Fosgate 1000a2 with blown output - Page 3

81300sd · 5th April 2009, 05:05 AM

TH1 is 4.95 and .65

TH2 is 4.95 and 4.95

Perry Babin · 5th April 2009, 05:08 AM

Remove TH2 from the circuit.

The amp should power up. Take the normal precautions that you would when powering up an amp that you don't know is in good working order.

81300sd · 5th April 2009, 05:19 AM

Ok, it powered up. I suspect one of the resistors is bad that is inline with that thermistor.

Probably should check out d12 too.

Do you happen to know what the part # of that thermistor is?

Perry Babin · 5th April 2009, 05:24 AM

I don't know the part number of the thermistor. If it's defective, Rockford may have a replacement.

Measure the resistance across the thermistor. If it's ~10k ohms, it's likely OK. If you heat it and the resistance goes down, it's almost certainly OK.

81300sd · 5th April 2009, 02:52 PM

Thermistor is confirmed dead. Getting about 3.5 ohms on the dead one and about 8600 on the good one.

81300sd · 5th April 2009, 05:06 PM

Hooked it up to the car. I have limited output and the previously dead side is very noisy. I suspect LM317 to be bad as the voltages are spiking all over the place on it. I have some so I think I will change it just to be sure its good.

Just realize I never changed Q321 and Q322 so I will change them also and see what it does.

81300sd · 5th April 2009, 06:47 PM

That didn't do it.

Just testing it. For a minute it was clean sound then it started crapping out.

Checking U6 and U8 middle leg(mur1610ct, mur1610ctr)

When it is crapping out I have 0 volts on the middle leg of u6 and ~108v on the middle leg of u8, something is shorting.

Perry Babin · 5th April 2009, 06:56 PM

Are you sure that no outputs are shorted?

81300sd · 5th April 2009, 09:53 PM

No I am not sure, but all that I am testing looks good. Maybe I am not testing it right.
Rail voltage on the irf9640's is ~108v and 0 on the irf640's

Output voltage is 54v

81300sd · 5th April 2009, 10:29 PM

Not sure if this is important at all, but I noticed when powered up, the first 5-10 or so it seems fine, then it goes bad.

5th April 2009, 05:08 AM	#22
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Remove TH2 from the circuit. The amp should power up. Take the normal precautions that you would when powering up an amp that you don't know is in good working order. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

5th April 2009, 05:24 AM	#24
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	I don't know the part number of the thermistor. If it's defective, Rockford may have a replacement. Measure the resistance across the thermistor. If it's ~10k ohms, it's likely OK. If you heat it and the resistance goes down, it's almost certainly OK. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

5th April 2009, 06:56 PM	#28
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Are you sure that no outputs are shorted? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

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5th April 2009, 05:05 AM	#21
81300sd diyAudio Member Join Date: Feb 2009	TH1 is 4.95 and .65 TH2 is 4.95 and 4.95

5th April 2009, 05:19 AM	#23
81300sd diyAudio Member Join Date: Feb 2009	Ok, it powered up. I suspect one of the resistors is bad that is inline with that thermistor. Probably should check out d12 too. Do you happen to know what the part # of that thermistor is?

5th April 2009, 02:52 PM	#25
81300sd diyAudio Member Join Date: Feb 2009	Thermistor is confirmed dead. Getting about 3.5 ohms on the dead one and about 8600 on the good one.

5th April 2009, 05:06 PM	#26
81300sd diyAudio Member Join Date: Feb 2009	Hooked it up to the car. I have limited output and the previously dead side is very noisy. I suspect LM317 to be bad as the voltages are spiking all over the place on it. I have some so I think I will change it just to be sure its good. Just realize I never changed Q321 and Q322 so I will change them also and see what it does.

5th April 2009, 06:47 PM	#27
81300sd diyAudio Member Join Date: Feb 2009	That didn't do it. Just testing it. For a minute it was clean sound then it started crapping out. Checking U6 and U8 middle leg(mur1610ct, mur1610ctr) When it is crapping out I have 0 volts on the middle leg of u6 and ~108v on the middle leg of u8, something is shorting.

5th April 2009, 09:53 PM	#29
81300sd diyAudio Member Join Date: Feb 2009	No I am not sure, but all that I am testing looks good. Maybe I am not testing it right. Rail voltage on the irf9640's is ~108v and 0 on the irf640's Output voltage is 54v

5th April 2009, 10:29 PM	#30
81300sd diyAudio Member Join Date: Feb 2009	Not sure if this is important at all, but I noticed when powered up, the first 5-10 or so it seems fine, then it goes bad.

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