I have a Dedicated Micros UP07223010 power supply that gives out a chirping noise. A voltmeter attached to the terminals shows a swing for each chirp. A few days ago, my HP laptop power supply developed the same chirping problem and had to be replaced. So I assume it is quite common. Here is a picture of the interior. The three bigger capacitors near the center with gold marking (3300 uF, 16V) look to be a bit bloated. Could they be the problem? enter image description here

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    \$\begingroup\$ If they're bloated, yes they could be the problem. If they aren't THE problem then they certainly are another problem. That unbloated one looks to be a different type or brand, but if it's the same brand as the other three I would replace it also. I would replace all the cap brands matching the bloated ones. Probably using the same bad formula. \$\endgroup\$ – DKNguyen Jul 12 '19 at 4:43
  • \$\begingroup\$ I’ll give your hypothesis a high probability of being correct. \$\endgroup\$ – winny Jul 12 '19 at 21:38
  • \$\begingroup\$ The tops of the three black and gold capacitors are popped. They are bad. No need to test them. Replace them. If it still doesn't work correctly, then you have another problem. The capacitors are a problem. As long as you have bad ones there, you can't really troubleshoot the rest of the circuit. \$\endgroup\$ – JRE Jul 13 '19 at 7:46

'Chirping' comes from the power supply restarting over and over again. The typical cause is an external overload, but defective internal parts can cause the same effect. The power supply is trying to run but is encountering an over current condition that prevents the output voltage from rising to a preset level by a preset timeout of one second or less.

You mentioned bloated capacitors. Generally it is a single part that fails, either a diode or capacitor in the output stage. However a component failure in the feedback loop can cause the same effect.

Note that over time constant restarts will burn out the control IC or MOSFET. Testing with a good DVM could help find out where the proper rise in output voltage is being cutoff. Be careful! The primary side (before the transformer) has about 240 to 340 vdc, very painful to touch.

It has been suggested and is recommended that all bloated capacitors be replaced with same value parts, rated for \$105^o C\$ and with a low esr value. Though the fail mode may not be a short, their value could drop to 1% of rated value, preventing a stable voltage from building up before the startup times out.

The 'chirp' sound is from an initial series of startup pulses in the transformer windings and core. On a good startup you would hear this just one time and it maybe too brief to hear.

  • \$\begingroup\$ Dear OP , when the caps bloat C drops towards 1% and ESR rises towards >1000x thus causing overvoltage (yet clamped) and overcurrent when Ic/C=V/L =dV/dt at some frequency. These birdies are common due to high temp rise near or inside caps that accelerate failure rate. Only use 105’C or greater ultralow ESR caps. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jul 12 '19 at 14:38
  • \$\begingroup\$ I took out the three 3300uF caps and tested them on an $5 eBay LCR tester. They all showed up as diodes. \$\endgroup\$ – user1596683 Jul 12 '19 at 19:28
  • \$\begingroup\$ @user1596683 You should replace all parts with irrational values. First make sure your LCR meter will read known good parts correctly. My LCR meter was $420 USD. It mostly means a wider range and more accuracy. Give large value capacitors time for a stable reading, as initially they appear to be a short-circuit. \$\endgroup\$ – Sparky256 Jul 12 '19 at 21:32
  • \$\begingroup\$ Finally, the caps arrived. It is fixed. Thank you all for your kind help. I wonder how much electronic waste we can eliminate if we start to fix these birdies. \$\endgroup\$ – user1596683 Aug 8 '19 at 19:34

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