Hello everyone, I bought an electric machine to make some repairs smarthphone, but it is blocked at 28.6V and can increase to 50v

The problem is that I need a minimal voltage for telephone repairs, between 0 and 28V, how can I do this?

here are 2 photos to illustrate the problem, thanks for your help.

 

Welcome to AAC!

It appears that your power supply isn't working. Have you measured the output voltage to verify that it agrees with what's displayed?

Was it purchased new?

 

That model power supply P-3005D I thought has a maximum output of 30V 5A. Did you buy this new?
I would measure the output, check if the panel meter is just reading wrong.

 

but it is blocked

What do you mean by "blocked"? Do you mean that the output voltage cannot be adjusted below 28 V? If so, are both the coarse and fine adjustments turned all the way to the left?

Manufacturer / product web page / user manual / model number - ? Also, photo of the inside of the supply.

ak

 

Thank you for your reactivity, the output voltage is equal to the one displayed on the screen.

Yes, the power supply is new.

The knobs are turned all the way to the left, so it doesn't go below 28v.

Brand Sunshine model P-3005D

Michael

 

Yes, the power supply is new.

Return it for a replacement. Hopefully you opening the case didn't void any warranty.

 

Return it for a replacement. Hopefully you opening the case didn't void any warranty.

I have no warranty on it, which is precisely why I'm trying to solve the problem.

 

Hello,

It could be a broken wire or potmeter.
When the bottom wire or connection is open, the pometer can not work.

Bertus

 

@Michael476
Have you tried turning the pots fully clockwise?
Please keep us posted (Updated).
Good luck............

 

Don't turn all the knobs counter-clockwise.
Set all knobs to mid-range.
You ought to see 0 on the CURRENT readout and somewhere around 15V on the VOLTAGE readout.
If you cannot control the VOLTAGE then the PSU is busted.

If you take photos of the top and bottom side of the control board I might be able to find the schematics.

 

Try putting a small load (10K resistor) on the output.

 

Well, it clearly is a linear supply (not all of them are). If you had a schematic, we could work through this pretty quickly. The open pot connection is a good suggestion. It is suggestive of something that there still is adjustability in the obviously wrong output.

What is the output voltage range spec?

ak

 

What is the output voltage range spec?

The Sunshine P3005D is an adjustable 0 to 31 volt, 5amp supply with a 220vac input.
Post #1 shows a 50 volt output in the first photo. Maybe the output transistor(s) is shorted.

 

The Sunshine P3005D is an adjustable 0 to 31 volt, 5amp supply with a 220vac input.
Post #1 shows a 50 volt output in the first photo. Maybe the output transistor(s) is shorted.

I am thinking the voltage feedback network is broken, that is why I suggested a small resistor, which might change things if I am right.

 

Service manual here...

https://elektrotanya.com/hy_3005_dc_power_supply.jpeg/download.html#dl

 

@Michael476 , Update please.

 

Hello everyone, I bought an electric machine to make some repairs smarthphone, but it is blocked at 28.6V and can increase to 50v

The problem is that I need a minimal voltage for telephone repairs, between 0 and 28V, how can I do this?

here are 2 photos to illustrate the problem, thanks for your help.

A power supply like this is designed for a load. It will not give you a valid voltage reading without an actual load within it's engineering spec. Put a load on it, and see what it reads.

 

A power supply like this is designed for a load. It will not give you a valid voltage reading without an actual load within it's engineering spec.

Why do you think that? Which portion of the schematic, or what aspect of the circuit topology, needs a minimum load?

ak