New power transformer in Fender Bassman AB165 buzzing

[prairie]

Hi there,

A little while ago, I received a Bassman AB165 that had been modified in the power section (different power transformer, some super sketchy wiring).

I pulled the old transformer out and rewired everything that was messed with, and I just dropped a new power transformer into it (Hammond 290EX), double checked, all of my wiring, and the rest of the circuit, and I can’t find anything that is wrong based on Fender’s layout diagram or schematic. Solder points have been checked and are good. When I lift the centre taps for the 6.3VAC and HV windings, I have no continuity with ground (putting these CTs to ground gets me continuity again, as expected). Filter caps are all new.

However, when I power up the amp, I am getting a very loud buzzing from the power transformer. Like, much louder than any other transformer I’ve heard before.

Any idea what this could be from? I’ve confirmed that none of the primaries are grounding out. Is this just a normal sound from this model of transformer?

Here’s a video. This is with no power tubes, with a speaker load attached. This is the sound coming from the transformer itself.:
https://youtube.com/shorts/lKRZ22rxHAQ?feature=share

[neskor]

so many buzzing Hammond 200 series power transformers check here:
https://www.diyaudio.com/community/thre ... zz.121194/

[maxkracht]

Make sure all of the screws are tight. If the laminations are loose it will make noise. Possible you will need to take off the end bells to make sure everything inside is tight and there isn't anything weird going on in there. Could be faulty in some way, but that's pretty rare in my experience. Chinese made hammonds can look a bit sketchy, so I wouldn't doubt it, but haven't had a bad one myself.

Are you getting the expected ac voltages from each winding?

[Leo_Gnardo]

Do you see expected voltages from the secondaries? How much current does the amp draw from the AC line while transformer is making its racket? Also would be interesting to know if the transformer carries on buzzing when driving no loads, and what the AC current draw is in that condition.