Siglent SPD3303X-E missing chip? - Page 1
Forum section: electronics / repair

author: R-1125F
author_rank: Regular Contributor
timestamp: November 11, 2022, 08:24:09 pm
content: I bought a broken Siglent SPD3303X-E that someone had already been into. It appears that an 8-pin chip on the main board is missing. The problem is that I have no idea what the chip is. The space is marked UA9. The photos show where the chip is missing and the part number of for the board I am working on. It does look like there may have been a chip there at one time.Could someone tell me what the part number is for the chip that is supposed to be there?I noticed in Dave's teardown video on the SPD3303X that the space is populated. It is my understanding that the hardware in the SPD3303X is identical to the SPD3303X-E. Is this incorrect?A schematic would be really useful here. Are you listening Siglent?

author: R-1125F
author_rank: Regular Contributor
timestamp: November 11, 2022, 08:25:08 pm
content: I add a photo of the board part number.

author: R-1125F
author_rank: Regular Contributor
timestamp: November 11, 2022, 09:26:55 pm
content: I got a message back from the seller that the chip is a TL072 dual opamp.

author: tautech
author_rank: Super Contributor
timestamp: November 12, 2022, 11:15:27 pm
content: UA9 is 741CUA5 is TL072C

author: R-1125F
author_rank: Regular Contributor
timestamp: November 12, 2022, 11:17:59 pm
content: Thank you. You saved me from installing the wrong chip.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: November 14, 2022, 06:51:06 am
content: It also looks like CA3 and UA1 should be there ?Might be also worth checking if CA26 and JA2 should be populated too ?

author: tautech
author_rank: Super Contributor
timestamp: November 14, 2022, 08:19:11 am
content: Quote from: TheDefpom on November 14, 2022, 06:51:06 amCA3 = 100uF 35VUA1 = L78L05CA26 = UnpopulatedJA2 = Unpopulated

author: R-1125F
author_rank: Regular Contributor
timestamp: November 14, 2022, 02:29:58 pm
content: Thank you for the reply.I had removed CA3 and UA1 to find a short. I still have not found it. The output to ground of the 78L05 measures about 1 Ohm resistance. When I powered it on with the 78L05 in place, the voltage dropped to near zero. With out the 78L05 in place, the input voltage is fine. I am still hunting for the problem. I see the same short conditions around UA20, UA9, QA19, and QA15. I am really hoping that the AD7792 is not bad. Any thoughts on this area would be appreciated.But there's more. There is a similar short condition around the 3.3V (U2) regulator on the digital side. With U2 removed, the resistance to ground is about 0.2 Ohms. Again, hoping that the STM32 is not bad. I have not started hunting on that side yet.Could there be a common cause for these conditions? Without a schematic is very hard to figure out.

author: 2N3055
author_rank: Super Contributor
timestamp: November 14, 2022, 10:20:17 pm
content: Look for a shorted MLCC capacitors ...

author: TheDefpom
author_rank: Frequent Contributor
timestamp: November 14, 2022, 10:26:52 pm
content: Quote from: 2N3055 on November 14, 2022, 10:20:17 pmI was thinking the same thing.... more likely to happen than a failed IC (apart from the IC it kills in the process).

author: R-1125F
author_rank: Regular Contributor
timestamp: November 15, 2022, 12:03:14 am
content: I had that thought too. I think I will try removing the caps that show the lowest resistance first while monitoring the resistance. If there is no change in resistance I will put the cap back. My last resort will be to apply power from a bench supply while and see what gets hot.

author: R-1125F
author_rank: Regular Contributor
timestamp: November 15, 2022, 08:09:20 pm
content: Well, this is not good. I applied 5V to the shorted part of the circuit and the only thing that got hot was the AD7792BRUZ. I removed the chip and the short was gone. The only source I can find are ebay sellers in China. I can't trust them. The regular suppliers aren't going to have them for quite a while.The next part is to find the short in the digital side. If things go like this, the problem is going to be the STM32 processor. Also, not easy to find.Also, I seem to lost CA21 in the process. Could someone tell me the value of this chip? I suspect it is a .01.