| |
G8MNY > TECHNI 08.11.26 10:24l 60 Lines 2882 Bytes #999 (0) @ WW
BID : 10550_GB7CIP
Read: GAST
Subj: HT diodes in Drake L-4/4B PA
Path: DB0FFL<OE2XZR<OE6XPE<DB0RKB<DK0WUE<PD0LPM<PI8ZTM<CX2SA<OK2PEN<GB7CIP
Sent: 261108/0914Z @:GB7CIP.#32.GBR.EURO #:10550 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (New Nov 26)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄ¿
³ÚÄÄÄ¿ _ _ ³³ ³
³ÀÄÄÄÙ (_) (_) ³³ ³
³ÚÄÄÄ¿ _ ³³ ³
³ÀÄÄÄÙ (_) ø ø³³ ³
³ o [|]³³ ³
ÀÄÂÂÄÄÄÄÄÄÄÄÄÄÄÂÂÄÙÀÂÂÄÄÄÂÂÙ
This USA made Drake PA as a pair of 3-500z valves at 2000 & 3000 Volts in the
earier (1960) L-4, and 1800 & 2800 Volts in the later (1965) L-4B version.
ÚÄÄ´>ô>ô>ô>ô>ô>ô>ÃÄÄÂÄÄÄÄÂÄRfuse>+HT
CW Tune ³ 270K ===120u
LÄo-oÄÄo/oÄÂÄÄÄÄÄÄÄÄÄÄ\ oÄÄÄ¿_ ÃÄÄÄÄÄ¿ ÃÄÄÄÄ´
Fuse 1 on ³ oSSB _)||(850V ³ 270K ===120u
³ ³TUNE³_ ||(on ³ ÃÄÄÄÄ´
³_ _ ³______)||(TUNE ³ 270K ===120u
115V)||(_5.5V ³_ ||(mode ³ ÃÄÄÄÄ´
_)||(_30A )||(or ³ 270K ===120u
³_ || _ 115V)||(1.2kV³ ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄ´
115V)||( 18V _____)||(on ³ ³ 270K ===120u
_)||(_0.5A [o-o__ ||(SSB ³ ³ ÃÄÄÄÄ´
³ Fuse 2 )||(Mode ³ ³ 270K ===120u
Transformer³ 115V)||(@ 2A ³ ³ ÃÄÄÄÄ´
in PA³ _)||( ³ ³ 270K ===120u
NÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ HTÀÄÄÄÄÄ)ÄÄÙ ÃÄÄÄÄ´
Transformer ÚÄÄÄÙ 270K ===120u
À´<ô<ô<ô<ô<ô<ô<ÃÄÄÁÄÄÄÄÁÄÄÄÄÄÄ>-HT
The diodes are 1N5407 on the L-4 and smaller 1 amp 1N4007 with 1kV 1nF across
each on the L-4 (not shown). The R fuse is large a distroyable carbon 8R!
FAULTS
I have had 2 diodes fail in the heavily used L-4B PSU, but so far none in the
earier version with the bigger diodes & no added suppression caps. There are
different diodes used both in long strings of 7 on tags strips next to the 4
caps + & - capacitor banks.
Symptons were a bruning smell thought originaly to be from the PA, but when I
saw only half HT, I investigated the PSU and saw a broken 1N4007 diode and a
1nF cap unsoldered. I tested the cap and replace the diode all was well. But
later after some mains arcing, I retested the PSU and found another faulty
diode, this time a shot circuit that would not have show up other than with a
meter!
The mains acring was found to be the Hi/Lo mains power switch that was dirty,
and needed some spray contact cleaner to sort out.
See my Tech bul on "ALC line for Drake L-4B PA", "PTT Line for Drake L-4B PA",
"Power Factor of Drake L-4/4B PA", "Drake PA 3-500 valve repair" & "Using 2 HF
PAs".
Why Don't U send an interesting bul?
73 de John, G8MNY @ GB7CIP
Lese vorherige Mail | Lese naechste Mail
| |
