Problem: Severe power transformer and choke vibration - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 25th February 2008, 07:34 AM   #1
diyAudio Member
 
Join Date: Oct 2006
Location: Los Angeles
Default Problem: Severe power transformer and choke vibration

I recently complete yet another EL34 SE. Problem is that the Hammond power transformer and choke have a severe mechanical vibration. This vibration can be felt throughout the chassis and well as on the opts (via mechanical coupling). The result is an audible 50Hz/60Hz hum on the speakers that can be heard from a meter away. What could this mean? Is my power transformer and choke saturated?

The transformer is 375CT @ 200mA. My current draw is all within limits. My PSU is a CLC filter rectified by a 5U4G. The first cap is a 5uF Solen followed by a 10H hammond choke and then a 100uF panasonic (at 1000V). The supply provides 420V for the EL34's and 290V for the 6SL7. The power transformer in question had been in another amp that had an electrolytic leak with fumes (yuck).

Any suggestions would be helpful and I would also go buy a new transformer if I had to. What do you think it is?
  Reply With Quote
Old 25th February 2008, 08:43 AM   #2
SHiFTY is offline SHiFTY  New Zealand
diyAudio Member
 
SHiFTY's Avatar
 
Join Date: Jul 2002
Location: New Zealand
Try a larger first cap- instead of 5uF try 20uF.
With 5uF at the front it's effectively a choke input filter and many transformers (& chokes) don't like this.

You can also try switching on with no tubes installed- if you still get vibration then it's the power transformer. Also double check you don't have any shorts to ground- measure the current draw across the dropper resistor...
  Reply With Quote
Old 25th February 2008, 07:49 PM   #3
diyAudio Member
 
Join Date: Oct 2006
Location: Los Angeles
Thanks for the suggestions shifty. I checked all the grounds and they seem to be ok. Also if I change the 3uF cap won't it change my pus output voltage? The reason I had 3uF was because it gave me 420V; any higher capacitance gives me 450V; I simulated this in PSU designer. Also I've gone through a lot of fuses between yesterday and today. The fuse goes off with a pop and a bit of light suggesting that the power transformer is pulling too much current (spike?)

Today I will try swapping the power transformer with another one (the same model. I really hope my choke isn't saturated too....
  Reply With Quote
Old 25th February 2008, 07:58 PM   #4
SHiFTY is offline SHiFTY  New Zealand
diyAudio Member
 
SHiFTY's Avatar
 
Join Date: Jul 2002
Location: New Zealand
It will give you a higher voltage yes- but you should use the correct transformer for the job or design the circuit to handle it.

Try connecting it with a dummy load (5Kish) after the last cap instead of your circuit.
  Reply With Quote
Old 26th February 2008, 03:09 AM   #5
diyAudio Member
 
Join Date: Oct 2006
Location: Los Angeles
Turns out it was a bad transformer; I replaced it and the hum disappeared. Thanks for the input Shifty.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Hail to Vintage Power Transformer & Choke? zxx123 Tubes / Valves 13 19th November 2007 06:53 PM
Using an old power transformer as a choke? aletheian Tubes / Valves 11 25th November 2005 04:07 AM


New To Site? Need Help?

All times are GMT. The time now is 01:48 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2