Modifications for the Kenwood R-5000

Modifications for the Kenwood R-5000
Kenwood R5000 Modification Notes

The following describes some option jumpers and other features I have found in the Kenwood R-5000 receiver.

The R5000 is fairly delicate internally, so you should not undertake these modifications if you are not fairly confident of your ability to work with delicate electronics (or to repair it if necessary). In particular, the receiver's numerous circuit boards are connected together with wire harnesses made of relatively fine and delicate wires. Also, some of the boards (particularly the IF board) have small "daughter boards" containing small surface mount parts vertically attached to the main board. These are also fairly fragile, and caution is required in handling them.

EXPANSION FEATURES

The R5000 has six "Expansion Feature" options which are not documented in the user manuals. These are controlled by jumpers (actually diodes) on the CPU board, which is attached to the back of the receiver's front control panel, underneath a metal RF shield. Unfortunately, you must completely remove the receiver's covers, and unfasten the front panel, in order to access these.

Gaining Access to the Jumpers

To access the jumpers, remove the top and bottom covers of the receiver by removing the eight silver screws which hold each cover in place. Use caution at this point, since the radio will be sitting only on its internal chassis, and delicate parts will be exposed.

Next, remove the four flat silver screws which were *under* the covers (NOT the black screws that are visible with the covers on) which hold the front panel onto the main chassis. Be sure the receiver is sitting on a solid table so that the front panel will not fall off when you do this, since there are a large number of wire harnesses connecting to the CPU board. Very carefully pull the front panel forward and rotate it so that you can get access to the back of the front panel.

Loosen the five small metal screws (two at the top, three at the bottom) which hold the RF shield in place over the CPU board. The holes in the shield the screws go into are slots, which allow you to slide the shield off without removing the screws completely. This is fortunate since the screws are fairly small. Remove the RF shield.

One other thing to note involves installing the optional filters.
First, I found that the AM filter which came with the radio introduced a whistle into most AM signals. I replaced it with the optional AM filter, and it eliminated the whistle (and gave a "fuller" sound to the AM).

Also, note that if you install other filters, you have to install them "in order" -- in other words, the narrowest has to go in the N position, the next narrowest in the M1 position. Note that the M2 position is already occupied (as shipped) by a high-quality SSB filter. The reason they have to be in order is that as you select narrower and narrower filters, the wider filters remain in the circuit, so if you put a narrower filter in M1 than you have in N, it will stay enabled even when you select the wider filter, causing the wider filter to have no effect.

It's a little unfortunate that it works that way, since the M1 filter is only enabled by the switch (not in AUTO mode), which would be ideal for the very-narrow YK88CN filter. I have identified a modification to make M1 be selected only when the switch is in the M1 position; it involves disconnecting 1/2 of a dual diode and soldering a diode between two prod the PK232.
R-5000 No Freq. Change thru Computer Interface

R-5000 receivers below serial number 804xxxx may not change frequency when operated with a personal computer/interface. To allow correct operation, replace IC-52 on the Control Unit. The correct part number for IC-52 is MBM27C128-25JA2.

CAUTION:

The R-5000 incorporates CMOS technology. Observe precautions for handling electrostatic sensitive devices.

This modification may be performed under warranty.