Transformer Ratio Meter

[AlanBeckett]

As an old Salesman said to me 'In the end someone has to put their Knob on the Block'
Go for it.

Alan

[SurreyNick]

As an old Salesman said to me 'In the end someone has to put their Knob on the Block'
Go for it.

Alan

As I said somewhere else - you're crazy, just plain crazy Alan, ha, ha.

[John M0GLN]

I've always found labels for panels a bit of a pain, even when printed off from a labelling machine its getting them on square and spaced evenly, what I have done and it looks quite good but unfortunately takes a bit of extra work is to draw, in your case the complete set of legends etc and print them out on one piece of paper cut to size, then make a matching cover from say 1.5mm clear acrylic, cut holes in both the paper and acrylic to match your panel and then they can be assembled using the various switches, sockets etc to sandwich them all together.
It does need access to a CAD program and a bit of care cutting and drilling the acrylic but it looks OK and with the CAD program you have a wide choice of fonts, colours etc.


John

[Radio Fixer]

It may look OK on a piece of test gear but don't do it on a radio. Even dials made that way don't look good as you can see where they aren't sandwiched properly and other optical effects.

Decals are pretty easy to put on straight and square as you have more time than peel off. Just need a good ruler, square and the critical eye.

Gary

[SurreyNick]

Mmm. It doesn't work....

I don't know if I've wired the power transformer incorrectly, or if it is duff.

I've attached a pic and wonder if you could give me your thoughts?

I have the incoming mains neutral connected to the SCN pin and the incoming mains live (via an spst switch and fuse) to the 250V pin. No connection to the 0V pin on this side. I have the circuit of the ratio meter fed from the transformer side marked OUTPUT. The thing is I have continuity on the output side pins, but only on the input side pins between 0V and 250V. There is no continuity between the SCN and 250V pins and also not SCN and 0V pins.

This is the first time I have wired a power transformer so have no experience to draw upon. I am assuming therefore that I either should have wired the incoming mains neutral to the 0V pin rather than the SCN pin, or that the transformer is dud. Any thoughts?

Thanks

Nick

[Refugee]

You have the transformer wired incorrectly.
It is 0V to neutral and live to 250V.
SCN can either be left open circuit or better connected to earth. It is a noise screen between the windings and will make little difference in the equipment you are building at the moment.

[pwdrive]

The neutral should connect to the 0 volts tag on the primary, the scrn (screen) should be connected to mains earth.

Lawrence. EDIT: Whoops, crossed with ref's post.

[SurreyNick]

Ooops!

That's better. It works now

Just the calibration to do and it's job finished.

Thanks

Nick

[SurreyNick]

Well here it is, finished, and I used it today for the first time.

I have quite a few 1920s/1930s AF transformers where the model number is no longer legible and from this pile I picked out an old Ferranti Output transformer, one of the OPM range from the early 1930s. I set the Ratio Meter on the 0-10v range and as can be seen in picture four below it gave a perfect 10:1, from which I can deduce it is the OPM5.

Very quick, very easy. Just my cup of tea

My thanks to all of you for the help and advice along the way, especially to Hugh.

Next project?..... mmm, I think it'll be a simple, triode valve curve plotter.

Nick.

[pwdrive]

Good result Nick.

Not a 'scope plotter for triode's but an idea for something else:

http://www.r-type.org/articles/art-118.htm

Lawrence.