[TenTec] Omni C + new Ham = Oops.

[Dave Edwards]

You are probably doing more soldering than I do, and I would not want to 
be without my
solder station.
I had the nice Weller one...with digital readout of tip temperature. But 
as slick as it was, it just
one day crapped out.
Replaced it with a Hakko station. Still using it.
The trick is not on the wattage of the iron, but in the tip being used.
I have several tips that go from what you are talking about...down to 
SMD stuff.
If I have to solder a wire to a chassis...or heavy boat anchor 
transformer wires, I break out
the old Weller gun.
Not a new Weller gun...with the set screws holding the tip. They are junk.
The old ones with a nut holding down the tip are the ones to have. 
Plenty found at garage sales,
flea markets, and tons on ebay....but of course, you pay premium there!!
....Dave



On 10/15/2013 3:08 PM, Paul Harker wrote:
> Before I go at it, any tips on desoldering the power transistors? My 35W
> iron is not up to the task unless I cut the foil leads beforehand. A bigger
> iron might be in my future.
>
>
> On Tue, Oct 15, 2013 at 1:03 PM, Mike Bryce <prosolar at sssnet.com> wrote:
>
>> excellent troubleshooting
>>
>> although the diodes on the swr board don't control the PA in anyway.
>>
>> but it could be that a spike came down the coax and took a few things out.
>> It's possible.
>>
>> if you can get to the base of the transistors in the PA, in the lock
>> posistion position and the drive all the way down, you should see supply
>> voltage on the collectors, zero on the emitter and .7 on the bases.
>>
>> since the base resistors are toasty, be sure you replace them with like
>> units, carbon flim or metal film and not wirewound.
>>
>> call RF parts and see what they have in stock. I'm not much for matched
>> pair in simple PA designs like the ones in the Omni, so save some money
>>
>> mike
>>
>> Mike, WB8VGE
>> SunLight Energy Systems
>> The Heathkit Shop
>> http://www.theheathkitshop.com/
>> J e e p
>> o|||||||o
>>
>> A man with one clock knows what time it is. A man with two clocks is never
>> sure.
>>
>>
>>
>> On Oct 15, 2013, at 12:23 PM, Paul Harker wrote:
>>
>>> Well... here is where I'm at:
>>>
>>> Checked the 914 diodes on the SWR board and sensing diode (D1) was bad
>>> (leaky reverse biased). A big smile.
>>>
>>> I replaced the offending diode, put everything back together, attached a
>>> dummy load to the output and turned up drive to see how much current was
>>> drawn. I noted a 3 amps input power increase, and smoke. Smile goes away.
>>>
>>> Tearing it back down I discover 3.3 ohm R5 and R8 have acquired deep
>> tans.
>>> These couple the impedance matching transformer to the bases of the power
>>> transistors. A subsequent check verifies proper bias voltage to the final
>>> stage.
>>>
>>> Though toasty brown, and slated for replacement, R5 and R8 are still
>>> correct values.
>>>
>>> Unless I'm missing something major (always a possibility) I'm thinking
>> that
>>> this kinda seals the deal on the power transistors being bad.
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