[Icom] R75 went deaf after lightning

Mon, 14 Oct 2002 16:41:02 +0000

Hi Ray,
thanks for the advice,
I have got the schematics, but didn't know where to start.
The Rx still receives, but with very much attenuated levels.

The Preamp 1&2 still work, just not reaching same levels as before.
The Attenuator does work as well.
The (low) level is the same on both Antenna inputs.

The problem will be to get spare parts and to change them, I assume they =
are=20
SMT parts, and I hate un/solderign those, hi.

Thanks, I will make morechecks.

73,
Ekki, DF4OR

Am Montag, 14. Oktober 2002 15:46 schrieb Roy Sakabu:
> Often times it is the first semiconductor unit in the RF chain.  I've f=
ixed
> a couple of other manufacturers receivers this way.  In the R-75 Yahoo
> groups files section, there are complete schematics and block diagrams.=
=20
> You can follow the RF path in the block diagram as well as the Schemati=
cs,
> especially Main Unit (1).  That's probably where your blown front end i=
s.
>
> You said deaf on all bands.  Is it also deaf with the Preamp on/off,
> Attenuator on/off also?
>
>  I would first check R102 and R112 to make sure they didn't fail to sho=
rt
> circuit (assuming that your R-75 is deaf on BOTH A and B antenna inputs=
).=20
> I would then check to make sure D141 and 142 (the "protection" diodes)
> didn't short to ground.  Then check Q471, then Q441 and Q442.  By then =
you
> should probably have found the culprit.  Q441 and 442 are part of the m=
ixer
> circuit and Q471 is part of the IF amp/AGC circuit.
>
> Good luck
> Roy
> AD6ZU
>
> > ----------
> > From: =09Ekki Plicht[SMTP:[email protected]]
> > Reply To: =[email protected]
> > Sent: =09Monday, October 14, 2002 7:37 AM
> > To: =09_icom
> > Subject: =09[Icom] R75 went deaf after lightning
> >
> > Hi,
> > while running my R75 receiver on an indoor dipole, a thunderstorm cam=
e
> > along.
> > While there was no direct hit to my house or in the close vicinity, t=
he
> > Rx is
> > deaf nevertheless. My guess is that the closest lightning struck abou=
t
> > 500
> >
> > mtrs away from me.
> >
> > Does anybody know where to start looking or how to indentify the faul=
ty
> > component? The rx is deaf on all bands.
> >
> > TIA,
> > Ekki, DF4OR
> >
> > ----
> > Your Moderator: Dick Flanagan W6OLD, [email protected]
> > Icom Users Net: Sundays, 1700Z, 14.315 MHz
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