NI USB-8473 USB-CAN Repair - Page 1
Forum section: electronics / repair

author: strahd_von_zarovich
author_rank: Contributor
timestamp: December 18, 2024, 10:20:00 am
content: Hi everyone,My NI USB-8473 converter has been damaged (I’m not sure why).I tried to identify the damaged part, and it appears to be the IC below. Hopefully, it’s the only damaged component. It has a “Q” marking, so it is likely a transistor array (since it has six pins).I tried to find the exact part number but had no luck. The board has two physically isolated sections, and this IC is connected to the transformer.

author: MichaelPI
author_rank: Contributor
timestamp: December 18, 2024, 11:11:03 pm
content: My initial guess would have been one of the devices from the SN6505 family by TI, as those push-pull drivers are typically used for isolated CAN interfaces. But the marking would be something like '65AQ'. The marking shown in the picture seems to be '67h'. Do you have more pictures showing the part of the board, in which the desoldered IC was located? Based on that, you can rule out certain types of components.

author: strahd_von_zarovich
author_rank: Contributor
timestamp: December 19, 2024, 09:46:52 am
content: Dear Micheal,Thank you for your answer.The marking seems to be "67h" , you are right.Here are pictures of the board. The desoldered component is Q6 below the CE marking.It would be weird, If it is a driver IC and they marked it as "Q"Looks like pin-1 and pin-4 are connected to the ground.

author: MichaelPI
author_rank: Contributor
timestamp: December 20, 2024, 08:11:44 pm
content: Hi,interesting, it seems as if NI decided to build a discrete push-pull transformer driver. Initially I thought, NI uses a driver from Maxim (ADI) as the datasheet of HALO TGMR340 recommends the usage of drivers by Maxim. I could not find any driver IC by Maxim with the correct pin count, hence we can rule out the usage of any highly integrated solution. The marking Q6 in the solder resist is probably correct and it is indeed a bipolar bipolar transistor / mosfet. The typical topology of a push-pull transformer driver gives some clues, that it is most likely a dual NMOS device.The two diodes (44t marking) are BAT54SW schottky diodes by Nexperia. The two ICs (BEL marking) are 74AHCT1G08DCKRE4 by TI are AND gates.The weird thing is, I could only find NUP4302MR6 (TVS diodes) by ONSemi for the "67" marking. That does not fit...Both pins 1 and 4 connected to ground, which makes perfect sense for dual NMOS device (source connected to ground) in a SOT363 package like the NX3008NBKS ...

author: Xelima
author_rank: Newbie
timestamp: August 22, 2025, 09:30:56 pm
content: Hello everyone,I am experiencing the same issue with my NI USB-8473 device. The Q6 component is damaged, and I am unable to identify it. On this PCB board, it is marked “TD P,” while on another PCB it reads “67x.” I am wondering if "TD P" could be the same as “67h”Additionally, I have had no success identifying the “64t” diodes, they appear to function as some sort of surge protection for CAN.I would appreciate any help I can get.Thank-you

author: gamalot
author_rank: Super Contributor
timestamp: August 22, 2025, 10:46:20 pm
content: Try this:https://www.onsemi.com/download/data-sheet/pdf/nup4302mr6.pdf

author: Xelima
author_rank: Newbie
timestamp: August 23, 2025, 06:14:35 am
content: Thank you, gamalot. I’ll give that a try.Before I proceed, I need to identify these "64t" diodes, as they might also be faulty.

author: gamalot
author_rank: Super Contributor
timestamp: August 23, 2025, 09:56:44 am
content: 64t is BAS40-04W：https://assets.nexperia.com/documents/data-sheet/BAS40-04W.pdfand please ignore my guess about 67h, I think I was wrong.

author: gamalot
author_rank: Super Contributor
timestamp: August 23, 2025, 10:02:16 am
content: OK I got them！67h is FDG6317NZhttps://www.onsemi.com/download/data-sheet/pdf/fdg6317nz-d.pdfand TD p is TPM4401NEC6https://www.lcsc.com/datasheet/C2928733.pdf

author: Xelima
author_rank: Newbie
timestamp: August 23, 2025, 01:25:04 pm
content: Thanks a lot, gamalot. How did you manage to find these datasheets? I’ve spent days searching without any luck. I’ll definitely give them a try and share the results here in case others are experiencing the same issue.

author: gamalot
author_rank: Super Contributor
timestamp: August 23, 2025, 02:42:58 pm
content: Quote from: Xelima on August 23, 2025, 01:25:04 pmIf I can't find the results I want, I will search in Chinese. Most of the components in the world are produced and shipped to China.

author: Xelima
author_rank: Newbie
timestamp: August 28, 2025, 04:59:01 pm
content: I attempted to source the FDG6317NZ, but it’s obsolete. Based on the manufacturer’s recommendation and the similar electrical characteristics outlined in the datasheet, I opted for the NTJD4401NT1G as a replacement. Unfortunately, upon connecting the USB, Q6 (NTJD4401NT1G) immediately overheats and emits smoke.Attached is an image of the working PCB board, where I have marked the measured voltages for reference.With the NTJD4401NT1G installed, I measured 3.8 V across the plus and minus pins and 0.2 V at the gate pins VGS(TH).

author: MichaelPI
author_rank: Contributor
timestamp: September 16, 2025, 03:24:45 pm
content: The immediate destruction of the replacement IC (NTJD4401NT1G) is a bit suspicious. Does your PC detect the USB-CAN interface upon connection (without Q6)? I would expect the USB-CAN interface gets at least detected, if not something else is probably defect too.Do you have any possibility to do a measurement with an oscilloscope? Could you measure the gate signals at pin 2 and pin 5 against ground (without Q6 of course)? If you are unable to see two PWM (one of them needs to be complementary) signals with a bit less than 50 %duty cycle, the culprit will be somewhere else and the defective Q6 is just the symptome.Without reverse engineering NI's circuit (take this with a grain (or shovel) of salt), I would image the FPGA is responsible for the clock (PWM) generation (potentially as well the dead time generation, in case the FPGA generates the complementary signal as well) of the push-pull transformer circuit. The AND gates could function as gate drivers for the Dual-Channel NMOS transistors. The signals from the FPGA at R138 and R139 seem to me (based on the provided images) connected to the AND gates and could be the source of the PWM signal(s).If for whatever reason the gate signal at one of the gates is stuck at "1", Q6 will be destroyed due to the short circuit via the transformer windings, hence I would check, if the gate signals are plausible before any further replacements of Q6.

author: Xelima
author_rank: Newbie
timestamp: September 20, 2025, 01:35:16 pm
content: Hi,I got NI USB-8473 working with the BSS138DW-7-F, which is also dual N-channel MOSFET, just like the NTJD4401NT1G. I’m thinking the NTJD didn’t work out because it switches too fast and probably got too hot because of that. I’ve attached some oscilloscope measurements. The waveforms look pretty similar, but the NTJD has a ton of ringing and noise going on.Thanks everybody for your help!