Sprague Powerlytics - still good after 50 years


2018-08-31 12:32 pm
So I had this old amplifier apart and thought I'd check the bulk capacitors out.

These are Sprague Powerlytic 36D rated 23000u and 50VDC. Have been in an amplifier PSU for most of their lives, I don't know the history before that.

Capacity: one is between 30 and 31000uF depending which meter you believe (Uni-T UT61E or the component tester). The other is between 26 and 28000uF. Both above spec at any rate.

The ESR measured .55 on one and .46 on the other. Respectable I think for this size and rating. But it's just one of those cheap component testers so I may repeat it with a scope and sig gen to be sure.

Leakage is also respectable. I don't have a super accurate rig but set my PSU for 28v and measured current flow after initial charging it was below 80uA for both and generally closer 40-50 after settling.

If I'm reading the date code right these were made in 69 which puts them at almost 50 years old! And they are still trucking. Not going to bin these just yet. IMG_20191019_113610_505.jpg IMG_20191019_120522_518.jpg IMG_20191019_121839_855.jpg