Hum from X250 amp itself

[richmond5]

X250 recently develop hum problem, from the amp itself, not from the speakers. It only happens if running for more than 2 hr. If turn on, but in idle, nothing happens. Thanks for any advice.

 

[Michael Rothacher]

Has the transformer become loose over time, perhaps?

 

[Zen Mod]

DC in mains ?

 

[impuls]

Connect transformer for a higher mains voltage

 

[tiefbassuebertr]

Dear Mr. Pass,
a friend recently bought this power amplifier and observe the same issue. Maybe a dc filter is necessary - go to
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?
Best solution could be this one from post #159 under
dc filter
and
http://scintilla-buizenversterkers....erkers/zelfbouw/zelfbouw sites/DC-Blocker.htm
An other possibility are not good working electrolytic caps because the age.

Furthermore, he observes that the house fuse frequently blows out when switching on (maybe inrush current limiter don't work).

First step is download the service manual. Unfortunately I don't find the appropriate portal. Thank you for advice. If no longer online available here my email address:
kirschner-hifi(at)web.de

P.S.: sound quality is wunderful

 

[tiefbassuebertr]

according the images in post #2 under
Pass labs X250 - how to adjust/check bias, offset
there is in use an inlet filter (FN 9222 IEC inlet filter - a combination of an IEC inlet and mains filter) like this
IEC inlets with mains filter, CS-001F/3/N, CS-001F/10/N |EN|
or this
Roxburgh RID IEC Inlet Filter - Low Cost - Roxburgh EMC
or this
https://www.infinity-electronic.hk/datasheet/83-FN9222S1-10-06.pdf

What is the probability that an internal error is causing the in my previous posting mentioned issues?

 

[2 picoDumbs]

Start by confirming all basic operating parameters are correct.
Check the ground lift is working correctly etc.

Caps in psu might need replacement.

 

[tiefbassuebertr]

First step is download the service manual. Unfortunately I don't find the appropriate portal. Thank you for advice. If no longer online available here my email address:
kirschner-hifi(at)web.de

P.S.: sound quality is wunderful

Check out post #17 under
https://www.diyaudio.com/forums/pass-labs/327244-pass-x250-repair-2.html#post6351652

 

[tiefbassuebertr]

X250 recently develop hum problem, from the amp itself, not from the speakers. It only happens if running for more than 2 hr. If turn on, but in idle, nothing happens. Thanks for any advice.

I observe the same (not permanent but temporary).
If DC on the mains the reason, check out post #184 on page 19 under
https://www.diyaudio.com/forums/pow...zzing-toroid-transformers-19.html#post6455036