Wall PS how to check volt a diff points (pulsating problem)?

[Serge125]

Hi all

   Ok I have an inflatable Christmas decoration and the blower motor "pulsates" and I would like to find from where in the SP it's doing this. I have checked the fan motor with my bench PS and the motor is turning as it should so traced the problem to the wall PS. I did an amp test with my meter to see if it would get the value and I do get the 1.7-1.6 amp (same value on mu bench PS) BUT when I did this test the fan ran normally and the moment that I re solder the PS wire back to the motor it's just keep pulsating again. So I wanted to check voltage values at some points on the PS motherboard but there isn't a chassis like a tv to put my - lead on. Can I use my bench PS gnd input as a substitute "chassis" for this? If not how can I check voltage a diff points on the PS.

THANKS for any helps!!

Serge

[Serge125]

any one???