[Elecraft] Woops something blew !!

[Brian H.]

Thanks Phil for all the idea's. You are correct, I didn't touch the RF
board, only the CB. I looked closer at the 4 transistors Q1, 2, 3 and 4. Q1
looks OK but the pin furthest from the top of the CB board on Q2 is the one
that goes from 8V to 0.6V, same pin on Q3 goes from 0.0 to 8V. On Q4 the
middle pin is at 0V always and the furthest pin from the top goes to 4.5V to
8V !!

I haven't had much luck tracking anything else down, hopefully the info
above gives you some ideas. Recall that I had the IO board working until I
tried to tune the K2 remotely, I got a low power message even tho I was
running 5W. This condition remained the same for 1-2 minutes potentially
with no antenna attached.

I am now at the limited of my debugging and equipment capabilities so if the
above doesn't lead to anything I'll contact Elecraft to look into returning
the radio.

Again thanks for the help.
Brian
----- Original Message -----
From: Phil Wheeler
To: Brian H.
Sent: Wednesday, May 29, 2002 7:43 AM
Subject: Re: [Elecraft] Woops something blew !!


I just added the CB ckt changes to the diagram I have in front of me.  I
have trouble seening how ANY of them could cause the symptom you have.  I
would check the added 0.001 cap at P4 for a short, though.  I'd also look at
all places where you added things (wires, the cap) and make sure a solder
bridge did not get added, too.

One thing you might do is measure the resistance to ground from the
collector of Q2 (8R) with the CB plugged into the RFB and then with it
removed, to see if something on the RFB is loading the 8R line..  I'm not
sure 8R goes anywhere else on the CB (or FP) or not -- it's like looking for
a needle in a haystack with these diagrams :-\

Hmmm -- FWIW, 8R does go to the collector of Q12 (AGC) and to pin 9 of P4;
I'd definitely take a close look at P4.

But this is smelling like an RF Brd problem pulling down 8R; but you made no
changes there that I can remember.

73, Phil

Brian H. wrote:

Hi, Yes , basically the only connection to the top of the case is thespeaker
cable, ie, the battery, IO, Tuner are all out of the picture(although I did
not change any menu settings). Also, yes the noise in thespeaker and the
"changing" voltages do occur slowly - perhaps 2-3 secondsfor the 8V to drop
to 0.6V !!I did continue tracking voltages and found that the voltages on
the E,B,C ofQ1 are correct, but on the collector of Q2 ( the pin furthest
away from thetop of the control board) I see an initial 8V that drops to
0.6V after a fewseconds. Q1 and Q2 are both on the control board.Recall I
just added the AF and IO options. Everything appeared to work OKafter I
added the AF, the problems started when I added the IO option andconnected
to a computer - does anyone know what would happen if I did notcorrectly cut
the track on my rev A board as required by the IO instructions? I think I
did cut the track t
hru but it is very hard to tell, also Isuppose if the multi layer board is
very thin the I could have shorted thruto the next layer. Is there any pins
I can measure on U6 to verify ?I have copied all the detail from previous
messages in order to listeverything in 1 message.Thanks for all the
help,Brian***********************************
Brian,I don't recall your test config.  Am I correct in thinking that the
KIO2is *not* in when you get the following results?In
4) D2 at the far end of the RF board initially reads 8/7.5V (
Cathode/Anode) and then drops to .6/.1 V after 6 seconds !!
5) Rechecking the 8V regulator shows a constant 8V over time6) Pin 21 of
connector P2 ( main connector from the control board to the
RF board shows 8V DROPPING to 0.6V !!
Are these drops gradually (R-C time constant sort of thing) or like astep?
If the latter, I would look for something shorting or openning updue to a
thermal condition..  BTW -- what page of the ckt dgm is D2 on(I'm not
finding it), and are you measuring the 8V regulator voltage atthat component
or elsewhere?
************* Second message ****************First, thanks everyone who sent
me some ideas. I did some tracing of thevoltages around the different boards
and here's what I found;1) As I said in my first message the noise in the
speaker disappears afterabout 6 seconds. The LCD never lights up.2) I
totally disconnected the battery and connected to the AC and still havethe
same problem.3) The 8V and 5V regulators are OK4) D2 at the far end of the
RF board initially reads 8/7.5V ( Cathode/Anode)and then drops to .6/.1 V
after 6 seconds !!5) Rechecking the 8V regulator shows a constant 8V over
time6) Pin 21 of connector P2 ( main connector from the control board to the
RFboard shows 8V DROPPING to 0.6V !!Obviously it looks like something along
the lines of a capacitor (RC timeconstant ??) is causing a problem but does
anyone have ideas ??************* First
message ****************Hi, I just installed the KIO2 kit in my K2 (
includes the Tuner, SSB, AF,160 and battery). Initially everything worked
well for a few minutes then Istarted to remotely "Tune" the rig and got a Lo
Power message. I turned uppower to about 8W and still got the same message
.. then everything died !!No LCD readout, no relays clicking, no signal
nothing except some noise thruthe speaker which does appear to be affected
by the volume control. I triedto "remove" the IO board but that doesn't
appear to make any difference.Anyone have any idea's ? My debugging skills
are rather limited ( the K2 wasmy first ever kit !!).ThanksBrian, KD7Z
Serial Number 301Need to get this sorted out ASAP, the K2 100W PA is in the
mail (hopefully)!!

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