My LA-1K has developed an issue in the internal SWR protect circuit. When I key the amplifier in STBY mode with only 10 watts drive, the amplifier sees a HIGH SWR on the output and the internal protect circuit places the amplifier into "Bypass SWR" protect error mode. I placed a 50 ohm dummy load direct on the amplifier output RF connectors (1/2/3) and it still does the same. In the past this error was "Intermittent" however now its happing 100% of the time. It appears there is a failure with the internal SWR protect circuit of the amplifier.?

Has anyone else seen this issue?

Thanks, Thomas NE7X...

Hi, Tom
Never had that problem but it sounds to me more like an intermittent SWR issue caused by bad coax, faulty PL-259 or bad SWR in the load itself (ant or dummy load). Does it work ok into an antenna presenting a known SWR of less than 2.5 to 1 SWR? What does it do when presented with an antenna with known high (greater than 2.5 to 1) SWR? If the transceiver has an internal tuner, make sure that is bypassed. Does the transceiver show a good swr when the dummy load is in line? Could be lots of reasons other than the LA-1K itself. Good luck with it!
--
GL es 73 de Bill, NT1N

开云体育

I have the same issue after upgrading my Yaesu FTDX10.

I contacted Mark at Palstar and performed all his recommended tests, including connecting a 50 ohm dummy load direct to the LA-1K RF Output. It should be noted, I have two LA-1K amplifiers. My second LA-1K is working perfect, no issues. I swapped the amps around between my IC-7610 and Flex6400M and the issue follows the amp. No matter what I do each time I key the amplifier with 10 watts drive the LA-1K goes into "Bypass STBY" and shows a high 3.2-3.4 SWR reading in red. I boxed up the amp and Fed-Ex it to Palstar. Mark will take a look at it in the next week. Once I receive his diagnosis, I will post the results to the forum.
Thomas NE7X...

UPDATE
I talked with Mark at Palstar today. He received my LA-1K and validated that it does have a SWR issue. He said the SWR circuit is reading high in both Forward and Reflected. I'm happy to hear this, for it validates the issue is not with some environmental issue in my shack. He said Palstar is "really busy" with build orders (guess that's good) and plans to schedule time next week to identify what the root cause is. I will update this group once Mark has the final diagnosis.
Thomas NE7X...

On Thu, Sep 28, 2023 at 01:23 PM, Thomas NE7X wrote:

I talked with Mark at Palstar today. He received my LA-1K and validated that it does have a SWR issue. He said the SWR circuit is reading high in both Forward and Reflected.

Hi Thomas,

I'd be very much interested in knowing Palstar's failure analysis determination relative to your LA-1K SWR issue, since it might give me an idea of what could be causing the SWR discrepancy exhibited on my LA-1K as captured by the video clip I included in my 3-May-2023 posting /g/la1k/message/1255.

Thanks for sharing!

73
Ray
KJ5MI

Thomas
Thank you for bringing this issue up as I also reported it to Mark this week on my used 4 year old LA-1K that I purchased just last week. ?I just sent it in yesterday to Palstar. ? So I added this issue to what I asked Palstar to review and fix. ?It also needed the new input protection board added and the Filter Board updates since it’s ’so old’.
--
Glen, WB4KTF, Austin, TX
Licensed since 1968

Palstar has finished repairing my LA-1K.
Its currently in transit via Fed-Ex back to my home QTH, due to arrive this Sunday.
Here is what they indicated on the work order:

Repaired LA-1K, SN 31599, AMPLIFIER
Replaced R-9/C-1
INSTALLED REAR PANEL
UPGRADED to PURE SIGNAL
THANK YOU! 73

I'm not sure what R-9/C1 is. I don't have a schematic.
Does anyone have a schematic that can identify these parts?

NE7X...

开云体育

Forgive my ignorance, but what is “pure signal” ??

On Fri, Oct 13, 2023 at 03:40 PM, Thomas NE7X wrote:

I'm not sure what R-9/C1 is. I don't have a schematic.
Does anyone have a schematic that can identify these parts?

Hi Thomas,

In my post /g/la1k/message/1311 you will find a link to the FCC.gov page that has a list of documents relating to the LA-1K.? Click on "Users Manual 2" (bottom of that list) will take you to the initial-released copy of the LA-1K Technical Manual as submitted to the FCC for consideration.? On page 14 of said technical manual, you will find a "LA-1K BLOCK DIAGRAM" which is the closest thing to a schematic of the LA-1K that I could find, since acquiring my LA-1K brand new directly from Palstar in January 2023.

I understand repair action of your LA-1K to be remove and replace of R-9/C-1, but has Palstar's failure analysis determination successfully identified the root cause, that Mark Ward (Palstar technician) told you he will "identify what the root cause is" as I read in your post /g/la1k/message/1423 dated September 28, 2023?? If so, has Mr. Ward shared with you the root cause in question?

73
Ray
KJ5MI

On Sat, Oct 14, 2023 at 06:48 AM, tuneupmagic (null) wrote:

I understand repair action of your LA-1K to be remove and replace of R-9/C-1, but has Palstar's failure analysis determination successfully identified the root cause, that Mark Ward (Palstar technician) told you he will "identify what the root cause is" as I read in your post /g/la1k/message/1423 dated September 28, 2023?

It's also important for Palstar to identify in their work order the specific LA-1K circuit card or circuit cards in which they removed and replaced R-9 and C-1.? Again, said repair action, in and of itself, isn't the root cause!

Remember ever using the 5-Whys approach to determinate the root cause of a problem?

In the case of an incorrect LA-1K SWR readout, it might go something like the followings:

1. Why? - SWR circuitry malfunctioning.
2. Why? - defective R-9 and C-1 on circuit card # 1 and circuit card # 2, respectively.
3. Why? - R-9 and C-1 are of very poor manufacturing quality.
4. Why? - Acquiring components from questionable PRC sources of supply.
5. Why? - Reducing costs of LA-1K manufacturing to maximize profits.

Oh, PRC = People's Republic of China

73
Ray
KJ5MI

On Fri, Oct 13, 2023 at 05:28 PM, David Hussey wrote:

Forgive my ignorance, but what is “pure signal” ??

Hi David -

This DX Engineeering link will take you to a review of the LA-1K by Dr. Terry G. Glagowski, W1TR, published back in 2018.? Dr. Glagowski made mention, throughout the article, of the term "PureSignal" that you might find helpful.

73
Ray
KJ5MI