No, they're not for feedback; these resistors are from base to ground and even from base to base, there are three, and are different types than those used in the attenuator for example, look modern; besides, the input attenuator looks good (I did not measure individual resistor values yet, they're all old 2 watt dark brown, carbon types). Anyway, today I'll get a better idea of how they're connected.
If I could have some data about that CD4778.....
Thanks
Best regards
Guillermo - LU8EYW.
craxd escribi:
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Guillermo,
Is the resistors in mention connected across the base and collector of each transistor? If so, someone could have been trying to add feedback to the transistors. Generally though a capacitor is in series with the resistor and the resistor-capacitor is connected across each collector and base. The cap blocks the DC at the collector from going to the base. If it had a +DC voltage from the collector going to the base, you would most assuredly have some burnt out transistors.
The RF input attenuator in that amp is probably made with resistors too. Is it possible it could be these?
Best,
Will
--- In ham_amplifiers@..., GGLL <nagato@...> wrote:
I'm searching for a solid state amplifier circuit, a Henry model
C130A30 (for
VHF FM). The one I have seems to have been modified, I see some
resistors
strangely connected both at base and collector; also after an
extensive search
(Google, Alltheweb, data sheet pages, and so) I did not yet found
nearly a
bare specification of the transistor used. Input is specified in the
range of
20..40 Watts, and output of 130 Watts, and as I see it, the circuit
consists
of a resistive input attenuator, then follows a first stage with a
CD-4778,
which drives three CD-4778 (yes, the same) in parallel. All four are
B-E open.
It has a nice LPF at the output. Very good components with the
exception of
the above stated resistors.
Thanks in advance
Best regards
Guillermo - LU8EYW.
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