[Amps] MLA-2500

[Pete Smith]

Have you run the amp into a 50-ohm dummy load? It really doesn't make sense 
to me that the load cap would be near minimum (or maximum) capacitance into 
a 50-ohm load on all bands.

As for gold sputtering, let's not go there - that's one guy's crusade, 
which has long since gone beyond engineering into personalities and 
historic grievances.

73, Pete N4ZR



At 11:01 AM 1/25/2008, n4zed at comcast.net wrote:
>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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