[WriteLog] Re: [ic756pro2] Service manual

[Georgek5kg at aol.com]

In a message dated 3/8/2003 9:19:55 PM Eastern Standard Time, w8aef at att.net writes:

Paul, here are some questions/comments:

> Thanks for the info.  I am having a discrepency with my PROII.  I am attempting to drive an Alpha 76A and during QSK the output waveform has an odd shape.

How do you know what the waveform looks like?  Tell me more about what you mean by "waveform has an odd shape". 

How are you keying the Alpha from the 756Pro2?  You should be using an external circuit to create the ground during transmit.  The 756's internal reed relay will not withstand more than 200 ma current. I know, I zapped mine!

  Any time I increase the drive above 50 watts (the Alpha requires 80 watts for 1500 out) the first element is OK but subsequent elements have a reduced output at the leading edge and ramps up to the higher power output.

What do you mean by "first element".  Are you referring to the leading dit or dot of a cw character?  I don't really understand: "subsequent elements have a reduced output at the leading edge and ramps up to the higher power output".  Please explain this in terms of sending a cw msg.  For example, what happens to the power level if you send "CQ CQ CQ DE W8XX W8XX K".

   This only occurs while I am driving the amplifier and am running QSK.  I suspect that the PROII's ALC is doing something wierd but don't really know.  Just gotta get it 
> on the bench and do some looking around.

Are you using an ALC line from the 756 to the Alpha?  If so, try disconnecting it and see what happens.  However, be very careful to keep the drive under control.

73, George, k5kg