Siglent SPD3303X Power Supply turn off and on all the time

[jrgandara]

Hello!

I saw Dave´s review for this power supply and I bought one some years ago. Worked fine until two months ago. No it will turn off by herself and turn back on again. in the beginning it turned off and back on immediately. But now the time to turn back on again is getting longer and longer. I remove the cover and search for bad contacts without luck. The AC is passing by the switch and reaching the transformer. Looks like the problem is in the controller board. In the back of the front panel (top right corner) there are two TO-220 component which feels a little warm, even when the PS is dead. Eventually it will turn on again and work for some minutes or maybe hours and turn off again. Somebody else with this problem? Where to get the schematics or maybe a service manual for this equipment? Send it abroad for service is not an option here in Brazil. Any suggestions welcome.

Thank you!

[tautech]

Interesting.
Have you worked through the Hardware troubleshooting section in the Service manual ?
https://siglentna.com/wp-content/uploads/dlm_uploads/2019/08/SPD3000X-Series-Service-Manual.pdf

[jrgandara]

I did not know that this manual was available for download! I'll perform the hardware troubleshooting and then I'll comment what I find. Thank you!

[jrgandara]

I checked the "Service manual" and all the voltages are going OK to the main board. There is some problem with this board since when it is off and I force one of it's connectors the power supply comes back to live. But in question of seconds it will goes off again. This called service manual is not really a service manual. There is not schematic or block diagram.

Any possibility of someone have the real service manual for this power supply? This document say oif the voltages are ok the PCB should be replaced. Well, this can be easy since you are not in Brazil. Importing a PCB replacement like this could cost as much as someone living in US buying a brand new PS due to import taxes.
 
Any ideas?

[tautech]

I checked the "Service manual" and all the voltages are going OK to the main board. There is some problem with this board since when it is off and I force one of it's connectors the power supply comes back to live. But in question of seconds it will goes off again. This called service manual is not really a service manual. There is not schematic or block diagram.

Any possibility of someone have the real service manual for this power supply? This document say oif the voltages are ok the PCB should be replaced. Well, this can be easy since you are not in Brazil. Importing a PCB replacement like this could cost as much as someone living in US buying a brand new PS due to import taxes.
 
Any ideas?

That screams a dry/cracked joint to me. Have you carefully checked the soldering near this connector ?
BTW, the service manual linked is all that's available as I've tried to get schematics of the output stages but none are available.

[jrgandara]

I checked everything with magnifying glass. I even resoldered the connectors and most of the solders and nothing. This "service manual" is useless for any problem in the main board. I sent an e-mail to Siglent U.S. and still no answers. The big problem for me is be in Brazil where we don't have any support from Siglent. This power supply is very heavy and ship for another country for service is not an option. Probably will cost almost as inporting a new one. Everything we import here over U$50 will add a 92% extortion fee from the government with the shipping costs included. 

I'm stuck.

[Alexandre1978]

Hi,
I'm encountering exactly the same problem. PSU switching randomly Off and On again.
Someone could solve the problem in the meantime ?

BR,
   Alexandre

[tautech]

Hi,
I'm encountering exactly the same problem. PSU switching randomly Off and On again.
Someone could solve the problem in the meantime ?

BR,
   Alexandre

It's a warranty failure.
I had one do this a few months back and Siglent sent us a new control PCB.

[Alexandre1978]

Hi,
Many thanks for quick reply.
Already wrote to Siglent, hope will get reply soon.

BR,
   Alexandre

[gizzmonic]

its a small round bridge on the control board  with an output of 9vdc. As it heats it will slowly droop, when it drops to 3vdv it reboots.

[DavidAlfa]

Thanks for the tip, finding that issue would have taken ages.
I had a SPD3303C with this issue, randomly turning on and off every few minutes, found no cracked solder joints, so I replaced the mentioned rectifier.
Maybe it's too small for the power, runs hot and eventually fails?
Anyways, I installed a larger rectifier with a heatsink, fixed with a long hex spacer.

Yet to see if it's fixed, but this was a so simple fix that I decided to go for it and test my luck.

[tautech]

Thanks for the tip, finding that issue would have taken ages.
I had a SPD3303C with this issue, randomly turning on and off every few minutes, found no cracked solder joints, so I replaced the mentioned rectifier.
Maybe it's too small for the power, runs hot and eventually fails?
Anyways, I installed a larger rectifier with a heatsink, fixed with a long hex spacer.

Thanks for sharing your solution.

Yet to see if it's fixed, but this was a so simple fix that I decided to go for it and test my luck.

First C model I've heard of with a faulty bridge which must be from a production run that used the troublesome batch of them.

Haven't had a C with this issue as we have only supplied few, instead mainlining on the X/X-E model that also used this tiny circular bridge until the HW version was changed recently and a beefier bridge fitted.

Anyways, you should be all good to go now. 

[nidlaX]

This sounds like a design defect. I replaced the rotary encoder in my SPD3303D/S recently, and I noticed that this aforementioned rectifier is running extremely hot.

Apparently multiple design revisions inherited this flaw.

[tautech]

This sounds like a design defect. I replaced the rotary encoder in my SPD3303D/S recently, and I noticed that this aforementioned rectifier is running extremely hot.

Apparently multiple design revisions inherited this flaw.

It wasn't.

Instead we suspect bridge suppliers were changed or bridge quality diminished and these faults appeared as early units haven't these problems.
The new HW version has eliminated this happening.

More reading and history here:
https://www.eevblog.com/forum/repair/siglent-spd3303x-e-reboot-problem/

[DavidAlfa]

Aha, I see we're all taking the same path!

[DavidAlfa]

Well, 3 days on, no restarts or weird behavior, so I'd say that was it!
My manager passed by to ask how it was going, he instantly said "Wow the display is so much brighter now!"
Apparently he had compared it against a newer SPD3303C we have before giving it to me and noticed the led display was much dimmer in the failing unit, unlucky me he forgot to mention that.
But I quickly found this thread before going deeper (Saved some hair ).