[AMPS] MLA2500 Problems

[km1h @ juno.com]

On Thu, 23 Oct 1997 05:54:13 -0500 bob alexander <realex@flash.net>
writes:
>Virtuiso@aol.com wrote:
>> 
>> I am trying to fix a MLA2500 amp that was zapped on the CY9AA 
>expedition.
>> Having little more than a DVM, I am at an impass.
>> 
>> We do have:
>> o  High voltage on the tubes
>> o  Filaments (tubes get warm)
>> o  Relays operating (time delay, T/R)
>> o  Some cathode voltage
>> o  Some grid current when excited
>> 
>> We DON'T have:
>> o  Idling plate current in transmit
>> o  Any plate current when excited
>> o  Any output in transmit
>> 
>> The amp went "zap" and quit working, after 3 days of intense use.
>> 
>> I welcome any and all suggestions of what to check next and how and, 
>is it
>> down to tubes?
>> 
>> Thanks!
>> 
>> Tom Taormina, K5RC/7


If that amp was run on 12M a blown plate choke is a real possibility.
About 5-7 turns up from the B+ end.
GL  Carl  KM1H


>Hi Tom,
>I'm not sure if you measured B+ at the tube plate or at the p/s.
>Sounds like you might have an open plate choke...in any case, no
>B+ on the plate.
>Another possibility is the keying circuit is changing antenna/
>driver inputs ok but not placing the amp in the TX mode even
>though the relays actuate.
>This may not be it but its a starting place.
>
>How's it going...been a while since we talked.
>73, Bob, W5AH
>
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