Lets get something straight right off. There is nothing wrong with the
design that would cause your symtoms. Ive already outlined the few design
problems.
Gold sputtering is a myth that has been pushed by one person that makes a
profit selling junk science "kits". Nuff said on that subject.
I agree that it may be an assembly issue. If the 10M mod was done after it
was sold Id suspect that for starters. It pretty much sounds as if the
complete tank circuit has been moved over a switch position.
BTW, I have 2 MLA-2500's here and am a bit familiar with the design.
Carl
KM1H
Amplifier Service since 1965
----- Original Message -----
From: <n4zed@comcast.net>
To: <amps@contesting.com>
Sent: Friday, January 25, 2008 11:01 AM
Subject: Re: [Amps] MLA-2500
>I suspect something is wrong also but I think it is in the design and not
>in any particular component failure. I've done the usual Google search and
>found the loading problem is common with this amp. During the search I
>have found no fixes to the problem.
>
> This amp had never been powered up when I got it about 3 months ago.. The
> power cable had never been connected to a plug and the tubes were still in
> the original boxes from Eimac. The relay contacts as far as I could tell
> had never been energized and showed no sighs of any electrical contact at
> the contacts(that sounded weird), none of the connectors on the rear had
> any sigh of a connector being screwed on or pushed on.
>
> There are places on the web that covers a gold sputtering problem with the
> 2500 and the 8875 tubes due to VHF parasitics and other high Mu tubes for
> that matter.
>
> There are others that say they have ran their 2500 for 20 years and had no
> problems.
>
> The amp works fine, good output, good reports. So why fix something thats
> not broken right? I just want to keep it that way, the tubes are way too
> expensive to replace. One good thing about buying something that has been
> out in the field a long time is that you get to see what kinds of problems
> there were with the design and hopefully fix it before it hits you in the
> wallet or something very close to the wallet.
>
> Ken
>
> *************************************************************************
>
>
>
> Somethings definitely wrong then.
>
> Id start by closely inspecting the bandswitch and plate choke.
>
> BTW, the cover has to be in place when tuning, the steel that close to the
> coil has a huge effect.
>
> Carl
> KM1H
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>
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