I need to lose that Hummmm - 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 1st February 2012, 09:57 PM   #1
diyAudio Member
 
trondareo's Avatar
 
Join Date: Feb 2009
Location: Trondheim
Default I need to lose that Hummmm

I made the nicest little amp, with the sweetest sound. No hum in the speakers. But my power transformer hummmmmms - a lot.
Type Musical Power Supplies 190.2i

Its mounted tightly with rubber washers. I can try adding more or removing those.
The end bells are polished and the iron painted white. Everything is tightened down afterwards.

It has the following outputs, most of which are lightly loaded:
240 v in - I have 238V
190 - 0 - 55 - 190 at 120mA - I measure 80mA at 385V, 55V not used
6.3V 3Amp - I use 6.3V 2 Amp
6.3V or 5V 2 amp - I use 5V 2Amp (Right at the limit)

Do I need another transformer, or do you have any Ideas?
__________________
Im doing stuff at http://taooftubes.wordpress.com/
  Reply With Quote
Old 1st February 2012, 10:46 PM   #2
Jebem is offline Jebem  Portugal
diyAudio Member
 
Jebem's Avatar
 
Join Date: Dec 2011
Location: Lisbon
Nice amplifier... I like the build quality. You must have real high sensitivity speakers to take advantage of so little power.

It doesn't look an overload from the secondaries loads.
But You can always check it by unplugging all the tubes, and power on the amplifier unloaded.

Being a new amplifier and new transformer, did it start humming since the first day of use?

That white paint on the transformer iron came from the manufacturer, or did You apply it afterwards?
The transformer may have excessive iron losses, sometimes caused by bad isolation between the core silicon steel sheets. This is caused by oxidation but it takes long years to happen, usually.
Or if You used a conductive paint, then it is shorting the core lamination causing abnormal iron losses on a new transformer.
If this is not the case, then the transformer winding may be loose and vibrating when loaded, so it is defective and I would return it to the manufacturer.

Cheers.
__________________
If You need something done properly, do it yourself (and ask help from DIYaudio... )
One of my SE 211 tube amps: http://sites.google.com/site/sunajeb...ificador-211se
  Reply With Quote
Old 1st February 2012, 11:03 PM   #3
diyAudio Member
 
trondareo's Avatar
 
Join Date: Feb 2009
Location: Trondheim
Im happy you like it
Im using 96db/W Visaton 200B on open baffle, and dreaming of making a back loaded horn.

Thanks for several useful ideas.
I became aware of the hum after maybe the first hour or so. but in the beginning I was focusing on voltages and bias and playing loud so I cant say if it was there at the start.
I did the painting several months ago. I cant remember whether I had the screws in when I painted. So I may have gotten some paint between the laminations. In the old days sink was used a a pigment in white paint. I have no idea what is in the one i used tho. It is an acrylic car touch-up spray. The laminations were pretty heavily coated with some glossy stuff from the factory. I roughed it up for painting but did not remove it, figuring rust and isolation was a good thing.
Ill check no load tomorrow - its getting late here.
__________________
Im doing stuff at http://taooftubes.wordpress.com/

Last edited by trondareo; 1st February 2012 at 11:06 PM. Reason: added speaker info
  Reply With Quote
Old 1st February 2012, 11:11 PM   #4
M Gregg is offline M Gregg  United Kingdom
diyAudio Member
 
M Gregg's Avatar
 
Join Date: Jun 2010
Location: UK
Is it the end bells?

If you press on the end bells of the Tx does it stop or reduce?
Edcor tend to do this so I took it apart and filled the inside of each with a layer of sealant as thick as possible but not in contact with the windings..
You have to take into account how hot it gets..
Another thing is a shorted turn..ie if 2 bolts come into contact with each side of the laminations there should be insulators to stop this..
Either plastic inserts or fiber washers..test on ohms between each bolt and the laminations or between each bolt and each other bolt..there should be no connection..
One in contact is OK for earthing the laminations (only one)with no connection to any other bolt that goes through the laminations.

Regards
M. Gregg
__________________
What is the sound of one hand clapping?

Last edited by M Gregg; 1st February 2012 at 11:19 PM.
  Reply With Quote
Old 1st February 2012, 11:26 PM   #5
diyAudio Member
 
trondareo's Avatar
 
Join Date: Feb 2009
Location: Trondheim
Ok - I tried no load - taking out the tubes. Hum was very slightly lower - could be my imagination.
Then I put in the tubes again and tried pressing the end bells firmly. A very slight difference. I could probably use the sealant trick.
I also tried pushing it from different directions relative to the chassis. Pushing it towards the front helped a bit.
So it may be a combination of several factors. Ill try removing the rubber grommets next.
__________________
Im doing stuff at http://taooftubes.wordpress.com/
  Reply With Quote
Old 1st February 2012, 11:37 PM   #6
M Gregg is offline M Gregg  United Kingdom
diyAudio Member
 
M Gregg's Avatar
 
Join Date: Jun 2010
Location: UK
Are you sure you don't have a shorted turn?
I'm not talking about the windings..

Three of the screws through the laminations should be insulated from the end bells and the laminations..


Regards
M. Gregg
__________________
What is the sound of one hand clapping?
  Reply With Quote
Old 1st February 2012, 11:43 PM   #7
diyAudio Member
 
Join Date: Aug 2005
Have you tried taking the bells off?

If for instance you used long bolts that contact both the bells, it will effectively create a sorted winding.
  Reply With Quote
Old 1st February 2012, 11:45 PM   #8
diyAudio Member
 
trondareo's Avatar
 
Join Date: Feb 2009
Location: Trondheim
All four screws have nylon washers, and I remember putting heat-shink on the screws before mounting them, as there was no isolation originally. Ill open them up and check whether the heat has made them shrink and open a connection. Heat shrink may not have been a smart idea. Is there a point about having one screw connected?
__________________
Im doing stuff at http://taooftubes.wordpress.com/

Last edited by trondareo; 1st February 2012 at 11:50 PM.
  Reply With Quote
Old 2nd February 2012, 03:00 AM   #9
diyAudio Member
 
Join Date: Dec 2011
I recall that many of the power transformers I encountered years ago had a wide copper strap that went around them covering sides of the winding area under the bells and visible going up and over the outside of the far sides of the "E"s. The strap continuous being soldered to itself. I never measured idle currents, but recall that those transformers were quiet.
  Reply With Quote
Old 2nd February 2012, 03:04 AM   #10
GloBug is offline GloBug  Canada
Banned
 
Join Date: Jun 2011
Quote:
Originally Posted by M Gregg View Post
Are you sure you don't have a shorted turn?
I'm not talking about the windings..

Three of the screws through the laminations should be insulated from the end bells and the laminations..


Regards
M. Gregg
This is interesting. perhaps he can take the screws out and try it. Easy enough to find out.
  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
Help: Need to lose some volts Decker Chip Amps 15 7th October 2005 08:47 AM
Amp to Computer Hummmm ralph-bway Solid State 3 15th February 2005 01:46 AM
How much flux do you lose if... 454Casull Multi-Way 11 18th January 2005 10:05 PM
I could lose some heat - suggestions? 7V Tubes / Valves 11 1st February 2004 01:56 PM


New To Site? Need Help?

All times are GMT. The time now is 03:46 PM.


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