[ARC5] "ART-13" Fun

[arc5 at ix.netcom.com]

I've been working over an Collins ATC for a friend.
It was refurbed in 1954 by "Jackson Electric."

Above the ATC nomen plate it is marked "T-47/ART-13"
Also has "mod" M-markings 1 through 6.

Very nice DY-17A dynamotor.  
Yes- I know that's not "correct" for the ATC.  ;-)
Just got the autotune working and it's putting out about 
10 watts in TUNE, but no more in "OPERATE."
PA Grid drive is very low.  
I can trouble-shoot it, of course, but I wonder:
lots of you have more time with the ART-13 than I do.
Is there something common that kills grid drive?

Also- I haven't made a study of the ART-13 yet.
Will one of you smarter-than-me folks tell me 
what the m-1 to m-6 mods are?

I do love bringing the dead back to life..... ;-)

73 Dave S.