[jshorva65]

This past weekend, I scored a second Eico 368 without the post-marker upgrade as described in the April, 1969 issue of Service magazine installed yet. I plan to recap this one, replace some terminal strips to facilitate a "star ground" configuration which will break up internal ground loops in its original construction, rewire tube heaters with twisted-pair wire to further reduce line-frequency noise, and complete a customized version of the post-marker upgrade featured in Service, but accomplishing a less-cluttered panel layout by using a dual-concentric pot for the Trace Size and Marker Size controls and subbing a pot with a pull-on/push-off switch for the 10K Sweep Width pot, switching the Blanking tube's cathode circuit to enable mirroring two "S" curves into an "X" pattern for FM Discriminator alignment so that the "X" display makes the center of the "S" curves much easier to spot when viewing the scope trace from a distance. In its original pre-marker configuration, the effect of the internal ground loops present in the original construction on the scope trace was far less. The addition of the upgrade without also eliminating the internal ground loops, however, tends to worsen the appearance of the noise introduced by those ground loops on the trace due to the tendency for the upgrade's marker-adder circuitry to amplify the unwanted ground loop noise along with the composite trace and marker signal which the post-marker upgrade was constructed to produce. The amplified 60 Hz ground loop noise appears on the scope screen as a tilting of the trace. The degree of tilt is proportional to the input sensitivity setting of the scope. The goal of upgrading this one to star grounding as part of the upgrade procedure will be to eliminate the "tilt" which I was only able to diminish significantly on my other Eico 368, which I purchased with the upgrade already installed.