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RF
Power Mod by N6TV
Problem: When the RF speech processor is
activated, adjustment of the the "RF PWR" control becomes very critical --
output power can jump from 40 watts to 100 watts when the control is rotated
only a few degrees. The Rig: Yaesu FT-1000MP (new units may not have this
problem)
Solution: Add a jumper wire and cut a trace
(detailed instructions below)
Disclaimer: I am not a Yaesu service
technician. The modification described below was shown to me at the 1997 Fresno
DX. Convention by "Winston" of Yaesu service, but NO ONE AT YAESU HAS REVIEWED
THESE INSTRUCTIONS.
If you mess up your radio attempting to install this modification yourself, do
not blame me or anyone at Yaesu. All responsibility lies solely with you. If in
doubt, send your rig to Yaesu. The good news: I installed this mod on two
FT-1000MPs, and it worked fine. I have not noticed any unwanted side-effects.
What you need:
1. Good eyesight
2. Steady hands
3. A small soldering iron, and experience using it
4. About 6 inches (15 cm) of No. 24 or 26 AWG insulated wire
5. Metal tweezers or forceps
6. A small knife with a sharp tip for cutting one trace
If you do not have ALL of the above, you should not proceed any further.
The wire size is critical. Anything larger will not fit into the tiny holes in
the circuit board. Radio Shack stocks only ONE kind of wire this small: Cat. No.
278-857, 2-conductor "Rainbow Wire." Only one conductor is used; I unzipped the
tiny "zip cord" to get the length I needed. If you have No. 26 insulated wire
around, use it instead.
Detailed Instructions Follow (print with fixed-pitch font, such as Courier)
1. Remove top cover
2. Remove bottom cover
3. Orient the radio so that unit is upside down (bottom side up), and the rear
of the radio is nearest to you. The circuit board that will be modified is the
"AF Unit," which is in the lower left corner. It has a shiny shielded metal box
in the middle.
FT-1000MP Bottom View
Front
+===============================+
| |
| |
| |
| |
| |
| |
| _________ |
|| AF | |
|| Unit | |
||_________| |
+===============================+
Rear
4. Locate diode D3023 in the lower left corner of the AF Unit, about 1 inch (2.5
cm) from the left and 1 inch from the rear. Just below it (nearer to the rear)
is a small trace that runs right to left, terminating in a small solder
"island." The trace is completely surrounded by a wide metal trace. The island
has a small "through-hole" in the center that is filled with solder, but has no
visible components. The island is completely "in the clear." Do not confuse this
with the island immediately UNDERNEATH
D3023.
AF Unit (lower left corner)
|
|
| D3023
| -==-
| wide metal
| area |
| |
| /--------------/
| ( ()============ <--- Narrow trace terminating in solder island
| \--------------\ Jumper will be soldered to this island and
| | trace will be cut
| wide metal |
| area
|
|_____________________________
5. Locate trim-pot (variable resistor) VR3011, labeled "AM", near the top left
center of the AF Unit. It is white, square, and clearly labeled, and "in the
clear"
AF Unit (top left center)
______________________________________
|
| VR3011
| +----+
| | |
| +----+ <--- jumper will be soldered to this leg
| AM
|
|
|
|
6. Cut a length of No. 24 or No. 26 insulated wire long enough to reach from the
solder island near D3023 to the lower right corner of VR3011. Strip 3/16 inch (5
mm) of insulation from each end.
7. Important: Tin both ends with solder. You just want a thin coat -- no "blobs"
8. This is the hardest step. If you can get through this, the rest is easy.
Point the tip of the wire into the center of the solder island using tweezers or
forceps. Heat the WIRE with a soldering iron until it melts the solder in the
through-hole, then push the hot wire into the hole and let it cool. When
soldering, be careful not to touch other wires with the soldering iron. Do not
push too much bare wire into the hole, just enough to make a good connection to
the through-hole. It may be helpful to pull back a little more insulation before
soldering, then push the insulation back down after soldering. Make sure there
are no solder blobs shorting to the surrounding traces.
9. Tin the lower right leg of VR3011 with a little solder, then solder the other
end of the jumper wire to this leg. Do not use too much heat.
10. Using the tip of a sharp knife, gently cut the small trace leading to the
solder island as shown below. You do not have to cut too deep, but be sure the
cut is wide enough and that there are no shorts to surrounding traces:
AF Unit (lower left corner)
|
|
| D3023
| -==-
| wide metal
| area |
| |
| /--------------/
| ( ()=====\ \==== <--- Cut trace as shown
| \--------------\
| |
| wide metal |
| area
|
|_____________________________
11. Re-install bottom cover and top cover
12. Turn on the radio and verify that the RF PWR knob now controls output power
smoothly, both with and without the speech processor active.
Good luck everyone. Bob Wilson, N6TV
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