Adjusting Linear Power Supply?

[Intenso]

Well I guess I should have known better but I took a punt on the following LPS from Chinese ebayer;

http://www.ebay.co.uk/itm/111328891082?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

I specified 5v and 15v to use with my SBT and Beresford DAC and have today received a LPS that outputs 12v and 10v.

Would this be adjustable in anyway or have I been sold a Pup :)

[Puffin]

A schematic of the circuit would be helpful, but it may be that there is one 7810 and a 7812 regulator in the supply. There are two regs shown in the pics (one for each output I presume) These could be changed for regs giving the power output you require so long as the transformer secondaries, after rectification would support that voltage. I suspect that as the ebay page shows multiple voltages available that the transformers are probably the same for each application and the supply is regulated by the voltage regs. If they sent the wrong one, tell them and they should send you the correct voltage unit.

[struth]

there are 2 grey little boxes with gold screws. the screws are the adjusters.

[Ali Tait]

If you look at the picture, next to the small green capacitors, there is a grey/green box with a small screw on the bottom corner. These are variable resistors which are adjusted to give the required output voltage. You need a multimeter and a small screwdriver. Measure the DC output whilst turning the screw on each until you have the desired output voltage.

[Ali Tait]

Also, I would check with Stan that 1A is ample to run the dac.

EDIT- just checked, should be fine.

[Puffin]

there are 2 grey little boxes with gold screws. the screws are the adjusters.

Should've gone to Specsavers.......:rolleyes:

[Intenso]

Thanks Guys,

I managed to adjust the 12v side up to 14.9v which is the closest I could get without shooting up to 15.2v.

The other side would not reduce below 10.7 but would go higher.

Here's a pic of the supply.

I'm not tech but I suspect that the right side is not the right transformer?

[Arkless Electronics]

It won't work as there will be different mains transformers for the widely differing output voltages. You'll need to send it back.

[Ali Tait]

They may send you the right trannie if you ask, quicker than sending yours back then waiting for the other to come.

[Intenso]

Well its working fine on the 15v side.

Might be a blessing on the 5v side.

Probably would have fried my SBT!

[Theadmans]

I have the same supply as you with 15v and 5v.

Mine arrive as specified but does occasionally drift so I leave the top allen keys undone so I can adjust more easily.

BTW my left display (when looked at from the front) is 15.0v (to one decimal place). I can always get it to 15.0v with a little patience.

..and the right display is 5.00v (to two decimal places). This tends to drift more because of the greater accuracy needed for 2 decimal places.

BTW don't feel embarrassed about not seeing the adjustment screws. My 50 year old eyes did not spot them either. I sent a photograph to Stan for help. When I viewed the photo lit up brilliantly by the flash it was more obvious though.

Also as the voltage cockup was down to the seller. I would say there is a good case for them letting you keep the existing power supply and sending you another. That way you can use the existing one for now on the SEG only whilst waiting for the replacement. Once the new one arrives you can then keep the wrong voltage one as a spare or use it to power other stuff.

[Intenso]

Hi Adam

Is your 5v transformer the same as my one in the pic.

Mine wont go below 10.7v?

[Arkless Electronics]

It won't... and if it did it would overheat big time.

[Theadmans]

Ok the green transformer on my PSU on the right is Part M15-01B. I assume this is the one giving me 5v as it is behind the 5.00v LED. I cannot see the part number on yours in the photo as it is obscured by the wiring. However, the output voltages look the same as mine. Is yours M15-01B?

The other transformer on the left I have part number M15-04 whereas you have M15-03. Here my output voltages are listed as 15v/7.5va whereas yours are 12v/7.5va.

Are you trying to get 5v on the left or the right LED? My 5v is on the right LED.

[Intenso]

Yes the one on the right is the M15-01B but doesn't seem to want to drop voltage below 10.7.

The supplied lead also doesn't fit the SBT, not that I would connect it to this anyway.

You right the one on the left is meant to be for 12v unlike yours and not what I asked for.

Despite this it is sitting stable at 14.9v without a stutter.

I've emailed the seller, so will see what they say.

[Arkless Electronics]

Ok the green transformer on my PSU on the right is Part M15-01B. I assume this is the one giving me 5v as it is behind the 5.00v LED. I cannot see the part number on yours in the photo as it is obscured by the wiring. However, the output voltages look the same as mine. Is yours M15-01B?

The other transformer on the left I have part number M15-04 whereas you have M15-03. Here my output voltages are listed as 15v/7.5va whereas yours are 12v/7.5va.

Are you trying to get 5v on the left or the right LED? My 5v is on the right LED.

For 5V you will need the 7.5V transformer and will also need to locate a fixed resister coming from the "Adj" (adjust) pin on the regulator to the trimmer pot and reduce it by approx x 3 in value. Doing just the latter will enable you to set it to 5V but it will overheat like a twat.... and the transformer probably won't last long...