Re: [Elecraft] KLPA3A power transistor thermal stress concerns

If anyone requires someone to assist in REALLY getting "nutty" about thermal control/dissipation on electronic components, I'd be happy to oblige from my experience. I have had some fairly extensive hand-on experience.  Once upon a time, I invented Arctic Silver thermal compound and adhesive.

Re: [Elecraft] KLPA3A power transistor thermal stress concerns

Bill is entirely correct. Once in my prior career, I did a study of Mean Time Between Failure for IC circuits (same applies to transistors).  That study had to consider the case temperature of the IC (or transistor) with respect to the junction temperature. The specification for the IC or

Re: [Elecraft] KLPA3A power transistor thermal stress concerns

Yes. But I believe that is Junction temperature, not case on heatsink temp. Remember the case bottom is heatsink for those. Make sure screws are tight. Sent from my iPhone ...nr4c. bill > On Oct 27, 2017, at 12:19 PM, N2TK, Tony wrote: > > 50C is not hot for a

Re: [Elecraft] KLPA3A power transistor thermal stress concerns

50C is not hot for a transistor. Commercial transistors are usually speced to 85C. JANS (space) transistors are speced to 125C and actually baked without bias for 320 hours at 200C. The hFE is measured before and after to check for change. 73 N2TK, Tony Sent from my iPad > On Oct 24, 2017, at

Re: [Elecraft] KLPA3A power transistor thermal stress concerns

Don't think so from the description Wayne gave on the KX3 Yahoo group. Wes N7WS On 10/25/2017 8:48 AM, Ignacy wrote: I assume that the LPA in K3 is similar to the amp in KX3. Ignacy, NO9E __ Elecraft mailing list Home:

Re: [Elecraft] KLPA3A power transistor thermal stress concerns

Did they do IMD as a function of frequency? On 10/25/2017 8:48 AM, Ignacy wrote: Seems a bit artificial problem, unless someone is driving an amp that requires 12 W. My modified Expert 1.3k-fa requires about 6W to 8 W for 1 KW output. If a serious concern, increase voltage to 15V. The

Re: [Elecraft] KLPA3A power transistor thermal stress concerns

Personally, I would, and do, avoid that region.  The difference in received strength between 10 and 12W is imperceptible if the HPA isn't installed. If it is installed, crank the power up to 20 or so and you're out of danger. Wes  N7WS On 10/24/2017 8:31 AM, Mike via Elecraft wrote: The

Re: [Elecraft] KLPA3A power transistor thermal stress concerns

Seems a bit artificial problem, unless someone is driving an amp that requires 12 W. My modified Expert 1.3k-fa requires about 6W to 8 W for 1 KW output. If a serious concern, increase voltage to 15V. The Yahoo KX3 group has graphs of IMD3 as a function of power and voltage. Increasing voltage

Re: [Elecraft] KLPA3A power transistor thermal stress concerns

Nick, Yes, I believe that should be no problem. 73, Don W3FPR On 10/24/2017 8:57 PM, Nick - VE3EY wrote: Hi Don Good question.   I happen to have a Infrared Thermometer.   After bashing at it for about 20 minutes, the temperature in the vicinity of two transistors (as measured against the

Re: [Elecraft] KLPA3A power transistor thermal stress concerns

Hi Don Good question. I happen to have a Infrared Thermometer.After bashing at it for about 20 minutes, the temperature in the vicinity of two transistors (as measured against the bottom cover) peaked at 50 degrees Celsius (122 F) but it did not go beyond that. I ran the rig at 10 watts on

[Elecraft] KLPA3A power transistor thermal stress concerns

I agree and I have previously mentioned this on the Elecraft list. it would be nice if you could control when the 100W PA engages. I would prefer 10 watts. John KK9A KD8RQE wrote: The K3/100 switches to the KPA3A at 12 watts. So is there a 2w range (10-12w) where the KLPA3A is putting out

Re: [Elecraft] KLPA3A power transistor thermal stress concerns

The K3/100 switches to the KPA3A at 12 watts. So is there a 2w range (10-12w) where the KLPA3A is putting out unacceptable IMD? Is there a way to make the switch at 10w, or should we just avoid that 2w "danger zone"? 73 Mike KD8RQE In a message dated 10/24/2017 10:56:38 A.M. Eastern

Re: [Elecraft] KLPA3A power transistor thermal stress concerns

The K3/10 will output 12W. That said, based on IMD measurements I have performed I would NEVER run a K3/10 at 12W out.  Frankly, with my K3S with the latest rev KLPA3A to keep 3rd order IMD below 30 dBc, I would throttle it back even more above 18 MHz. Wes  N7WS On 10/24/2017 6:27 AM, Rose

Re: [Elecraft] KLPA3A power transistor thermal stress concerns

Nick, What is the "12 watt" version you're referring to? 73 K0PP On Oct 24, 2017 5:29 AM, "Nick - VE3EY" wrote: > I have a K3s/10 (12 watt version) which I intend to use in the upcoming cq > ww cw contest. This unit does not have KPA3A power brick and cooling fans >

Re: [Elecraft] KLPA3A power transistor thermal stress concerns

Nick, It all depends on your perception of "fairly hot". My 'rule of thumb' is that if you can hold your fingers on the surface, then it is not too hot. 73, Don W3FPR On 10/24/2017 7:27 AM, Nick - VE3EY wrote: I have a K3s/10 (12 watt version) which I intend to use in the upcoming cq ww

[Elecraft] KLPA3A power transistor thermal stress concerns

I have a K3s/10 (12 watt version) which I intend to use in the upcoming cq ww cw contest. This unit does not have KPA3A power brick and cooling fans installed. While doing some trial runs I noticed that the area around the KLPA3A power transistors is getting fairly hot after prolonged contest