A mint Kenwood KA-907 amp is arriving, I need help/info/advice on restoring it. - diyAudio
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Old 19th September 2005, 08:36 AM   #1
Kuja is offline Kuja  Yugoslavia
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Cool A mint Kenwood KA-907 amp is arriving, I need help/info/advice on restoring it.

Hello,

I just won on eBay a mint Kenwood KA 907 amplifier - first owner, all the original papers, etc.

Here's the link to the auction:
http://cgi.ebay.de/KENWOOD-KA-907-tr...QQcmdZViewItem

It will be here very soon.

I plan to overhaul it completely.

The same way I did with my speakers:
http://www.kujucev.com/ar98ls/ar98.htm

New caps, new internal wiring, new everything that should be replaced
...and it will be replaced with highest quality parts that I can get.

In case of my speakers, it was not only a restoration job - they were significantly improved by using modern, much higher quality components than original. The difference in sound was unbelievable!

Anybody has a service manual?

I would appreciate any advice or tip!!!

Are there any quirks specific to KA-907?

Things to adjust - bias, DC offset...

Anything and everything that comes to your mind!

I will document the whole process with my camera and I'll post it online the same way I did with my ARs, but with more details. The AR page is not finished yet...

Thanks in advance,

Aleksandar

PS
I've found this page so far:

http://www.amplifier.cd/Verstaerker/...07_english.htm

Anything more that I should know?
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Old 19th September 2005, 09:37 AM   #2
Kuja is offline Kuja  Yugoslavia
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I forgot to mention that I'm really a newbie, who reads lots of stuff and is willing to learn.

So please be more descriptive in your answers

The actual restoration is going to be performed by a much more experienced friend.
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Old 20th September 2005, 10:20 AM   #3
Kuja is offline Kuja  Yugoslavia
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Anybody?
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Old 20th September 2005, 08:19 PM   #4
Zimo is offline Zimo  Finland
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Hey!

Well Im not maybe the right person to tell you about restoring this amp, but Im trying to.

I have a Yamaha CA-1010 which is restored quite well.. most of it is done by my friend (re-capped everything) but Im done something also.

If I would restore your kenwood I would maybe first readd all new electrolytic capasitors except the four "Big" ones in the power section.. (why not them?, I absume that those are not easy to find and it would chance the look of the amp radically). Only chance if those are leaking or voltage rails are dropping seriously under load.

Next I would take a look to preamp polyester caps and see are those cheap models or good quality ones.. (my Yamaha had everything quality except a few ones in a important position ) (I readd good quality Wimas)

After these I would check amps power supply board. What to look at there is that has the amp being going too hot and what have that affected to components on that board. Some parts are too often without heatsink and are not working in their SOA area. You will be able to see that with our own eyes if the board is darker near the power transistors that elsewhere.

I have to say that CA-1010 have problems with power supply board.. I had to add one heatsink and change some "hot" components to bigger ones. When changing new caps check are those 85 or 105 degree models. To places like power supply board and main board choose the better ones that can handle higher temperatures.

What next? I always check solderings of my old ones. Especially from main circuit board and where wirings meets the boards. (I have worked in a TV-repairing and have seen something you wouldnt even believe!)

Of course you have to check potentiometers (clean them if frizzling), I think you should also clean the contacts of the connectors. Maybe also contacts of relays.

After these I would check bias and DC offset and take a few hours with cleaning the body and knobs. And then take my favourite CD and let the beast handle else!

Of course there are plenty of work to get an old amp to sound and look like a new one. (Is that the goal? No!) And my advises were just a part of it...

By the way your speakers looks great
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Old 21st September 2005, 04:03 AM   #5
Leolabs is offline Leolabs  Malaysia
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Thanks for the link,Kuja. As i was going to do some restoration of my Proton AM455
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Old 22nd November 2011, 12:46 AM   #6
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Default How's the amp

Did you ever get that amp and did you overhaul it. I have the same amp and mine is like new. If fact it went unused/unapreciated for years. Then I took it out and realized just how good it is.
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