[hpsdr] Hermes/Anan 10 Drift?

[Brian Lloyd]

On Thu, Mar 14, 2013 at 3:12 PM, Mike Monnier <w8bac at comcast.net> wrote:

> **
>  "There was a bad value in the Schmidt-trigger squaring circuit for the
> 10MHz reference input. R141, the emitter resistor of the differential pair,
> has the wrong value. It should be 50Ξ©, not 100Ξ©. Change that an you won't
> have any problems with using your external reference.Β "
>
> I see some odd type from time to time on this reflector. In your post (cut
> and pasted above) you are talking about R 141. A resistor I assume and it
> should be 50 ohm? Not 100 ohm? Is that right?
>

Yes, yes, and yes.


> I am not able to replace an SMT component on a 5 layer board.
>

Why not? Hot-air rework tools are pretty cheap now. This is what I used:

http://www.circuitspecialists.com/csihotgun-2.html

You can't go too far wrong for $89.

Heat up the resistor with the hot-air rework tool; remove the resistor with
tweezers; use an iron and solder wick to get rid of that wicked, nasty RoHS
solder crap; put down a couple of dabs of good PbSn solder paste; heat
again with the hot-air tool; put it all back together; and go play radio.


> I'll have to think about this. What is the power rating of R141? I may
> have to find a SMT tech to do this for me. I have two Anan-10 rigs. They
> both will need the modification.
>

It doesn't dissipate any power to speak of. Use the same size component.

>
> Your reply is exactly what I was looking for Brian. Thank You Very Much
> for your help.
>

You are welcome.

-- 
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian at lloyd.com
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)
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