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LA8AK > GERAETE 29.01.94 11:26l 54 Lines 2347 Bytes #999 (0) @ WW
BID : 60450_LA9K
Read: GUEST
Subj: DRAKE 2-B modifications made:
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Sent: 940127/2100Z @:LA9K.XND.K.NOR.EU #:60450 [Kr.sand] FBB5.15b $:60450_LA9K
From: LA8AK@LA9K.XND.K.NOR.EU
To : DRAKE@WW
the following modifications have been tested with drake 2-B receivers.
1) Converting product detector from 6BE6 to semiconductor, solid state BFO
2) Drake R-4B AGC system
3) solidstate audio amplifier
4) 12AT7 line amplifier
5) 12AT7/12AX7 instead of 8BN8(6BN8) - audio amplifier.
6) silicon diodes instead of 8BN8 rectifiers
7) silicon diodes instead of 6X4 rectifier
some electrolytic capacitors must be replaced because of the higher anode
voltage.
AGC was slightly better with R4B (R-4C) type AGC system
there were no reason to replace product detector and audio by solid state
devices.
anode voltage is increased to increase the reduced emission because we used
220V mains supply (transformer is made for 240VAC/120VAC) - somewhat lower
heater voltage is result.
sometimes mains transformer gets very hot at 50Hz when made for 60Hz, we cannot
verify if this is a fault ....or is it just the way components are rated
(underrated) in USA?
With the described way of improving the Drake 2-B, and R-4C substantial amount
of load is removed from the mains transformer
73 de jan-martin
ps. Drake 2-C operates on 120VAC only, it has an early R-4'type AGC circuit.
this is good enough
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