Help identifying transformers
Moderators: pompeiisneaks, Colossal
Help identifying transformers
I was at a property recently and saw an old radio console in the junk pile with tubes and transformers showing. Turns out it had el84's and two Mullard 12ax7. The transformers look to be in good shape but don't have any name or label to identify. There are numbers on the bottom of each but a search doesn't turn up any information. Please see attached pictures. Any help identifying would be appreciated
You do not have the required permissions to view the files attached to this post.
Re: Help identifying transformers
At least you know the tubes used. That will tell you a a great deal, for example:
1) Power transformer minimum current supply for the filament winding is 2.12A. If there is a pilot lamp running on the filament winding, I'd add that, depending on the bulb. Let's guess total capacity is 2.4A or 2.5A. At that load level, you can probably expect about 6.8V or 6.9V from the 6.3V secondary. That is because that piece of equipment looks old enough to believe wall voltage was 110V when that was made. Today, voltage is typically 117-127V depending on where you live and the time of day. (Really, check your wall voltage several times during the day. You'll be surprised.) You might be able to squeeze a 3rd 12AX7 into a build and maybe not. It's nice to be able to have 2 gain stages and a PI tube.
2) Power transformer secondary is going to be appropriate to the tubes. You can test for this, but I'd expect the PT to produce B+ in the neighborhood of 250VDC and maybe as high as 310VDC on account of the wall voltage being ~10% higher.
3) You don't mention a tube rectifier. I think I see enough wires for a 5V supply on the PT.
4) On the output transformer, maybe 8K3 means the primary winding is 8.3KΩ and maybe it means something else. 8.3KΩ would be appropriate to a pair of EL84's. Armed with this assumption, you can reasonably test for the turns ratio, which will tell you the secondary (output) impedance. Here is how to do it, however, assuming 8.3K primary, you'll be reversing the math. You can use the filament winding on the PT to test the output transformer. http://www.sarris.info/main/calculating ... -impedance
5) Since you know the power tubes were EL84, the power output is probably more than 12W and less than 18W. I'd say 15W is a safe guess. Don't try to push it much more than that.
Note to moderators. This post looks misplaced. Maybe you'll move it to the general section and delete this comment.
1) Power transformer minimum current supply for the filament winding is 2.12A. If there is a pilot lamp running on the filament winding, I'd add that, depending on the bulb. Let's guess total capacity is 2.4A or 2.5A. At that load level, you can probably expect about 6.8V or 6.9V from the 6.3V secondary. That is because that piece of equipment looks old enough to believe wall voltage was 110V when that was made. Today, voltage is typically 117-127V depending on where you live and the time of day. (Really, check your wall voltage several times during the day. You'll be surprised.) You might be able to squeeze a 3rd 12AX7 into a build and maybe not. It's nice to be able to have 2 gain stages and a PI tube.
2) Power transformer secondary is going to be appropriate to the tubes. You can test for this, but I'd expect the PT to produce B+ in the neighborhood of 250VDC and maybe as high as 310VDC on account of the wall voltage being ~10% higher.
3) You don't mention a tube rectifier. I think I see enough wires for a 5V supply on the PT.
4) On the output transformer, maybe 8K3 means the primary winding is 8.3KΩ and maybe it means something else. 8.3KΩ would be appropriate to a pair of EL84's. Armed with this assumption, you can reasonably test for the turns ratio, which will tell you the secondary (output) impedance. Here is how to do it, however, assuming 8.3K primary, you'll be reversing the math. You can use the filament winding on the PT to test the output transformer. http://www.sarris.info/main/calculating ... -impedance
5) Since you know the power tubes were EL84, the power output is probably more than 12W and less than 18W. I'd say 15W is a safe guess. Don't try to push it much more than that.
Note to moderators. This post looks misplaced. Maybe you'll move it to the general section and delete this comment.
-
Reeltarded
- Posts: 9955
- Joined: Sat Feb 14, 2009 4:38 am
- Location: GA USA
Re: Help identifying transformers
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.