[Elecraft] K1-4 low power and poor receive on 40 meters

[Don Wilhelm]

There is the possibility that the 40 meter crystal has low activity.
Check the RF voltage at pin 4 of P1 on the band board.  You should read 
70mV or more with an RF Probe or 200mV+ peak to peak if using a 'scope 
with a 10X probe.

A good working K1 will develop at least 5 watts.
Make up an RF probe if you don't have one.  It does not have to be 
fancy, just stick the component leads through a piece of cardboard and 
solder the leads together.  You need a 1N34 diode (not a silicon diode) 
Elecraft does have a kit.

73,
Don W3FPR

On 5/20/2020 1:35 PM, rocketnj at gmail.com wrote:
> Hi Don
>
> I have done that using the Marconi for RX, then touching up for TX. I understand 40 is a combo of 30 & 40 settings. After carefully retuning (done it several times) the best I can get on 40 is about 60 to 75 mW. 30 makes better than 2 watts. The menu for power out is set to 2.0 on 40. Receive sensitivity is 10 to 15 dB down from 30 meter receive.
>
> I read that the windings on T3 and T4 are critical. I have counted the turns and verified which side #1,2,3 and 4 are coming off the core. Both T3 and T4 appear to be fine. There is enough wire left over in the box the radio was in so I can rewind T3 or T4. From what I see on the schematic T4 would most likely be the suspect (if it is the transformer.)
>
> I am going to borrow an RF Power meter with probe and check 30 vs 40 meter readings on the Premix in & out and the RF filter in & out. That will greatly help pinpoint the issue.
>
> 73
> Dave wo2x
>
>
> -----Original Message-----
> From: Don Wilhelm <donwilh at embarqmail.com>
> Sent: Wednesday, May 20, 2020 11:39 AM
> To: rocketnj at gmail.com; elecraft at mailman.qth.net
> Subject: Re: [Elecraft] K1-4 low power and poor receive on 40 meters
>
> Dave,
>
> Refer to the K1FL4 instructions and re-tune the trimmers on the filter board.  They MUST be done in the proper band sequence - 30 meters before 40m, 15m before 20m.  The PreMixer portion is usually the most critical for power output.
>
> 73,
> Don W3FPR
>
> On 5/20/2020 11:20 AM, rocketnj at gmail.com wrote:
>> Hi All,
>>
>>    
>>
>> I am going to sell a K1-4 (4 band 40, 30, 20, 15) for the estate of my
>> Elmer. In testing the radio I found 40 meters is about 15dB less
>> sensitivity than 30 and power out about 75 mW. I have double checked
>> the values of components on the filter board to ensure they are
>> correct and installed correctly. I also checked T3 and T4 which can
>> cause issues on 40. T3 has 23 turns on the secondary with three turns
>> on the primary. T4 has 24 turns on secondary and two turns on primary.
>> Another symptom is the CH trimmer cap seems to be at one end of tuning range (not seeing double peak).
>>
>>    
>>
>> Note - the radio does not have the ATU option and 30 meters is set for
>> 10.1 MHz and not 10.0 (double checked crystals).
>>
>>    
>>
>> >From what I can measure so far the relays seem to be working "as designed".
>> When I switch from 15 meters to 40 meters I can see the pulses to the
>> relays to switch them (latching relays. I did notice in the 4 band
>> filter manual it says K6 relay is not active on 40 but I do see it
>> active and looking at the schematic K6 switches between 15/20
>> operation and 30/40 so I think there is a typo in the filter board manual at the bottom of page 23.
>>
>>    
>>
>> I am using a Marconi service monitor for testing. I have not built an
>> RF probe yet and hoping someone has seen this symptom before. I would
>> like to get the K1 fully operational as the proceeds are going to my
>> Elmer's widow 100%
>>