--- In TekScopes@..., "Philip" <ndpmcintosh@...> wrote:
I have been studying and working with an FG 502 function generator. I recently went through the adjustment procedure and was able to do everything that did not require a distortion analyzer or spectrum analyzer. Actually I did those adjustments too but eyeballed the sine shape and used my best judgement as what gave the best appearance.
I am not convinced it is operating properly though. I uploaded three picture and perhaps someone who has experience with this unit can tell me if this is as good as it gets or if there is an indication of a fault or two somewhere.
The closeup of the sine shows (barely) that it appears to be composed of a number of signals closely bunched together.
The low frequency square shows that there are a number of tops stacked upon each other. This does not appear at high frequency.
Finally, the closeup of the high frequency square shows what it looks like at high frequency.
I also am unable to adjust the 20V power supply below 21.9 V. I replaced one cracked resistor on the front end of the power supply and am continuing to troubleshoot that problem.
Thanks for any insights.
Phil...
Check the power supply rails for ripple. A fat horizontal trace like those images show is typical of power supply ripple. Loose grounds and shield connections also can cause it, but if your shields and scope are all properly connected, ripple is the most likely problem.
Are your DM500 unit and your scope plugged into the same outlet? If not, you might be experiencing a ground loop. Plug both the TM500 and the scope into the same AC receptacke and see if the trace clears up.
Cheers,
Dave M
