Hello Everyone

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I will be picking up my new LA-1K sometime early in December.

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A few questions for current owners.

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I presently have a dedicated 120 V line into my shack, with a 15 amp breaker.

For years I ran an Ameritron AL-80A on this circuit, up to 800+ watts at tines with no issues.

So I am wondering if the LA-1K will be fine at reduced power output (700-800 watts PEP on SSB) on that same circuit.

I will eventually get around to running 220 into the shack once I pick up some wire etc etc.

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But for now I would like to run it off the 120 V line.

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Does anyone foresee any problems with that?

Thanks, 73, Rick VE3PP

There is no issue running the LA-1K with 120v.? I ran my amp on 120v for the first week until I was able to run a dedicated 240v line to my amp.? It works well on 120v but really performs on 240v.? I do not foresee any problems as the LA-1K is designed to operate on both voltages.

Thanks Bob that is good to know. And yes I will check that switch!

I will likely get a 220 run into the shack after I get the amp. Just need to pick up the 10/2 wire and outlet receptacle.

To those who also replied, thanks for the information.

Happy Thanksgiving
73, Rick

Hi Rick:
?My LA-1K has the Auto-Sensing power supply and does NOT have the 120/240VAC switch to select.? The label on my LA-1K rear panel (below the AC input receptacle) states "20AMPS at 120VAC. 10AMPS at 240VAC".? If you have a 15A / 120VAC circuit, then your 120VAC circuit is BELOW the recommended current draw for the LA-1K.? Even worse if there are other power consumers on the same circuit.??

I suggest driving the LA-1K at a lower level while using your 120VAC circuit. Or... In the alternative, put a clamp-meter on the power cord and measure what current the LA-1K ACTUALLY draws at various exciter levels. It'll work fine at a lower output level.? Pesky Ohm's Law at work.
73,
Jerry
KB1N

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Hi Jerry

Well to be honest I do not plan on running the amp at 1000 PEP. 600-700 is more than enough for my use.

My old AL-80A ran just fine on the dedicated 120 V circuit, but at full output it only drew around 12 AMP. I could drive that amp up to 1000 PEP output, but rarely ran it above 700 watts for use on 75 M SSB.

So for now I will simply drive the amp with less power and eventually get the 220 wired into the shack.

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I have a 20A ~120V circuit with a single outlet for my LA-1K. These
are the amp's drive and output numbers into a dummy load.

5 in => ~150 out
10 in => ~270 out
15 in => ~400 out
20 in => ~500 out
25 in => ~600 out
30 in => ~700 out
35 in => ~800 out

Generally I run 10 or 15 watts input to a full-wave 160M loop using a
Palstar BT1500A tuner. After 17 months with amp I have no complaints
or concerns.

73 de n4jvp
Fritz

Hey Fritz,first off Happy Thanksgiving from Canada!

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Second, those output numbers look pretty good to me, Honestly I never ran more than 700 or 800 with my old AL-80A so I doubt I would drive the amp with 55 watts even if I had 220 in the shack.

Thanks, 73, Rick

The concern is with the current draw, as Jerry Webb clearly and accurately posted. According to the manual, at 120 VAC the maximum current draw for the LA-1K is 33 amps.

It is false security to assume all must be well if circuit breakers rated at 20 amps don't trip. It is impossible to know what is happening to wiring behind sheet-rock, to the plastic connectors splicing them, and the insulation encompassing them.

In the realm of solid state amplifiers, to be safe the rule of thumb is:

120VAC supply: limit RF output to 500 watts

240VAC supply: limit RF output to 1500 watts

73,
Kent
K9ZTV

On Thu, Nov 23, 2023 at 02:19 PM, Kent Trimble, K9ZTV wrote:

According to the manual, at 120 VAC the maximum current draw for the LA-1K is 33 amps.

Happy Thanksgiving Kent,

On page 15 of the currently available LA-1K Technical Manual it states in part,?under the "POWER SUPPLY PERFORMANCE" section, "If the LA-1K is used with 120VAC the max current rating is 33A."? In other words, the medical grade power supply's (found in earlier version of the LA-1K) rated output current is 33ADC maximum, with an input voltage of 120VAC.

Please note that page 15 of the currently available LA-1K Technical Manual makes absolutely no mention of the magnitude of the AC input current associated with either 120VAC or 240VAC input voltage of the medical grade power supply.

Your thoughts?

73
Ray
KJ5MI
PS - Referring my 30-Mar-2023 post /g/la1k/message/1152 "Mr. Ward advised me to ignore the power supply information in whole, as printed on Page 15 of the technical manual (hard copy) that came with my LA-1K shipment, since Palstar failed to update their LA-1K technical manual."? Page 15, as currently written, doesn't apply to my LA-1K since the thing doesn't have the medical grade power supply in question.? For the benefit for our new members, Mr. Ward is the Palstar techician.

On Thu, Nov 23, 2023 at 06:38 PM, tuneupmagic (null) wrote:

Please note that page 15 of the currently available LA-1K Technical Manual makes absolutely no mention of the magnitude of the AC input current associated with either 120VAC or 240VAC input voltage of the medical grade power supply.

Your thoughts?

Kent, K9ZT,

Were you referring to another version of the LA-1K manual from Palstar that has been revised to include specifications of the power supply installed in the LA-1K amps that are currently being manufactured, when stating "According to the manual, at 120 VAC the maximum current draw for the LA-1K is 33 amps." in your 23-Nov-2023 post?

If that's the case, how would one get a copy of that revised manual?

73
Ray
KJ5MI

On Thu, Nov 23, 2023 at 02:19 PM, Kent Trimble, K9ZTV wrote:

According to the manual, at 120 VAC the maximum current draw for the LA-1K is 33 amps.

Hey Kent,

Thought I'd follow up with you after getting no response to my posts /g/la1k/message/1460 and /g/la1k/message/1461 regarding your insights on the LA-1K power supply.

Please kindly identify the manual in question, that prompted you to state "According to the manual, at 120 VAC the maximum current draw for the LA-1K is 33 amps."

73
Ray
KJ5MI

I was assured by the Palstar Tech rep that the amp does not draw anywhere close to 33 amps on 120 V. The sticker on the back of the amp under the power cord states 20 amps and I was told it would not draw that either.

Thanks to being licensed we know:
P = U * I

so
120V * 15A = 1,800W
240V * 10A = 2,400W

We remember that legal limit is 1,500W, although the LA-1K should only be run up to 1,000W.
Some power goes out in heat.? Maybe 200W? [shrug]

In the manual the specifications states: "AC POWER 100-125VAC @ 15A or 200-250VAC @ 10A".

With all this information, that you as a technician operator have, you can be assured that a 15A circuit on 120V is fine.? The trouble is we extras have taken the technician exam so long ago we forgot the basic formulas.

The mysterious 33A is in a section of the manual where also the LA-1K 50V Vd is mentioned.? Hey, since we are technician we quickly realize that 50V * 33A = 1,650W.? This section is talking about the amplifier shutting down when this current exceeds 33A (i.e. we're taking the amp to it's limit). It seems reasonable when maxing out the amp that 1,000W (or more) goes to RF and a hole bunch of additional power is used to generate heat.? We can conclude that this is not the current on your outlet!? I do agree this section is not written clearly and can be confusing at first.

73,
? Claus (AE0S)

On Mon, Dec 4, 2023 at 07:46 PM, Claus (AE0S) wrote:

In the manual the specifications states: "AC POWER 100-125VAC @ 15A or 200-250VAC @ 10A".

Claus,

Please be advised the currently available LA-1K Technical Manual doesn't apply to LA-1K?with a serial number (S/N) higher than 37055 in terms of the installed power supply.? My LA-1K has S/N 38935.

As stated in my 30-Mar-2023 post /g/la1k/message/1152 "Mr. Ward advised me to ignore the power supply information in whole, as printed on Page 15 of the technical manual (hard copy) that came with my LA-1K shipment, since Palstar failed to update their LA-1K technical manual."

Palstar still hasn't updated their LA-1K Technical Manual as of this writing.? As such, if you are quoting information taken from the currently available LA-1K Technical Manual, said information is irrelevant for the power supply installed in my LA-1K as well as those currently in production.

73
Ray
KJ5MI

On Mon, Dec 4, 2023 at 06:11 PM, VE3PP wrote:

I was assured by the Palstar Tech rep that the amp does not draw anywhere close to 33 amps on 120 V.

Rick VE3PP,

Have you brought Kent's insights /g/la1k/message/1467 about the LA-1K power supply to Mr. Mark Ward's attention at Palstar?

73
Ray
KJ5MI

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The 33 amp statement applies only to the maximum current rating when using the amp on 120 VAC.? That's not its nominal draw, that is the maximum that the amp can tolerate.? Above 33 amps and the amplifier shuts down.? Taken from page 8 of the online manual in the LA-1K section:
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As I said earlier, the rule of thump for long-term viability of solid state amps is:? if the supply voltage is 120 VAC, one should limit RF output to 500 watts; if the supply voltage is 240 VAC, one can run a 1000-watt rated amp at 1000 watts RF output.

End of my end of the discussion.

73,
Kent
K9ZTV