Help with amp repair

yobobrox · 27th May 2009, 02:37 AM

Alright, I've been lurking here for a few months trying to figure out what to do with my damaged Kicker KX700.5 and I've finally caved in and registered so I can ask for some help. I've read over a lot of Perry Babin's site, and I've read a lot of posts, but I'm not sure what to do next...

My amp was attacked by rainwater that leaked into my trunk somehow. Now, it's stuck in protection mode. So, I pulled it open and found (what I think is) a FET that was highly corroded, along with a few tiny resistors. Nothing else appears to be affected. I cleaned the corrosion off with acetone and alcohol. Then, I tried powering up the amp without any speakers attached and it still went straight to protection mode. I have a DMM, and I tried testing some FETs and resistors, but got pretty mixed up and wasn't sure if I was even identifying FETs properly. I'm hoping someone here can give me some tips on what to do....it's a bit overwhelming.

Thanks

Perry Babin · 27th May 2009, 07:35 AM

Can you send me a few photos off the damaged area and one showing the overall layout?

babin_perry@yahoo.com

yobobrox · 27th May 2009, 03:22 PM

Absolutely; coming up within an hour.

Perry Babin · 27th May 2009, 06:28 PM

When checking the power transistors (those mounted to the heatsink), you should not read anything near 0 ohms between the legs of any individual transistor. Did you have any that read near 0 ohms?

yobobrox · 28th May 2009, 03:45 AM

Ah, ok. That was where I was getting confused. I wasn't sure if polarity of the meter mattered or if I was supposed to be testing between all the legs (giving 3 combinations to test for a 3 legged part).

Alright, I tested them again and found around 5 that read ~0 ohms. I'm going to try more cleaning of the board around them (one is on the bottom row of transistors, and the others are on the top row), but I imagine that they are toasted. If so, I just read the numbers off the part and purchase replacements? Where do I purchase replacements? And do they all have to be the same batch? I read something about problems between batches, but I didn't understand it all.

Perry Babin · 28th May 2009, 08:14 AM

What are the numbers on the ones that appear shorted.

yobobrox · 28th May 2009, 12:03 PM

I said that backwards - one is on the top of the board and the rest are on the bottom. I can point them out in pictures if needed.

Perry Babin · 28th May 2009, 12:14 PM

What are the numbers on the ones that appear shorted.

yobobrox · 28th May 2009, 08:52 PM

Hmm, I can't figure out what the deal is, but I got different readings on several of the transistors today (checked out OK today). Anyway, I desoldered 4 of them that all read zero ohms across the two outside legs. The part numbers are:

Top Row, 5th from right:
YG225N2
(NPN diagram)
35

Top Row, 6th from right:
YG225C2
(PNP diagram)
35

Bottom Row, 5th from right:
YG225N2
(NPN diagram)
35

Bottom Row, 6th from right:
YG225C2
(PNP diagram)
35

Perry Babin · 28th May 2009, 08:57 PM

Those are the rectifiers. The outer legs are shorted by the transformer windings when they're in the board. That's normal.

Are any others shorted?

27th May 2009, 02:37 AM	#1
yobobrox diyAudio Member Join Date: May 2009	Help with amp repair Alright, I've been lurking here for a few months trying to figure out what to do with my damaged Kicker KX700.5 and I've finally caved in and registered so I can ask for some help. I've read over a lot of Perry Babin's site, and I've read a lot of posts, but I'm not sure what to do next... My amp was attacked by rainwater that leaked into my trunk somehow. Now, it's stuck in protection mode. So, I pulled it open and found (what I think is) a FET that was highly corroded, along with a few tiny resistors. Nothing else appears to be affected. I cleaned the corrosion off with acetone and alcohol. Then, I tried powering up the amp without any speakers attached and it still went straight to protection mode. I have a DMM, and I tried testing some FETs and resistors, but got pretty mixed up and wasn't sure if I was even identifying FETs properly. I'm hoping someone here can give me some tips on what to do....it's a bit overwhelming. Thanks

27th May 2009, 07:35 AM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Can you send me a few photos off the damaged area and one showing the overall layout? babin_perry@yahoo.com __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

27th May 2009, 06:28 PM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	When checking the power transistors (those mounted to the heatsink), you should not read anything near 0 ohms between the legs of any individual transistor. Did you have any that read near 0 ohms? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

28th May 2009, 08:14 AM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	What are the numbers on the ones that appear shorted. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

28th May 2009, 12:14 PM	#8
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	What are the numbers on the ones that appear 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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27th May 2009, 03:22 PM	#3
yobobrox diyAudio Member Join Date: May 2009	Absolutely; coming up within an hour.

28th May 2009, 03:45 AM	#5
yobobrox diyAudio Member Join Date: May 2009	Ah, ok. That was where I was getting confused. I wasn't sure if polarity of the meter mattered or if I was supposed to be testing between all the legs (giving 3 combinations to test for a 3 legged part). Alright, I tested them again and found around 5 that read ~0 ohms. I'm going to try more cleaning of the board around them (one is on the bottom row of transistors, and the others are on the top row), but I imagine that they are toasted. If so, I just read the numbers off the part and purchase replacements? Where do I purchase replacements? And do they all have to be the same batch? I read something about problems between batches, but I didn't understand it all.

28th May 2009, 12:03 PM	#7
yobobrox diyAudio Member Join Date: May 2009	I said that backwards - one is on the top of the board and the rest are on the bottom. I can point them out in pictures if needed.

28th May 2009, 08:52 PM	#9
yobobrox diyAudio Member Join Date: May 2009	Hmm, I can't figure out what the deal is, but I got different readings on several of the transistors today (checked out OK today). Anyway, I desoldered 4 of them that all read zero ohms across the two outside legs. The part numbers are: Top Row, 5th from right: YG225N2 (NPN diagram) 35 Top Row, 6th from right: YG225C2 (PNP diagram) 35 Bottom Row, 5th from right: YG225N2 (NPN diagram) 35 Bottom Row, 6th from right: YG225C2 (PNP diagram) 35

28th May 2009, 08:57 PM	#10
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Those are the rectifiers. The outer legs are shorted by the transformer windings when they're in the board. That's normal. Are any others 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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