[Test-Equipment] AN/PRM-10 Question

[Brooke Clarke]

Hi Richard:

Can you post a photo?

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.End2PartyGovernment.com/


Richard Knoppow wrote:
> ----- Original Message -----
> From: "Richard Knoppow"<1oldlens1 at ix.netcom.com>
> To:<k2cby at optonline.net>; "Discussion of Electronic Test
> Equipment"<test-equipment at mailman.qth.net>
> Sent: Wednesday, November 02, 2011 2:04 PM
> Subject: Re: [Test-Equipment] AN/PRM-10 Question
>
>       One last time. I fixed the internal oscillator, not
> sure what I did but think it may have been a dirty normal on
> the external modulation jack. Maybe something else because I
> resoldered a couple of things. Also, the 1 meg resistors I
> thought were half-value are effectively in parallel for the
> ohm meter, they are fine when lifted at one end.
>       Now, the main problem is the brush contact that
> connects the tuning capacitor rotor to ground through a 470
> ohm resistor. The brush is a spring contact with a button on
> the end. Its held in place on a small Bakelite insulator
> which is screwed to the side of the capacitor frame and
> designed so that the button projects though a small hole in
> the frame where it is supposed to contact the geared drive
> wheel for the capacitor. The problem is that it does not
> reach and there is no adjustment. If I try to push it
> further the spring contacts the frame. The rotor is properly
> centered so adjusting its bearings is not possible. I don't
> know why the contact is so far off, it does not appear to be
> wear and there is nothing else that can move much. The only
> solution I can think of is to enlarge the hole it projects
> through enough to allow bending the spring so that the
> button rides on the gear as its supposed to. I can imagine
> that there might be something missing but I can't figure out
> what it could be. The whole arrangement is not very well
> designed; I can think of a couple of better ways to connect
> the rotor and still allow it to move freely. The designer
> used a similiar brush to ground the brass intermediate gear
> that drives the variable resistor used to equalize the
> output, probably to eliminate static build up. This gear
> drives the capacitor gear through plastic gears. At any
> rate, unless I hear from someone who knows for certain that
> there is some adjustment for the mechanical alignment I will
> haul out the hand drill and enlarge the hole. The dead spots
> in the output are due to the rotor floating so its necessary
> to fix this. Once done, assuming my cure actually works, the
> thing should be complete and working properly.
>       I am just home from work and need some sleep so will
> check the list later.
>
>
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com
>
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