[Milsurplus] Fwd: 2019: A TCS Oddity

[AKLDGUY]

---------- Forwarded message ----------
From: *AKLDGUY* <neilb0627 at gmail.com>
Date: Sunday, January 27, 2019
Subject: [Milsurplus] 2019: A TCS Oddity
To: David Stinson <arc5 at ix.netcom.com>


I'd suspect a mis-connected antenna relay allowing transmitter power
directly into the receiver. Maybe antenna and receiver cables misidentified
and inadvertently connected to each others' sockets.

Neil ZL1ANM


On Sunday, January 27, 2019, David Stinson <arc5 at ix.netcom.com> wrote:

> Been working on a long article about reviving TCS
> receivers.  Found a nice-looking, unmolested TCS-6
> at the HamComm 'fest in Plano last June, so put it
> on the bench to resuscitate.  Doing the job and
> taking notes will prevent my either forgetting
> steps or trusting in memory, which can lead to
> some dumb writing I'd have to correct.
>
> So did the Clean-Lube-DeOxIt ritual and replaced
> the bad caps in the main chassis, then measured
> the B+ busses, which looked OK.  Haven't pulled
> the modules for their "transplant surgery" yet.
> Decided to see if the thing could breath.  Brought
> the B+ busses (pins 2 and 3) up slowly to 200V
> sans filaments and watched the current for a half
> hour- all seemed well, so powered the filaments.
> The audio and other stages seemed to be working,
> but the set was deaf.  Could barely hear a strong
> broadcast station at 1500 KC.   Touched the
> antenna, through a capacitor, to the C206 at the
> RF Amp's grid.  The radio took a deep breath and
> started bellowing accordion Mexican music.  The
> alignment had received "The Golden Diddle-Stick,"
> but that's "no hill for a stepper," as my father
> the DI would say.
>
> First thought was that the Antenna section of the
> band switch had a broken contact wiper- a
> too-common and almost-always fatal condition.  You
> ain't seen nasty until you've tried to change a
> TCS band switch.  But very careful examination
> with a strong light showed it intact.  A lot of
> head-scratching and poking around, then I put the
> Ohmmeter on the Antenna coil primary switch.  It
> should read near-short to ground, but it showed
> open.  All three of them.  Grabbed a strong
> flashlight and looked down the inside of the
> Antenna coil forms.  On all three coils, the tiny
> pigtail of wire that goes through the ceramic form
> to the Primary input side was melted open.
> Someone, for some crazy reason, put voltage on the
> Antenna connector and than racked the band-switch,
> burning-open all the Antenna coil primaries.  This
> is going to be bear to fix.
>
> In the mean time, I connected a 30 pFd capacitor
> from the Antenna lead to the Antenna coil
> Secondary switching contact on the end of C206 and
> this has got the radio playing until I can fix
> these coils.  We'll probably never know how it
> happened, but it would be an interesting story.
>
> GL OM ES 73 DE Dave AB5S
>
>
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