[Boatanchors] B&W 850A Doc(s) needed

[Gary Schafer]

Hi Bob,

I assume that the detent plate for the band switch is also there on the
opposite end that the large ceramic switch plate is?

What you are calling the "beginning of the front coil" is actually the
output end of the coil, the end with the #10 wire. There should be a strap
that goes from the end of the wire coil back to the band switch. That end
connects to your loading capacitor and output connector of the amp. It is
also connected to the center terminal of the switch.

The band switch will short out the coil from the output side (center rotor
of band switch is connected to the output lead of the coil).

The flat strap (10 meter) coil free end connects to your plate tune
capacitor and plate blocking capacitor.

The other end of the flat strap coil should be connected to the end of the
copper tubing part of the coil and a band switch terminal. 

The other end of the copper tubing part of the coil is soldered to the start
of the #10 wire coil.


Some people remove the 10 meter coil and mount one end on the ceramic switch
plate (still connected to the same switch contact) and the other end over to
your plate tune capacitor depending on how your layout is constructed.

Be sure you get the switch into the detent when changing bands. If you stop
midway between detents you can get some fire works as the switch may arc.

73
Gary  K4FMX

> -----Original Message-----
> From: Rbethman [mailto:rbethman at comcast.net]
> Sent: Tuesday, May 09, 2006 9:36 PM
> To: garyschafer at comcast.net; boatanchors at mailman.qth.net
> Subject: Re: [Boatanchors] B&W 850A Doc(s) needed
> 
> Gary,
> 
> I see the connection on the rear of the 850A that goes to the beginning
> of the front coil, I see the switch pads for band switching., AND I have
> and see the 10 mtr strap coil on the rear ceramic plate.
> 
> In a PI network, the beginning of the coil comes off the tuning VAR cap,
> and the END of the output of the last part of the switched coil goes to
> the Loading coil - Correct?
> 
> I also do NOT have the escutcheon to display the band positions.
> 
> Before I go off the DEEP end, I want to be reasonably sure NOT to let
> the "smoke" out of a 3+KV circuit.
> 
> In past jobs I have experienced 4160VAC and 13,800VAC loose in and over
> the cover of an enclosure.
> 
> I SINCERELY do NOT wish to repeat these incidents.  I find it preferable
> to KNOW more before I dig in and wire things up!
> 
> Would love to find the escutcheon for a B&W 850A. to assist forgetfulness!
> 
> I'm using a Harris 3KV to 4KV power supply.  I also have an extra one.
> 
> I'm off down the path to building a 4-1000A GG amplifier.
> 
> Prior to this I have only built a pair of 813s and a pair of 572Bs.
> 
> I'm going to use either a DX-60B and/or An Apache to drive "Sasquatch"!
> 
> I also run a pair of BC-610s.
> 
> I just don't want to "Screw the pooch"!
> 
> Bob - N0DGN
> 
> Gary Schafer wrote:
> 
> >Hi Bob,
> >
> >Ok Jim and another Bob also straightened me out! The 852 was the one I
> was
> >thinking of that had all copper tubing.
> >
> >I have an 850A like yours in a pair of 4-400 amp and yes it does have a
> few
> >turns of tubing and the large wire and the strap coil for 10 meters.
> >
> >What info are you looking for?
> >
> >73
> >Gary  K4FMX
> >
> >
>                        Bob Bethman - NØDGN
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