Gainclone power supply transformer - Help!

[DJ Exprice]

The "BEEP"( which is really a short tester function ) for around 100 to 0 ohms measurer on my multimeter is what I used. I can go back and measure in actual precise ohms, if that means anything.

The secondaries were all "Beeping" as well.

I have a RadioShack digital multimeter with a good fuse. The "BEEEEEEP"


This could be because it is a big coil on the inside . I could always set up a test circuit with a fuse...hmm...not a bad idea

[AndrewT]

Hi,
the "beep" confirms continuity.
set your meter to lowest ohms scale (200r?)
measure each of the windings.
Those that are supposed to be the same should measure the same.

The primaries are likely to measure about 2r to 10r.
The secondaries will be less than 1r.

Did I say something about a light bulb four posts ago? DO IT!

[DJ Exprice]

How the heck do I use the light bulb? How do I need to set it up?

Whats 2r to 10r? 2 Ohms to 10 Ohms?

[AndrewT]

Hi,
I have described the series mains light bulb a few times. Here's one http://www.diyaudio.com/forums/showt...574#post927574

You can adjust it to suit different projects, low power bulb for low power projects, high power bulb etc.

Keep for every new mains powered project for first time start up and also when you carry out any maintenance. It can sometimes allow a failed project to start up for measuring & debugging.

It's main purpose is to stop you injuring yourself at switch on.

[DJ Exprice]

So if the light flashes and then dims, huh?
Wouldn't it stay on full no matter what? The transformer would have enough current to let the lightbulb be on full all the time, like ac wiring anywhere would...right? I'll try this idea.

This is what you mean, right?

[cpemma]

Originally posted by DJ Exprice
So if the light flashes and then dims, huh?
Wouldn't it stay on full no matter what? The transformer would have enough current to let the lightbulb be on full all the time, like ac wiring anywhere would...right? I'll try this idea.

This is what you mean, right?

No, the light bulb should be in series with the transformer primary winding, you're showing a parallel connection. This is series:

L----------Bulb----------+
                         |    
                    Transformer
                     Primary
                         |
N------------------------+

[jaycee]

The reasoning behind the series lightbulb trick is this. With no load your transformer will draw a little current, not enough to light the bulb so the circuit works as if the bulb isnt there.

If there was a fault in the transformer windings that caused it to draw a large current, the bulb would light brightly, which a) warns you something is wrong and b) limits the current to minimise damage.

As this is a transformer sourced from a junk pile, i'd strongly recommend you power it up this way!

24VDC rails is fine for a gainclone. This will give you about 30W into 8 ohms which is plenty for domestic listening.

[DJ Exprice]

I get it now! Yay! I'll have to test this transformer to see if it's good!

Thanks for clearing that up for me