Harman Kardon Citation A Preamp Help...

Discussion in 'General Electronics Chat' started by hifinatic, Dec 6, 2009.

  1. hifinatic

    Thread Starter New Member

    Mar 19, 2008
    Hello folks,
    I'm new here and this is my first self authored thread. I recently purchased a Harman Kardon Citation A preamplifier. It was from the original owner and came with it's original shipping carton and manuals, schematics etc. It's physical condition when received was close to new with even the internals looking as if they just came out of the factory. This particular unit by the way is factory wired as this preamp was also sold in kit form. This unit also came with the beautiful optional walnut cabinet. After doing some research I found out this was the first solid state preamplifier unit and HK pulled out all the stops and built this unit right. Glass Epoxy Circuit Boards and Ducati and Neuberger caps. A test report done by High Fidelity in 1963 stated the following. "Superb response characteristic is not matched by any other known preamplifier", this included the four top tube preamps at that time. "Citation A literally has flat response to beyond one million cycles and distortion that is non-measurable by the usual methods", "Excellent transient characteristics and virtually no phase shift throughout its extremely wide range", "Harmonic distortion is actually less than the residual distortion of the measuring equipment", "It's listening quality is superb.... The overall effect of listening to the Citation A is simply, more music and less fatigue". When I received the unit I pulled the cover and after drooling over the internal craftsmanship I sprayed all of the controls with Caigs Deoxit. I then did a light cleaning and put it all back together. I placed the Citation A into my system after removing my Technics SU-9070. I now had the Citation A, Technics SE-9060 power amp and my Sony SCD-777ES Super Audio player and circa 1984 Infinity speakers. I put on a reissue of a Verve recording, Ella Sings Broadway which is a superb 1962 recording. From the opening track all I can say is that I WAS BLOWN AWAY! My jaw dropped! I thought the floor had fallen out beneath me. I had never heard the wide open expansiveness like this before. Voicing, instrumentation, placement, highs and lows that were sensational. After all of the pieces of vintage audio and some new stuff as well I've collected over the years I must say that the Citation A dollar for dollar is the best purchase I've ever made. It's like listening to all of my music for the first time again. Honestly words can't describe the pleasure I've gotten out of this preamp. But now I get my reason for posting this thread. Even though this preamp looks new it's still 46 years old and even if it wasn't used much the components still age. Much to chagrin but I wasn't surprised after about 2 weeks it started showing it's age. After turning the unit on (this unit has a built in time delay of 20 seconds to let all of the capacitors energize) I started noticing a hissing sound in the left channel. The hissing replaces any sound on that channel and is not sharing music with it. When I push the reverse switch it's the same so I know it's coming from the left channel. I disassembled it and tried some more Deoxit and checked for anything unusual and saw nothing. I put it back in the system, powered it up and it was fine for about a minute or two and the the left channel went to hiss again. It sounds as if a component is getting to operational condition and then failing. Any thoughts would be greatly appreciated. I've attached some pics. Thanks for sticking with me in this long winded thread. Bruce
  2. flat5

    Active Member

    Nov 13, 2008
    I would think it is a noisy transistor.
    Try tapping things lightly with an insulated tool.
    Perhaps an old plastic tooth brush.
    It could be a resistor or a bad solder connection or almost anything really :)

    I would also investigate replacing the transistors with similar modern types that will have lower noise figures.

    Also the electrolytic capacitors are forty years old and might need to be replaced.

    If the pre-amp only gets noisy after it warms up then a can of cold spray may be useful to locate the noisy component. Likewise, a soldering iron brought near a component causing more noise may help to find the bad part. Try this last.
  3. Duane P Wetick

    Senior Member

    Apr 23, 2009
    Circuit freeze has saved me plenty of trouble shooting headaches! What a work of art this pre-amp is! I say that you must fix it!... if only for listening to Ella Fitz...but maybe Sarah Vaughn too!

    Regards, DPW [ Spent years making heaters out of op-amps.]
  4. mik3

    Senior Member

    Feb 4, 2008
    The case of working and not working is worse than the case of non working at all. In your case the most usual fault is a bad connection, either a lose wire or bad soldering on the PCB. The reason it worked is because the bad connection moved and was conducting by the vibration you caused when you was working on it. Another, option to this fault is the pot which adjusts the volume of the left channel. Its wiper may worn out and it is not have a good contact with the resistive part of the pot. Try to hit this pot some times to see the difference.
  5. kubeek


    Sep 20, 2005
    I suggest you ask at http://diyaudio.com , there is lots of advice about high-end amplifiers like this one. You should be able to find a schematic there, and maybe even a thread that covers your problems.
    (i just can´t get myself to read that block of text, try to use paragraphs next time)
  6. SgtWookie


    Jul 17, 2007
    What a beautiful piece of machinery.

    Electrolytic capacitors generally don't age very well. Sometimes, they can be re-formed if they haven't dried out, leaked, or shorted and blown. It's a rather lengthy and involved process, though.

    The old brown-body cylindrical carbon resistors don't age well either. I've seen them shift a very large amount in value; some over 300%, even those that had never been installed in a circuit.

    Component values on your boards may have shifted enough to cause transistors to be improperly biased. Some "freeze" spray might help quite a bit to track down overheating parts.

    Dirty pots are another possiblity. The unit doesn't look like it's seen much use, but corrosion is always a possibility, particularly in something that old.

    Cracked solder joints or even cracked board traces are another possibility. After a number of heating/cooling cycles, the stress can cause metal fatigue, just like flexing a soda can tab back and fourth a number of times. The same thing can happen inside transistors and IC's.

    Intermittent problems are the hardest things to troubleshoot.
  7. bertus


    Apr 5, 2008

    How about the contacts of the vertical boards?
    Are they clean and having good contact?

  8. hifinatic

    Thread Starter New Member

    Mar 19, 2008
    Hi Everyone,
    Thanks for all of your suggestions and positive comments. As I stated this Citation A really does look to have had little use and so I think the task ahead shouldn't as hard. I really fell in love with this preamp and I am motivated to fix it. Fortunately there are no IC's and proprietary components. Are there any suggestions for possible cap replacements in the power supply and elsewhere? I've read that Black Gates are great but are no longer available and if they are they are expensive. Any help would be appreciated. By the way the gain control is a 4 variable resistor affair. I'll try and load some additional pics of the insides once I figure out how to do it. Thanks again.
  9. hifinatic

    Thread Starter New Member

    Mar 19, 2008
    Hi Bertus,
    The vertical boards are wired on the bottom. The boards can be pulled up and out of its position so it can be easily troubleshooted and repaired. When I first opened the unit I pulled one of the boards and it's possible that since I was probably the first person to move the board in 46 years and it could have loosen the wiring. Thanks.