Electronics > Repair
Power supply ripple on UA723 based circuit
(1/7) > >>
RichardM:
I am repairing a spare R&S SMS signal generator and have noticed the ripple on the 5V supply is well above spec. It’s about 60mVrms and should be < 0.4mVrms. I have attached an image of the 5V part of the power supply circuit.

The adjacent +-15v rails have <1mV ripple. There is also a similar small ripple at MP1 on the positive side of C1. The 60mv ripple appears at MP2. I have swapped the UA723 and 741 opamp with new ones but that did not make a difference. Any thoughts on what the most likely culprit is or what to check first is appreciated. Can a noisey T1 or T4 be the reason?

Cheers

Richard
ondraN:
I would suspect C1 in the first place.
RichardM:
Ok, the ripple on C1 at MP1 is 0.2mv and C1 measures above 20,000uf ? Could it still be the problem?
ondraN:
Are some ripple on MP3? It is power suply for 723 and 741 and can cause some problems.
iMo:
Doublecheck the MP1 voltage as well, it could be too small for proper regulation (you want 5.39V out with 8.2V in)..
..and look at the ripple at R12 too..
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod