[Heathkit] 807 vs 1625 as DX-100B modulator

[Rick Poole]

One of the modulator tubes in my DX-100B just developed a short 
(confirmed on my TV-7 tube tester) and so I have ordered a few spares 
from RF Parts, hoping that they have some in stock.

I'm told that 1625's are getting a bit hard to find, and in fact the 
only ones that RF Parts has are shown as NOS which makes me wonder if 
anyone is making them anymore.

If the time comes when I can't get 1625's any longer, any particular 
reason I can't just rewire the filaments in series rather than in 
parallel and use 807's?

Rick WA1RKT