Good Day all! Through the great help from Keith and all the support team at Elecraft, I've narrowed down my problem of the "High Sig" error and oddly behaving S -Meter to failing Q8 and Q9 transistors. The Q8 is an easy to find PN2222A, but the Q9 is an MPS5179 which has been discontinued. Does anyone have one they can spare or can point me to a RELIABLE source for the part? I love my K3 and hope I can keep her going for many more years!

Rich

KQ9L

https://www.jameco.com/z/2N5179-Major-Brands-Transistor-2N5179-General-Purpose-NPN-12-Volt-0-05-Amp-TO-72_140373.html

Thanks Wes, components are surface mount, prob should have mentioned that.

Thanks, take a look at this pic, q9 has three leads on one side and one on the other. I’m not sure the replacement you suggest will work, but thank you.

Perhaps have a look at this one, I think it has the pin out you are after, BFU580QX available from Digi-Key. If the Q9 you are referring to is the one on the K3 RF Board - a NE46134 then the BFU580QX is a closer match than the 5179.
Cheers
Greg VK3VT

 

Thank you Greg, I’ll check it out. Elecraft has the part for $8, it would be nice if there are other equivalent options that are available. I guess they anticipated the end of life of the part and have a stock pile of these. 

Hi Rich,
There is an error somewhere.
Q9 on my 2007 version of the circuit diagram is a NE46134 medium power SMD transistor with 1.5dB NF.
The MPS5179 is a completely different transistor which may work in the circuit but has a 5dB NF.
Looking up the K3s circuit diagrams, both Q8 and Q9 are NE46139 transistors and are described as the post amplifier.
The NE46139 is available on both US and UK Ebay from local suppliers or in bulk from China.
73, John

Thanks John, I’ll double check my manual. My K3 is an early one SN341 and the part my have changed as the product matured and/or morphed into the K3S. Very much appreciate the pick up!
Rich

John you are correct! I checked the schematics and the part is a NE46134! In retrospect, I just realized that I had looked at an online parts manifest (Googled) and it was from a K2 and not K3 even though my search parameters were correct. Wow you really saved my neck! This is another reason why Elecraft is so awesome— the user base is so helpful and supportive!

Actually, we did change the part along the way, but either should be fine;
K3S; Q4, Q8, Q9 BFQ19S,NPN,SOT89,SMD Elecraft #E580079 Infineon BFQ19SH6327XTSA1 Digikey BFQ19SH6327XTSA1TR-ND 

Rich, Yes, NE46134, sorry for typo in earlier post, the K3s transistors are NE46134 also.
I replaced a NE46134 in my K3 and it was not too difficult with a head magnifier.
Thanks again to Keith of course,
73 gl with replacement
John

More info, it wasn't until Aug 2017 that we went to the E580079 due to EOL (end of life) of the E580033.
Keith Q4,Q8,Q9 Remove E580033 (EOL) Replace with E580077

Keith,

so you are suggesting replacement of Q4,Q8,Q9 and what about R66? And again you believe this will solve my HI Sig and widely fluctuating S meter?

rich
kq9l

On Mon, May 23, 2022 at 08:28 AM, WE6R wrote:

Actually, we did change the part along the way, but either should be fine;
K3S; Q4, Q8, Q9 BFQ19S,NPN,SOT89,SMD Elecraft #E580079 Infineon BFQ19SH6327XTSA1 Digikey BFQ19SH6327XTSA1TR-ND 

K3 Q4,Q8,Q9   NE46134,NPN,SOT89,SMD E580033       Digikey NE46134-AZTR-ND T&R Y NE46134-AZCT-ND
We have these if you can't find them.
Keith WE6R Elecraft K3/K4 Tech

 

 Have you posted these changes on the website someplace?