Re: K2 troubleshooting
Posted by
John Wiener on
May 30, 2006; 8:01pm
URL: http://elecraft.85.s1.nabble.com/K2-troubleshooting-tp390323p390325.html
Don,
Driver Output RF last measured at 2.3V rms (earlier it was 3.6)
which I think is normal.
PA Input RF(Q7) was .55 and (Q8) was .55 which I think is also normal.
John
AB8WH
On May 30, 2006, at 12:15 AM, Don Wilhelm wrote:
> John,
>
> The PA Transistor Test values will vary depending on your
> particular DMM -
> some will show forward voltage while others will show ohms. Your .55
> reading on the base to emitter with the probes either way would
> indicate
> something to be concerned about - but since you are testing in-
> circuit, the
> problem could be something other than the output transistors (we
> can get to
> that later if need be).
>
> When doing the transmit measurements (DC Voltages or others), it is
> always a
> good idea to connect a 50 ohm dummy load. Make your measurements
> during
> quick key-down (or TUNE) periods, and give things a chance to cool
> down
> after each measurement.
>
> Your RF voltage measurements look OK for a K2 that is not developing
> sufficient power output - the 'too high' readings are to be
> expected under
> such conditions. What is the Driver Output RF Voltage and the PA
> Input RF
> Voltage? These measurements will tell if the problem is the driver
> or the
> finals. If the Driver Output is low, the first thing to check is the
> emitter resistor for Q6.
>
> 73,
> Don W3FPR
>
>
>> -----Original Message-----
>> Now, Here are the aberrant values:
>>
>> Band-Pass Filter Output: 0.12 (Expected is .03)
>> T-R Switch #1 Output: .141 (Expected is .029)
>> Driver Input: 0.16 (Expected .026)
>> RF Detector Input: 0.7 (Expected is 2.0)
>> Q7 and Q8: both have been replaced once already
>> Transistor test Pos. Lead on Base: E and C both read about .55
>> (volts, I guess..."k" is listed in the manual)
>> Neg. Lead on Base: "OL" on C, .55
>> on E(expected is 1.3)
>>
>> That's where I am at the moment.
>>
>> If someone can explain what the settings should be for DC Voltage
>> tables during TRANSMIT, I would really appreciate it.
>> In the manual (p14) It says no antenna...this doesn't sound right for
>> transmit. What did I miss? Then, I can tackle the DC readings.
>>
>
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