Heathkit Apache TX-1

[Charles]

Try  re-setting ALL of the ground screws and bolts. Charles
----- Original Message ----- 
From: "Michael Waldrop" <w5rkl at YAHOO.COM>
To: <BOATANCHORS at LISTSERV.TEMPE.GOV>
Sent: Saturday, September 01, 2007 11:44 PM
Subject: [BOATANCHORS-TEMPE] Heathkit Apache TX-1


>I am wondering if there is anyone who has experienced a modulation
> transformer failure in a Heathkit Apache TX-1? What symptoms did you
> experience prior to the transformer failing?
>
> My Apache, in transmit, has a noice that appears to be a very short arc
> that sounds like a "tick" noise that can be heard by standing in front of
> the transmitter. The sound appears to be loudest at the left front. The
> modulation transformer appears to be warmer than normal. When the sound
> occurs the mod idle current drops to zero but returns to 50ma or there
> bouts. The mod idle current does increase to around 60ma when keyed
> with no modulation.
>
> I've changed the 100uf modulator biasing filter cap plus the diode and
> cleaned the pot but the problem is still there. The pot does adjust the
> mod idle current when set to 50ma. I've even changed the pot to a new
> pot and the problem still occurs. The mod tubes are EL-34/6CA7's from
> "Harmonic", purchased them from Fair Radio Sales.
>
> The modulation is good and clean when the problem is not occuring. I'm
> stumped. I am leaning towards arcing in the final or one of the 5R4GY
> recitifier tubes. The recitifer tubes are at the left rear which, if
> the tubes are arcing, would seem the noise is heard the loudest at the
> left front.
>
> Unfortunately, I don't have a spare 5R4GY recitifer tube so I can't
> determine if it is the tube or not. The tube does show questionable
> on the tube tester even though the tube tester doesn't apply 750VDC
> and test at 225ma to the tube during test.
>
>
> 73's
> Mike W5RKL
>
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