I have a Hafler se 120. I am just curious why one side the DC offset is 2MV and the other channel is 60MV when on for about ten minutes, no load attached. Is this something to worry about. also when i try to cool the high channel it actually goes higher which seems very strange. i check all the solder connections and no problems. Any troubleshooting would be appreciated. The electrolytic show no bfldgin or leaks. They are only 50vDC and the unit mains are 54V. I don't understand how Hafler makes this work.
The 60mV DC offset is not unusual at all, and is nothing to worry about. The circuit cannot reach thermal stability
without the cover installed, though.
If the voltage on the main capacitors is 54v when they are rated for only 50V, your AC line voltage probably runs high.
Try measuring it.
without the cover installed, though.
If the voltage on the main capacitors is 54v when they are rated for only 50V, your AC line voltage probably runs high.
Try measuring it.
Last edited:
Go to Hafler's website and find archives, you will find the manual for the SE120. P3 & P4 adjust bias and " balance", balance is dc offset adjust. First set bias then dc offset to lowest value.
The P4 pot cannot be used for DC balance adjustment, because the NFB loop includes a capacitor
that reduces the DC voltage gain to unity. The pot is a factory adjustment that is best left as-is without
the proper factory adjustment procedure, which is not in the manual.
that reduces the DC voltage gain to unity. The pot is a factory adjustment that is best left as-is without
the proper factory adjustment procedure, which is not in the manual.