A very basic question about transformers and schematics.

Dave Lowther

Joined Sep 8, 2016
140
What is the question. I'm guessing it might be one of:
- Would this transformer be suitable?
- How would I use this transformer to build a suitable power supply?
- Can I reuse other parts of the Pioneer amp, in addition to the transformer, to make a power supply?
- Something else
Edit added: Does the transformer have any markings to indicate VA of the outputs?
 
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Thread Starter

Surtsey

Joined May 8, 2022
4
What is the question. I'm guessing it might be one of:
- Would this transformer be suitable?
- How would I use this transformer to build a suitable power supply?
- Can I reuse other parts of the Pioneer amp, in addition to the transformer, to make a power supply?
- Something else
Edit added: Does the transformer have any markings to indicate VA of the outputs?
The question is: what are the outputs on the transformer. I assume from the labels some are 12v and some are 9v but what are the others?
 

BobTPH

Joined Jun 5, 2013
4,897
The CT are center taps for the respective output.

The BAC is s bit puzzling. Tube amplifiers sometimes called the high voltage supply B+, is this a tube amp?

Bob
 

Thread Starter

Surtsey

Joined May 8, 2022
4
The CT are center taps for the respective output.

The BAC is s bit puzzling. Tube amplifiers sometimes called the high voltage supply B+, is this a tube amp?

Bob
Thanks Bob. No, it's not a tube amp. It's 30w+30w+43w 2.1 transistor amp. But I believe you've set in on the right path.
 
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BobTPH

Joined Jun 5, 2013
4,897
Okay, I am going to guess that it is a higher voltage used for a bipolar supply for the output stage. Connect the primary (carefully) and measure the BAC1 and BAC2 to BCT to see what voltages it might be. For 43W into 8 ohms, you need a bit more than ±19V, so I suspect it is in that range.

Bob
 

MrChips

Joined Oct 2, 2009
26,088
What you have is a power transformer with three separate secondary outputs.

The first thing you need to determine is that the transformer is designed to accept the AC Line voltage in your country (230VAC for UK).

The three outputs are:

Terminals 1 & 2 = 12VAC
Terminals 3, 4, 5 = BAC with centre-tap
Terminals 6, 7, 8 = 9VAC with centre-tap

What we do not know at this point is the current capabilities of each output.
I am going to guess that the BAC output is the high voltage and high current output which is what you seek for a power amplifier.

For a first analysis, apply AC line power to the primaries and measure the unloaded AC voltages at the secondaries with a DMM set to measure AC voltages in the 0-700VAC range.

Measure between the terminals:
1 & 2
3 & 5
6 & 8
 

eetech00

Joined Jun 8, 2013
3,149
Suggestion.....

Make the measurements as descibed in post #7.
However, you don't need to use mains voltage to check the secondaries.
You can use the turns ratio to determine a close approximation of the secondary voltages.
Then, use a signal generator (or variac) to apply the required primary input voltage, and measure the voltage across each secondary windings.

Example:
Vpri=120
Vsec=9
Turns Ratio = Vpri/Vsec = 120/9 = 13.33/1

So...

Vin_pri is 13.33 VAC (RMS)
Vout_sec is 1VAC (RMS)

Use this same method to check the other secondary voltages
 
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