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G8MNY  > TECH     14.06.18 07:45l 70 Lines 2747 Bytes #5 (0) @ WW
BID : 25164_GB7CIP
Subj: FT290/690/790 DC Power mod.
Path: ED1ZAC<ED1ZAC<IW0QNL<JH4XSY<JM1YTR<JE7YGF<GB7CIP
Sent: 180614/0532Z @:GB7CIP.#32.GBR.EURO #:25164 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To  : TECH@WW

By G8MNY                                              (new Graphics Feb 06)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
 _____________________________________
³  _  ÚÄÄÄÄ¿ ÚÄÄÄÄÄÄÄÄ¿           /~\ ³
³ (_) ³====³ ³ 4.5000 ³  ""  ""   \./ ³
³     ÀÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÙ  ÜÜ  ÜÜ       ³
³              ./"~"\.   ÜÜ  ÜÜ  /~~\ ³
³  /~\   /~\   |     |   ÜÜ  ÜÜ |    |³ 
³  \./   \./   `\._./'   ÜÜ  ÜÜ  \../ ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ

THE ORIGINAL CIRCUIT

+ve outer
  Power     o )ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄ>Rig supply
Switched    ³ ^ÄÄÄÄ¿            2.5mm       ³
  Jack     _³_     ÃÄÄÄÄ´<ÃÄÄÄÄ<charge      ³
           /_\    +³            ³jack       ³+
      Idiot ³    ÄÄÁÄÄ NICAD    ³          ===
      Diode ³     === PACK      ³           ³1000u
           _³_    _³_          _³_         _³_

WHAT'S WRONG
1/ The original external power jack uses the dangerous +ve outer standard so
   that the when connected to other kit there is a risk of shorting.

2/ The jack switch is supposed to disconnect the +ve battery lead when the
   external power is applied. This depends very much on the make/type of plug
   used, & it is easy to draw high current though the battery pack & cook the
   cells & holder & possibly the rig!

3/ An reverse polarity idiot diode is provided, but on the -ve connection. So
   if the rig is connected to other kit (e.g. a powered speech processor) the
   protection is negated, & the mic lead now carries the rig current!

4/ The Plugtop raw charging (hummy battery) is via a 2.5mm jack socket that
   shorts out the charger while being plugged in/out. There is no indication
   that the charger is not being shorted out!


Here is my circuit that solves most of these problems...

+ve centre 
power Jack  (oÄÄoÄoÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄ´>ÃÄÄÄÄÄÄÂÄÄÄ>Rig supply
Switch      ³ wire    2.5mm   LAMP             ³
unused      ³ fuse    charge>ÄÄÁÄÄ´>ÃÄÄÂÄÄ´>ÃÄÄ´
RE-MARKED   ³ 1A         ³             ³       ³+
            ³            ³     NICAD ÄÄÁÄÄ    ===
            ³            ³     PACK   ===      ³1000u
           _³_          _³_           _³_     _³_

It uses most of the existing components. The fuse is just 1 cm of very fine
relay wire in case of disaster. The lamp is a wire ended 12V fairy light that
provides low trickle current when the rig is 10-14V powered.

Some rigs also include a small 1000uF 16V by the jacks. The 12V jack is
remarked with a +ve centre with a RED felt pen.

The disadvantage is that there is now a diode in the battery supply lead to the
rig, I feel this is a worth while loss for protecting the battery pack from
damage!


Why Don't U send an interesting bul?

73 De John, G8MNY @ GB7CIP


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