salvaged OT, right connections (edit)headphone trick ???

[ward]

I'd like to use a salvaged transfo in my guitar amp I'm building.
If someone wants to have a look at how I think it should be connected ...

I have a schem but the color coding of the OT is unfortunatly unreadable
http://img.photobucket.com/albums/v54/perki/18watt/tekadew488.jpg
top side connections:

Bottom side connections:

What I make of it:
the green and blue on the bottom go to pin7 on the EL84's so these must be the primary connections.
the pink on the bottom goes to the capcan and the choke, this is the center tap on the primary according to me.
the small black one on the bottom: ???
the red and orange go to connections on the back of the radio, ?? connections for an external speaker perhaps ?
The black shielded cable goes to the treble pot which has 5 terminals ?

on the top side two black cables heavier gauge come out of the transfo, these must be the 4ohm speaker connections I guess.

 

[12afael]

the treble pot could have a switch for disconect the tweeter.

on the top side two black cables heavier gauge come out of the transfo, these must be the 4ohm speaker connections I guess.

did you measure the DCR? sometimes transformers have a shield and must be conected to ground.

I must say it these schemes are beautiful is like modern art or something. even look like watercolor and chinese ink. :shock:

 

[ward]

[quote author="12afael"]the treble pot could have a switch for disconect the tweeter.[/quote]
right!! checked it, and indeed.

did you measure the DCR? sometimes transformers have a shield and must be conected to ground.

Is DCR = DC resistance ?
Can it be measured with a multimeter on resistance ?

 

[ward]

As I see it now the small black cable going to the underside is just part of the tweeter filter network.

 

[12afael]

Is DCR = DC resistance ?
Can it be measured with a multimeter on resistance ?

yes, you can know if a pair of wire are a primary or secondary if they measure something(from few ohms to hundred ohms), if you have infinte they are not conected internally.

on small transformers like mic and line input measure DCR could magnetize the core , so special care should be taken, but on a power amp transformer is not a problem.

 

[drpat]

[quote author="12afael"]

I must say it these schemes are beautiful is like modern art or something. even look like watercolor and chinese ink. :shock:[/quote]

I'd hang the bottom one in my living room "as is"

 

[12afael]

I'd hang the bottom one in my living room "as is"

it just need the sign of the author . I imagine it on a art gallery on new york. it has a type of balance that is perfect.

 

[ward]

[quote author="drpat"]I'd hang the bottom one in my living room "as is"[/quote]

[quote author="rafa"]it just need the sign of the author . I imagine it on a art gallery on new york. it has a type of balance that is perfect.[/quote]

You guys are sniffing solder just a bit too much. :razz: :razz:

thanks for the help.

 

[ward]

I measured the dc resistance:
green to pink 75ohm
blue to pink 75ohm
green to blue 152ohm
red to orange 1,2ohm
So I've got 'em right.


I tried the headphonetrick described here:
http://ax84.rru.com/FAQs/general.html#ot-place
But I hear absolutly nothing, wherever I put the OT ???

 

[ward]

primary of the pt connected to mains.
secondary (red-orange) connected to headphone;

I tried with a scope, nothing.

 

[12afael]

mmm maybe a gain stage could help here . or try with a headphone with a greater impedance or sensitivity.

 

[ward]

I gave the headphone trick up,
the ot passes music, so I thought ...
Maybe it's good news I've got no hum.

Trew it in, and finished the amp,
now I 've got nothing else than loud humm.

If you want to read the whole story.
http://www.18watt.com/modules.php?name=Forums&file=viewtopic&t=14095#133410
You need to be registered to read!

 

[12afael]

it don´t pass signal?
it is 60/120Hz hum or a high squeal?

if it don´t pass signal and is a high squeal cut the feedback cable , if it work you must swap the primary plate wires.

if it is 60/120Hz, check your connections.(grounds, filters, etc.)

 

[ward]

It works :grin: :grin: :grin: ,

I had two mistakes, and by not understanding those cliffjacks I burned my OT.
Luckily in a spot where I could fix it.

Now it works,
I tried it five minutes ago on a real guitarspeaker,
...
NICE
:green:

And it is quiet, without headphonetricks.thanks afael

 

[12afael]

congratulations!!

12 = R

Rafael

 

[drpat]

Nice ambiguous use of negative space... :green:

Sorry I couldn't be of any help, but I glad you got it working!