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G8MNY > TECH 27.12.18 09:00l 60 Lines 2417 Bytes #999 (0) @ WW
BID : 51291_GB7CIP
Read: GUEST
Subj: Valve Heater delay Drake L-4B PA
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VE3UIL<I0OJJ<GB7CIP
Sent: 181227/0656Z @:GB7CIP.#32.GBR.EURO #:51291 [Caterham Surrey GBR]
>From g8mny%gb7cip.#32.gbr.euro@i0ojj.ampr.org Thu Dec 27 07:57:27 2018
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>From: g8mny@gb7cip.#32.gbr.euro
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From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Update Dec 18)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄ¿
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³ÀÄÄÄÙ (_) (_) ³³ ³
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³ÀÄÄÄÙ (_) ø ø³³ ³
³ o [|]³³ ³
ÀÄÂÂÄÄÄÄÄÄÄÄÄÄÄÂÂÄÙÀÂÂÄÄÄÂÂÙ
This USA made Drake PA as a pair of expensive (RCA=$750ea) 3-500Z valves in it.
These have a seperate heater transformer in the PA unit.
To reduce the heater inrush current, that can eventually blow the bright direct
cathode filement, I added a 400R NTC 5W Thermistor (ex Valve TV heater chain)
instead of the 220V bridging strap of the 2x 110V windings. The thermistor is
put in a heat proof silicon sleeving & heatshring on leads, as it is on mains
circuit & hot.
CW/tune
LÄo-oÄÄÄÄo/oÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ\ oÄÄÄÄÄÄÄÄÄÄÄ¿_
Fuse 1 on ³ oSSB __)|| _
³ 200VA Heater ³ TUNE³__ ||(
³____ __ ³_____________)||( 850V on
110V)||(__ 5.0V ³__ ||( TUNE mode
400R _________)||(__ 25A )||( or 1.1kV
Therm_________ || __ 110V)||( in SSB Mode
³110V)||( 18V _____)||( @ 2A to
FAN )||(__0.5A [o-o__ ||( the Voltage
ÃÄÄÄÄÙ Fuse 2 )||( Doubler
³ Transfomer 110V)||(_
³ in PA _)|| 2.2kW Peak
NÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ HT Transformer
Results is, the heaters now take 4 sec rather than 0.5 sec to warm up now, &
the filement volts have dropped a bit from 4.9V to 4.6V. But RF power still
900W max on low power HT tune setting. So the heaters are bright (hot) enough!
See my Tech bul on "ALC line for Drake L-4B PA", & "PTT Line for Drake
L-4B PA".
Why Don't U send an interesting bul?
73 de John, G8MNY @ GB7CIP
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