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Old 18th February 2009, 07:57 PM   #201
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Quote:
Originally posted by AndrewT



this is not right.
The bulb must be off when both switches are off.
The bulb must not flash, not even briefly nor dimly, when the ON switch is pressed and there is no load.

The bulb must go out, if it is already glowing or lit, when the bypass switch is pressed.

A big load would be a kettle, fan heater, iron, toaster etc.
Sorry Andrew I am an idiot (I can see you nodding your head!) It must be the late nights

I am using these switches because it was all I could get at the time.

http://www.maplin.co.uk/module.aspx?moduleno=34858

1. The bulb does not light when when the switches are pressed

2. No load - Nothing connected to the IEC plug=Light does not flash.
It doesn't flash when I have the transformer and bridge rectifier connected.

3. Ive just plugged in my coffee machine and the light glows brightly and turns off when I press the bypass button.

The light bulb tester must be fine
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Old 18th February 2009, 08:04 PM   #202
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Quote:
Originally posted by audio1st
I hope this shows it better..

Thanks Barry

I will check this now and report back
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Old 18th February 2009, 09:00 PM   #203
AndrewT is offline AndrewT  Scotland
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the light bulb tester does not need any switches.
A basic tester is just a plug top to connect to the mains.
A bulb holder.
A socket outlet to send power to your project.

The switches are add ons for those that want to do further experimentation and be able to conveniently switch off.
We have switched wall socket outlets, or we can just pull the plug.
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Old 18th February 2009, 09:28 PM   #204
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Quote:
Originally posted by AndrewT
the light bulb tester does not need any switches.
A basic tester is just a plug top to connect to the mains.
A bulb holder.
A socket outlet to send power to your project.

The switches are add ons for those that want to do further experimentation and be able to conveniently switch off.
We have switched wall socket outlets, or we can just pull the plug.

Progress!!!


I cut the various tracks and added links as Barry suggested and I now get a 24-25v output. (Thanks )

The bulb tester has come to my aid already, when I applied the power the bulb dimly glowed and it appears 'R2' 0.25w 130R resistor was over heating.

Click the image to open in full size.

Should I change this for a 0.6w resistor or is it something more sinister?
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Old 18th February 2009, 09:40 PM   #205
AndrewT is offline AndrewT  Scotland
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R2 should only be passing a few mA.
It should run near cold. Id=8mA gives about 8mW of dissipation.
Check the voltage across R2.
Check the voltage across the Zener. Check the voltage Vds across the FET.
These should add up to the supply voltage. I suspect that either the Zener is back to front and/or the FET is damaged.
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Old 18th February 2009, 09:43 PM   #206
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I think you have shorted the legs on the J309.
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Old 18th February 2009, 09:48 PM   #207
mjf is offline mjf  Austria
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hello.
what's the matter with r1(pos. rail),is it overheated too?
i think 0,25 w is too small.........
you can measure the voltage drop across r2,square it and divide it by 130 that gives you the power (probably around 0,3watt).
try 0,6w or more.
greetings.............
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Old 18th February 2009, 09:55 PM   #208
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The voltage is decreasing on the output if I hold the 'on button'

R2 has the same voltage as output and the J309 has a reading of less than a volt.

Is the voltage decreasing because the resistor is getting hotter?
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Old 18th February 2009, 10:00 PM   #209
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Check these tracks are not touching adjacent tracks..
Attached Images
File Type: jpg pcbbottom2.jpg (95.5 KB, 649 views)
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Old 18th February 2009, 10:08 PM   #210
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by mjf
you can measure the voltage drop across r2,square it and divide it by 130 that gives you the power (probably around 0,3watt).
mjf.
to get 300mW dissipation in R2 it must pass 48mA.
0.048^2 * 130 = 0.2995W and that would develop a Vgs of -6.24V.

How would you get 48mA through the series combination of Zener 24V + jFET + 130r?
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