How to find out obscure mixer PSU transformer max current

I'm in the middle of upgrading a mixer and its PSU, and I got slightly concerned over the fact I've nearly doubled the amount of current draw (opamp upgrades).

I improved the PSU filters and regulation, and I know for a fact it will now handle my needs very well, on paper and in real life. It measures like any good PSU would, even with all the current draw.

But now I have safety concerns over the PSU transformer. It's not putting out smoke, or running red hot, but being a curious git I'd still want to know what it can handle.

It doesn't have specs printed on, or any code string I could google.

Schematic tells me windings are 20-0-20V and 46V. I'm only really interested in the 20-0-20V used to supply 17V rails. It has 1.6A fuses for both the 20VAC secondaries, which is a reasonable indicator.

But how can I find out the max current this transformer is really rated for? I'd like to know if I'm running in the 60-80% use safety zone.

Mike

I've the same need for many projects..
Was thinking about a cheap multi-section rheostat like this one,
then with 2 multimeters you measure the voltage and the amperes, and how hot the transformer become, when you lower the rheostat load.

I wonder if the physical size of the transformer would give a good estimate of its current delivery capabilities, knowing at least the VAC specs of the windings.

Thickness of the wires wound on the transformer can help to give estimations about their raitings.
But I don´t have any tables handy right now.

I assume that the original 1.6A fuses didn't blow, right?
You can measure the actual current draw on each rail, using those fuses holders for instance... If you read, say : 1.5 A, I would say you're in for another upgrade...

Temp of the transformer is also a good indicator of your safety margin...

Axel

some good ideas from prr

http://www.groupdiy.com/index.php?topic=32850.0