PPI 1400.1 does not turn on

durwood · 27th February 2010, 04:37 AM

Now that I fixed my 2300.2 I've got a 1400.1 that is very similar but this one won't turn on. I replaced all the bad power supply fets and 3/4 of outputs with some driver replacements. It will not turn on however.

Upon closer inspection buried in thermal paste I found a broken thermistor which I assume is for some type of thermal rollback? Problem is I don't know if it was a NTC or PTC one or what the value was. I popped a 7.2K resistor in there to get me by but in the circuit it is reading ~4ohms and in the working PPI I just fixed it reads about 7.4K in circuit. Could this cause it not to turn on?

Perry Babin · 27th February 2010, 04:48 AM

In the amps I've measured them in, they were 50k NTC thermistors. Other values may have been used. 4 ohms is definitely too low. I would expect the amp to power up without it. These were used for thermal protection and to control the fans in amps that had fans.

durwood · 27th February 2010, 04:59 AM

Now after I post this it turns on but now draws excessive current. I'm going to go through and check the same stuff as the 2300.2 but if anyone knows what the thermistor is supposed to be I'd appreciate it.

durwood · 27th February 2010, 05:03 AM

whoops meant 4kohms not 4 ohms. No fans in this little guy.

durwood · 28th February 2010, 01:12 AM

I replaced a couple of a06's and a56's but they were not too far off from new ones. I measured all points and they are not drastically different.

Current draw is still excessive. So I check back at the SG3525 and I believe it is bad. Vref is supposed to be ~5.1V +/-1% and I'm already over that with the voltage sitting around 10V. If I allow more current this jumps into 6V+. Anyone ever had one go out? What would cause an SG3525 to go faulty?

Perry Babin · 28th February 2010, 02:42 AM

These fail just like any other IC. Sometimes the failure is simply a random failure. Sometimes it's due to outside causes, especially on amps where the IC drives FETs directly.

durwood · 28th February 2010, 03:30 AM

Quote:

Originally Posted by Perry Babin

Sometimes it's due to outside causes, especially on amps where the IC drives FETs directly.

Ah you have a good point. I like to think about what causes the failure and in this case with all outputs blown, power supply was about 75% dead on all fets, I have to wonder if the PWM chip caused it, or if the fets/ too much strain on PS destroyed everything.

durwood · 28th February 2010, 09:55 PM

Nothing like paying 4 times the price for a part and finding it locally.

Final piece of the puzzle - SG3525 replaced and all is well. Probably why it would randomly not turn on too.

27th February 2010, 04:37 AM	#1
durwood diyAudio Member Join Date: Oct 2006	PPI 1400.1 does not turn on Now that I fixed my 2300.2 I've got a 1400.1 that is very similar but this one won't turn on. I replaced all the bad power supply fets and 3/4 of outputs with some driver replacements. It will not turn on however. Upon closer inspection buried in thermal paste I found a broken thermistor which I assume is for some type of thermal rollback? Problem is I don't know if it was a NTC or PTC one or what the value was. I popped a 7.2K resistor in there to get me by but in the circuit it is reading ~4ohms and in the working PPI I just fixed it reads about 7.4K in circuit. Could this cause it not to turn on?

27th February 2010, 04:48 AM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	In the amps I've measured them in, they were 50k NTC thermistors. Other values may have been used. 4 ohms is definitely too low. I would expect the amp to power up without it. These were used for thermal protection and to control the fans in amps that had fans. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

28th February 2010, 02:42 AM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	These fail just like any other IC. Sometimes the failure is simply a random failure. Sometimes it's due to outside causes, especially on amps where the IC drives FETs directly. __________________ 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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27th February 2010, 04:59 AM	#3
durwood diyAudio Member Join Date: Oct 2006	Now after I post this it turns on but now draws excessive current. I'm going to go through and check the same stuff as the 2300.2 but if anyone knows what the thermistor is supposed to be I'd appreciate it.

27th February 2010, 05:03 AM	#4
durwood diyAudio Member Join Date: Oct 2006	whoops meant 4kohms not 4 ohms. No fans in this little guy.

28th February 2010, 01:12 AM	#5
durwood diyAudio Member Join Date: Oct 2006	I replaced a couple of a06's and a56's but they were not too far off from new ones. I measured all points and they are not drastically different. Current draw is still excessive. So I check back at the SG3525 and I believe it is bad. Vref is supposed to be ~5.1V +/-1% and I'm already over that with the voltage sitting around 10V. If I allow more current this jumps into 6V+. Anyone ever had one go out? What would cause an SG3525 to go faulty?

28th February 2010, 09:55 PM	#8
durwood diyAudio Member Join Date: Oct 2006	Nothing like paying 4 times the price for a part and finding it locally. Final piece of the puzzle - SG3525 replaced and all is well. Probably why it would randomly not turn on too.

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