[TenTec] Omni C + new Ham = Oops.

[Mike Hyder -N4NT-]

I've seen the thread about hot versus not so hot soldering irons and will 
relate my experience in specific terms:

I use Weller soldering irons, they are blue and the tip can be replaced. 
I've used the 40 watt irons with a 'screwdriver tip' about 1/8 inch across. 
They were too hot for circuit board work (for me) but worked well on bigger 
solder lugs with big wires attached.

I prefer the 25 watt model Weller with a screwdriver tip 1/16 inch or 
slightly smaller for circuit board work.

These Weller things may be long gone from the market place, but watts is 
watts.

NOTE: Your mileage may vary.

73 and good luck,
Mike Hyder -N4NT-

----- Original Message ----- 
From: "Paul Harker" <paul.r.harker at gmail.com>
To: <tentec at contesting.com>
Sent: Monday, October 14, 2013 17:28
Subject: [TenTec] Omni C + new Ham = Oops.


>I am a new member of the amateur radio community, and my first HF rig is an
> Omni C. I was attempting to tune an antenna with a MFJ949E, with the mode
> select switch (SSB-R / SSB-N / CW / LOCK) switch in the LOCK position, and
> DRIVE set just high enough to allow tuning.
>
> Suddenly the antenna tuner needles dropped to zero, and it appears I no
> longer have RF output. The Model 255 power supply did not shut down, and
> the receiver is still functioning. I am assuming that I managed to blow 
> the
> MRF458 output transistors due to doing _something_ wrong. Maybe just a
> matter of fiddling too long and letting things get too hot. I don't know.
>
> Measuring the MRF458 with a meter suggests they might be bad, but it isn't
> a case of a dead short, and in the past I've found that power transistors
> can be deceiving when doing an in-circuit test.
>
> So... I looked for any sign of a fusible link or other protective circuit
> in the Omni schematics and didn't see any, but I thought I'd ask the
> experts before pressing "sumbit" on a transistor order.
>
> And any hints tips corrections to keep me from repeating my bungle would
> also be appreciated.
>
> Much thanks,
>
> Paul
> AC8OI
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