Delta DPS-250AP-62 Schematics?

[dicky96]

Hi guys does anyone have a schematic for this PSU?

DPS-250AP-62

I have the DPS-250AP schematics from elektrotanya but they are not the same

As far as I can see this PSU (which comes from a Fujitsu TX100 S3 and are not cheap to buy!) has a problem with the standby PSU not running

When powered on via a light bulb it takes a surge of power then drops to nothing.

I have about 285V across B+ and B- going to a TNY777 which I am certain is supposed to be the 3.3V SB PSU - but it isn't running and so the main capacitors take a very long time to discharge to a safe level!

I suspect the main PSU section is probably OK

But before I take it apart to get the PCB out, which gonna be a bit fiddly to do, I was wondering if someone could kindly give me the schematic.

Best regards
Rich

[stj]

Re: Delta DPS-250AP-62 Schematics?

get rid of the rubber around the tny chip so you can see if it;s damaged and replace the 2 caps next to it - the small one starts it up.

[dicky96]

Re: Delta DPS-250AP-62 Schematics?

Sorry - TNY277 not TNY777

[dicky96]

Re: Delta DPS-250AP-62 Schematics?

I cleared off all the rubbery shite. The TNY277 looks OK

I changed both caps - though to be honest the original ones tested fine on my capacitance and ESR meters. Anyway it made no difference.

I had to go do some onsite work so didn't get further but tomorrow I'll check for around 280V on pin (Drain) and see if there is 5.85V on pin 2

There is a funny looking resistor near the TNY277 marked black gold gold which doesn't make sense. It's definitely marked as R801 on the silk screen so it is a resistor for sure. Anyway it's reading about 1M0 in circuit. It's not a start up resistor as the TNY does that internally and I don't know what value it is supposed to be - may that is the problem?

Rich

[R_J]

Re: Delta DPS-250AP-62 Schematics?

It would be nice to know where that resistor connects, It could be from the feedback/run diode going to pin2
Maybe there is another band, IE: brown,black,gold,gold (1Ω)

[dicky96]

Re: Delta DPS-250AP-62 Schematics?

Yeah I'll have a look to see where it is. You can see it clearly in the 2nd pic on #4 next to the wire B+, its black gold gold. There is no space for another band before black

Hmm I wonder if it is supposed to be a fuse inline with B+ 280V because it's right next to that.

But I never saw one look like that before if it is

[dicky96]

Re: Delta DPS-250AP-62 Schematics?

Oh I'll bet it's that resistor you can see in Figure 1. on the datasheet, connected to + on the HV DC input and the diode cathode

https://pdf1.alldatasheet.com/datash...T/TNY274P.html

[R_J]

Re: Delta DPS-250AP-62 Schematics?

A picture of the bottom of the board would help to see where the resistor is connected. That resistor could also be in the VCC supply for the pfc ic. Check if it connects to Q901
The resistor has another color band (violet?) Could it be violet,brown,gold,black? If the resistor ran hot the colors could change slightly.

[stj]

Re: Delta DPS-250AP-62 Schematics?

looks like black, brown, brown, purple to me

maybe desolder the transformer and check for broken windings

[dicky96]

Re: Delta DPS-250AP-62 Schematics?

OK guys mystery solved

I removed the odd looking resistor - it's Yellow Blue gold gold Black so that would make it 4R6 if it is 4 band as gold is not valid as band 3 of 5 band. Maybe actually it is a 4R7 and the violet has turned blue with age

The resistor is open circuit and it is in line with the B+ connectred to Drain on the TNY277

The resistor didn't look 'stressed' but I didn't have any 4R7 resistors of that size so I connected 2x 10R in parallel and fitted them

I left the light bulb in series with the mains and when powered on it was lit up to about half brightness continually

I didn't have any 3.3V standby.

Obviously that current draw was too much for a PSU in standby so I checked TNY277 Drain to Source and it's reading about 27 ohms. I removed it and confirmed it is low resistance D-S

I guess that explains why the resistor went open

I'll order some TNY277, I don't have any in my component stock. As usual Ill order a pack of 5 or 10 as they are cheap.

Unless it is really expensive, I always do that when i come across a faulty component that I don't have in stock, on the basis that if I saw one faulty one I will most likely see another at some point.


Rich

[dicky96]

Re: Delta DPS-250AP-62 Schematics?

Pic attached