Alpine 3553 not turning on

Dr Zeus · 28th November 2011, 11:14 PM

Alpine 3553 looks very much like the 3552 on the DVD, only this one has an input/xover daughter board, plus each channel output pair has its own individual thermistor like I have not seen on any amp before.

This amp appears to ave a failed power supply with all 2SD1669s shorted from legs 1-3. (Measuring exactly 4.3 ohms on all 6)

I carefully lifte all 1&3 legs off all PS transistors and to my surprise they actually measure OK. From pads 1 to 3, I still measure 4.3 ohms.

What gives?

The amp will not power up and does not draw anything.

1moreamp · 28th November 2011, 11:31 PM

Your reading those 1/2 watt resistors right in front of the 2Sd1669's. If the 1669's are ok I would look for a open trace, or a bad turn on transistor in the supply....

Dr Zeus · 03:35 AM

OK i found a bad trace to ground. Amp tried to power up but fails.

TL494
Pin 1: 0.002
Pin 2: 4.98
Pin 3: 0.089
Pin 4: 4.96
Pin 5: 1.663
Pin 6: 3.666
Pin 7: 0.001
Pin 8: 13.75
Pin 9: 0.001
Pin 10: 0.001
Pin 11: 13.75
Pin 12: 13.75
Pin 13: 4.99
Pin 14: 4.99
Pin 15: 4.99
Pin 16: 0.001

The amp is pulsing slightly every 6~7 seconds. During which, all 4 channels appear to have some DC voltage across them. Voltage numbers on the TL494 dont change very much.

Perry Babin · 29th November 2011, 06:48 AM

Find the PNP transistor with it's collector connected to pin 4 and remove it. That should disable the protection circuit (so be careful) to allow you to see if there is a problem with one of the channels.

Dr Zeus · 29th November 2011, 03:23 PM

Cool I was looking for something like that last night. I bleieve that is Q525 to be pulled. I'll work on it tonight.

Thanks

Dr Zeus · 1st December 2011, 02:29 AM

Removed Q518. Amp powers up. +-26v rail. it appears there is no negative regulated voltage on the opAmps.

IC404
Pin 1: 13
Pin 2: 2.9
Pin 3: .25
Pin 4: .9
Pin 5: .25
Pin 6: 2.9
Pin 7: 13
Pin 8: 13

After about 5 minutes of power-on time, the ps and outputs start to get pretty warm.

I believe I just found an open/burned 1/8w resister R528 and a 1/2w R530 next to the negative voltage regulator, Q514

Dr Zeus · 1st December 2011, 03:59 AM

I also found a 25v 100uF cap leaked nearby to this regulator - It probably shorted and blew open, which in turn took out the above resistors.

Upon replacing all three pieces, plus re-installing Q518, the amp powers and plays across all 4 channels.

Thanks perry!

Dr Zeus · 1st December 2011, 04:07 AM

Upon assembly, I also remember the following on this amp; Cold solder on one of the torroid legs, and cold solder on one of the rail busbars.

28th November 2011, 11:14 PM	#1
Dr Zeus diyAudio Member Join Date: Oct 2010	Alpine 3553 not turning on Alpine 3553 looks very much like the 3552 on the DVD, only this one has an input/xover daughter board, plus each channel output pair has its own individual thermistor like I have not seen on any amp before. This amp appears to ave a failed power supply with all 2SD1669s shorted from legs 1-3. (Measuring exactly 4.3 ohms on all 6) I carefully lifte all 1&3 legs off all PS transistors and to my surprise they actually measure OK. From pads 1 to 3, I still measure 4.3 ohms. What gives? The amp will not power up and does not draw anything.

29th November 2011, 03:32 AM	#3
Dr Zeus diyAudio Member Join Date: Oct 2010	OK i found a bad trace to ground. Amp tried to power up but fails. TL494 Pin 1: 0.002 Pin 2: 4.98 Pin 3: 0.089 Pin 4: 4.96 Pin 5: 1.663 Pin 6: 3.666 Pin 7: 0.001 Pin 8: 13.75 Pin 9: 0.001 Pin 10: 0.001 Pin 11: 13.75 Pin 12: 13.75 Pin 13: 4.99 Pin 14: 4.99 Pin 15: 4.99 Pin 16: 0.001 The amp is pulsing slightly every 6~7 seconds. During which, all 4 channels appear to have some DC voltage across them. Voltage numbers on the TL494 dont change very much. Last edited by Dr Zeus; 29th November 2011 at 03:35 AM.

29th November 2011, 06:48 AM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Find the PNP transistor with it's collector connected to pin 4 and remove it. That should disable the protection circuit (so be careful) to allow you to see if there is a problem with one of the channels. __________________ 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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28th November 2011, 11:31 PM	#2
1moreamp diyAudio Member Join Date: Dec 2005 Location: Northern California	Your reading those 1/2 watt resistors right in front of the 2Sd1669's. If the 1669's are ok I would look for a open trace, or a bad turn on transistor in the supply....

29th November 2011, 03:23 PM	#5
Dr Zeus diyAudio Member Join Date: Oct 2010	Cool I was looking for something like that last night. I bleieve that is Q525 to be pulled. I'll work on it tonight. Thanks

1st December 2011, 02:29 AM	#6
Dr Zeus diyAudio Member Join Date: Oct 2010	Removed Q518. Amp powers up. +-26v rail. it appears there is no negative regulated voltage on the opAmps. IC404 Pin 1: 13 Pin 2: 2.9 Pin 3: .25 Pin 4: .9 Pin 5: .25 Pin 6: 2.9 Pin 7: 13 Pin 8: 13 After about 5 minutes of power-on time, the ps and outputs start to get pretty warm. I believe I just found an open/burned 1/8w resister R528 and a 1/2w R530 next to the negative voltage regulator, Q514

1st December 2011, 03:59 AM	#7
Dr Zeus diyAudio Member Join Date: Oct 2010	I also found a 25v 100uF cap leaked nearby to this regulator - It probably shorted and blew open, which in turn took out the above resistors. Upon replacing all three pieces, plus re-installing Q518, the amp powers and plays across all 4 channels. Thanks perry!

1st December 2011, 04:07 AM	#8
Dr Zeus diyAudio Member Join Date: Oct 2010	Upon assembly, I also remember the following on this amp; Cold solder on one of the torroid legs, and cold solder on one of the rail busbars.

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