[Amps] Upgrades for LK500ZC?

[Carl]

----- Original Message ----- 
From: "Zev Darack" <zevdarack at gmail.com>
To: <amps at contesting.com>
Sent: Tuesday, July 17, 2012 2:10 PM
Subject: [Amps] Upgrades for LK500ZC?


>I am in the process of upgrading an LK500ZC and am looking for 
>recommendations:
>
> I am currently working on the following:
> 1. Installing the Harbach Power Supply

I see absolutely no reason to waste money on that, just buy new caps from 
Ameritron


> 2. Installing the Harbach Soft Start

Most ZC's came with it but none of the earlier models had a problem 
withoutit....its just a useless frill in that amp that can cause its own 
problems.

> 3. Replacing the Plate Choke which was rewound by someone with an
> Ameritron Plate choke.

They work well


>
> The amp also has a fuse between the Zener diode and the QSK board so I
> am going to install a panel mount fuse holder for this.

If the fuse blows you better go inside and find out why instead of drilling 
holes.


> KM1H recommended I install Glitch protection.

Yep


> The current tubes are showing a blue color during transmit so I will
> be replacing the tubes as well.  Eventually one of the tubes flashes
> over and causes the fuse on the zener diode to blow.  The amp is
> putting out over a KW so I think everything else is ok.
>
> Questions:
> 1. Glitch protection: I plan to add 3 10 ohm RCD 175P-10R0-FBW
> resistors in series in the B+ line.

Whatever they are?
Why not just one 20 Ohm 25W enamel wirewound?


 Looking for advice on where/how
> to mount this in the amp?

Replace the small RFC at the base of the plate choke with the resistor.


> 2. Recommended mounting location for the soft start in the amp?


The factory one mounted above the power distribution board


> 3. Is there anything else I should look at that could have caused the
> tubes to go bad?


Lack of use and regular gettering


> 4. Are there any other recommended upgrades for this amp?


The Ameritron choke will improve 160M output. Id measure the parasitic 
resistors and if out of spec replace with Ohmite OY type from Mouser.
At the front wafer, right side support make sure there are no sharp edges on 
the 160M lug. Also paint the junction of the ceramic spacer, nylon washer, 
and wafer with an anti corona dope or something else to prevent an arc to 
that 160M contact.

Carl
KM1H



>
> Thanks es 73,
> Zev N2WKS
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