YO3HJV: Kenwood R-5000 filter add-on

02 aprilie 2015

Kenwood R-5000 filter add-on

A few days ago, Tony, YO3FXF came to our laboratory with a very nice looking Kenwood R-5000 Communications Receiver.

He asked us to install the optional filters and gave us a YK-88SN and a YK-88C IF filters.

The first one is a SSB 1.8kHz SSB filter while the second one is a 500Hz CW filter.
Both of them (like the other two already installed filters) are centered on 8,830.7 kHz and compatible with other Kenwood transceivers (TS-440, TS-430 etc.)

Another thing Tony asked us was to take some pictures while working in the radio. So we documented the operation.

First step was to take a look to the Kenwood R-5000 Service manual.

We learn that the filters are connected one after another, in cascade.

The wider filters are maintained into the circuit wjile selecting the narrower ones. This method is credited with mode efficiency in rejecting unwanted signals.

Preparing for opening the upper panel.

Inside view.
The IF and audio board with a lot of conectors and wires.

Old style power supply with a bulky transformer, rectifier filtering and stabiliser.

We put a label on each connector. On the PCB is a small number circled. That is the connector numer.
Some of the wired connectors are not connected, hence the "NC" on that!

All the wires removed from the PCB.

Some sort of Christmas tree appears!

The bare circuit board outside the case.

The filters are prepared to be installed.

We marked the screws with a black permanent ink to know from where was removed.

It looks that someone removed at one time some filters. Might be some flux marking from the factory.

We soldered the new filters on their places.
On the "M1" we put the YK-88SN and on the "N", the YK-88C. We also clean the solder with isop. alcohol.
A close inspection revealed that we did a good job.
By the way, the original soldering was made with no-ROHS alloy.
We could work at abt.370 Celsius degrees; less thermal stress on the board and filters.