Hi Tom,
Thanks for the reply.....I will answer each question below:-
----- Original Message -----
From: "Tom Arntzen" <[EMAIL PROTECTED]>
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" <[EMAIL PROTECTED]>
To: "Elecraft Reflector" <[email protected]>
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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