problem with Delta GPS750AB A PSU. No +5v VSB

[smile]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

TNY280PN datasheet:
https://cdn.badcaps-static.com/pdfs/...953d6e2eb9.pdf

R1 was 4.33K +5vsb unstable
replaced with 1K 5V stable, but when soldered back supervisor IC and other smaller board, instantly burned.

It's hard to tell what original resistor was as it overheated (was coated all in resin) the color code read as 4.33K

[smile]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

Instead of 1K, I put 1.5K now it burns when starting the PSU with green+black wires shorted.

The PK6E200A diode measures as good, one way O.L the other way 0.516V
The other small one D5 measures only one way. so it's good.

[smile]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

PK6E200A diode is a TVS diode Working Voltage: 171 V
These can't be tested with DMM right?

https://eu.mouser.com/ProductDetail/...FymH4LMw%3D%3D

[CapLeaker]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

as long it isn't shorted, it's good. Those are TVS diodes and yours can't be bad. However, maybe you did misread the resistor...
Take that supervisor IC back out and see if any pins are shorted to GND? Maybe take a lab PSU and give the supervisor IC power and see if it draws excessive current or something.

[smile]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

Nothing else except the resistor that burns get hot. This is after few minutes being off.

[smile]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

Maybe take a lab PSU and give the supervisor IC power and see if it draws excessive current or something.

supervisor IC Dwa108-A same as TPS5510
https://www.eevblog.com/forum/repair...that-dwa108-a/

Draws 1mA on VCC pin (the VCC is 16V so how can it be related to +5vsb???), 16ma on 3.3pin 38mA on +5Vpin

Why it does not draw any power 1mA on VCC??? damaged?

[smile]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

I take that back, supply current is specified as 1mA in datasheet. So it's working OK.
The voltage is same as +5vsb. But the resistor gets burned.

[sam_sam_sam]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

Either one of two things are issue

One you do not have the right wattage resistor or you have a short or something is wrong with current on that resistor ( or you have the wrong resistance value ) or you have to much current draw on that power supply rail

[smile]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

400C with removed supervisor IC, so the problem is with ???
With 4.33K +5vsb unstable so that's why it does not burn? When there is 5V stable the rapid heating starts and resistor blows, but who could be using the current.

[smile]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

This video shows same chip problem fix
https://www.youtube.com/watch?v=vGS6Y8Z9dAM&t=1259s

The author also mentions the resistor going bad and replaces it.
However the resistor is 2Ohm !!!!

The author shows same datasheet and same diagram for TNY280PN.
As you know on diagram there is no 2Ohm resistor but 1K

[CapLeaker]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

I did check a few power supplies schematics and I even saw this resistor value down to 10 Ohms.

[R_J]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

I found this schematic that suggests a 1KΩ It may be that the tvs diode is bad.

[smile]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

I found this schematic that suggests a 1KΩ It may be that the tvs diode is bad.

So multimeter can't test 100% TVS diode, I need to get new one to test?
Multimeter measures only one way, so I would say it is OK

[CapLeaker]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

Your TVS diode should read like a regular diode. One end OL which it did and the other way around with a voltage drop of something like 0.6V - 0.7V, which it did too. You could test it with a bench psu that has CC / CV, but again I don’t think that diode is the problem.

While checking schematics for my troubled PSU I did check for the resistor in yours. I came up anything between 10 and 1k Ohms as a value. Others have no resistor in between the diodes.

[smile]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

While checking schematics for my troubled PSU I did check for the resistor in yours. I came up anything between 10 and 1k Ohms as a value. Others have no resistor in between the diodes.

So the guy putting 2Ohm resistor in video then? 2Ohm is basically short circuit compared to 1K.

Should I just replace the resistor with a wire and see what burns next?
Should I remove resistor and inject some voltage to see what get hot?

[smile]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

OK,

1. I replaced TNY chip with another one.
2. Replaced TVS diode
3. added a 2Ohm resistor (two 1Ohm resistors in series). Tried 1K but it burned.

Now the PSU does not burn the resistor and starts fine. I tested it with 50W light bulb. So the datasheet is wrong about resistor value !!!!!!

Another problem:

There is chirping sound from PSU once every second when I start it with NO LOAD.
Unstarted it is silent and stable 5VSB output.

If I connect 50W lamp, the sound gets faster every half secod.

You can hear it with load attached in file.

[R_J]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

So multimeter can't test 100% TVS diode, I need to get new one to test?
Multimeter measures only one way, so I would say it is OK

The tvs diode is a zener diode, how can you tell using a multimeter, what it is zenering at? 100v? 130v? 200v?

[CapLeaker]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

So the guy putting 2Ohm resistor in video then? 2Ohm is basically short circuit compared to 1K.

Should I just replace the resistor with a wire and see what burns next?
Should I remove resistor and inject some voltage to see what get hot?

No wire. I think they use the resistor as a fuse. Also maybe try 10 ohms.

OK,

1. I replaced TNY chip with another one.
2. Replaced TVS diode
3. added a 2Ohm resistor (two 1Ohm resistors in series). Tried 1K but it burned.

Now the PSU does not burn the resistor and starts fine. I tested it with 50W light bulb. So the datasheet is wrong about resistor value !!!!!!

Another problem:

There is chirping sound from PSU once every second when I start it with NO LOAD.
Unstarted it is silent and stable 5VSB output.

If I connect 50W lamp, the sound gets faster every half secod.

You can hear it with load attached in file.

A chirping of the PSU is usually a shorted voltage rail. PSU tries to start and shuts down. Do some measurements on the high voltage main filter cap and all output rails. See if a voltage rail is missing.

[CapLeaker]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

The tvs diode is a zener diode, how can you tell using a multimeter, what it is zenering at? 100v? 130v? 200v?

Somewhere between 150v and 200v is my guess.

[R_J]

Re: problem with Delta GPS750AB A PSU. No +5v VSB

Somewhere between 150v and 200v is my guess.

What I am saying is you cannot determine the zenering voltage of the tvs diode with a meter. It can check ok but what if it is supposed to zener at 180v but is conducting at, lets say 100v it would blow the resistor in series with it.