G8MNY > TECH 14.06.18 07:45l 70 Lines 2747 Bytes #5 (0) @ WW
BID : 25164_GB7CIP
Subj: FT290/690/790 DC Power mod.
Sent: 180614/0532Z @:GB7CIP.#32.GBR.EURO #:25164 [Caterham Surrey GBR]
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
THE ORIGINAL CIRCUIT
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_
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...
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
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
Read previous mail | Read next mail