Siglent SPD3303X-E Rebooting

[Finn]

Hi All, posting my quick fix incase it is useful for anyone else.

I have several Siglent SPD3303X-E power supplies, they are excellent value for money! but...

2 of them reboot after running for a short time (about 10 mins) and continue to reboot occasionally during use. Obviously this isn't good enough for lab equipment so i disassembled them to see what I could find. The problem is pretty typical of a thermal issue so I had a look around with the FLIR thermal cam and found a few hot spots around the devices. There are a couple of current sensing shunt resistors that get up to about 85 degrees but they max out there and don't really get any hotter.

The main problem appears to be the small bridge rectifier in the front panel power supply, it gets to about 105C+ and then the device reboots, it cools slightly and runs for a bit longer before doing it again.

There are a few things that could be done to fix this problem (not an exhaustive list obviously):

• The bridge rectifier could be replaced with a higher current option
• It could be soldered higher above the PCB for better cooling
• A small heatsink can be used to cool it down a bit

I chose to do a test with a small copper heatsink just stuck on top of the rectifier with thermal adhesive and the temperature difference was dramatic! After running each test overnight to give it enough time to reach steady state:

• Before: 105C and rebooting
• After: 67C and not rebooting anymore

Not sure how they could possibly send these out with several components running so hot, they obviously didn't do much thermal testing! Out of the 4 units I have, 2 had the rebooting problem and the other 2 didn't but all of the bridge rectifiers ran extremely hot. Atleast it's an easy fix, I hope this info can help someone else.

[tautech]

Welcome to the forum.

Excellent work and yes the problem with the circular diode bridge Siglent are very aware of and although I don't know for sure just yet but may bring about a HW change.
We had a very new unit do this which we instantly replaced under warranty and then sourced repair HW from Siglent for it which consisted of a replacement but upgraded control PCB, that is the one directly behind the front panel.

Instead of the 2A circular bridge a SIL bridge was bodged in its place and leads left full length to get it well off the PCB. Siglent also sent us a small pack of these SIL bridges should we need to undertake this bodge rework and TBH I'd rather not if just the placement of a heatsink on the bridge can fix it.
However I do wonder if the stress the bridge has undergone has permanently damaged it for it to fail at some later date.

Anyways, please keep us informed how this pans out for you and please do some documentation about which units are affected, their SN#'s and have a look in their Sys Info for boot #'s and any other info you might think as relevant.

Siglent will come to the party if it's not sorted but do keep good records to refer to should it all turn to custard and warranty needs be called upon.

[Finn]

Tautech, Good to know they are working on a fix! It's not often you see a company that actually listens to their customers and fixes stuff 
Thanks for confirming I was on the money with the fix, I did consider replacing the bridge rectifier with a SIL packacke rated for higher current but the heatsink is working perfectly, they have both been running flat-out on the load tester for several days now so i'm going to call them done!

If the diodes have any underlying damage and fail in the future (I don't expect this to happen), i'll just replace the part and be done with it.

[tautech]

Tautech, Good to know they are working on a fix! It's not often you see a company that actually listens to their customers and fixes stuff 
Thanks for confirming I was on the money with the fix, I did consider replacing the bridge rectifier with a SIL packacke rated for higher current but the heatsink is working perfectly, they have both been running flat-out on the load tester for several days now so i'm going to call them done!

If the diodes have any underlying damage and fail in the future (I don't expect this to happen), i'll just replace the part and be done with it.

We've sold a good few of these PSU's and only had one failure and that was the one already mentions back in Jan 22.
On connecting with Siglent about it they were very aware there are issues in some units but for your 2 and our one this is the very first I'd heard of which proves I don't know everything. 

That was SPD3XIDX5R**** range SN#, what are yours ?
I suspect they had a suspect batch of bridges ............

[Rasz]

Didnt Dave make a video about it like 5 years ago? sure enough 7 years https://www.eevblog.com/forum/blog/eevblog-828-siglent-spd3303x-precision-lab-psu-teardown/msg817283/#msg817283

https://www.youtube.com/watch?v=mdOauVzY9OU?t=1564

90 C rectifier fitted snuggly between electrolytic caps.
https://www.eevblog.com/forum/blog/eevblog-828-siglent-spd3303x-precision-lab-psu-teardown/msg3496026/#msg3496026 says 2020 finally fixed it, Siglent finally coming around to fixing something spotted 5 years ago, good on them 

[Finn]

Yeah 2020 definitely didn't fix it, these are the newer model power supplies with better banana posts, etc. Still has the problem. Dave mentioned that it was hot in the video but nothing about rebooting, etc that's why I made this post to help others with the same issue.