Modifying the Maxon SP2000
for BNC Socket.
By Simon Watt-Wyness ZL1SWW
The Maxon SP2000 has a strange socket for the
rubber duckie, which is not useful in the Amateur fraternity.
I have provided some pictures of the procedure
and comments on what to watch out for.
Tools which make the job easier… .
Drill press or something that will take a BNC in the chuck
Flat File for milling down the BNC in the drill press
Small flat file for filing the PCB
Small Phillips and flat blade Screwdriver.
Needle nose pliers and side cutters.
Small set of Allen keys for top knobs.
1. With the aid of a small flat blade screwdriver,
peel off the rubber caps off the two knobs off the top.
2. With the Gas Tongs, carefully grip and unscrew
the ferrule around the antenna socket, be sure not to scratch the top panel
with the tongs.
3. Switch the volume control off and the channel
switch to position 1.
4. Remove the knobs by the means of the Allen
keys. Note that there are two on the Channel Knob.
Position of Washers – Note O Ring on Volume.
The washer stops Volume knob chaffing.
5. Remove the Bottom screws off the radio, all
need to come out. Note any differences in lengths.
6. Prise off the cover, the flat blade will help.
The Front Panel removed
Note position of the tang on the channel switch
it should be hidden behind the shaft in channel
7. Remove the ribbon cables carefully by unclipping
the cable release, the release slides away from the base of the connector.
8. Unscrew the screws holding the board.
9. Carefully remove the board and put it in a
static protection bag until needed again.
10. Remove 3 screws – 2 in the top panel and one
holding the shield plate to the bottom standoffs.
11. Remove the shield .
12. Unscrew the standoffs and note that the one
of them is shorter, this is the one that is supporting the shield off the
bottom of the case.
The shield and the screws.
The bottom board and standoffs.
13. Remove the screws holding the heatsink and
PTT switch from the side of the case, note the length of the middle screw,
it is longer.
14. Coerce the battery connector through the hole
in the bottom of the case. Note the battery clip assembly and location
of the retaining steel plate and the spring clip. Most likely it has parted
company anyway before this step.
15. Gently slide the bottom board and the top
panel together to remove the board. You may have to wiggle it a bit.
16. Once removed, remove the two screws anchoring
the front panel to the main PCB.
17. Remove the top panel carefully. This is done
by pushing the antenna socket against a table edge and holding the top
panel (not your best dining room table or any table you value, as it will
dent the wood!!! I used the edge of my workbench) by wiggling, there are
rubber seals in the channel shaft so it will be a little tight.
The Top Panel removed with the position of the
channel shaft (it has the habit of falling out!)
18. Remove the Tab by filing / grinding ( a Dremel
drill with a grinder is good), if filing, try not to scratch the dge of
the panel with the file.
File off the tag that will stop the BNC nut from
seating against the top panel when tightened.
19. Mill down the BNC socket flange by putting
in the drill press to spin up and run the file on the edge to reduce diameter.
Do the milling in small steps to make a snug fit. You can see the shiny
bit where I have filed in Fig 7.
20. Using a sharp knife or razor blade remove
a bit of the plastic insulator to keep the overall length of the BNC
shorter. This is to give more room to solder and not foul any components,
it is tight in there!! See Fig 7.
21. Chop the Shaft of the lug and mill smooth
as shown in Fig 7.
22. Try fitting the socket into the front panel
and see that it sits flat. If not, use a round file to take a bit out of
the panel hole, I rounded out the side that is closest to the edge opposite
the flat on the inside.
23. Use a toothbrush to brush out all filings
and swarf from the rubber seal around the edge.
24. Once all is fitting nicely, put on the earthing
lug and the nut and tighten so that the lug is touching the die cast lug
on the longest edge of the top panel. This is so that we can earth the
lug to the PCB. You will have to chop up the lug a bit to mate up with
the PCB – this will require a few goes.
25. Check for a good fit to the PCB, you will
most likely have to file a bit off each edge of the PCB to accommodate
the nut. Do this carefully with a small fine file and try not to file through
the through hole plating. You should only need to file just up to it. Position
the lug to hover over the ground pad near the screw hole, see Fig 9.
26. Be sure that you can see the screw holes through
the PCB to assure the correct location.
27. Once happy with the fit, scrape a bit off
the coil wire where shown in Fig 8 – tin it and solder a short piece of
TC onto the edge of the coil without shorting the wire to the groundplane
of the PCB.
Filing the left and right edge of the recess
and soldering the TC to the coil and pad.