[EDIT] I have built a PSU - and now TOO much volts

This is my first build
Bo Hansens 48v Phantom PSU...
The bottom one on this diagram..
http://w1.316.telia.com/~u31617586/#48%20volts%20phantom%20power%20supply
Can anybody give me any pointers...
SOrry no diagrams of my PCB - nothing to write on or load them

This is what I have done...
Created a PCB and installed all the components...
Got an male IEC inlet put a 250ma slo blow fuse it in and crimped some spades onto some wire and attached them to the live neutral and earth terminals of the IEC inlet
Put the other ends of the earth wire to the 0V out (I haven't built my box yet - in the end this will go to a chassis lug)
Put the neutral and live wires into the PCB and attached them to a transformer
The transformer is a 120-0 120-0 on the input and a 24-0 24-0 on the output
Following Mark Burnleys diagram of how to wire up a transformer..
On the PCB I made the folowing tracks...
Attached the neutral wire to the last 0 of the primary trafo - the live to the first 120v - then connected the middle 0 and 120 together

On the Secondary I connected the middle 24 to the middle 0 and took a feed from the last 0 to one of the ~ terminals on the bridge rectider
I took a feed from the first 24 and fed it to the other ~ terminal of the bridge rectifier

I also slightly changed the circuit by adding a 10k (actually measures 8.89k resistor from from the 48v rail to 0v - as the last section of the circuit) and then added a blue LED

Plugged a kettle lead I had from the garage (that came with some audio equipment) - it has a 5 amp fuse

Got out a cheap digital multimeter and started to gingerly use the probes..

Basically I am getting about 0.4-0.6 volts on the multimeter (I put the black probe to the 0V line) and poked around with the red probe
I am not at my bench at the moment so I am doing this from memory

So I took the red probe by itself and tried the IEC live out - only 0.6v
(is this safe - should I put the black on the earth terminal of the IEC?)

THinking his was weird i Them took the probe and stuffed it in the kettle lead female live socket - still 0.6v
(was this dangerous??)
FLumuxed I tried an analogue multimeter - same thing...
I then maybe stupidly maybe not - stock the red probe into the actually wall socket live terminal - fultuates btewen 215 and 230v...

Is the kettle lead knackered?
Or what do I do next - am I testing right

BTW - the LED didn;t come on - but when tested with a multimeter it was fine (it shone blue)
the
Other diodes beeped when tested
DOn;t know what do do next - apart from change the kettle lead...

Its hard to imagine whats going on from just words...but I would check how you transformer is wired first.

make sure your getting 48V AC out of the secondary of the transformer before you go any further.

..and be sure to set your meter to AC or DC respectively. You could simply ohm the cable in question, if you suspect it's faulty.

Jakob E.

[quote author="gyraf"]..and be sure to set your meter to AC or DC respectively...[/quote]
That was my first thought, too...

Keith

[quote author="uk03878"]
I also slightly changed the circuit by adding a 10k (actually measures 8.89k resistor from from the 48v rail to 0v - as the last section of the circuit) and then added a blue LED

...[/quote]

Simon,
Either 48v > 10K > LED > Ground
Or 48v > LED > 10K > Ground
Not 48v > Ground and an LED somewhere..!!

Also make sure you have ground connected from the board to IEC ground.

peter

[quote author="peter purpose"][quote author="uk03878"]
I also slightly changed the circuit by adding a 10k (actually measures 8.89k resistor from from the 48v rail to 0v - as the last section of the circuit) and then added a blue LED

...[/quote]

Simon,
Either 48v > 10K > LED > Ground
Or 48v > LED > 10K > Ground
Not 48v > Ground and an LED somewhere..!!

Also make sure you have ground connected from the board to IEC ground.

peter[/quote]
Thanks for all your comments....
I did switch between DC and AC on the 2 multimeters
Peter - that made me laugh... I did do..
48v > LED > 10K > Ground
Off tonight to find a new kettle lead

If I read your description correctly, you get 0.6v AC from your power cord (kettle lead). You get no AC to the transformer. Get another cord and try. Sorry if I misunderstood.

[quote author="thomasholley"]If I read your description correctly, you get 0.6v AC from your power cord (kettle lead). You get no AC to the transformer. Get another cord and try. Sorry if I misunderstood.[/quote]
Thats' right.///
Of to check tonite

> Is the kettle lead knackered?

Put it back on the kettle and see if it makes tea!

I would not be surprised if you've shorted the whole mess and blown fuses. (Thank goodness for the UK custom of fused plugs.)

"Put it back on the kettle and see if it makes tea!"
:green:

Unfortunately the kettle has one of those moudled base lead thingies...

Anyway... finally figured out how to use a multimeter
After a weekend of checking and reading internet articles I have a fantastic blue led shining very very brightly
I also did my metal work over the weekend...

I now have a BIG Problem - too much volts..!!!!

On my crappy digital multimeter I am getting some weird volatages

Mains Socket - 290v AC
IEC inlet - 290V AC
Bridge Rectifier - 73v AC and 96.6v DC

Output from circuit - 57.6v DC
Output just before LED diode - 3.6v (I think I was expecting this...)
Output at diode on feedback(??) to the TL783 - 57.6v DC


I assume that the high voltage coming out of circuit is due to the massive AC in coming from my mains sockets
I have checked a coouple of sockets - always late at night though
Surely the voltage doesn't go through the roof late at night???
(it's a 20 year olf rented house.... with a newish fuse box)

Check the battery on your multimeter - I hear some models give weird values when the battery is fading.

I routinely get about 250+ V AC at the wall in the UK (within site of 3 power stations on a clear day!) , but have never seen 290V.

[quote author="uk03878"]On my crappy digital multimeter I am getting some weird volatages

Mains Socket - 290v AC[/quote]
Is your meter one of the nice ones that cost about £2 in a supermarket? If it is, they do not like any kind of abuse. If you overload them slightly they will start to act weird... So if the battery is OK, buy a new meter! Perhaps a £20 model this time :green:

Best regards,

Mikkel C. Simonsen

[quote author="zebra50"]Check the battery on your multimeter - I hear some models give weird values when the battery is fading.

I routinely get about 250+ V AC at the wall in the UK (within site of 3 power stations on a clear day!) , but have never seen 290V.[/quote]
This should be number one thing to do.....
Replaced the batteries....
Everything now fine
238v on the AC
60V AC coming out of the transformer (it is supposed to be 48 v )
80v DC or something like that coming out fo the bridge rectifier
46.8v DC coming out of the end of the circuit (or it could be 48.6v - I forget...)