[ICOM] IC781 Tx problem

[Paul Playford]

I had a similar problem with my PROII when using the keying lead on the din 
connector (instead of the RCA connector relay output) to put my Alpha in the 
transmit mode.

The signal on the din keying lead appears after transmit rf is being 
generated (cw), which meant the PROII was transmitting into an open circuit 
(while the antenna relay in the Alpha was switching), resulting in a high 
swr that caused the PROII's swr detection circuitry to shut the transmitter 
down with a slow recovery to full power output.

Easy to check: connect a dummy load directly to the RF spigit on your 781.

de Paul, W8AEF

ZF2JL/ZF2TA  FO8DX/FO8PLA  8Q7AA  XZ0A  VU7RG  TX5C



----- Original Message ----- 
From: "Jaime Gomez" <jgomez2005 at gmail.com>
To: "ICOM Reflector" <icom at mailman.qth.net>
Sent: Thursday, December 11, 2008 17:54
Subject: [ICOM] IC781 Tx problem


>I still have the problem in Tx with my 781. I rebuilt the ALC circuit as 
>per
> K1FV corrections, but the problem still remains. The DC Tx voltage is
> turning OK (No delay at all) when I operate the send switch, but the
> carrier, no matter what mode, power or band I am using is delaying about 2
> to 3 seconds before it gets to full power output. The power control is
> working OK once I have carrier, so I doubt it can be. I have checked all 
> the
> DC voltages and are OK, I can see (with my scope) the problem in the RF IF
> signal out from the IF board. Anybody has experienced something like this?
> Any hint? I really appreciate any help. It is impossible for me to send it
> back to US for repair,
>
> Jim, HK1N
>