Kenwood makes an "adapter" that consists of an external power connector and the internal connector to plug into connector 51 on the DC power board.  I choose to "roll my own".

Because I have been working on my R2000 for about a month, and because I wanted to eliminate or reduce sources of trouble I removed the added internal power supply parts and will re-install them in the near future.  At the present time my R2000 is being powered by the normal AC Mains connector.  This does make the R2000 run much warmer then when powered from DC.

I purchased an 5.5mmOD/2.1mmID coaxial connector from Radio Shack, and a couple of thin washers from the local hardware store.  I removed the cover, held on by 2 small Phillips screws, and installed the connector and washers.  I did not have the proper connector to mate with connector #51, so I soldered a thin wire to the anode of D1.
I placed a ferrite torroid choke in series with an 1.5A micro fuse.
I ran a piece of ground wire from the negative terminal on the coaxial connector to a ground lug that I placed under one of the mounting screws of the DC power board.  I also connected a 15V Zener diode from the anode of D1 to this ground lug.  This provided both protection from external over voltage and protection from a reversed DC connection.  I also placed a bypass capacitor across the positive and negative terminals on the coaxial power connector.  The total cost was less then $10 (USA) because I had the Zener in my junk box.

My R2000 internal DC power supply produces 14.75V DC when operated from AC.  The slight difference in voltage from the AC or my external DC has no real effect on the operation of the R2000.  The display is slightly dimmer and the overall gain of the radio is slightly lower when powered from the external supply versus the internal AC derived supply.  But the R2000 has enough gain so the minor decrease is not an issue.  There were no noticeable differences in overall sensitivity or in the stations received.  My R2000 runs much cooler when operated from external DC because the internal AC power transformer is the main source of heat.

This is a very simple, yet useful modification.  It allowed me to take my R2000 out into the woods with a small gel cell and get hours of listening.  I also made a set of cables to allow the R2000 to be connected to a car battery.  My wife likes the ability to listen to the R2000 while on picnics.  I made the modification to the R2000 within the first month that I had it.  I recently changed the DC power coaxial connector to theRadio Shack one because the one I had was rather flimsy and the bronze contact for the outer sleeve had become intermittent.

As always the standard disclaimer applies:

* Proceed at your own risk.

* It is your radio and your responsibility to determine if you have the skills to do this modification and to operate it in a safe manner from an external DC power source.

* DO NOT leave out the fuse or the protective Zener diode or you will FRY your R2000!

There are three photographs that show points of interest for the DC power hookup.

The first one above was an outside view of the coaxial power connector showing the Radio Shack connector, and the washers I used to fill in the stock mounting hole.

The second one below here is the inside view of this same connector.  Again, notice how I used washers to fill in the stock mounting hole:

The final one below here shows the point where I feed the external power.  I chose to bypass the stock entry point because it has an Si diode to prevent reverse power application, but that diode steals 0.7V and because I am already operating at less than the voltage produced by the AC Mains power supply, I could not afford the extra loss.  The Zener will limit reverse voltage to about 0.7V and the fuse blows so fast that no damage should occur.  I have used this technique on many devices and, while I have blown more than my share of fuses, I have never had any equipment suffer damage.  Again it is your radio, so take the steps that you feel are acceptable.

(The CW Narrow Collins Mechanical filter can also be seen.  This is one modification that I would not do today, because at 170Hz the bandwidth is just too narrow to be useful.)

One minor point, because I thought I might not be able to repair my R2000, I bought a DX-398 and will be taking it on picnics from now on.  At 14+ years, I suspect my R2000 will last much longer if it is not bounced around on trips into the woods.  The DX-398 is a very good receiver, not quite as good as the R2000, but at the closeout price of $100, it was a great bargain.

I will restore the "standard" power connection to my R2000 in the near future.