500c buzzing power transformer

Vintage Asylum

Classic gear from yesteryear; vintage audio standing the test of time.

I found a Fisher 500c receiver in excellent condition at a garage sale at a great price. I started to do a mild rehab on it and ran into a problem. (I was planning to replace the coupling caps, the selenium bias supply rectifier and caps, and the B+ rectifiers and caps) Without any tubes, with the B+ secondary disconnected, and with the bias supply rectifier and caps replaced, I brought the line voltage up with a variac. (My line voltage measures 122 V) The power transformer buzzes loud enough to hear in the next room. It was loud enough that I thought it was going to burn out. If I put a clamp across the end bells, or even squeeze it with my hands, the buzz drops to a low level, but doesn't disappear. I measured the primary and secondary resistances on the transformer, but didn't see anything obviously wrong. I am planning to measure the current through the primary with nothing connected, but haven't done that yet. Can someone offer some advice? Is there something else I should test? Is the power TX shot? Or is this normal, and I should find a way to clamp the end bells tight?

This post is made possible by the generous support of people like you and our sponsors:

Parts Connexion

Topic - 500c buzzing power transformer - floydandrews 11:53:09 03/29/14 (10)

Moral of the story: test your transformers first - floydandrews 12:14:37 03/31/14 (0)

RE: 500c buzzing power transformer - mark.korda@myfairpoint.net 13:39:03 03/29/14 (8)

RE: 500c buzzing power transformer - floydandrews 13:48:48 03/29/14 (7)

RE: 500c buzzing power transformer - Michael Samra 14:56:47 03/29/14 (5)

RE: 500c buzzing power transformer - floydandrews 17:17:09 03/29/14 (4)

RE: 500c buzzing power transformer - Michael Samra 18:16:04 03/29/14 (3)

RE: 500c buzzing power transformer - FenderLover 18:51:13 03/29/14 (2)

RE: 500c buzzing power transformer - Michael Samra 21:19:58 03/29/14 (0)

Sweet drawing! - Mossback 20:46:33 03/29/14 (0)

RE: 500c buzzing power transformer - mark.korda@myfairpoint.net 14:24:39 03/29/14 (0)

FAQ

Post a Message!

Forgot Password?

Moniker (Username):
Password (Optional):
	Remember my Moniker & Password (What's this?) Eat Me
E-Mail (Optional):
Subject:

Message:	(Posts are subject to Content Rules)

Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:	Automagically notify you when someone responds.

To view your new posting or follow-up, click on the RELOAD or REFRESH button on your browser.