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Old 19th January 2009, 10:12 AM   #1
paco161 is offline paco161  United States
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Default Citation 12 help

Hi all,
I'm new here to the forums so I hope this is going in the right place. If not, well oops. Anyways, I recently bought an old HK Citation 12 off of the bay that is, believe it or not, in very good condition considering it's age and the fact that it was assembled from a kit, and not at the factory (yes I checked all the connections and they are sound). However, it has one problem. When it's getting power, the amp clicks, pops, and occasionally thumps. What I mean by that is that the clicks and pops remind me of what you would get off of an LP and the occasional thumps are much akin to that of a turn on thump, but this is all while the amp is playing also while it doesn't have power. Because the thing doesn't have a power switch, I have to unplug it until I can jerry rig something, but the amp still pops and clicks, even without power! Because of this, the only assumption I can come to is that the power supply caps have gone bad, but I'm not sure. Any help is greatly appreciated! Thank you very much and sorry about the lengthy post!

Paco
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Old 19th January 2009, 01:00 PM   #2
steenoe is offline steenoe  Denmark
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Hi Paco. You might want to ask over in the Pass section. The Citation 12 is one Nelson Pass's older constructions. Do a search in the Pass section too, there are some threads about the Citation 12.



Citation12 repair!!
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Old 19th January 2009, 02:33 PM   #3
DRC is offline DRC  United Kingdom
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This maybe due to a faulty capasitor, most likely a 'small' one on the main pcb.

BTW, i don't think this is one of NP's designs - but there are plans for a 'PASS' rebuild using mosfets ...
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Old 19th January 2009, 04:07 PM   #4
paco161 is offline paco161  United States
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Yeah, I'm talking about an original Harman/Kardon Citation 12. Honestly, I have no idea what the problem would be or what to look for that might be the problem...
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Old 19th January 2009, 05:47 PM   #5
paco161 is offline paco161  United States
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Actually, I was doing some research and came across a page talking about modding a Citation 12 with "ultra linear transistors", but that's besides the point. What it mentioned are some of the problems with the Citation 12s, more specifically this, "a problem in which the proprietary six-lead dual input transistors would develop loud, random, spike pulse noises, which would drive the amplifier to full output, or to blown outputs, often taking out the attached speakers' tweeters." Unfortunately, I don't yet know enough about amps to know if this is what's going on. Here's the page. http://slbender.exactpages.com/citation.html It details a number of problems, but I couldn't begin to tell which I'm dealing with. Honestly, any kind of clue as to what the problem may be is greatly appreciated. Thanks!
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Old 21st January 2009, 12:57 AM   #6
paco161 is offline paco161  United States
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Anyone?
I bought this thing over buying a good condition Hafler XL-280 and I really hope I didn't buy a lemon, or at least something I can't figure out how to fix myself, with a little help...
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Old 21st January 2009, 08:22 AM   #7
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Default well ......

this is one amplifier that extensivly has been talked all over in the forum ..... you will find many threads including infos about specs performance trouble and variations .....

expecting any fast food solution it will never come from any forum member about the specific problem

in general ......

unit like that aged that much will need a total recaping and this is not a sugestion it is simply a fact ....

then also due to that age they might be many things that could create complications like soldering bad contacts cleaning and so on

if you like to play with it and you have enough skills you may wana look at the above link that explains a lot but requires an ammount of skills to proceed in repairs or upgrades


vintage amplifier repair/upgrade manual

finally i would never spend time and money in the amplifier circuits included in this box .....unless you are the type of person that like to keep things as made

if not my recomendation will be to remove all the guts of this amp keep the rest and install inside more modern boards ..... that will outperform the original circuits for breakfast

best regrads sakis
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Old 21st January 2009, 11:08 PM   #8
paco161 is offline paco161  United States
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Yeah, I was thinking of just replacing everything that I can and keeping the original PCBs for convenience's sake, especially since I have no idea how I would track down replacements. Replacing that caps and anything else (resistors too? Maybe?) sounds like a fun project, something I was looking into doing anyways. My only worry would be about finding replacement transistors if need be...thanks!
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Old 21st January 2009, 11:46 PM   #9
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The HK12 had a whopping big thump - that's normal.

You can best reduce it by using a constant current source to bias the
input diff pairs.

As to the other noises, check the quality of connections for the plug-in
boards.

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Old 22nd January 2009, 03:06 AM   #10
anatech is offline anatech  Canada
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Hi Paco,
I completely agree with Nelson. Adding that current source will help with more than just reducing the "pop" (bang?). The use of a relay delay for the speakers would eliminate this problem. I would do both.

I'd like to add that the "proprietary six-lead dual input transistors" are simply a dual transistor and may be replaced by a pair of matched singles. Many amplifiers did use a dual transistor, so it's not all that strange a part. Most Japanese amplifiers used a 5 lead device. Same thing with a common lead for the two emitters.

Anyway, some of the early ones did have a habit of going noisy.

-Chris
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