PIONEER MAGNETICS HV Power Supply

[Dexter'sLab]

Hi, I have some questions on Pioneer Magnetics
Model: PM2675A-1-3

Theres a hissing sound in the power supply every time I tried to power up. Also, I should get 5v on the channel 1 output but I only got max of 4.5v even I adjust the trimmer.
Hope somebody can give me advice. Thank you so much.

-Dexter

 

[D.A.(Tony)Stewart]

Looks like a really old model that often required 10% minimum load to regulate properly on main 5V.

I have experienced hissing sounds from poor capacitive loading on boost PFM regulators that run from buck PWM step down main supplies, which might dependant on previous issue and or oxidized old caps from long periods of no excitation.

 

[Dexter'sLab]

Hi SunnySkyGuy,

Thanks for the reply.

Actually I have 2 same model power supply.
1st power supply failure: 4.7v output (should be 5v) and whistling/hissing sound from transformer.
2nd power supply failure: 5.033 to 5.05 (fluctuating) when put 2.5 Ω load. output become 4.86v. 4.92v (fluctuating). I am confuse because power supply output v should not be fluctuating right?