Kenwood TS-590SG TCXO Install

I had acquired a used but like new 590SG, with the intention of using it portable from the wall tent.  I found the radio liked to drift from around 30Hz low to 10Hz high depending on ambient temperature.  This was not going to cut it in the tent with temps being all over the place when camping, so I ordered the SO-3 TCXO.

I would recommend anyone who is thinking about installing one of these to do it.  It is about as easy as it gets without being plug in.  Yes, you need some soldering skill, but a little research of technique and some practice and anyone should be able to successfully complete this.

 

 

This is the TCXO and box it came in.

 

  

 

The TCXO and provided adjustment tool.

 

 

 

Put the radio on its top and remove the bottom cover. 

 

The yellow square below indicates the area of interest for the installation.

 

Unplug the connector noted by the red square.

Remove the indicated screw.  NOTE: A #1 Phillips is needed for this.

Remove the board from the radio.  The connector in the yellow circle is not removable, so don't try and force it.

Note the opening for adjusting the oscillator.  It must be mounted on the board so that it is over the silk screened circle.

I used an ESD safe soldering station set at about 750F.

Each leg of the metal housing and each of the two pins must be soldered to the board.  The metal housing soaks up a bunch of heat, so hold the iron on the tab and let it heat before touching the trace on the board.  The two pins soldered rather easy, but it did take a couple seconds of letting it heat before applying solder.  Look for a nice fillet of solder from the pins and tabs to the circuit board.  Be careful to not overheat the board and unsolder the surface mount components that are already in place.

Below is the underside of the board after soldering.

Now, to finish up is a simple matter of putting the board back in place and securing it with the #1 Phillips screw and re-connecting the four pin connector.

The green is the location for the TCXO, the red circled areas are the jumpers that must be moved. Simply pull them off the two pins and push them back onto only one of the pins.  

 

 After you have the TCXO installed, turn on the radio and allow it to sit for 10-15 minutes to allow the temp to stabilize in the TCXO.  If you have a good reference, use it to align the TCXO on frequency.  If you do not have a reference, WWV can be used.  I like to use the highest frequency WWV broadcast I can receive

Put the rig in CW and insure you do not have RIT on.

(If your radio has MARS mod. make sure you turn off break in so you do not transmit illegally.)

Connect a key or other means of closing the CW key circuit, not the keyer input.  You want a constant side tone.

If you are higher or lower than the frequency of WWV, you will hear a varying tone(Beat Frequency).  The faster the warble is the further off you are.  You may need to adjust the volume of the radio side tone to balance the RX signal level.

Adjust the TCXO, using the supplied tool, so that no beat is heard (Zero Beat) when the radio is tuned on the exact WWV frequency.  I will caution you that a very slight movement of the adjustment pot can move the frequency a lot.  Take your time and be patient and you can get it right on the money.

When you are exactly on it is nearly impossible to hear a difference when you key and un-key the CW side tone. (Unless you have the volume of the side tone rather loud of course.)

Now you can turn the radio off, put the bottom cover back on, turn it back up right and enjoy a nice stable rig.