Siglent SHS820 oscilloscope repair help needed - Page 1
Forum section: electronics / repair

author: R-1125F
author_rank: Regular Contributor
timestamp: January 02, 2024, 09:34:53 pm
content: I picked up a Siglent SHS820 oscilloscope that somebody plugged in the wrong power supply. It fried a couple of parts near the power input. I have not been able to identify the parts. One is marked 76H the other chip was completely destroyed. See attached photo. I think the chips are U24 and U25.

author: Chris56000
author_rank: Frequent Contributor
timestamp: January 04, 2024, 05:05:32 pm
content: Hi!I would say U24 is AMS1117–3.3 or MCP1702–3.3, but I'm not sure about U25 – you'll need to try and clean up that mess a bit more I'm afraid!Chris Williams

author: R-1125F
author_rank: Regular Contributor
timestamp: January 04, 2024, 07:30:35 pm
content: Thanks. I found another post about a similar repair. The parts are mosfets.It turns out that Siglent used a TI battery management chip and copied the application note schematic pretty close. Seehttps://www.eevblog.com/forum/repair/successful-repair-of-siglent-shs1102-oscilloscope-not-turning-on/msg2367912/#msg2367912The problem I have now is that when the parts went up in flames, they welded themselves to the circuit board. I have it cleaned up as best I can but there is some trace damage.What I could really use is a clear photo of that part of the board from any model of SHS800 oscilloscope. The SHS1102 in the post I mentioned is not exactly the same in that area.Anybody got a SHS800 open that can provide a photo?

author: tautech
author_rank: Super Contributor
timestamp: January 06, 2024, 12:38:30 pm
content: Quote from: R-1125F on January 04, 2024, 07:30:35 pmBump me in 10 days when I return to base.Have 800 main board.

author: R-1125F
author_rank: Regular Contributor
timestamp: January 06, 2024, 02:51:15 pm
content: Thank you. Will do.

author: tautech
author_rank: Super Contributor
timestamp: January 16, 2024, 08:10:39 pm
content: Hopefully enough detail in this iPhone pic......need to convert it in Paint, gimme a mo.

author: R-1125F
author_rank: Regular Contributor
timestamp: January 16, 2024, 08:38:54 pm
content: Thank you. This is very helpful.

author: tautech
author_rank: Super Contributor
timestamp: January 16, 2024, 10:36:04 pm
content: Quote from: R-1125F on January 16, 2024, 08:38:54 pmSing out if you need any traces buzzed out.

author: R-1125F
author_rank: Regular Contributor
timestamp: January 16, 2024, 11:37:03 pm
content: Thanks. I think I am good for now.Fortunately, Siglent used a TI BQ24170 chip and pretty much copied the schematic from the application notes. It should be noted that the TI application notes are for a 12V input and SHS800 is 9V.https://www.ti.com/product/BQ24170In mine, the mosfets near the connector went up in flames and burned through the first layer of the board. I can't install the original Q24 and Q25 to what's left of the traces. I am thinking of replacing these with dual channel mosfet in a larger package.

author: R-1125F
author_rank: Regular Contributor
timestamp: January 17, 2024, 03:19:45 am
content: I am curious; what is wrong with the board that you have?

author: tautech
author_rank: Super Contributor
timestamp: January 17, 2024, 06:18:08 am
content: Quote from: R-1125F on January 17, 2024, 03:19:45 amIt's a nonoperative board from a unit we fitted a new board to some years back.It was a unit we did not sell but was approached to fix it.Sorry, don't remember any further details other than it's stashed in a chest with other warranty replacement parts.