[Milsurplus] [MRCA] APR-4Y project

[J. Forster]

That sounds to me like a gas issue for 60/70 year old tubes. My suspicion
is that all would work just fine, if they were degassed a while before
powering the set... especially with the higher B+.

YMMV,

-John

======================



> Only had this receiver running a couple days now and the tubes that are in
> there are all tested good, just surprised by the high number of 6AK5 tubes
> that were found bad in both the receiver and the APA display. Check all
> the tubes before starting work was a rule that was beat into me at a young
> age. Maybe the question is if the 6AK5/5654 is just a piss week tube to
> begin with and when driven near maximum values they wear out fast? Look at
> the tube charts, max plate voltage is 185 VDC and typical plate voltage is
> the same? Suspect whoever did the initial conversion of the receiver did
> not do the little tubes a favor by running 250 VDC as B+ so now that its
> back to 185 will see how they hold up. The disturbing thing is that it's
> not just the 6AK5 tubes that were in the receiver but three of the four
> that I pulled from the APA-10 display were also bad. Will be pulling the
> rest this weekend and testing them.
>
> Ray F
>
> -----Original Message-----
> From: J. Forster [mailto:jfor at quikus.com]
> Sent: Friday, February 28, 2014 4:34 PM
> To: Ray Fantini
> Cc: Military Radio Collectors Association; Military Surplus Mail List
> Subject: Re: [MRCA] APR-4Y project
>
> Very nice! By eat, do you mean the tubes are failing?
>
> -John
>
> ================
>
>
>> The APR-4Y project, what tends to eat 6AK5 tubes! Between the receiver
>> and the panadapter requiring way more 6AK5 tubes then I would have
>> thought.
>> The receiver is now finished next will be the APA-10 display. Lots of
>> fun has already been had using the receivers wide band 30 MHz output
>> to drive a spectrum analyzer and listening to the FM broadcast band.
>> The next step after replacing  all the missing tubes from APA that I
>> stole  for the receiver is to get the display up and running.
>> Ray F
>
>