[Elecraft] new K1: 2W out, no more, CPU bug or ALC problem?

Sat Jun 15 12:17:03 2002

Update: my dad was using a digital meter to read D18, and
switching to a higher scale, the diode checks as good.

He believes the 5.8V out of the D/A converter would be correct
as the VCC is 6V...so it's something in the ALC buss I would
imagine. 

Still no pointers on this... Please email him directly at 
[email protected], or to the List. 

-Andy

> -----Original Message-----
> From: Wallace, Andy [mailto:[email protected]]
> Sent: Friday, June 14, 2002 8:10 AM
> To: '[email protected]'
> Subject: [Elecraft] new K1: 2W out, no more, CPU bug or ALC problem?
> 
> 
> Hi, Folks. My dad is finishing up a 2-band 40/20 K1, rev 1.09 
> firmware and serial 12xx. This is the new main board rev also. 
> 
> The K1 is operating properly -- BELOW 2 WATTS output!
> 
> Symptoms are:
> 
> 1) You can set OUT to 5.0 but transmitting only yields 2.1 or 
> so on 40m. This
> was confirmed on an OHR external wattmeter. The display only 
> shows two bars.
> Going back to OUT shows 5.0 remains. 20m yields only a watt. 
> 
> 2) Below 2.1W or so, the rig behaves normally. You can set 
> the power to 0.3W
> and
> see about 0.3. 1W is 1W. 
> 
> 3) Pressing the two TUNE buttons also yield 2W out. While in 
> tune mode,
> pressing
> the + and - buttons has NO effect. You can't turn it up OR down. 
> 
> 4) In troubleshooting with him today, checks with an RF probe 
> as described
> in
> the manual show many signals being off -- part of that could 
> be due to the
> fact
> we can't get 5W out and that's what the voltage readings 
> should be made at. 
> We noticed that the (transmit) ATTN test point read low, and 
> checked D18, a
> 1N4007. 
> It was completely open!  He substituted a silicon diode 
> temporarily and we
> continued to look around...
> 
> 5) The POWER signal going into the same transmit attenuator circuit is
> behaving
> strangely. This comes from the front panel board, the MAX518 
> D/A converter
> at
> U2. Now...here is a great piece of evidence...the POWER signal was
> approximately
> 5.8 volts (I believe) with OUT set to 5.0W. Setting OUT to 2W 
> also showed
> the
> same level on POWER. Going down to 1W, POWER did drop to less 
> than 4V or so.
> So
> the interesting thing is that the POWER SIGNAL REACHES A 
> PLATEAU AT 2W AND
> CAN'T
> MAKE IT ANY HIGHER. 
> 
> My gut feeling is there is something wrong with the MCU, 
> which feeds this
> D/A.
> Ideas? Does this sound plausible? Everything else appears to operate
> normally,
> receive and transmit seem to work fine otherwise. 
> 
> If it's not the CPU, could it be something which blew D18? 
> What would cause
> that? Sure looks like the problem is in the transmit attenuator/ALC
> circuits. 
> 
> Any help appreciated! 
> 
> -Andy
> 
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