[1000mp] More info on MkV blown front end.

Mon, 1 Sep 2003 20:15:12 -0700 (PDT)

Hi Guys. I have a mark V about 8 months old.  Has this happened to many other people?
Also is there anything else that I should watch out for?  Running scared.  Watt n5nf

"George, W5YR" <[email protected]> wrote:
Sound like the transistor is just a simple switch for the relay. When the
relay should be on, the base should be at an appropriate voltage for the
circuit in order to turn the transistor on. If the base is being switched by
the T/R logic and the relay doesn't come on, that pretty well points to the
transistor as being defective - replace it. If no base voltage change is
observed, then start working backwards through the T/R logic from there.

I wouldn't want to argue about it, but a curve tracer to evaluate the
transistor is a little overkill. It either switches or it doesn't.

73/72, George
Amateur Radio W5YR - the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
"Starting the 58th year and it just keeps getting better!"
[email protected]

----- Original Message -----
From: "Darrel Nichols" 
To: <[email protected]>
Sent: Monday, September 01, 2003 9:32 AM
Subject: RE: [1000mp] More info on MkV blown front end.

>
>
>
> > [Original Message]
> > From: lhlousek 
> > To: 1000mp list <[email protected]>
> > Date: 8/31/2003 11:10:10 PM
> > Subject: [1000mp] More info on MkV blown front end.
> >
> > I did some troubleshooting. There is a T/R circuit at the antenna input
> to the rig that employs three transistors, a pin diode switch, and a
> relay. The relay isn't being activated. I can make the relay work by
> supplying 12V to it and the rigs receives fine. The PNP transistor that
> operates the relay is either blown or isn't getting the correct input to
> switch the relay. I need to do some more signal tracing to see if I can
> figure out what's going on.
> >
> > Lou W7HV
> >
>
>
> Sounds like a job for a Curve Tracer. Found a page:
>
> http://www.old555.com/LPE/unit/5B680B4E0BE5E522.shtml
>
> Been using these for over 30 years and still am surprised to learn
> some don't know about it. You do need a simple scope though.
>
> N0DBX
>
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