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Author Topic: Amp Supply lk550za  (Read 1776 times)
W7HW
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Posts: 4




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« on: February 12, 2005, 05:46:05 PM »


Can anyone give some insight on this amp..........todays value considering average condition, tubes used ect.....appreciate your time and input.    73    w7hw   Duane


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K0BG
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Posts: 10248


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« Reply #1 on: February 13, 2005, 06:08:16 AM »

Personally, the "pretuned" one is junk and you end up having to have an external tuner just like you would if you had a SS amp. The standard amps seem to be okay, but the three tube unit isn't up to snuff. Most amps with just two 3-500s will our perform it.

On the pretuned units, if the final adjustments have been messed with, you'll have to build a temporary cover over them before you make the adjustments, or they will changes once you replace the factory cover. And be VERY careful, there is no interlock!

Alan, KØBG
www.k0bg.com
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I8VYE
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Posts: 16




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« Reply #2 on: February 14, 2005, 07:49:10 AM »

I have a Lk450nt (one tube, pretuned type). I agree with K0BG impressions. It's almost rugged and it has tuned input. But i've struggled a lot to tune in the pretuning caps. At the end i obtained correct tuning but i had to modify some fixed caps values to bring out pi in the range of both input and output capacitive trimmers. To obtain this i had to recalculate pi parameters and then had to try values. It was amusing and interesting, but lot of work with HV on and cover open..... BE REALLY CAREFULL: high voltage KILLS.

The transmatch has to be used to give right impedance to the out pi.

I bought the amp many years ago for a bargain, but now i really suggest not a pretuned type in accordance with K0BG.

On the other side, as i said, it seems rugged and i found a pretty good linearity.

73's de I8VYE/I0
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WD4NTK
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Posts: 5




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« Reply #3 on: February 16, 2005, 10:01:35 PM »

It looks like there is some confusion  here.  The lk550za is not  a NO tune version.  That would be a LK550-NTC.

I have a two hole unit -  lk500zc that I like fine.  I know that the 3 tube unit  with the external supply has been said to "put the fire in the wire" .

Regarding pricing, since the amps are no longer in manufacture, you can find good deals on them and I think they are well built for the money.

There probably are mod's to bring it up to a ZC ( I think this would include the full qsk w/vacuum relay) but am not sure on this.

If you need parts or details on the amp, check out
http://www.omega-electronics.com/

Bill is extremely knowledgable regarding these amps.  He worked for Amp Supply before the folded.  He probably still has parts for them if needed.

Good luck with it.

73's
Floyd
WD4NTK
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WD4NTK
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Posts: 5




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« Reply #4 on: February 16, 2005, 10:05:25 PM »

Oh yes - there is a known weak spot with the amps - the 160 meter padder caps are not typically what you would find in an amp of that power.  Several paralleled caps were used when a high rf current door knob would be better.

They will go up in smoke if you are not well matched on 160.

fwc.
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