Posted by
N8LP on
Dec 12, 2005; 3:45am
URL: http://elecraft.85.s1.nabble.com/K2-Armor-tp384498p384501.html
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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