Tek AA501A manual needed

Update on this topic - before selling my 501....

The unit I have is the 501A Mod WQ. It was made as part of a test set (TS-4553U) that also included two (also modified) Tek SG 505 low distortion oscillators. This test set was apparently designed to facilitate Level / Noise / HD and two-tone IM measurements for telephone communications - as the A weighting filter in the earlier units was replaced by a C weighted message filter. My unit dates from 1991, and believe that this was the last/latest iteration of Tek's analog distortion equipment.

In (successfully) troubleshooting an intermittent switching problem, I looked thru all of the available web info. NO one has come forth with a service manual for the Test Set where any mods to the 501A would be described and documented. The previous available 501A manual dated 1987 is INCOMPLETE as it is missing the Level / THD / IM switching (schematic) info as well as the HD / IM schematics for the (optional) A13 board. With the help of a gentleman at the Tek Museum, I was able to locate the A13 board schematics and posted them on the Tek500 groups IO site.

For this Test Set, many of the boards in the Mod WQ 501A were updated. BUT, thankfully, the unit OPERATES, just like the previous 501A, with the HD and IM options (per SMPTE/DIN/CCIF standards) - but with the "C" weighting filter substituted for the "A" filter. It appears that one could reverse this substitution if you have the time/parts/inclination. The Two 505 generators were also "updated" and had different faceplates.

Charles