[Amps] LK-550ZC fair price, tube testing

[Carl]

$1200-1500 including the PAC 5. Anything less is a give away, even the 
LK-500ZC can go for that range.

Without special equipment one way to regetter is to run the filaments and 
bias only on the power cord and rewire the HV transformer to run on a 
Variac. Then bring up the HV slowly while looking for the telltale blue 
glow. If there is none at ~ 3000V then bypass the zener with a clip lead; 
put in TX with no drive and again ramp up the HV until there is enough idle 
current to get a medium red anode color. Always monitor the grid current 
meter and the tubes for anything funny....Shut down if that happens and then 
bring the HV up again to just below that point. Keep nudging the HV up, this 
may take several hours to complete the regettering.

Then bring up the drive slowly while watching everything.
You are still running zero bias so a nice red anode will occur before the 
full HVpoint.

Next step is to remove the zener jumper and run the HV up to a full normal, 
test, and finally restore to original if no smoke.

If you are feeling real brave then use a 50 Ohm 50W glitch resistor and pray 
but do it one tube at a time!

Carl

----- Original Message ----- 
From: "Dick Green WC1M" <wc1m73 at gmail.com>
To: <amps at contesting.com>
Sent: Tuesday, March 27, 2018 4:27 PM
Subject: [Amps] LK-550ZC fair price, tube testing


>I have an Amp Supply LK-550ZC 1500W QSK amp that worked fine when I last I
> checked it maybe 10 years ago. I'm planning on offering it to local and
> regional club members, then to a hamfest if it doesn't sell. Wondering 
> what
> a fair resale price would be for this amp. Can't find any prices online.
>
>
>
> More details: Actually, it's an Amp International, which was the new name 
> of
> the company just before it went under. That means the amp was one of the
> latest models Denny produced. I did a lot of work on it about 18 years 
> ago -
> replaced all three tubes, replaced the plate choke with a higher-quality
> model, replaced the parasitic suppressors, fixed a broken 40m cap in the
> output network, replaced the meter covers, replaced/calibrated the meter
> calibration resistors, replaced a knob, added a glitch resistor and 
> modified
> the fans to reduce noise (higher speed in low mode so high speed doesn't
> come on as often, plus optional reduced speed in high mode.) Will include
> two spare 3-500Z tubes that were OK as recently as 10 years ago, and 
> another
> one or two of 3-500Zs of unknown condition. I'll setup the amp and verify
> that it works before closing any sale.
>
>
>
> Fair price?
>
>
>
> (The tubes being so old, I'm concerned that they could be gassy. I don't
> have a hi-pot tester. Any suggestions to prevent damage when testing?
> Hopefully the glitch resistor will protect the amp. I do have a Variac 
> that
> I think can handle the load, but don't know the procedure for using it to
> safely test the tubes.)
>
>
>
> 73, Dick WC1M
>
>
>
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