Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum. New: view Recent Searches.
New: visit Schematic Hell!
The sunn still shines online!

Listen to great tunes streaming live right now!

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  

Output Transformer Questions

1/22/2001 5:00 PM
Output Transformer Questions
Hi All,  
How can you tell when an output transformer has gone bad? What are the audible signals that its gone bad (hum, no sound, low output, etc)?  
Also, how can I determine whether the output transformer in my amp is working correctly? Can I test with my DMM to see if its operating correctly?  
1/22/2001 5:15 PM

Low power, no power, or massive distortion with low power.  
One tube is clipping way more then the other or no output on one side.  
Book Of The Day The Ultimate Tone, Volume III by Kevin O'Connor
Have you ever wondered if there is a better way to build a Bassman, Champ, Plexi, an 800, AC-30, Bulldog or Portaflex? Or you wanted to build an SVT with off-the-shelf parts? How about a master-volume amp that doesn’t change tone with the master setting? Everything you need to know is right here, including: proper grounding techniques, wiring methods, and mechanical considerations. Eighteen chapters cover the “iconic” amps everyone knows and loves, with schematics and layouts for each, along with the technical history of the product. Eyelet-board and chassis-mounted tube socket construction is used throughout, for easy servicing and modding. TUT3 is very accessible even if you cannot fully read a schematic and is a "must have" if you are going to build an amp for your self.

Note: The Ampage Archive is an Amazon Associate site. A small commission is paid to the site owner on any qualified purchase made after clicking an associate link such as the one above.
1/22/2001 5:19 PM
Bad output transformer can cause:  
- no sound (open or shorted secondary winding)  
- BAD distortion (open half-primary)  
- very low volume and/or distortion (resistive breakdown/internal short in primary or secondary)  
Any of these could also be caused by other things as well.  
You might want to read the applicable sections of the Tube Amp Debugging Page, which is intended to answer questions like these, and much more.  
In brief, use a DMM to verify that the windings are not open, and that they are not shorted to each other or to the core, and then use the output transformer short tester (article at GEO...) to verify whether or not there's an internal short.  
If it passes these tests and it ever once worked OK, it's good.
1/22/2001 6:02 PM

Thanks for the replies guys. Actually I did check the Debugging Page, but didn't find anything on output transformers. Then, I checked it again under the heading of "no sound" or some such thing and found the info you were talking about.  
   Page 1 of 1