On 4/24/2010 2:17 PM, Roger Johnson wrote:
Kenneth Scharf wrote:
Antonio Vernucci wrote:
ha scritto nel messaggio
...

This amp was built by P&H Electronics in Lafayette Indiana in 1956..It
used four 1625 tubes or 837 tubes in GG...The manual says that the
1625 tubes are modified ..Doesn`t say what sort of modifications they
have..Tube Manual shows same pin-out ,same socket ,same connections
etc..Anyone know what the modifcations might be...They both seem to
operate all OK with about the same power out..I seem to remember an
article some years back about removing the socket from the tube and
changing some pin connections or whatever...any help appreciated..

If I remember it correctly, the modification consisted in separating
the suppressor grid from the cathode, so that the tube can be
operated as a triode.

Actually within the socket there are two separate wires for the
suppressor grid and the cathode, both connected to pin 6. The
modification consisted in de-soldering the suppressor grid wire and
moving it to a free pin (pin 2 or pin 5).

Such a modification was not possible for the 807 (the 6.3V version of
the 1625), because it only has five pins in total.

73

Tony I0J

I seem to remember only certain brands of 1625 were suitable for the mod.
Some brands had the supressor connected to the cathode inside the envelope.
I don't know if this also pertains to 807s.

73, Roger


I have one of these that I horsetraded for a year or so ago, and it had
837 type tubes in it instead of 1625's. I think I read somewhere that
P&H used 837's in the later models. I have never had it on the air but
it looks nice and lights up.
73's,
Larry W4LK