[NJARC] Audio Tube Substitution Question: ( a 112A for a 71A ) ???

[Yardleyite at aol.com]

Hello All,
            Could  anyone in our group answer a question I have regarding a 
substitute for a  71A tube? Has anyone ever subbed a 112A for a 71A? The 
pinouts appears to  be the same, the filaments have different ratings (.25A for the 
112A and .5 for  the 71A) since one tube was designed for a battery set, and 
the other  for AC. 
 
I recently acquired an old  AC TRF set missing it's last audio tube  (71A) 
among others. I had everything else except the 71A. I do however, have a  112A I 
could use in it.
 
Sometime ago I acquired an Atwater Kent model 67 (DC  set) that calls for a 
pair of 71A's in the last stage of it's  audio. The way I got it the set had 
1ea. 71A and 112A in it's last audio stage.  Since I've yet to power up the AK 
67, I don't know if it'll work. Rather than  possibly destroy a perfectly good 
112A I was wondering if anyone could tell me  if the two are interchangable? 
Any advice will be appreciated.
                                                                    Best  
Regards,
                                                                              
          Joe  Cro N3IBX