[ICOM] IC781 Tx problem

[Larry Benko]

Please let me amend my previous statement.  All Icom radios I have 
looked at with the exception of the IC706 and IC7000 which do NOT have 
relay outputs to drive an amp were what I was referring to.

Thanks,
Larry, W0QE

Larry Benko wrote:
> Paul,
>
> I don't agree with your statement. I  have made several measurements 
> on the keying of Icom radios and the "hsend" line is timed extremely 
> close to the reed relay output.  Since Icom radios don't have any menu 
> adjustments for amplifier timing something must be amiss if your 
> measurements don't match mine.  Please take a look at  
> http://www.bnk.com/w0qe/amplifier_timing.html for my measurements.  I 
> have seen the symptom that was mentioned but it was fixed by a good 
> common mode choke going to the Acc jack on the Icom radio.
>
> 73,
> Larry, W0QE
>
> Paul Playford wrote:
>> 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
>>>
>> ----
>> Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net
>> Icom Users Net: Sundays, 1700Z, 14.316 MHz
>> Icom FAQ: http://www.qsl.net/icom/
>>
> ----
> Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net
> Icom Users Net: Sundays, 1700Z, 14.316 MHz
> Icom FAQ: http://www.qsl.net/icom/
>