[Elecraft] K1 transmitter problem...any help appreciated.

[Ron]

Hi Tom,
             Thanks for the reply.....I will answer each question below:-
----- Original Message ----- 
From: "Tom Arntzen" <tom.arntzen at online.no>


> Hi Ron!
> The TR1/BPF will have 1/3-1/2 level of BUF.
> After looking on the schematics I would like you to check following 
> points.

My measuremens show about 1/3 the level between in/out ....

> Measure DC-voltage collector Driver Q6.
> If missing check both sides of RFC5.

Voltages OK @12v.

> Also take a close look at T3 , high currents can go through T3 if Q7 is 
> fried the right/wrong way.

T3 appeared OK but I rewound that as well when I replaced the driver.( 
yes.... I double checked since)

> Also make DC measures to TR-switch D10 and D9 and see that D10 is closed 
> during TX.

Yes D10 is biased "on" during receive and "off" during Transmit ( by way of 
the 6R/aux and 6R_2 voltages being applied in receive and removed during 
Tx.)

> Also verify that D9 does it's job ok.

D9 is turned on OK by the 6T voltage during transmit.

> You may want to swap out or check r31 and r32.
> They are in the "dangerzone" during PA failure.
>

Both R31 and R32 have been lifed one end and each verified OK.

> I really can't see any points in path where the signal could get lost 
> between BUF and TR1 other than normal loss.

Nor can I !!

> I guess you can hear your K1 on the right frequencies on another rx when 
> sending , and the rx is OK.

Yes receive is fine and in the right place

> If so the problem is still in the PA or D9-D10.
>

D9 and D10 have been replaced...so has Q6 and Q7 ...the same manufacturer 
and part numbers.

> Hope you get on the air with your K1 soon.
>
Yes ...so do I.
I have even tried "bush practices" like disconnecting Q7 and lifting 
terminal 3 of T3 and using the old trick of connecting a very low wattage 
torch bulb from the removed lead to ground to see if there is drive....there 
wasn't enough to even get a glimmer.
Thanks for the suggestions Tom, but I think I have those covered.
> Tom LA1PHA
> K1 1491
Cheers......Ron ZL1TW  K1 #575
>

> ----- Original Message ----- 
> From: "Ron" <ron_w at clear.net.nz>
> To: "Elecraft Reflector" <elecraft at mailman.qth.net>
> Sent: Monday, August 20, 2007 2:18 AM
> Subject: [Elecraft] K1 transmitter problem...any help appreciated.
>
>
>> Hi Guys,
>>             As a last resort I am appealing to the "Elecraft collective" 
>> to see if I can get help with this problem.
>> I have a K1 that has been going great for years , but during a band 
>> filter change it was fired up without the ATU replaced and it fried the 
>> output transistor and D19.(also damaged T4 which has been re-wound....and 
>> double checked since)
>> I replaced both the output transistor and D19 and it "sort of " went for 
>> a while then decided to die on transmit completely.
>> I replaced the driver.....no change... Then I started looking with my 
>> very limited quality "scope". I appear to be getting drive through the 
>> Transmit mixer OK, and the buffer stage appears to giving me a 10x 
>> increase in drive level. The signal looks OK until I get to point "TR1" 
>> at the junctions of D5 and D14 where it goes into the BPF. There is not 
>> much drive appearing at point "TR2" ....certainly not enough to get the 
>> driver excited enough to work
>> This problem is common to each band on two different 2 x Band boards, so 
>> I have to presume they are OK.
>> Because the level drops at point "BPF" on the cct diagram, I immediately 
>> thought there was a problem in the T-R switching circuit.The diodes 
>> tested OK , but to make sure I removed all diodes and they did indeed 
>> test fine, so did the resistances associated with them. Q4 appeared to be 
>> doing it's job OK but I swapped it out for a new one....replaced all the 
>> diodes. OP1 still showed on transmit....nothing on the power meter.
>> I then decided it might be a lack of drive earlier on so replaced Q5 
>> ...still no change....from memory there was about 6v being applied to the 
>> Drain of Q5 from the MCU.
>> I might be wrong, but I expected to see about the same outputs from the 
>> Mixer/Osc chips U7 and U8.....they are pretty much the same.
>> The set receives just fine...another reason not to suspect the BPF's. If 
>> I listen to the weak signal that *is* produced, I can peak all the 
>> filters on it while listening to the signal on another receiver.
>> So...where does one look from here? What is a very basic transmitter 
>> circuit has me bluffed at present...luckily I have little hair left to 
>> pull out. Any Ideas???
>> Regards.....Ron ZL1TW
>>
>>
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