A few recent measurements of older amplifiers, including one that I did of Forte 1a, show a fairly high level of 120Hz or 2x the mains frequency. This appears to be the output frequency of a full-wave rectifier that's not completely eliminated by the filter capacitors.
How would I go about determining if this due to:
How would I go about determining if this due to:
- Undervalued capacitors, need to replace with larger ones
- Old capacitors that just need to be replaced with the same sized ones
- Poor PS design
- Something else?
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