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# Help with bridge rectifier

#### INJAC

Feb 1, 2017
20
Triple checked everything none restistance except 8-9 which gives as i previously said 1.6Ohm, others all say resistance infinite :/

#### tracy244

Jul 21, 2017
1
Hello, im using a transformer from an old Hi Fi and i want to build a new one, so this part is related to the power supply. Im a bit confused about the transformer since i cant find its datasheet there is nothing written on it, but i found the service manula from the hi fi and found how it was connected, if it helps. So my idea is to make +21 and -21 V, which i managed, i also want to use the 6 V and 8 V from the transformer, in order to get steady 9V DC from the 6V (with capacitors, voltage regulators etc) and get 12 V nad - 12 V (i dont know if its possible). So here is my circuit how i started it. Im confused how to make the bridge rectifiers after i did the 21V and - 21V, since the ground wont be the same? Thank you in advance

can't understand your questions,too complicated.

#### davenn

Moderator
Sep 5, 2009
14,297
can't understand your questions,too complicated.

#### kellys_eye

Jun 25, 2010
6,514
OK, if 8/9 is only 3.5VAC you could still use it if you used a voltage multiplier stage for rectification to bring the output up to around 9V (so a three-stage multiplier would be required) which could then be applied to the 5V regulator.
Another way would be to bridge-rectify the 3.5VAC (you'll end up with approximately 5V DC anyway) but feed it to a cheap buck/boost converter for a more stable 5V output. Such modules are available for a couple of \$.

If your 5V requirement is not for anything critical - i.e. just to drive some LED's etc then its stability isn't much of an issue. Just 'knock up' the simple rectifying/smoothing circuit and test! The 5V requirement for the Bluetooth module has a +/-10% tolerance (IIRC) so would work on anything from 4.5V to 5.5V anyway.....

#### INJAC

Feb 1, 2017
20
Yes i will do that, ill go today and buy components, for the rectifier and for the preamp, amp, will test all. Thank you very much

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