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 Post subject: its been a VERY good week!
PostPosted: Apr Sun 29, 2012 10:43 pm 
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Joined: Sep Mon 20, 2010 1:51 pm
Posts: 148
Location: Reading PA
this weeks finds are a Harman Kardon Citation 11 pre-amp and 12 power amp....work just fine
VERY clean AND I got the original manuals with them

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a set of Marantz Imperial 5 speakers...they work very nice as well....
I have the grills but thought you guys would dig the "nudies"

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and a $20 Marantz 2220B! needed the pots cleaned and some lamps replaced but sounds FANTASTIC

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my new and improved listening area
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 Post subject: Re: its been a VERY good week!
PostPosted: May Wed 02, 2012 5:38 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 8044
Location: Warner Robins, GA
A little OT, but is that fan in the picture an Emerson?


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 Post subject: Re: its been a VERY good week!
PostPosted: May Thu 03, 2012 10:53 pm 
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Joined: Sep Mon 20, 2010 1:51 pm
Posts: 148
Location: Reading PA
Tube Radio wrote:
A little OT, but is that fan in the picture an Emerson?


Yup its an Emerson Electric type 79648-AP-G

I picked it up for 10 or 15 dollars a couple years ago.......

Lubed the motor,white lithium grease on all the moving parts and put a new cord on it....

3 speeds and she occilates.....

Moves a LOT of air...we put the AC in that window in the sumertime with that fan blowing the cold air around the room......its GREAT!


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 Post subject: Re: its been a VERY good week!
PostPosted: May Fri 04, 2012 2:57 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 8044
Location: Warner Robins, GA
Cool.


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 Post subject: Re: its been a VERY good week!
PostPosted: May Fri 18, 2012 3:33 pm 
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Joined: Dec Wed 05, 2007 11:08 pm
Posts: 694
Location: Marietta/Moultrie GA
Citation 12 power amps are sweet- I've owned one for over 20 years.

One caveat to those- even if the amp works- I'd have the small transistors and electrolytic capacitors ALL replaced on the driver circuit card (its removable, on a long socket-row, so service is easy). I've seen lots of those go up in smoke, due to bad driver transistors and/or leaky caps.

In fact, I would usually recommend replacing the output transistors as well. The On-Semi modern replacements are relatively cheap, and they're better matched and more reliable than the originals.

One nice thing about re-working one of these this way is, if the tech is good about matching the gain and conductance of the diff amp transistors (I used a method published by the late Dr. Wm. Marshall Leach of Georgia Tech, creator of the Leach amps- it involves making a very simple battery-and-few-resistors "test bridge, to match transistors), you can, many times, even get these to turn on and off without any "thump" through the speakers. That "thump" is usually because of slight differences between the operational transistors on the "positive" and "negative" sides of the amp, in the original transistors. OTOH, get them matched, and the amp will usually turn on and off without audible noises!

Regards,
Gordon.

_________________
"It's the guys who think that attending meetings is real day's work that are the problem."- HepcatWilly (on AudioKarma)


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