[Milsurplus] [MRCA] APR-4Y project

[Ray Fantini]

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

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> 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