I think I checked the T/R switch already, but I'll double-check. 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.
>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:
[hidden email]]
>>Sent: Sunday, December 11, 2005 10:46 PM
>>To:
[hidden email]
>>Cc:
[hidden email]
>>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
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>--
>>No virus found in this incoming message.
>>Checked by AVG Free Edition.
>>Version: 7.1.371 / Virus Database: 267.13.13/198 - Release Date:
>>12/12/2005
>>
>>
>>
>>
>
>
>
>
>
>
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