It looks, smells & tastes like a NEC. NEC printed the boards with
a big NEC marking & all I remember had NEC branded tubes.
At this point get an RCA, GE, or Sylvania tube manual. that will
at least give you the tubes use, specs & pin outs. Curtis Mathes
( C-M ) also used a lot of NECs so you can look there. All the
others I saw were from unknown brands. I NEVER seen a NEC branded set
with tubes, the NEC branded sets suddenly appeared in the mid 80's.
& sold very well at the high end stores.
73 Zeno
LFOD !
BTW what is the problem with the set ??