EBF89 ok for EF89? No, but EAF42 ok for EF41. [Yet more nerdism...]
Martin Ackroyd
place of an EF89 [rf pentode].
This rang a bell, as I once had a radio that was working perfectly with
an EAF42 plugged in place of an EF41. So I checked up...
The pinouts are:
EBF89 EF89
1 g2 s
2 g1 g1
3 k,s k
4 h h
5 h h
6 a s
7 a'd a
8 a"d g2
9 g3 g3
The pentode anode of each valve is connected to a different pin.
CONCLUSION. An EBF89 cannot be directly used to replace an EB89.
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However...
The 8-pin miniatures have the following pinouts and characteristics:
EAF42 EF41
1 h h
2 a a
3 ad IC
4 g3 IC
5 g2 g2
6 g1 g1
7 k,s k (+pins 3,4**)
8 h h
gm 2.0 2.2 mA/V
ra 1.4M 1.0 M
**as revealed by continuity test on a Mullard UF41
CONCLUSION. You can probably use an EAF42 as a plug-in replacement
for an EF41. The unwanted diode anode will be grounded to the cathode.
But you'll need to check that pins 3 and 4 are connected to the
cathode pin.
The EF42 also has the same pinouts as EF41. However, EF42 is a hi-slope
pentode (gm = 9.5 mA/V). So an EAF41 would not be a good substitute.
But you are unlikly to find an EF42 used in a radio anyway. (Maybe
some early European FM sets used it...? Probably was never used in any
British radios. My ~1953 Peto-Scott 405 line single-channel (5) TV
is full of them, though.
Martin
walterh
Yes, there were many european radios (in the end 40ies, early
50ies) built, using the EF41 or the EF42 (but not that often as
the EF41). The direct replacement for the EF41 ist the 6CJ5. I
don't have found a direct substitution for the EF42, but this
tube is still NOS available.
Walter Haring
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Martin Ackroyd
That's interesting. I have seen the EF41 in a number of radios.
But I don't recall ever seeing the EF42 in a British radio.
Maybe that's because it would be used in FM radios (with its
high gm). By the time FM was introduced in Britain, the EF42 was
obsolete and so valves like EF85 were used.
Martin