RESTORING THE SR-2000
The restoration process for the SR-2000 includes a series of procedures that will ensure a stable, reliable, and trouble free radio. These procedures can be grouped in three categories, critical and absolutely necessary, should be done, and after production changes that improve the performance of the radio. I won’t say that it’s easy or quick but I can say that powering up a properly restored SR-2000 is a very special milestone. The following information will detail the various steps involved in the complete restoration of an SR-2000. If you find any step or information lacking clarity or details, please let me know and I’ll correct the inadequacy. Throughout the process, we will add links to photos of the pre and post work. I believe you will find the series interesting and useful as you pursue the process yourself.
The following steps will be composed in part with some of the service notes that we will add to the service notes section time permitting.
Some steps will reference service notes and photos with links that will be added over time.
1. MUST: Two metal screws replaced with nylon to prevent ticking in the receiver when high voltage is turned on. Caused by a corona discharge to the metal screw which is attached to the shell and chassis. See service note 003a and photo.
2. MUST: A jumper attached to both stator connectors on the rear final loading capacitor section to load share when using the 10 meter band. Prevents over heating of the connector. See Service note 004a, photo of jumper, and photo of overheated capacitor.
3. MUST: Copper butter (Penetrox D) applied in a thin film to all of the screws in the chassis and between the final compartment walls and chassis to prevent chassis loops. This procedure will preempt many problems that are associated with inadvertent chassis loops. Specifically affected is the inability to neutralize the finals and intermittent unexplainable erratic behavior both in transmit and receive mode. See Service note 001a and photo.
4. MUST: Test every ground to chassis connection for < 1 ohm.
5. MUST: Each riveted joint where you find a star washer between the component and chassis (Tube socket, terminal strip, plate, etc.) apply Deoxit or Fader lube and tap the washer lightly on the side to reestablish the bite. Aluminum chassis radios with stainless steel rivets, when subjected to hostile temperature changes (-20 to +100 degrees) e.g. when stored in a garage or attic tend to incur oxidation in the rivet joint. A good indicator as to where the radio spent its life is how much resistance each of these joints display. Pay special attention to the bracket that holds the USB and LSB crystals. Check to see if the rivets have loosened and add a screw if there is any play. Use a self-tapping screw or you will have to go through the VFO enclosure. See Service note 006a
6. MUST: Add an IERC heat dispersing tube shield to the 6AQ5A. A good odometer for the SR-2000 is just how burnt and charred the relay is that is mounted next to the 6AQ5A. Note: The 6AQ5A runs at 425 degrees “F” and after the heat shield is add, will run about 250 degrees “F”. The 6AQ5A does not last long without heat dispersion and quickly loses conduction. The cathode voltage from the 6AQ5A is used to open the diode gates for the heterodyne oscillator signal to the first transmit mixer and balanced modulator to 6GX6A when in transmit mode. The range is 1.5V to 16V and will not be happy if the 16V degenerates to 14V or lower. See Service note 07a and Photo of AQ5A IERC
7. Much more to follow