On going into SEND with key-down,
the output power goes to its normal
level, but it soon drops almost to zero; after a second or so, it
returns to the original level for a short time before starting on
another fold-down. The rate of the fluctuation seems to depend on the
power level: faster at high powers than at low power. The ALC level
always fluctuates in sync but in the opposite direction with the output
power. These doesn't seem to be any problem at power levels under about
10 watts. In all observations of this problem, the rig is driving a
perfectly matched load (near-zero reflected power.
When I send my call (KE2S) in cw, the power usually drops on the last
dah of the K, and the E gets sent at nearly zero power. Similar power
instabilities occur in ssb and in all other modes.
The problem you are having is a common one. There is this little DC-DC board X59-1100-00 that went out on me twice. 1st time I had Kenwood fix it, cost me $150.00. The 2nd time it went out, just this last December 1999, I decided to fix it myself. The board can be order from Pacific Coast Parts and cost about $10.31. The hardest part of the repair is getting the board unsolder off the RF board. The following is what was sent to me by K9NX on how to repair it. I will add my notes ***:
>My question is: Has anyone had experience removing this board and installing
>a new one? It is mounted vertically on the RF Unit board X44-3120-00. I
>would like to order the new board and install it myself if the job is not too
Been here done this.
What you need:
1) A really good temperature controlled, ESD safe soldering iron set at
about 700 deg F ( 800 is too hot !)**(I used a 30 watt soldering iron from radio shack with no problem)
2) A pair of small dikes (side cutters, nippers, etc)
3) a good solder sucker.***I also used solder wick from RS
What you do
1) remove the RF Unit from the rig, As I recall there are 4 or 6 screws and
several plug in cables.
***The RF unit is on the LEFT side of the TS-850S on top. You can identify it as it has some FM mike gain and deviation alignment control that you will see looking at the rig on the left side with the top and bottom covers removed. There are 3 cables that have to be unplugged. Going left to right, the first two have connectors on them and just unplug. The 3 cable is on the right is a flat ribbon cable that just pushes into the connector. It pulls right out, but be very careful not to twist or bend the cable. Once the cables are removed, there are 4 screws that hold the board in place, remove them and slide the board out the left side. The DC-DC board is marked with the part number, it is the last vertical board on the right side of the RF board. Remember that the component side of the board go's to the right.
2) Using the dikes cut the old DC-DC converter board pins one at a time. DO
NOT ATTEMPT TO UNSOLDER IT
***** I did not have a small enough dike to cut the pins. So I just rocked the DC-DC board back and forth until it broke loose. Then I was able to pull the pins out, one at a time, from the top while unsoldering from the bottom.
3) Using the iron and solder sucker remove the stubs of the cut off pins
from the RF Unit and clear the holes of solder
**** I used a 1/4 resistor wire to clean out the holes.
4) In doing step three above do every other pin/hole then come back and do
the remaining ones. This minimizes damage caused by heat build up..
5) Stick in the new board, solder the pins and then re-install.
**** Remember the new board component side goes to the right. There is no alignment. Just put the RF board back and carefully plug the cables back in.
Hope this helps, Let me know
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