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I just acquired a new LA-1K yesterday, and put it in
service that evening.? At first, with 35 watts drive in RTTY, the unit showed output on the LA-1K watt meter plus an MFJ watt meter that I have of near 1000 watts. In fact, with 40 watts drive, the unit was showing
well over 1KW output.? Over the next ten minutes, I
ran some on the air tests, and the unit performed perfectly, showing output of 1KW or more.? However,
after that short time, it quit putting out the higher power. Instead,
with 40 watts output using RTTY,? the output dropped to only 500 watts on? both meters. I tried using two different radios on several different bands,
and the result was the same.? SWR as shown on the LA-1K was in the
1.2-1.6 range. I do use a tuner after the amplifier to keep SWR in
control.? I did all these tests with the ALC line unplugged.? With a
voltmeter, I verified the supplied operating voltage was? 235-240 volts.
Vd on the LA-1K stayed steady at 50, and Id varied a little, but was always near 23.? I tried turning the amplifier on and off and all sorts of other "tests" to see if it would start to read 1KW again, but it never did go higher than 500 watts.? I also tried transmitting with a straight key on CW, and on CW key down, it showed the same output as RTTY did. At no time did I drive the amplifier with over 50 watts.?
I email Paul at Palstar, and he told me RTTY output is only 500 watts, so that's what I should expect it to show.? But, the unit was showing a solid 1KW when I first powered it on.? And, on CW, the specifications in the manual indicate the output is 1000 watts, not 500.? Yet, in both RTTY and CW, I am only getting readings of 500 watts.
My question is, do I have a problem?? Why would the amplifier first show 1000 watts out, and then moments later, drop to half that?? I did email Paul at Palstar back, but so far, no response.?
Thanks, Bob KU5J
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Look at the temperature...you are overheating the amp. RTTY is 100%
constant duty, SSB is not. You will see 1 KW in SSB. I use about 20
watts of drive for Digital for abt 400-450 watts out. If you can not
contact with 400..forget it. Tha LA-1K is NO 1000 watts in all
modes.
It is a great robust amp but you need to learn how best to use it.
Neil?? N4FN
On 20-Sep-18 3:12 PM, Bob KU5J wrote:
toggle quoted message
Show quoted text
I just acquired a new LA-1K yesterday, and put
it in service that evening.? At first, with 35 watts drive
in RTTY, the unit showed output on the LA-1K watt meter plus
an MFJ watt meter that I have of near 1000 watts. In fact,
with 40 watts drive, the unit was showing well over 1KW
output.? Over the next ten minutes, I ran some on the air
tests, and the unit performed perfectly, showing output of
1KW or more.? However, after that short time, it quit
putting out the higher power. Instead, with 40 watts output
using RTTY,? the output dropped to only 500 watts on? both
meters. I tried using two different radios on several
different bands, and the result was the same.? SWR as shown
on the LA-1K was in the 1.2-1.6 range. I do use a tuner
after the amplifier to keep SWR in control.? I did all these
tests with the ALC line unplugged.? With a voltmeter, I
verified the supplied operating voltage was? 235-240 volts.
Vd on the LA-1K stayed steady at 50, and Id varied a little,
but was always near 23.? I tried turning the amplifier on
and off and all sorts of other "tests" to see if it would
start to read 1KW again, but it never did go higher than 500
watts.? I also tried transmitting with a straight key on CW,
and on CW key down, it showed the same output as RTTY did.
At no time did I drive the amplifier with over 50 watts.?
I email Paul at
Palstar, and he told me RTTY output is only 500 watts, so
that's what I should expect it to show.? But, the unit was
showing a solid 1KW when I first powered it on.? And, on CW,
the specifications in the manual indicate the output is 1000
watts, not 500.? Yet, in both RTTY and CW, I am only getting
readings of 500 watts.
My question is,
do I have a problem?? Why would the amplifier first show
1000 watts out, and then moments later, drop to half that??
I did email Paul at Palstar back, but so far, no response.?
Thanks,
Bob KU5J
_._,_._,_
?
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Hello Bob, ?? I tend to think you have a problem with the amp.? If you continued to run it with 40 watts of drive on RTTY it should continue to produce 1kw until it overheats and shuts down at 100 degrees C.? This will be proven if 40 watts drive on SSB only produces 500w peak.? Usually, when one of the two LDMOS chips fail hard, (usually short on the input side of the chip)? the output drops to near zero, but there could be a failure mode on one chip that still allows half output if the input isn't shorted.?? I would contact Palstar by phone and let them know that the unit is only putting out 500 watts in any mode regardless of drive power and I'm sure he'll make it good.? If 40 watts of drive (in any mode) is only giving you 500 watts then there is an issue. ? Typically, with any manufacturer of LDMOS amps, you will likely get an entirely new RF block rather than replacing just one transistor. (guessing here)?
?? Sorry you're having this issue.? It's always a disappointment when an exciting new piece of equipment has a problem.? I use mine daily and for the first time today I hit 100 degrees C on a long AM transmission.? Normally that wouldn't be an issue with the 260ish watts of AM carrier, but I live at 9,000 feet where cooling efficiency is severely compromised.? When the temperature came down to around 70C or 80C (about 30 seconds or less) the amp operation returned to normal.? It continues to run 1kw with 40w drive. ? I'm friends with a gal who runs a traffic net for 5 hours a day working it hard the entire time.? She has one of the first LA-1K's off the production line, it's still running fine.? Of course, this could be a defective chip from the factory for it to fail so soon.? All of the above comments are based on the assumption that one of the chips has failed, there could be an issue with a combiner, LP filter, combiner, relay, etc... even the coax used in the transformers.? They will be able to diagnose it quickly.
Good luck and let the group know how it works out. Best, Dennis
On 9/20/2018 at 1:19 PM, "Bob KU5J" <valentines.49@...> wrote:
I just acquired a new LA-1K yesterday, and put it in
service that evening.? At first, with 35 watts drive in RTTY, the unit showed output on the LA-1K watt meter plus an MFJ watt meter that I have of near 1000 watts. In fact, with 40 watts drive, the unit was showing
well over 1KW output.? Over the next ten minutes, I
ran some on the air tests, and the unit performed perfectly, showing output of 1KW or more.? However,
after that short time, it quit putting out the higher power. Instead,
with 40 watts output using RTTY,? the output dropped to only 500 watts on? both meters. I tried using two different radios on several different bands,
and the result was the same.? SWR as shown on the LA-1K was in the
1.2-1.6 range. I do use a tuner after the amplifier to keep SWR in
control.? I did all these tests with the ALC line unplugged.? With a
voltmeter, I verified the supplied operating voltage was? 235-240 volts.
Vd on the LA-1K stayed steady at 50, and Id varied a little, but was always near 23.? I tried turning the amplifier on and off and all sorts of other "tests" to see if it would start to read 1KW again, but it never did go higher than 500 watts.? I also tried transmitting with a straight key on CW, and on CW key down, it showed the same output as RTTY did. At no time did I drive the amplifier with over 50 watts.?
I email Paul at Palstar, and he told me RTTY output is only 500 watts, so that's what I should expect it to show.? But, the unit was showing a solid 1KW when I first powered it on.? And, on CW, the specifications in the manual indicate the output is 1000 watts, not 500.? Yet, in both RTTY and CW, I am only getting readings of 500 watts.
My question is, do I have a problem?? Why would the amplifier first show 1000 watts out, and then moments later, drop to half that?? I did email Paul at Palstar back, but so far, no response.?
Thanks, Bob KU5J
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Hello there Bob,
Try Keying amp in RTTY , then switch to SSB.
Idle Drain Current ( ID ) s/b 2.1A.
If it's ~.9A you have a blown LDMOS chip.
rgds & good testing, Mike N7KR
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Had something similar happen to my LA-1K after about an hour of use(it was just a few days old). One of the LDMOS's died. I called Palstar, we ran some tests and I was told to send it back. So I boxed it up and $45 later it was on the way to Palstar. With-in a week the amp was back in the shack. Palstar paid for return shipping. While I run mine off of 120v, it is used nearly all day long and has been cycled tens of thousands of times. I've even configured fans on both sides of the amp in a push pull configuration. I've only seen it hit 70c once. I guess what I am getting at is once they get yours working, you will not be able to kill the thing.
Good luck with it,
John / AI4FR
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Hello there Bob,
Try Keying amp in RTTY , then switch to SSB.?
Idle Drain Current ( ID ) s/b 2.1A.
If it's ~.9A you have a blown LDMOS chip.
rgds & good testing, Mike N7KR
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Thanks for you replying, Dennis.? Yes, it's very frustration and disappointing when? new piece of ham gear fails.? I appreciate your thoughts and suggestion. I hope to have it on the way back to Palstar tomorrow. 73
Bob
On Fri, Sep 21, 2018 at 6:40 AM Dennis via Groups.Io <pegasus9000= [email protected]> wrote: Hello Bob, ?? I tend to think you have a problem with the amp.? If you continued to run it with 40 watts of drive on RTTY it should continue to produce 1kw until it overheats and shuts down at 100 degrees C.? This will be proven if 40 watts drive on SSB only produces 500w peak.? Usually, when one of the two LDMOS chips fail hard, (usually short on the input side of the chip)? the output drops to near zero, but there could be a failure mode on one chip that still allows half output if the input isn't shorted.?? I would contact Palstar by phone and let them know that the unit is only putting out 500 watts in any mode regardless of drive power and I'm sure he'll make it good.? If 40 watts of drive (in any mode) is only giving you 500 watts then there is an issue. ? Typically, with any manufacturer of LDMOS amps, you will likely get an entirely new RF block rather than replacing just one transistor. (guessing here)?
?? Sorry you're having this issue.? It's always a disappointment when an exciting new piece of equipment has a problem.? I use mine daily and for the first time today I hit 100 degrees C on a long AM transmission.? Normally that wouldn't be an issue with the 260ish watts of AM carrier, but I live at 9,000 feet where cooling efficiency is severely compromised.? When the temperature came down to around 70C or 80C (about 30 seconds or less) the amp operation returned to normal.? It continues to run 1kw with 40w drive. ? I'm friends with a gal who runs a traffic net for 5 hours a day working it hard the entire time.? She has one of the first LA-1K's off the production line, it's still running fine.? Of course, this could be a defective chip from the factory for it to fail so soon.? All of the above comments are based on the assumption that one of the chips has failed, there could be an issue with a combiner, LP filter, combiner, relay, etc... even the coax used in the transformers.? They will be able to diagnose it quickly.
Good luck and let the group know how it works out. Best, Dennis
On 9/20/2018 at 1:19 PM, "Bob KU5J" <valentines.49@...> wrote:
I just acquired a new LA-1K yesterday, and put it in
service that evening.? At first, with 35 watts drive in RTTY, the unit showed output on the LA-1K watt meter plus an MFJ watt meter that I have of near 1000 watts. In fact, with 40 watts drive, the unit was showing
well over 1KW output.? Over the next ten minutes, I
ran some on the air tests, and the unit performed perfectly, showing output of 1KW or more.? However,
after that short time, it quit putting out the higher power. Instead,
with 40 watts output using RTTY,? the output dropped to only 500 watts on? both meters. I tried using two different radios on several different bands,
and the result was the same.? SWR as shown on the LA-1K was in the
1.2-1.6 range. I do use a tuner after the amplifier to keep SWR in
control.? I did all these tests with the ALC line unplugged.? With a
voltmeter, I verified the supplied operating voltage was? 235-240 volts.
Vd on the LA-1K stayed steady at 50, and Id varied a little, but was always near 23.? I tried turning the amplifier on and off and all sorts of other "tests" to see if it would start to read 1KW again, but it never did go higher than 500 watts.? I also tried transmitting with a straight key on CW, and on CW key down, it showed the same output as RTTY did. At no time did I drive the amplifier with over 50 watts.?
I email Paul at Palstar, and he told me RTTY output is only 500 watts, so that's what I should expect it to show.? But, the unit was showing a solid 1KW when I first powered it on.? And, on CW, the specifications in the manual indicate the output is 1000 watts, not 500.? Yet, in both RTTY and CW, I am only getting readings of 500 watts.
My question is, do I have a problem?? Why would the amplifier first show 1000 watts out, and then moments later, drop to half that?? I did email Paul at Palstar back, but so far, no response.?
Thanks, Bob KU5J
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Mike Stephens
John - AI4FR