Option 7 for DC-508A


Does anyone happen to have a PDF of the instructions that accompanied the Tektronix 040-0789-00 field modification kit for adding Option 7 to the DC-508 or DC-508A counters?

Bruce, KG6OJI

Greg Muir

I unfortunately don’t have any documentation on this option but you might gain a little information by going here:



Nenad Filipovic

I don't have the original PDF, but I compiled and posted instructions some time ago on the group in a thread named "DC508A Option 7 installation guide":
Photos and instruction documents:


Thomas Voshell

I have a DC508A with option 7. I have never used it. It is used with a spec-a and/or a tracking generator to provide a readout of the frequency indicated by a “dot” on the spec-a screen. It is described on pp#6-1 & 6-2 of the DC508A instruction manual.
Apparently, there are modifications to your TM500 series power module as well.



My thanks to Greg, Nenad, and Thomas for providing all of the detailed information. I had never seen the TekScopes article about the TR-502 and found it most interesting.

I have a TR-502, but have converted it to act as a TR-503 for use with a 494 spectrum analyzer, where the frequency reading dot feature is not available. My interest in Option 7 was largely one of curiosity, with the thought that a successor-owner of this TR502 might wish to convert it back by reinstalling the enclosed original crystal and re-tuning the cavities.

My first impression was that providing Option 7 required adding an additional circuit board to the DC-508 counter. Then in looking at the DC-508 I saw the board was actually in place and it seemed necessary to only to add a few components. But then my ambitions were quieted when I saw the myriad of connections that must be added. I think I'll let a successor-owner worry about this.

Bruce, KG6OJI


The DC502 has a separate option 7 PCB that is not supplied with the base unit.
Option 7 on the DC502 also requires multiple wires soldered to the main PCB and some trace cuts if I remember correctly.requires.