[hpsdr] PCR100 10.7MHz Mods

[peter at gehughes.us]

For those Many who have bought the PCR100 and now have a lot of spare
time while waiting for Janus, Ozy , Mercury and all of the rest.....
And to tie this all together...
If you have a 30M Softrock then this will run right into it (OK..You do
have to shift the frequency of the Softrock just a bit)and from there
you can , when it arrives , run it right into your Janus

I have posted pictures of these mods at my public folder (N7BMG)on
HamSDR

 On page 38/41 of the servicemanual at 150% and looking at the far right
 with IC10 about half way down you can see Q29 above IC10. Just to the
 right of Q29 at the junction of C248 and L108 looks like the right
 place to tap off the 10.7 MHz signal. This is a nice place because L108
 is on the TOP of the PC board.
 
 The directions for the  Discriminator by SM3WEO say to tap off pin 8 of
IC10 .
 I think this is a typo. I think it should be pin 9 which
 matches with the drawing showing the cable. This is also a good place
 since there is a feed thru adjacent to pin 9 which again allows the
 signal to be taken from the top of the board. This will not remove the
 need to remove the board since this must be done to drill the hole to
 add the Audio Jack for the Discriminator and for the 10.7 MHz IF
 output.
 
 If you look at page 33/41, Main Unit Top View with the left edge of
IC21
 at the left side of the screen you will see FI6 and FI7 just to the
 right of center in the middle of the screen. Just to the left of FI7 is
 IC27 and just to the left of there is C616 Just below the middle of
C616
 is a feedthru. This is the Discriminator output from pin 9 of IC10
 
 To the left of here is X1 and then FI2 and FI3. Below these two parts
is
 L108 (a large tincan) The trace from the upper right terminal goes to a
 square pad. This is the 10.7 MHz output.
 
 As you can see both pads are easily accessible from the top of the
board
 making cable runs much easier than trying to snake them around
 underneath the PCB.

I brought out the 10.7 MHz on a piece of .085" Semi-Rigid to an SMA
connector and drilled out the Ground screw hole with a "G" size drill
(just over .25") to mount the connector .
Semi-Rigid is probably NOT a good choice since there are so many sharp
bends so just
use any small 50 Ohm Coax. I soldered the SemiRigid shield right on the
ground next to the pad.


BE SURE AND USE A DC BLOCK CAP ON THIS LINE. THERE IS +5 VDC HERE. 
I used a .068uF chip cap right on the pad at L108. 
You must remove 7 screws to lift the PCB out of the case. You have to
take the top off the shielded area to get to 3 of the screws. Be
careful when you slide the BNC out, it is rather fragile. You can
remove the BNC nut by turning  the nut slowly until the holes in the
nut line up with the tabs on the connector.

For the connector I used I had to take a small cut off the end of the
pad setting on the PCB and then file off about 1/16' of the end of the
PCB to make it fit. You may need to file more depending on your
connector.

Put together in reverse..Don't forget to reinstall the Ground tab behind
the SMA and the BNC connectors. And don't forget to put the top back on
the shielded area.
The holes WILL all line up with out any pushing or shoving so check for
errors before getting out the hammer.
 
 I printed out both sides of the artwork then matched them and stapled
 them together and then pushed a pin thru from one side to the other to
 assure registration and help with component location ..

As with all Mods...You have just voided your Warranty.. ??? and all work
must be undertaken at YOUR own risk... :-)
 
Comments welcome.....
 
 Thanks,
 
 Peter Hughes
 N7BMG