Hello
I have a tech 21 trademark 60 with a broken power transformer. Does anyone knows the transformer characteristics?
I have to replace it but i can´t find any schematic...
Thanks
First of all: why do you think the power transformer is broken?
Not impossible, but quite unusual.
Post a link for your exact amp model.
What´s the amp power rating (watts/ohms)?
Does it have a chip amp? Which one?
Post a sketch showing the transformer wires , colors, etc.
A sharp clean gut picture showing the transformer usually helps.
Good luck.
PS: você é Brasileiro?
Ou Lusitano?
I know of a Trademark 60 with a blown Transformer.
I don't remember exact details,,, but obviously an issue with them.
They use the LM3886 poweramp chip.
I do know that in *Australia* some imported gear uses power transformers that are not made to the correct specs and this can cause failures.
Not sure of details but something about,, wound for 220 VAC instead of 240 VAC.
Phil.
Hey you all
Thanks for the reply's
The power amp chip is the LM 3876
I took of the transformer socket from the board (so it has nothing connected to it) and, when connecting the amp mains, the fuse blew off. So, i believe that it might be the power transformer.
The transformer primary winding has about 2kOhm and the secondary has about 1.6 Ohm (about .8 Ohm in each tap) I think is a bit low...
I´ve attached a photo.
Hey sim sou de Portugal
Cheers
Yes, *if* you pull all a transformer´s external connections , leaving only the primary on, and it still blows fuses, confirmed , the transformer is damaged.
We can estimate its specs:
it seems to have only 4 secondary wires, (the white ones), yet the connector has only 3 pins, so it probably has 2 secondaries, wired in series, with the common point (2 white wires soldered together) being connected to ground.
Your picture shows 4 wires and the connector but *how* they reach it is invisible, please confirm.
The amp specifies (optimistically) 60W into 8 ohms, which require +/- 35V DC power rails, which need 2x24V AC secondaries, and at leat a 90VA transformer (100 to 150VA preferred), so now you can shop for a replacement.
Buy another LM3876 (or 3886) because it´s probably burnt/shorted and also check the power supply rectifiers and filter caps, because *something* burnt that transformer.
Good luck.
EDIT: the transformer diameter and thickness will let you pick a suitable replacement from a catalog.
Not smaller (weak) not much larger (won´t fit).
I would suggest this transformer:
http://www.antekinc.com/details.php?p=607
I really don't think you can find better prices anywhere. I've bought a couple of transformers from Antek and they are great. All of the mounting hardware is included too. Just double check the size but it will probably fit. (Here's the PDF spec sheet with dimensions http://www.antekinc.com/pdf/AN-1224.pdf )
-Matt