Been to a few radio rallies and at the CDARC surplus sale on the 13 February I recently bought a Heathkit GD-1U Grid Dip Oscillator complete with the original coils, a bargain at £10.

Thanks to Andy (G6OHM) for sending me the link to the service manual and David (M0ZEB) for the Assembly and User Guide.

GDO_Heath_GD-1U_schematic

GD-1U-GPO Assembly and User Guide (7.3Mb File).

GD-1A-GDO Assembly & User Guide.