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Icom IC- 3200A mods
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IC3200A.2
Subject: Fix for IC-3200A used on packet
R:880518/1202z 2985@N4KWB [Dade EOC - NTS SysOp BBS,FL] Z:33173
From: N4KWB@N4KWB
IC-3200A FIX
FOR THOSE POOR SOULS WHO ARE TRYING TO USE THE IC-3200A ON PACKET HERE IS
HERE IS SOME RELIEF.
THE PROBLEM IS THAT WHEN GOING FROM TRANSMIT TO RECEIVE THERE IS A DELAY
IN THE RECEIVE AUDIO TURN ON, WHICH IS ON THE ORDER OF 500 MILLISECONDS
AND MAY BE TOO LONG FOR SOME PACKET SITUATIONS UNLESS EVERYONE HAD THEIR
TXDELAY SET TO 750 MILLISECONDS.
THERE ARE TWO WAYS TO RESOLVE THE PROBLEM. BOTH ARE FAIRLEY SIMPLE.
THE EASIEST WAY IS TO REMOVE THE MUTING ON THE AUDIO P.A. I.C.
THE INSTRUCTIONS FOLLOW:
1. REMOVE THE COVER THAT HAS THE SPEAKER ATTACHED TO IT
(BEING CAREFUL OF THE WIRES)
2. WITH T2. WITH THE FRONT OF THE RADIO FACING YOU, LOOK FOR THE
AUDIO P.A. I.C. IN AUDIO P.A. I.C. IN THE RIGHT REAR PART OF THE RADIO NEXT TO
THE CHASSIS IT IS MARKED "UPC2002", LOOKS LIKE A TO-220
CASE TRANSISTOR, AND HAS FIVE LEADS ON IT
3. IMMEDIATELY TO THE LEFT OF THE "UPC2002" IS A DIODE STANDING
ON END, AND MARKED "D19" ON THE CIRCUIT BOARD THIS IS THE
DIODE THAT MUTES THE AUDIO P.A. I.C. DURING TRANSMIT
4. CUT ONE LEG OF "D19" AND THE AUDIO P.A. I.C. WILL NO LONGER
BE MUTED DURING TRANSM ITHIS IS ALL THAT IS REQUIRED AND MY TESTS HAVE
SHOWN THAT THE IC-3200A WILL WORK WITH OTHER TNC'S WITH TXDELAY'S SET AS
SHORT AS 150 MILLISECONDS WHERE BEFORE THIS MODIFICATION A TXDELAY OF ABOUT
600 MILLISECONDS WAS REQUIRED OF THE STATION TRYING TO COMMUNICATE TO THE
IC-3200A.
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