If the leads for the transformer are broken, it will likely have to be replaced.

seankane · 2012-10-20 7:52 pm

Could this condition cause no output?

Perry Babin · 2012-10-20 7:56 pm

Yes. For a BD amp to have output, both halves of the output circuits must be working properly. One half switches the rails. The other half is for audio output.

seankane · 2012-10-20 8:01 pm

Ok I will remove the board and desolder the transformer. It probably is broken as loose as it is. am assuming thats why U401 is getting so hot and the amp has no output.

I guess maybe I should replace both of them for good measure?

Perry Babin · 2012-10-20 10:59 pm

If you have to order the transformer from Rockford, you may as well get the IC as if they have it in stock.

seankane · 2012-10-21 12:20 am

I oredered the transformer from onlinecomponents.com already.

I had to order 26 of them but thats ok it was only $36 with shipping out of Neveda.

Do you think the IC will be defective?

seankane · 2012-10-21 1:50 am

Ordered 2 IC's from mouser.......OUCH!!!!!!@ $6.50 each!!!!!

Just going to replace both transformers and IC's for good measure!!!

Perry Babin · 2012-10-21 10:01 am

I don't know if the IC will be defective. I've never had to replace one but I don't work on many of the amps that use them.

seankane · 2012-10-21 11:05 am

OK well the parts should be here later this week, I am hoping this is the problem and its as simple as that.

I have another T15004 from the same guy, he lost several outputs then kept running it anyway and burned up alot of stuff on the board. Should be a fun one.

seankane · 2012-11-22 10:32 am

I replaced the transformer and the IC, the amp powers up now without chirping and pulsing and nothing is getting hot anymore.

The output is distorted, only producing the lower half of the waveform, and the p/s gates dont have a square wave its really funny looking.

I dont think the amp is powering the output board properly its hardly drawing any current.

When you first power up the protect light is on then it goes out and makes a funny noise like something is charging up then it quits.

Perry Babin · 2012-11-22 12:13 pm

Do you have a clean triangle waveform with virtually no DC offset on pin 7 of U303?

seankane · 2012-11-22 12:18 pm

Perry Babin · 2012-11-22 12:26 pm

Do you have a clean square wave on pin 7 of U301 and U302?

seankane · 2012-11-22 12:32 pm

No square wave on either and pin7 of U301 has -4.26 vdc and pin 7 of U302 has +5.10 vdc

Perry Babin · 2012-11-22 2:47 pm

Does turning the subsonic filter on reduce the DC on the output pins of those ICs to near 0v?

seankane · 2012-11-23 4:04 am

NO the voltage remains the same and also I tried all of the other switches and pots, no difference.

Perry Babin · 2012-11-23 4:08 am

Of U300, 301 and 302, which of the output pins have more than a fraction of a volt of DC (not including the pins you just checked)?

seankane · 2012-11-23 4:21 am

So you want the DC voltages on pins 1 and 7 of these 3 components?

seankane · 2012-11-23 4:54 am

U300

PIN1: 0.004 vdc
PIN7: 0.007 vdc

U301

PIN1: 1.730 vdc
PIN7: -4.26 vdc

U302

PIN1: -1.730 vdc
PIN7: 5.10 vdc

I cant imagine the DC offset on the outputs of the LM6172 U301 and U302 are doing the amp any good???

Rockford Fosgate T30001

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