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G8MNY > TECH 13.08.18 10:28l 60 Lines 2543 Bytes #999 (0) @ WW
BID : 33290_GB7CIP
Read: GUEST
Subj: Valve Heater delay Drake L-4B PA
Path: IW8PGT<IZ3LSV<I0OJJ<EA2RCF<EA5URD
Sent: 180813/0820Z @:EA5URD.EAMU.ESP.EU #:40514 XFBB7.04h Bid:33290_GB7CIP
>From g8mny%ea5urd.eamu.esp.eu@i0ojj.ampr.org Mon Aug 13 10:21:37 2018
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R:180813/0820Z @:ED1ZAC.EAC.ESP.EU #:56875 [C.D.G]{EANET1G.06}33290_GB7CIP
R:180813/0818Z @:GB7CIP.#32.GBR.EURO #:33290 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (New Aug 16)
(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) 3-500 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. I put the therm in
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 3 sec rather than 1 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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