Thanks Jack,
I'll call them, but I removed the KSB2 module and I still have the
problem. There appears to be plenty of drive either way. I ordered a PA
replacement kit just to have it on hand. I can get the xstrs locally,
but not all the mounting stuff.
Larry N8LP
Jack Brindle wrote:
Larry;
I suggest you call Elecraft customer support on this. Something tells
me they will want you to check out the KSB2 module to find the problem.
Good luck!
On Dec 12, 2005, at 7:52 AM, Larry Phipps wrote:
I think I checked the T/R switch already, but I'll double-check. The
thing that's weird is that the DC voltages and resistance checks on
the finals are OK. I never got a Hi-Cur warning at any time before
the failure (or since). The rig draws about 600ma during xmit.
Thanks for the feedback.
Larry N8LP
Don Wilhelm wrote:
Larry,
With those RF voltage measurements, I would say that the final output
transistors have likely failed - that goes along with your earlier
report
that the power out decreased rapidly to zip.
There is only one other possibility that I can think of, and that
would be
the transmit signal being shorted somewhere - so before blaming the
finals
themselves, check that Q2 is operating properly - the juction of D3
and D4
in the TR switch should be at a low voltage during receive and go up
somewhere close to 8 volts during transmit.
If the receiver is still functioning properly, a short in the Low Pass
Filter is quite unlikly because that kind of fault would drag the
receiver
way down too.
73,
Don W3FPR
-----Original Message-----
From: Larry Phipps [mailto:[EMAIL PROTECTED]
Sent: Sunday, December 11, 2005 10:46 PM
To: [EMAIL PROTECTED]
Cc: Elecraft@mailman.qth.net
Subject: Re: [Elecraft] K2 dead xmtr
Hi Don. The levels are high everywhere in the chain up through the
bases
of Q7-8. Requested power is immaterial in this case, since the ALC
sees
zero detected power, and therefore is pegged at 5v all the time.
I measured the levels with a scope, and divided the p-p values by
2.82
to compare with the voltage probe reference levels in the manual.
BTW, I
removed the KAT2 and KSB2 to simplify access and minimize the
number of
possible fault zones.
W6 - .28 Vrms
Q5 case- 1.4 Vrms
Q6 tab- 3.5 Vrms
Q7,8 base- 1.4 Vrms
RF out- .55 Vrms
Note: These waveforms are pretty dirty looking except on 10m, where I
made these measurements.
Larry N8LP
Don Wilhelm wrote:
Larry,
With the requested power set at 5 watts, send us the RF Voltage
levels at
the W6 jumper, Q5 collector (case), Q6 collector (tab), Q7,Q8
base, and the
RF Output jack. With that info, we should be able to home in on
the problem
area.
73,
Don W3FPR
-----Original Message-----
OK. I'm hoping someone has seen this before I start tearing into
things
(and tearing my hair out).
My K2 started to lose power yesterday. Within an hour, the output
dropped to close to zero (1mW on 160m, 40mW on 10m). There are
no signs
of distress or burning odors.
I checked the ALC... pinned at 5v. Everything looks good in
terms of
levels/frequencies thru the XMIT mixer and filters, except the
rf levels
are higher than indicated in the manual. I suspect this is due
to the
ALC being wide open.
The dc levels for Q5, Q6, and Q7-8 bases are normal, and the
resistance
checks on Q7-8 are OK. 8T looks fine. But the rf levels are all
considerably high, and look pretty ratty except on 10m. The rig
draws
about 600ma in xmit.
Anyone seen this before?
Larry N8LP
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