With the components having arrived in the mail the swap-out work can begin. Also the temporary components can be removed and replaced. Most importantly the precision resistors will all be replaced at this time. Calibration was re-done using the correct RMS method as mentioned in the previous video with corrections to the calibration technique..
Further testing as shown is compared against the HP 331A. This starts with comparing meter voltage and then a THD test off of the Feeltech FY3200S.
Another complication is that the Heathkit was not designed to observe the harmonics found in the modern Feeltech and becomes deaf at the high end. I had to switch the the Heathkit IG-72 audio generator as the signal source. But issues were evident.
Sad to say, something broke, or I broke something at this point and made reading initially taken somewhat inaccurate as shown. This lead to a marathon troubleshooting session to find the culprit. A nasty troll a forum used as a resource cut my efforts short there and I ended up going solo again.
Through the course of troubleshooting several components were replaced, though not the cause of failure, were on the border of being out of spec, and one was iffy. Sure enough though , a component ultimately failure invalidated the testing done. A bad resistor..... However, it would seem that in comparative testing, the more distortion a signal has, the more deaf the device is as compared to the HP 331A.
Just as testing continued, the IG-72 dropped dead, so work had to stop to see what was going on with the audio generator. Such is life with 70 year old test equipment.