[Elecraft] SSB TX signal mystery SOLVED !!!

[Cyberia]

Is your KSB2 manual revision E (July 20, 2004)??

If so, then you need to carefully examine the notes at the top of the table
for the ICOM mikes. The note at the top of the table says NOT to connect pin
2 unless the MIC is pre-amplified. It says to connect AF (pin1) to 5V
through a 10K resistor for HM-12 (your MIC) or 820 Ohms for HM-7.

De N3WZ - Jim.

> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net [mailto:elecraft-
> bounces at mailman.qth.net] On Behalf Of Ken G3WCS
> Sent: Wednesday, December 29, 2004 4:21 PM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] SSB TX signal mystery SOLVED !!!
> 
> Cyberia wrote:
> > I made that exact same mistake!!! When it came time to install R10,
> however,
> > I realized the through-hole should not be occupied, and I discovered my
> > mistake.
> 
> Make that three!
> 
> I just completed my KSB2 yesterday and very nearly made the same mistake
> with D14. I had placed it in the PCB and was just about to solder it
> when I thought it didn't look quite right. I quickly turned it through
> 90 degrees and soldered it correctly.
> 
> I think the thing that throws you is the fact that everything on the
> right hand site of the board up til this point is symmetrical, from top
> to bottom. Therefore I had subconsciously thought that D14 was a mirror
> image of D4 on the lower part of the board which is mounted 90 degrees
> differently.
> 
> It might be worth a quick one liner in the KSB2 manual to warn against
> this pitfall. My KSB2 is now fitted to my K2 (#4489) and I had my first
> SSB QSO on 40m's this morning. Reports were good. Touch wood, an XV144,
> XV50 and now my K2 has gone together perfectly without a hitch. Built
> the KNB2 today and will be fitting tomorrow.
> 
> Just one more small observation with regard to mic pinouts. I am using
> an Icom HM-12 electret condenser mic with my K2. Table 2 on P18 of the
> KSB2 manual seems to indicate that the 10K resistor to feed the DC to
> the mic should go from the 5V side of the mic config block to pin 2 of
> the mic. This is not correct, as according to the circuit of the HM-12
> in the Icom IC-735 manual, there is no connection to pin 2 in the mic
> itself. The DC voltage is fed up the audio cable (pin 1) and blocked
> from the audio path inside the mic by a capacitor and routed to the
> mic's internal pre-amp. Connected the 10k from 5v to pin 1 and away it
> went with stacks of audio.
> 
> Happy holidays and New Year.
> 
> 
> Ken.
> --
> 
> Ken G3WCS <ken at g3wcs.com>
> IO83rh : Cheshire : NW England
> (+44) (0)1606 892677 (home)
> (+44) (0)7733 400950 (mobile & sms)
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