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Author Topic: Need Help With Hendricks BITX20A Receive  (Read 3232 times)
AD6KA
Member

Posts: 2238




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« on: August 29, 2012, 04:50:19 PM »

Out of the blue I find that my BITX20A 20m QRP SSB
 transceiver is almost deaf. The xmitter works FB, 10
 watts out on peaks.
 
I am working two jobs because my wife is recovering from
 hip replacement surgery, so I don't have any
 time to work on this.
 
I am willing to pay (or trade) to have someone familiar
 with this rig to give it a once over.
It is not currently
 in an enclosure, nor do I have the frequency meter
 option, so it will be easy to work on. The only "non stock"
 thing I have done is add the Ten Turn Pot w/Varactor
 Tuning Mod by KC0WOX, which works VERY well.
 (The varactor/ten turn pot replaced a one turn Polyvaricon)
 
Any help would be greatly, GREATLY appreciated, Thanks!
Please use THIS email address to contact me:
kenp@socal.rr.com
TNX AGN ES 73, Ken AD6KA
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AD6KA
Member

Posts: 2238




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« Reply #1 on: September 20, 2012, 11:36:05 PM »

I replaced the MV109 Varicap Diode in the
Ten Turn Pot Tuning Mod and it solved the
problem completely.


Weird that the part would go out like that.
I've read that the failure rate in devices like
that are extremely low.
Maybe something else is going on in that circuit.....
Ken  AD6KA
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AB3LD
Member

Posts: 3




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« Reply #2 on: October 31, 2012, 07:42:47 AM »

Was the receive working well, but then went deaf?  Or was it deaf always?  If always:

Did you install the correct resistor at R21?  It should be 1K ohms, but there is a mistake in the assembly manual on the Hendricks website that gives the color code for 100 ohms instead (brown black brown).  This made my receiver deaf!  Once the 1K was installed it worked fine.
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AD6KA
Member

Posts: 2238




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« Reply #3 on: October 31, 2012, 03:20:19 PM »

Quote
Did you install the correct resistor at R21?  It should be 1K ohms, but there is a mistake in the assembly manual on the Hendricks website that gives the color code for 100 ohms instead (brown black brown).  This made my receiver deaf!  Once the 1K was installed it worked fine.

Thanks for the great info Joe, I didn't know about
the R21 errata. The receiver seems to be working FB
but I will check it.

I love this rig. Besides adding the Varactor and ten turn pot
tuning mod, I used a DFD1 frequency display with "Biggy"
display option from Almost All Digital Electronics.
DFD1: http://aade.com/dfd1.htm
"Biggy" LCD Option: http://aade.com/biglcd.html

This is a wonderful backlit LCD freq display,
(and Neil is a super guy to do business with, very helpful.)
You can jumper the DFD1 to also read "MHz" and "USB" after the freq.
(Or Khz & LSB, as well as other modes, CW, FAX, RTTY, etc).
Thanks again Joe!
73, Ken  AD6KA
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AD6KA
Member

Posts: 2238




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« Reply #4 on: November 03, 2012, 09:29:23 PM »

Quote

AB3LD:
Did you install the correct resistor at R21?  It should be 1K ohms, but there is a mistake in the assembly manual on the Hendricks website that gives the color code for 100 ohms instead (brown black brown).  This made my receiver deaf!


Hey Joe!

I finally got around to checking R21 on my BITX20A
and it IS the wrong value!
While its receiver is
not "deaf" by any means, I am looking forward to
seeing the amount of improvement the correct
resistor brings!

It is getting late, and I like to spend Saturday Night
with the XYL, so we will see what tomorrow brings
when I dig through my junk box for a 100 ohm resistor.

Thanks again for bringing the R21 errata to my
attention. I can't wait to check out the new part!
I will post the results here.

I also just ordered a spiffy Ten Tec enclosure to
accommodate the "Board & Parts Only" BITX I bought
plus the added Mods and extra devices I am building into
it. (Yes, at the very beginning of the Hendricks BITX offering,
he DID offer the kits as "board and parts only". Bummer
that they changed it.
73, Ken  AD6KA
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W4OP
Member

Posts: 436


WWW

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« Reply #5 on: November 03, 2012, 09:47:15 PM »

AB3LD posted that the resistor SHOULD be 1K- so don't go looking for a 100 Ohm.

Dale W4OP
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AD6KA
Member

Posts: 2238




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« Reply #6 on: November 04, 2012, 09:05:40 PM »

YEP! My bad....a senior moment!   Grin
Glad I didn't replace that resistor
Thanks for the post!
73, Ken  ADKA
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