A problem with Kenwood KAC-846

bega_83 · 10th October 2007, 10:55 PM

hi.
I got this KAC-846 that's really messed up, so i'd like to ask your opinion on it. (i'll post some photos of it as well).

It's in a really bad shape but since i can't afford a better one, i have to fix this one. I have a few friends that will help me fixing it because i'm not that good at troubleshooting at all.

Can u help me as well, at least with some guidelines?

It cannot be powered up when connected, so i took it apart. seems some parts are missing, but i cant identify them. I'm not an expert but i see some really weird wiring inside it.
I checked that other thread from eurospanks but this amp is in worse shape than his was.

Thnx in advance.

Perry Babin · 10th October 2007, 11:23 PM

Q27-Q30 are the power supply FETs. An IRFIZ44 is a good replacement.

bega_83 · 12th October 2007, 02:01 PM

Quote:

Originally posted by Perry Babin
Q27-Q30 are the power supply FETs. An IRFIZ44 is a good replacement.

Thnx Perry
Can i replace all of them with this one? I mean is there any significant difference?

And what are Q20 and Q18? They are also missing.

And should i remove these wires (they can be seen on this photo)

Perry Babin · 12th October 2007, 02:36 PM

Quote:

Can i replace all of them with this one?

Those are only used to replace the power supply transistors.

Q18 = 2SC5100
Q20 = 2SA1908

I can't really see much in the photo but I don't think two of those pads were intended to be soldered to the metal tabs sticking up. and I don't think the lower right is supposed to be conected to the other two points. It appears that there is some damage near the RCA jacks. Maybe someone was trying to restore a shield ground connection but that's just a guess.

bega_83 · 12th October 2007, 02:54 PM

Is there anywhere i could find the service manual for this one? Should be helpful.
I tried every possible search i could think of.
I would post some better pics but i can't due to size restriction.
If u want i could send them to you via e-mail.
Thnx again for bothering with me.

Perry Babin · 12th October 2007, 03:07 PM

Email me the photos but before you do, remove the jumper wires and remove as much solder as possible so I can see the board. Please zip the photos into one file.

babin_perry@yahoo.com

bega_83 · 12th October 2007, 04:24 PM

Perry, your guess about ground connection was right, all the jumper wires were connected either to chassis or ground(-) connection of the amp. I will send you pics as soon as possible.

bega_83 · 12th October 2007, 06:27 PM

Q18 = 2SC5100
Q20 = 2SA1908

I ve acquired those two.
Is there any way to test them before puttin them into the amp?

You'll get the pics tomorrow afternoon, i can't do it faster... Hope you don't mind.

Perry Babin · 12th October 2007, 06:42 PM

On the 5100...

Red lead on the first leg and black on either of the other legs should give you approximately 0.6v with your meter set to diode check. With the leads reversed, you should read infinite resistance (or open on diode check). There should be infinite resistance between legs 2 and 3.

For the other transistor swap the meter leads where they plug into the meter and perform the same tests.

bega_83 · 15th October 2007, 12:19 PM

Well, these were messed up too... I'm now searchin for new parts, but it'll take some time untill i get them.
There were also few broken resistors on board, which i already replaced.
It's beggining to look like there is hope to finish repair.
Thanks a lot.

10th October 2007, 11:23 PM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Q27-Q30 are the power supply FETs. An IRFIZ44 is a good replacement. __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links

12th October 2007, 03:07 PM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Email me the photos but before you do, remove the jumper wires and remove as much solder as possible so I can see the board. Please zip the photos into one file. babin_perry@yahoo.com __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links

12th October 2007, 06:42 PM	#9
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	On the 5100... Red lead on the first leg and black on either of the other legs should give you approximately 0.6v with your meter set to diode check. With the leads reversed, you should read infinite resistance (or open on diode check). There should be infinite resistance between legs 2 and 3. For the other transistor swap the meter leads where they plug into the meter and perform the same tests. __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links

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12th October 2007, 02:54 PM	#5
bega_83 diyAudio Member Join Date: Oct 2007 Location: Bosnia :)	Is there anywhere i could find the service manual for this one? Should be helpful. I tried every possible search i could think of. I would post some better pics but i can't due to size restriction. If u want i could send them to you via e-mail. Thnx again for bothering with me.

12th October 2007, 04:24 PM	#7
bega_83 diyAudio Member Join Date: Oct 2007 Location: Bosnia :)	Perry, your guess about ground connection was right, all the jumper wires were connected either to chassis or ground(-) connection of the amp. I will send you pics as soon as possible.

12th October 2007, 06:27 PM	#8
bega_83 diyAudio Member Join Date: Oct 2007 Location: Bosnia :)	Q18 = 2SC5100 Q20 = 2SA1908 I ve acquired those two. Is there any way to test them before puttin them into the amp? You'll get the pics tomorrow afternoon, i can't do it faster... Hope you don't mind.

15th October 2007, 12:19 PM	#10
bega_83 diyAudio Member Join Date: Oct 2007 Location: Bosnia :)	Well, these were messed up too... I'm now searchin for new parts, but it'll take some time untill i get them. There were also few broken resistors on board, which i already replaced. It's beggining to look like there is hope to finish repair. Thanks a lot.

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