Gigabit Managed Switch dead

[jabz]

Hi I have 3 Alloy Managed Gigabit Switches. 1 day one of them failed, I saw all the lights off, I tried another power plug and still not powering up.
I would like to try an repair it, at first I though maybe its a fuse.
But I couldn't see an easily replaceable one on the board, it appears the power board is separate. Can these PSU board be purchased from somewhere?

Whats the best way to conclude it is a PSU/Fuse issue? I see a fuse on the PSU next to the power socket, it looks pretty covered up. I have removed the PCB and PSU and can see no evidence of marks/leaks or anything.

I have a multimeter where should I put the points to check things are alive?
I have pasted the pics below.

Mainboard + PSU


PSU

[Kiriakos GR]

Re: Gigabit Managed Switch dead

You fuse is at the right of the plug (picture no2) covered with heat-shrink material.

[jabz]

Re: Gigabit Managed Switch dead

I've checked the fuse and it appears to be ok. I then checked for DC voltage on the outputs and got nothing, so it appears something on the PSU is dead.

Can someone help me find a source for this PSU online? The manufacturer and specs are here
http://pgb-tech.com/products_info.ph...83&pclass_sn=7

But I cant find a source to purchase it from.
Or an equivalent that has the same specs with the IEC power connector onboard and with the 4 Pin power connector that connects to the gigabit switch mainboard.
I am in NZ with 220V - 240V mains.

thanks

[rogfanther]

Re: Gigabit Managed Switch dead

You could try changing that small cap, between the transformer and the transistor, and also those from the secondary.

[ben7]

Re: Gigabit Managed Switch dead

You could try changing that small cap, between the transformer and the transistor, and also those from the secondary.

I second that.

Also, can we get a pic of the bottom of the PSU board? (Want to know if that board has a control IC or not)

[rogfanther]

Re: Gigabit Managed Switch dead

ben7, I wondered about it also. Could that transistor ( if it isn´t a TL431 ) near the corner of the transformer be part of the switching control circuit , like in a cheap walwart ?

[ben7]

Re: Gigabit Managed Switch dead

ben7, I wondered about it also. Could that transistor ( if it isn´t a TL431 ) near the corner of the transformer be part of the switching control circuit , like in a cheap walwart ?

If your talking about the little to-92 device, then, yes, there is a 99% chance that it is a TL431.

Most SMPS primary-side control chips are SMD.

[budm]

Re: Gigabit Managed Switch dead

If worst comes to worst, it is only a 5V 3A power supply, you may be easily find wallwart 5V 3A switching power supply and just wire its output to feed this unit.
I second that small start up cap by the heat sink also, or heat up the board with hair dryer to see if it wcome back on. by the way what happen if you disconnect its out put to the main baord and see if it will out out 5v isnce you may have shorted circuits on the main board that causes it to stay in shutdown mode.

[jabz]

Re: Gigabit Managed Switch dead

I'll take the pics to show you. I think I'd rather replace this PSU with a drop in replacement if one can be sourced easily enough, than attempt to replace components.

I tested the PSU output while it was disconnected from the mainboard, no 5V.

[PeteS in CA]

Re: Gigabit Managed Switch dead

Other than what is probably a ferrite rod inductor for high frequency noise suppression, I don't see an O/P inductor. My guess is that it's a self-oscillating discontinuous flyback - no PWM IC. Checking solder joints would be a good idea.

[jabz]

Re: Gigabit Managed Switch dead

Here is a pic of the back and sides.
Still looking where to get a drop in replacement.

[budm]

Re: Gigabit Managed Switch dead

Can you read the P/N on that SMPS IC (the one with 8 pins on the bottom side of the board)? It can be as simple as that small cap by the heat sink that you will need to try out since it does not look like you are going to be able to buy on that will fit the chassis.

[momaka]

Re: Gigabit Managed Switch dead

Still looking where to get a drop in replacement.

Personally, I don't think drop-in replacements are a good idea, especially if these PSUs like to fail a lot. If you do get an identical drop-in replacement, chances of it to develop the same problem are high.
If a power supply is designed well but fails due to shoddy caps, I rather rebuild it and know that it will last rather than replace with identical PSU that will eventually fail too.

[jabz]

Re: Gigabit Managed Switch dead

Hi seeing as I couldn't find the same drop in replacement or an alternative easily that will fit, I am going to power the switch via a 5V 4amp wall wart I have, its a Class 1 power supply.
Specifically this one here
Once I rewire the output to the power connector on the switch mainboard. Do I need to worry about earthing the chassis?

[ben7]

Re: Gigabit Managed Switch dead

Hi seeing as I couldn't find the same drop in replacement or an alternative easily that will fit, I am going to power the switch via a 5V 4amp wall wart I have, its a Class 1 power supply.
Specifically this one here
Once I rewire the output to the power connector on the switch mainboard. Do I need to worry about earthing the chassis?

If the chassis was originally earthed, then yes you should have it earthed.

[jabz]

Re: Gigabit Managed Switch dead

Yes it was the original open frame PSU in the above pics, that earth wire is a soldered connection to a pad that the chassis screw goes through.

So since I am using a standalone class 1 DC adapter, I will run a wire from the chassis screw to the DC adapter 3 PIN Mains connector and solder to the earth pin.