DAQ PCB data link led flickering

[Jinghao]

I come across an issue of flickering data link LED on the DAQ board, which keeps the miniscope from connected (same mscam retrieve error as expected). The board was OK before yesterday but it ran into this flickering problem today.

I tried connecting with the same coax cable&connector, same miniscope, same USB3.0 cable, and just a different DAQ board, the LED stays solid on and everything was fine, so it seems some issue with the pure DAQ PCB.

I am wondering if I can get some advice from you about the potential solution to this issue.

[Daniel Aharoni]

Hi Jinghao,
This is an interesting issue. Usually when the Data Link LED flickers it is due to an issue with the coax cable or the solder connection between the coax cable and PCBs. I haven't see this issue arise from the DAQ PCB itself but it could be possible. Can you try the following:

• If you have another CMOS PCB. Hook it up to the DAQ PCB with the issue and see if the Data Link LED still flickers.
• Hook up the first CMOS PCB to your working DAQ PCB and shake the coax cable around and see if you can cause the Data Link LED to flicker or the connection to drop.
• Make sure all the switches on the DAQ PCB are fully locked into the correct orientation.
• Did you ever connect a CMOS PCB to the DAQ PCB where the coax cable had a short across the inner conductor and outer shield? This is the most common cause for damaging the DAQ PCB and could cause the Data Link LED to flicker.

Once I have a bit more information hopefully we can fully debug the issue.

[Jinghao]

Hi Daniel,

Thanks for the reply and the advice.

I have another cmos, and that also makes the led flicker, so in addition to the other pairing (second DAQ with first cmos), it is most likely the DAQ pcb is not properly functioning.

2nd DAQ + 1st cmos, and shaking the coax cable does not render flickering.

All switches are in position.

I always test coax cable with a multimeter before connecting to the DAQ pcb, and it was good before this problem or after. But probably the connection of the coax was not stable, which caused the sudden huge current in the chips.

I read through the circuit diagram, and checked the 914A chip on the DAQ pcb. I have several guesses: 1. The v3p3 might be unstable; 2. the LOCK on 914A might oscillate between H and L. I will find some time to test whether the voltage is stable. If stable, does it mean that somewhere of the chip is malfunctioning?

Thanks for the help.

[Dongil Keum]

I had same problem after replacing DS90UB914, due to bad ground. Base metal of the chip should be soldered. The lock led had been dimmer than others and flickered after clicking connect button. If you see the 'flicking lock' led, the chip is functional but the connection has some problem. I think it is related to power supply.