[TenTec] Omni C + new Ham = Oops.

[Mike Hyder -N4NT-]

My Wellers are the models WP-40 and WP-25. My 'screwdriver tip' on the WP-25 
is probably 1/32 across the rounded tip.

Mike -N4NT-

----- Original Message ----- 
From: "Mike Hyder -N4NT-" <Mike_N4NT at charter.net>
To: <tentec at contesting.com>; <paul.r.harker at gmail.com>
Sent: Friday, October 18, 2013 18:31
Subject: Re: [TenTec] Omni C + new Ham = Oops.


> 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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>
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