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Dead FARNELL LS 30-10 Power Supply

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dkn

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Hi.

I am searching for a person who has one of theese variable power supplies.

**broken link removed**

Mine has been dead for a long time due to some highvoltage backfire.
But it would be so nice if it could be repaired.

Problem is that a resistor at R13 is blown and I am not able to read its color code.
Further more the reason to why is blew was a to large fuse mounted, so when i finally find this resistor, I need to find the actual reason for the shorting.

**broken link removed**

Could very well be the component located at the heatsink, but I have not been able to find a datasheet, and the blown resistor has erased some part of the name.


Hope someone could be helpsome and open their psu, and maybe take a pic of this area.

Thank you for your time.

Regards
Dennis[/img]
 

I find Farnell are very helpful. Try contacting them to see if you can get the manual or if they can tell you who actually manufactured it.

Brian.
 

Hi.

Thanks for the reply. I have sent a message to Farnell, I hope they will be helpfull ofcause, but I have my doubts.

So if anyone has this powersupply, I would be really happy if you could take a picture of the area mentioned before.

Thanks
 

Hi,
Can you tell pls what kind of a regulator is on the side?
Hopfely is it only a typical (application) circuit & you can become a resistor value...
Otherwise is it possible, taht you trys "reengineering" & takes/drows a schema from your PCB?
K.
 

    D

    dkn

    Points: 2
    Helpful Answer Positive Rating
I have taken a couple more photos to get a better overview.

**broken link removed**
**broken link removed**
**broken link removed**
**broken link removed**

As it looks to me, this is the source of the actual voltage to be outputted. There is a smaller transformer right behind the net connector, and it goes to the usual 7805 and 7812, so that must be for the control print. I suppose this part have not been damaged.

So it must be some kind of switchmode mosfet located at the heatsink, and the resistor that is blown, could be the shunt resistor used to meassure ampere usage i guess. It was raised a lot above the print, and must have been a 5 or 10 w. So maybe the resistor is not so hard to figure again, properly a low value like 0.1ohm. That means i could try low values until the ampera display show correct. ( if its the right guess of its use ofcause... )
But why it should be located at highvoltage side seems a little odd maybe...

Well brings me back to the mosfet looking guy at the heatsink, but there i need a datasheet before making a replace.

Thanks again for trying to help me out here.

//Dennis
 

Hi, I too have this sort of Power Supply (Slightly Faulty). Mines actually badged and made by Wayne Kerr. From your photographs I would say it's Identical.

The Resistor (R13) is 1R0 and looks like a Carbon Resistor, which by it's dimensions would make it 1W. However Metal film resistors of the same dimensions are 2W.

The Transistor you refer to (Q2) on my unit is a Texas Instruments TIPL762A, which is a NPN Silicone Power Transistor. For some reason I couldn't find any data on this on TI's website, however data is available at **broken link removed** for the Bourns device.

By the way the resistor is on the Mains side of the Switch Mode and has nothing to do with current sensing for the front panel meter.

I remember the user manual for this unit included a schematic and full parts list. Unfortunately I've lost mine and Wayne Kerr wanted to charge me £60.00.

Chris
 

    D

    dkn

    Points: 2
    Helpful Answer Positive Rating
Hi dkn,
Im sorry, at home I can not open your host w. the photos... Here is a datasheet of the TIPL762:
https://pdf1.alldatasheet.com/datasheet-pdf/view/20180/POINN/TIPL762A.html
As I can see it from chris photo; the resistor must be a Philips type!:)
It existed between 1...3W, you must tell the measures from it...Maybe D=3xca. L=10-11mm.
K.

Added after 2 minutes:

@ ChrisGn,

Maybe you can us give knowed the Wayne Kerr Typ Nr. pls?
Tnx!
K.
 

Hi,

The resistor is about 16mm long by 5.5mm Dia.

The Wayne Kerr model number on the front panel is identical to the Farnell one, ie LS30-10. In fact the only difference with the front panel is that Farnell is printed instead of Wayne Kerr. There is a Model number on the back panel just above the serial number. This is 11LS3010.

If anyone does get the cct diagrams for this then let me know. The problem I've got with mine is that when I press the Output power button the unit goes into current limit for a few seconds, ie, a far too slow rise time, and I don't fancy reverse engineering that part of the circuit.

Chris
 

Hi,

Impressive with all the help, very kind of you all : )

I soldered off the power transistor and tried to turn it on, and then there comes light in the display and fuses stop blowing. So I think there is a good possibility that its the faulty component.

I have been looking around for a replacement, can't find the exact same. And im very surprised that RS has such a limited selection.

I have found this elsewhere:
http://www.datasheetcatalog.org/datasheet/philips/BUT12.pdf

Should that not be good enough? Ofcause not same package, but thats properly the least problem.

//Dennis
 

Hallo,
Maybe not, becouse nobody knows how muchcurrent must swit the transistor & with what a frequency?
The TIPL has ca. double so much peak current & (maybe is more relevant) ca, 10x shorter switch & edge + storage times...
I think; you can take a risk & change the transistor to BUT12:)
Hopfely will be the original heatsink enough?...
Did you checked for TIPL by ...Mouser.com & ...//octopart.com too?
K.
Octopart brings two distis for the original Transistor!:):
**broken link removed**
 

Hi,

Got a TIPL762A from a local store and replaced it.
And its working again now! So I am super happy, you don't now what you got until you lose it : D

ChrisGn and karesz can't thank you enough for your help!

//Dennis
 

Hali dkn,
:)
You are welcome, but "to end" you are on the solder iron:)!
Because you have a new 1 Ohm/2-3W; did you checked the current limit function too pls?
Yet I remember, these is in primary part, maybe for "in-rush" current limiting...
Be happy w. it!

Hi ChrisGn,
What is your "Slightly Faulty" problem pls. with your Wayn Kerr?
K.
 

Hi dkn, Glad you got it going...

karesz,

The Slightly Faulty problem my PSU is suffering from is that on pressing the Output power button, the PSU's current limit kicks in for a few seconds causing the output voltage to rise far too slow. It does this under no load conditions.
As you can imaging this causes problems when I'm testing something that has an R/C power on reset cct. What I'm having to do is to connect what ever it is I'm testing after I've turned on the PSU's output.

It's almost as if there's a ruddy great big capacitor connected across its output.

And before you ask, the voltage sense inputs are strapped to the outputs properly.

I must admit the PSU's been behaving like this for a few years now and I've got used to this quirk. I just keep searching the net occasionally to see if I can find a cct diagram, then maybe I'll get round to mending it, as it's not really top of my priority list.

Chris
 

Current limit seems to work fine and be accurate enough.

ChrisGn -> Are you sure that there is a problem with your psu?
Mine is also slow a rising, especially when cl is under 1 amp, it takes a few sec.
I think its just meant to be this way, unless you remember your unit to function different?
Maybe its just a very gentle power supply : D

//Dennis
 

Dennis,

Maybe your right, the Voltage rise never was fantastic when the CL was set low and I am being a bit finicky. It's just that I remember testing a load of uP based boards when the PSU was new, and had no problem with the uP's R/C reset circuit. If I test the same board(s) now the reset often doesn't work properly. Maybe it was marginal then, and it's component ageing (something we forget about) on either the PSU the uP boards or both. Most likely though it's my brain that's ageing and I was testing then with a far higher CL than I should have been!

Anyway, the PSU works for what I need it for, so I won't be spending any time on trying to fix a fault that maybe isn't there.

Chris
 

Hi Chris,
ChrisGn said:
...I won't be spending any time on trying to fix a fault that maybe isn't there.Chris
Click to expand...
We have all the problem with time:-(...
In all case_a rising of much seconds as you wrote it: I believe is not very good to use & is not a reklam for vendor Farnall/Wayn Kerr...
A problem is of course to find some circuits over them.
K.
 

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