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G8MNY > TECH 11.08.04 18:45l 46 Lines 1721 Bytes #999 (0) @ WW
BID : 5115_GB7CIP
Read: DL4DBX GUEST DG6OU OE7FMI
Subj: FT290/690/790 DC Power mod.
Path: DB0FHN<DB0FOR<DB0SIF<DB0EA<DB0RES<ON0AR<ZL2TZE<GB7YFS<GB7CIP
Sent: 040811/0850Z @:GB7CIP.#32.GBR.EU #:5115 [Caterham] $:5115_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY
WHATS 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 & possably he rig!
3/ An reverse polarity idiot diode is provided, but the the -ve connection. So
if the the rig is connected to other kit (eg a powered speech processor) the
protection is negated, and the mic lead now carries the rig current!
4/ The Plugtop raw charging (hummy battery) is via a 2.5mm, that shorts out
the charger when plugged in/out. There is no idication 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´
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 Lamp is a wire ended 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.
Why Don't U send an interesting bul?
/QSL
73 De John, G8MNY @ GB7CIP
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