The KA-9100 restoration.

hopjohn

Silver Face
It's time to begin another big project. Up now a Kenwood KA-9100. The top of the line integrated for 1977. This particular amp was provided by fellow AKer and committed bronzed-face Kenwood collector, gort69. Sixty-nine? is that his favorite year or favorite something else, who knows, but he parted ways with this all-stock, silver faced beauty for undisclosed fortunes. Now, after a trip to the lone-star state, it's in my loving hands and time to restore it.

Get your popcorn ready Kenwood lovers.
 
An Introduction to the KA-9100

KA-9100 Service Manual Download

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In all seriousness, thanks again to gort69 for selling me the amplifier. It's been a glaring hole in my collection for several years now and he gave me a very fair deal on it so many props to him for allowing this to happen.

Let's start by discussing the disassembly and serviceability. The 9100 seems to have a reputation, by multiple accounts on these forums, to be a rather difficult amplifier to work on. I would tend to agree even though I was expecting something frighteningly worse. The front boards require you remove an alarming number of screws to access. The sub-frame that houses the meters, two control boards, right side switches and volume pot has to be completely removed for recapping and adequate switch cleaning to take place.

EDIT: Here's a photo showing just how much hardware is holding it all to the front sub-frame. There are more screws that can't be seen on the interior top edge and of course on the sides that meet the heatsinks.
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The preamp is the hardest part to disassemble and to reassemble. My tip is to separate the metal bracket, after you have removed the screws, from the left and then work to the right. Do the opposite when installing. There's also a fragile black wire that connects the two control units (that's what they're called in the manual but they contain the eq switches and knobs). I would note the position of that wire and desolder it on one side until your done.

I had to go into the preamp three times, first time during the recap, the second time to fix the black wire and the third time when I opened all the switches and cleaned them (solved intermittent problems that spraying deoxit just didn't solve). It's a great amp.
 
You're welcome John, and thank you for the purchase - saved me the ebay headache....plus I figured you were frustrated thrashing on pipsqueak amps and need something to sink your teeth into. Looking forward to the thread.

I would note the position of that wire and desolder it on one side until your done......the second time to fix the black wire

You too, huh? I had to send an emergency PM to a member who had just buttoned one up. It broke off so cleanly I had no clue. He assured me his had broken off as well so I didn't feel so bad. I replaced the wire with a longer piece of stranded.
 
You too, huh? I had to send an emergency PM to a member who had just buttoned one up. It broke off so cleanly I had no clue. He assured me his had broken off as well so I didn't feel so bad. I replaced the wire with a longer piece of stranded.

My black ground wire broke off during disassembly as well. Fortunately, I was given fair warning so it'll be replaced before all goes back together.

Here's the little bugger on Pin 12 of the "rear" control board.
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Hmmmm - that's not the wire I was talking about. It's this one - connects to pin #8 on the rear board and J6 on the front board.

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There's also a fragile black wire that connects the two control units (that's what they're called in the manual but they contain the eq switches and knobs). I would note the position of that wire and desolder it on one side until your done.

If I'd read more closely I'd have known what you meant, my apologies. Probably not a bad idea just to replace that one with some stranded as gort69 pointed out.
 
Another rather difficult part of restoring a 9100 is the work required on the two diode boards. These boards contain the main rectifiers and portions of the protection circuit. They are mounted in place with the four primary filter caps. In order to reach the component side of these two boards the filter caps need to be unsoldered from them. The large surface area of the pads and foil pattern makes using a smaller iron quite the task. I keep a 63 Watt Hakko 456 soldering iron around for chassis work and jobs such as these. With the use of the 456 and some solder wick, quick work can be made of removing the caps.

Foil side of the diode boards with one of the four caps desoldered.
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You too, huh? I had to send an emergency PM to a member who had just buttoned one up. It broke off so cleanly I had no clue. He assured me his had broken off as well so I didn't feel so bad. I replaced the wire with a longer piece of stranded.
Yup, but I didn't catch it until after I started testing. I took forever since I thought that maybe I inverted a cap.
 
The KA-9100 uses a couple of my least favorite style switches with the Meter Range and Loudness control. The conventional Deoxit cleaning approach on these guys typically doesn't do much but make a greasy mess. It really comes down to the lack of good access to the contacts. Since I really don't want to have to dig back into the front panel I felt like it was best to do a disassembly of them.

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They get pretty bad, the separate switch on the back is mad the same same way. It;s a little easier
to open or clean.
 
They get pretty bad, the separate switch on the back is mad the same same way. It;s a little easier
to open or clean.
Those angry switches are the worst! :D

I disassemble mine also but I also discovered to use either deoxit gold or fader to protect the silver contacts.
Yes sir, I like me some Deoxit Gold for preservation. I just had the tiny tube of it and ran out, more is on the way. I used Fader Lube for now. I also like Super Lube for the mechanical portions.
 
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