As I recall, there's a plate on the bottom of the casting to which the first
two coils (associated with C301 and C302) were mounted using screws. There
may be other screws also attaching that plate to the chassis. On some units
the plate is soldered around the perimeter to the casing, on some it isn't.
Even if yours isn't soldered, you'll still need a lot of heat to un-solder
the coils/caps from the casting (soldered at the top at the cap, and at the
bottom at the cold side of the coils). You want to remove turns off the top
side of the coil - the coils are tapped near the bottom and you don't want
to alter that.
I have a big 175 watt Weller pencil iron that has a lot of mass that works
great for stuff like this. Google "Weller SP175".
--- Jeff
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Chris Curtis
> Sent: Monday, June 29, 2009 2:42 PM
> To: [email protected]
> Subject: RE: [Repeater-Builder] Exec II receiver fiddling
> WAS:MastrII Receiver Failure
>
>
>
> On my exec II receiver, the "casting" is just screwed together.
> Correct?
>
> Chris
> Kb0wlf
>
> > -----Original Message-----
> > From: [email protected]
> <mailto:Repeater-Builder%40yahoogroups.com> [mailto:Repeater-
> > [email protected] <mailto:Builder%40yahoogroups.com>
> ] On Behalf Of Jeff DePolo
> > Sent: Friday, June 26, 2009 9:00 PM
> > To: [email protected]
> <mailto:Repeater-Builder%40yahoogroups.com>
> > Subject: RE: [Repeater-Builder] MastrII Receiver Failure
> >
> >
> > Chuck's got you going down the right path. At 51 MHz, you probably
> > only
> > have to take one turn off of each of the first two coils.
> At 52 MHz or
> > higher, you might have to take off two. You need a lot of
> heat to get
> > the
> > casting open (hint: a soldering gun, even a 300 watt Weller, ain't
> > gonna cut
> > it). Removing the coils/caps once you have the casting
> apart is pretty
> > straightfoward, as is removing one turn from each. It's not that bad
> > of a
> > job once you've done one or two, but the first one may
> cause you some
> > grief.
> > You should find that after the mods the receiver is plenty hot and
> > should
> > easily beat spec by a few dB. The LO/multiplier stages don't require
> > any
> > mods.
> >
> > If you want to cut corners, you might first see what your effective
> > sensitivity is at your repeater site on 6m. You may find that the
> > noise
> > floor is elevated substantially, and that getting the "bench"
> > sensitivity
> > down from 1 uV to 0.3 uV isn't going to make a damned bit
> of difference
> > in
> > the real world.
> >
> > --- Jeff
> >
> >
> > > -----Original Message-----
> > > From: [email protected]
> <mailto:Repeater-Builder%40yahoogroups.com>
> > > [mailto:[email protected]
> <mailto:Repeater-Builder%40yahoogroups.com> ] On Behalf Of
> Chris Curtis
> > > Sent: Friday, June 26, 2009 4:16 PM
> > > To: [email protected]
> <mailto:Repeater-Builder%40yahoogroups.com>
> > > Subject: RE: [Repeater-Builder] MastrII Receiver Failure
> > >
> > >
> > >
> > > You are correct sir, no mesh.
> > > Isn't that that pits.
> > >
> > > So I take it I'll be removing some windings from the underside of
> > said
> > > trimmer caps?
> > > Or is there an easier route to sensitivity?
> > > =]
> > >
> > > Chris,
> > > Kb0wlf
> > >
> > > > -----Original Message-----
> > > > From: [email protected]
> <mailto:Repeater-Builder%40yahoogroups.com>
> > > <mailto:Repeater-Builder%40yahoogroups.com> [mailto:Repeater-
> > > > [email protected]
> <mailto:Builder%40yahoogroups.com> <mailto:Builder%40yahoogroups.com>
> > > ] On Behalf Of Chuck Kelsey
> > > > Sent: Friday, June 26, 2009 12:09 PM
> > > > To: [email protected]
> <mailto:Repeater-Builder%40yahoogroups.com>
> > > <mailto:Repeater-Builder%40yahoogroups.com>
> > > > Subject: Re: [Repeater-Builder] MastrII Receiver Failure
> > > >
> > > > Do the two front end trimmer caps still have some "mesh"
> > > left, or are
> > > > they
> > > > at minimum capacitance? That may be your problem.
> > > >
> > > > Chuck
> > > > WB2EDV
> > > >
> > > >
> > > >
> > > > ----- Original Message -----
> > > > From: "Chris Curtis" <[email protected]
> <mailto:demoman%40rollanet.org>
> > > <mailto:demoman%40rollanet.org> >
> > > > To: <[email protected]
> <mailto:Repeater-Builder%40yahoogroups.com>
> > > <mailto:Repeater-Builder%40yahoogroups.com> >
> > > > Sent: Friday, June 26, 2009 10:45 AM
> > > > Subject: RE: [Repeater-Builder] MastrII Receiver Failure
> > > >
> > > >
> > > > I have a mastr EXEC II receiver (33 split) that I can't get
> > > sensitivity
> > > > to
> > > > increase.
> > > >
> > > > I replaced the fet as outlined below on the mastr II query.
> > > > No joy though.
> > > >
> > > > I'm using an am/fm-1200s to tune the receiver.
> > > >
> > > > .5~1uv is where the receiver is coming to life.
> > > >
> > > > I have a couple vhf and uhf exec II receivers that tuned up
> > > nicely in
> > > > the
> > > > .19~.2uv range so I "think" I'm doing/reading it correctly.
> > > >
> > > > Original freq was in the 46~49mHz range.
> > > > Current crystal (icom sent to and received from Bomar)
> on 51.75mHz.
> > > >
> > > > Any tips/hints/tricks to get a little more sensitivity?
> > > >
> > > > Thanks for the bandwidth!
> > > >
> > > > Chris
> > > > Kb0wlf
> > > >
> > >
> > >
> > >
> > >
> > >
> > > No virus found in this incoming message.
> > > Checked by AVG - www.avg.com
> > > Version: 8.5.339 / Virus Database: 270.12.85/2193 - Release
> > > Date: 06/26/09 05:53:00
> > >
> > >
> > >
> >
> >
> >
> > ------------------------------------
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> > No virus found in this incoming message.
> > Checked by AVG - www.avg.com
> > Version: 8.5.375 / Virus Database: 270.12.83/2191 - Release Date:
> > 06/26/09 05:53:00
>
>
>
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.5.375 / Virus Database: 270.12.85/2193 - Release
> Date: 06/29/09 05:54:00
>
>
>
