Golborne Vintage Radio

I have acquired a 650VA transformer that previously lived in a slot arcade machine that was stripped for spares and scrap. As it is potted it was offered for free on another forum due to this lowering the scrap value. The windings are just marked with voltages and nothing else.
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The testing it a little bit technical as you have to load up the windings with an entire army of dummy loads and do some ohms law.


The trick is to load each winding while monitoring the voltage until it falls from the open circuit voltage to about half way down to the marked loaded voltage remembering that these will drop a little bit when the more powerful windings are loaded.

In this example I started with the biggest dummy load I had on the 11 volt winding as it read so low with a DMM that there was no chance of getting anything useful from the DC resistance.
I had to load this with 2 ohms to get it down from 12.7V to 11.7V.
This must be something like 110VA.
The 9.5V winding came in at about 2A so that is 19VA.
The 7V winding came in at about 3A so that is 21VA.
The 40 volt winding came in at about 6.25A with a nice toasty dummy load at 250VA.
The 50 volt winding rolled in at 5A with another toasty dummy load at another 250VA.

The totaling based on the size and weight of the transformer is:-
11V 110VA plus 9.5V 19VA plus 7V 21VA
We now have 150VA
Add the two powerful windings at 250VA each and we have a reasonable estimate of the individual ratings of all the windings on this 650VA lump.

Impressive testing Refugee (as usual ).

Hopefully I'm never going to come across anything like that. Well outside my range for 30's radios.

Good stuff though !

Gary

I expect for the greater majority of forum members they intuit the procedure you are adopting Refugee. For the likes of me (i.e. a bit slow on the uptake ) if you get the time could you provide a step-by-step guide and provide a description of the testing board with the various loads on it too? It would be most helpful.
Many thanks.
Nick.

A splendid Beast!
Why does it say 'Very dead' on it? Was that for the whole unit?

Alan

The big dropper section is four ohms and is rated at several amps continuous.
The panels have banks of 47 ohm 10 and 25W resistors.
I also have big 10 ohm and 25 ohm droppers.
DC resistance gives a clue as to the currant capacity of the winding and loading it until the voltage drops by 5% gives a more accurate clue.
Ohms law gives the actual figure.
Very dead means that it was salvaged from a dead power supply chassis. I was told that there was an SMPSU downstream of it that had a bad reputation for blowing up leaving a good transformer.
The biggest dropper is a serious bit of kit and is used for windings rated at 10 amps or so.

Makes my HT one look pretty tin-pot
I'll have to set to an Bigger one.

Alan

I call it mu "purging" resistor if there is talk of audiofoolery in the air.
The five sided former makes the bad electrons go round the corners and they don't like that so they leave the amplifier.
It can be used to soak test big amplifiers.

Mm. Real heavyweight stuff. I think I'll be sticking with my 'wee testers'. Well for the time being at least
Nick