[Icom] 761 Help

Fri, 11 Apr 2003 12:07:12 -0500

Hi Ed,

Bingo, how right you are, it is indeed a MI204.  I used a magnifying glass
under my magnifying light on the service manual and it was an I and not a
1.

Thanks a million.

Now back to the scope and the DMM

        William J. Diamond (Bill)
        Rogers, Arkansas USA
        [email protected]

        Ham Radio Operator WROT
      Flying The Flag Long Before
            It Was Popular
   Please Visit My New Icom Radio Page

 http://pages.sbcglobal.net/wjdiamond/index.html

-----Original Message-----
From: [email protected] [mailto:[email protected]]On
Behalf Of [email protected]
Sent: Friday, April 11, 2003 8:04 AM
To: [email protected]
Subject: Re: [Icom] 761 Help

Please check the part number again......

Although I don't have a reference.....

Are you sure it's not an MI204 or possibly an MI402 if 204 is a typo?
That's a letter I instead of a one after the M.

This is a typical PIN diode that is used instead of a transmit/receive
relay for switching the RF signal path.  There are typically two of them
used in the circuit.  One to carry RF from the transmitter to the antenna
and the other from the antenna to the receiver.  The two might be the
same, but probably not since you are working with "high" power on the
transmit.  They should be DC biased for forward conduction in which ever
mode they are required to conduct....  that is, the transmit one should
be biased on in transmit and the receive one biased off to prevent
transmit RF from getting to the receiver.

Ed
K1ZOK

On Thu, 10 Apr 2003 22:52:31 -0500 "wjdiamond" <[email protected]>
writes:
> Hi Gang,
>
> Now I am really perplexed.  The reading that I get on each side of
> Diode D
> 47 are exactly opposite of what they should be.
>
> According to Icom and the manual the cathode side should read 9.4 RX
> and
> 9.7 TX
>
> The Anode side should be 8.8 RX and 13.8 TX
>
> Mine reads the exact opposite I guess the black band is still the
> cathode
> today as in many years ago. I always considered the Anode side to
> look like
> an arrow on the schematic.
>
> This is a weird diode also it is a M 1204 and I cannot find a cross
> for it
> anywhere.
>
> What am I missing??
>
> Thanks
>

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