Sanding down Hammond transformers - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

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 14th December 2010, 05:36 PM   #1
diyAudio Member
 
Join Date: Oct 2007
Location: Quebec
Default Sanding down Hammond transformers

Hi,

Since the quality finish on Hammonds transformers is not quite nice, I'd like to know if I can sand down the sides and top of the cores to redo the painting.

I'm asking because I do not know much in transformer design and aint sure if each core plate is isolated from one to another and if it will short circuit them if I sand down to metal.

All comments appreciated as if I should or not do it.

Thanks!
Attached Images
File Type: jpg DSCN0320_20101214_143113.JPG (517.4 KB, 275 views)
  Reply With Quote
Old 14th December 2010, 05:44 PM   #2
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
My understanding is that each lamination is poorly insulated from its neighbours, but as all these weak barriers are in series the result is a higher resistance so only small eddy currents. Sanding the ends could create dead shorts so increasing eddy current losses. I would leave it as it is. If you don't like looking at it then add a perforated cover.
  Reply With Quote
Old 14th December 2010, 06:18 PM   #3
diyAudio Member
 
Join Date: Mar 2010
I don't believe you will cause a problem, especially if you use sandpaper and not emery or a file. Metal filings aren't good. Tighten the mounting screws before you proceed. Sand lightly, just enough to do the job.

Note that the mounting screws have insulating washers. Don't compromise that insulation.
  Reply With Quote
Old 16th December 2010, 01:33 AM   #4
diyAudio Member
 
Join Date: Oct 2007
Location: Quebec
DF96, bob91343,

Thanks for your replies gentlemen it was very helpfull and answered my question. I will sand them down beeing carefull to only remove the small impureties that built up in the original finish (not to bare metal). I would have liked to remove every thing and start from new with a nice copper finish but I dont want to take any chance and alter their performance.

Thank you!
  Reply With Quote
Old 16th December 2010, 01:59 AM   #5
diyAudio Member
 
Zero Cool's Avatar
 
Join Date: Sep 2004
Location: MN
I know of one MFG that does this to every exposed transformer without ill effects. has been doing it for years and even has a full time employee that does not but this! they sand the sides flat and smooth then repaint!
__________________
It's not about what you can BUY...It's about what you can BUILD!
  Reply With Quote
Old 16th December 2010, 03:42 AM   #6
diyAudio Member
 
Join Date: Sep 2010
Location: Melbourne
Why sand it down, the usual technique to pretty up industrial hardware is to use body filler or spray putty then sand down that till it is smooth. As for the insulation between the plates, it is common practice to weld a lamination stacks together evidently with no ill effects (this is done on one side of the stack only) so I cannot see a bit of sanding causing problems.
  Reply With Quote
Old 16th December 2010, 04:52 AM   #7
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
the rough surface you see at the edges are caused by the insulation varnish used in making the traffo, the vendor did not see it fit to smoothen them up before painting.....

but you can make it smooth if you want to repaint, sandpapering will do...then apply gray primer and then the black paint....
__________________
the best advertisement for a good audio design is the number of diy'ers wanting to build it after all the years....never the say so of so called gurus....
  Reply With Quote
Old 16th December 2010, 10:11 AM   #8
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
You won't see copper however much you sand the laminations, as they are made of iron/steel.
  Reply With Quote
Old 16th December 2010, 10:48 PM   #9
db! is offline db!  Canada
diyAudio Member
 
Join Date: Nov 2009
Location: Ontario
Dip the affected side in a very shallow tray (Don't fill it more than a couple mm's) of lacquer thinner; the varnish should be soft enough to scrape off after an hour. Just make sure you don't get any on the windings, bobbin or wires.

Last edited by db!; 16th December 2010 at 10:50 PM.
  Reply With Quote
Old 17th December 2010, 02:14 AM   #10
diyAudio Member
 
Join Date: Oct 2007
Location: Quebec
Quote:
Originally Posted by Zero Cool View Post
I know of one MFG that does this to every exposed transformer without ill effects. has been doing it for years and even has a full time employee that does not but this! they sand the sides flat and smooth then repaint!
I have emailed Hammond today to have their expertise on that. The sales rep told me I could sand down to metal but I'll try to speak to an engineer tomorrow for approval. I want to make sure this in no way will affect the performance. The rep also proposed to have the transformers sent back to the place where I purchased them and they would take care of all the shipping expenses (mine and the store). Not bad, but I'd rather not go through that hassle and wait a week or two. I haven't mentionned either to you guys that the varnish (not paint) on the 193M choke end bells is peeling off very easy. It's supposed to be baked. If I gently touch with my fingernail, air penetrates between the metal bell and the lacquer coat. It's sad that they don't use the same finish as the OPT and PT, this one is very nice and clean. Check my picture...

Thanks!
Attached Images
File Type: jpg DSCN0321_20101215_232644.JPG (524.0 KB, 177 views)
  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
hammond transformers? ipop07 Tubes / Valves 21 14th June 2011 03:00 AM
For sale: Hammond transformers eitanwaks Swap Meet 4 6th September 2007 08:33 AM
hammond transformers eitanwaks Swap Meet 0 13th May 2007 09:20 AM
Hammond Transformers Ham Swap Meet 2 16th March 2007 10:45 PM
Hammond Transformers Gabevee Tubes / Valves 0 5th April 2004 02:47 PM


New To Site? Need Help?

All times are GMT. The time now is 12:05 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