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  #1  
Old 05-09-2013, 03:59 PM
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futureman futureman is offline
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Op amp rolling in a Kenwood Basic C2

I have a Kenwood C2 on its way to me, and I was thinking of a full recap. One can buy a recap kit for this unit online for about $16 (all Nichicon caps).

While I'm at it, I was considering replacing the original op-amps (NJM4560). I've read that the power supplied in this unit is greater than the +/-18V of these op amps, so replacing them with something like NE5532s (+/-22V) would be desirable. Does this seem right/advisable, or is there some other consideration I may be missing here?
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Old 05-09-2013, 05:41 PM
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sKiZo sKiZo is offline
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If you've got viable alternatives listed as compatible, hey, go for it. You may ... or may not ... be pleasantly surprised. Only suggestion I'd make is to socket the chips so you have an easy fallback position.

I recently rebuilt a Carver H9AV holographic generator and had some fun with new tech op amps to replace the old school items available back in the day. Burr Brown hadn't even been born back when those were made - I would have used more of those, but those BrownDogs ain't cheap. Settled for real TI P3s instead of the Malaysian knockoffs elsewhere. Added some bypass caps in strategic locations, and a bit of this and that. Magic moment firing it up the first time, and many many grins since.

BEFORE >>



AFTER >>



I mean ... like ... what's the worst that could happen?

ZzzzZZT! Oh, the humanity ... film at 11 ...
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Old 05-09-2013, 05:48 PM
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Hey, that looks really nice. Apart from basic recapping I have not done very much. So I am not sure what it means to socket the op amps. Could you give me a brief explanation?
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Old 05-09-2013, 06:02 PM
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static14 static14 is offline
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these are sockets for op amps



instead of soldering in a new op amp you solder in a socket for it that way you can insert and remove op amps with having to break out the soldering iron they make for a really simple way to quickly change them out, or "roll" as its called!
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Old 05-09-2013, 06:05 PM
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Ah! Makes perfect sense. Thanks.
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Old 05-09-2013, 06:49 PM
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sKiZo sKiZo is offline
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... and might I suggest, go with the gold pin sockets. They don't cost a lot more, and they're a lot easier to get into them lil holes in the board. Flex-locs (the ones with the skinny bent pins that grip the holes) are the work of the devil in retrofit projects.

Speaking of which, you'll also want to head on over to Rat Shack and get one of their desoldering tools ...



Best $15 you'll ever spend for this type of job. Let it heat up, squeeze the bulb, drop it on the pin, and let the bulb go when the solder pools. Clean as a whistle.

Little tip ... you'll have a few clean looking pins that will stick to the board. Doesn't take a lot of solder to make them fight you. That RS tool comes to the rescue once again. Just drop the tip over the pin and wiggle it a bit - you'll feel it pop loose. From there, just carefully pry the old chip off the board.

You can probably tell by now why sockets are a good thing. Besides making it easier to roll op amps, they also keep the soldering heat away from the chips themselves, so less chance of forping those ...
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Old 05-10-2013, 01:49 PM
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nerdorama nerdorama is offline
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If you don't already have it, you can download the C2 service manual from the AK database here:

http://akdatabase.org/AKview/thumbnails.php?album=2

On the schematic, it shows the opamps being powered by at 18.6V by a discreet regulator using zeners as the reference. Probably could replace the zeners with a 15-16 volt version and reduce the output to +/-15V is newer opamps won't stand the 18V supplies.

Keep us posted.
Thanks,
John
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Old 05-10-2013, 02:06 PM
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Thanks. I may simply replace the caps and hear how things sound before tackling op amps.
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  #9  
Old 05-18-2014, 05:35 PM
Smallies Smallies is offline
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My solder sucker is mangled. Went to the Shack and they've incorporated it into a $35 package kit so I just bought a $10 iron and boy am I in misery right now. and somebody stole or threw away my op amps.
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Old 05-20-2014, 07:09 AM
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It's been a few years since I've been inside a C2, but I seem to remember that the op amps were the SIP-9 variety, where the new ones you'll be using are DIP-8. So you'll need an adapter, recommended is the Brown Dog series.
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