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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