>Hi Guys,
>
>Got the below email, so am putting in on TT for help. Please
reply
>directly
>to Joe, N3JW. Thanks.
>
>Ted Leaf, K6HI
>Kona, Hawaii
>
>From: Joseph Adams <n3jw@netscape.net> Save Address Block
Sender
>To: Ted Leaf <tleaf@hotmail.com>,
>TO: The Ham Gang
>
>Subject: Help!
>
>We have been able to form a new ham club at a local school
(New
>Horizons
>Learning Center, across from Haney Tech) which serves
>"difficult" students in
>the middle to high school grade levels. The early success in
>this venture has
>exceeded expectations and young lives are literally being
turned
>around!
>
>Our problem is the station's R-7 HF antenna (a 40-10 meter
>ground independent
>vertical type) which has become defective. Attempts to
identify
>the defective
>component have hit a wall (Cushcraft insists on us buying the
>entire MN-7
>matching network for $150, even though the unit is easily
>serviceable <4
>screws secure the cover>, and the ARRL and several individuals
>have failed to
>follow through with their promises going back almost 8
months).
>
>You appear to be the last hope and follows is our request for
a
>worthwhile
>project. Please contact me if:
>
>1. You can possibly "id" the part. (description below)
>2. You know someone who you think can help (persons @ ARRL,
>Engr, or??)
>3. You have an inroad with Cushcraft (around the Mktg Dept)
>4. You know someone with an R-7
>5. You could make an educated guess as to part and its value
>from a
>schematic of the MN-7 Network unit (I'll scan the info and
>e-mail to you)
>6. You know where we might post this request on the Internet
>
>Obviously, we are trying to avoid the very tedious and
>time-consuming approach
>of subbing and trying different values and parts in the MN-7!
>Someone out
>there has got to know the answer. (BTW, we e-mailed the
>network's designer,
>Joe, now retired from Cushcraft. No response)
>
>Here's the general info. The antenna suddenly failed to show a
>low (below
>2.5:1 swr) on any band. It had been doing so. Checked the
entire
>system from
>exciter, thru coax, connectors and connections, to the
antenna.
>Next, dropped
>antenna and opened MN-7 matching network at the bottom of the
>radiator. Found
>"disintegrated" (not charred or burned) component located just
>to the left and
>between the two toroidal xfmrs on the circuit board.
>This is the only component in this location and is easy to
spot.
>It appeared
>to be a high voltage type disc capacitor.
>
>Electrically, this "unknown" is in parallel with the
>output/input leg of the
>two toroid xfmrs (between them) and the ground (coax shield
and
>counterpoise
>radials). Its the only component there, as otherwise it is a
>direct connection
>between the 2 xfmrs! This "thing" just connects from that leg
to
>ground!
>
>Thank you for taking the time to read this info and for
>considering trying to
>help us. We'll cover research expenses, buy the part from you
>(if you can
>supply) and otherwise make this worth your while.
>
>Its for a good cause!
>
>73, N3JW n3jw@arrl.net 850-747-5500(w) 271-2588(h)
>
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