Issue with CH341A Programmer - Power LED Dims When Chip Connected


I’ve recently purchased a CH341A USB programmer, when plugged into my laptop its recognised and I’ve installed the correct drivers for the device (found on a Youtube vid via Google).

However, when I attach the SOIC clip to the BIOS chip (MX25L12872F) I notice that the red Power LED dims in brightness, followed by the typical Windows 10 USB device disconnected sound in the background. The BIOS reader then becomes unresponsive until I disconnect the clip.

I’ve checked the positioning on the clip and orientation upon the USB device’s motherboard, all seems to be good.

Is there something I’m missing? Is this related to the 3.3V/5V circuit design flaw of the CH341A platform?


[Guide] Using CH341A-based programmer to flash SPI EEPROM (49)

Thanks for the link MeatWar.

The only difference reading through the thread is that my CH341A programmer doesn’t have both LEDs lit at the same time whilst the fault occurs, its only the red Power LED that is on and initially shining bright, then dims down in intensity as the fault occurs.

Its a shame that the USB device doesn’t have some form of error logging capability outside of the software packages for Windows/Linux.

Oh then is a worst cheaper version… and still u ask for error log.
Same issue… as that user, Battery/AC or CMOS.

So I’ve done some more testing…

Just so happens that I bought a backup CH341A programmer, as they are cheap(ish) and liable to faults ocurring - both devices were bought from different inline stores.

I had already removed the BIOS/CMOS battery and the main laptop battery (as well as any mains charger).
I even removed the SSD and Wifi cards to be sure no charge had been left in the system.

Still, I have the dimmed Power LED when connected to the chip via SOIC clip cable.
I tried a second clip cable, with the same results.

Strange thing is that the dimming of the LED only occurs when pins 7 and 8 of the BIOS chip are connected via the clip cable, the other points of contact work fine??

According to my experience , both run(yellow) & red(power) leds glow dimly only if I plug into a power supply or keep the battery connected. Actually the bios chip could be detected only if an external ac charger is plugged in & battery disconnected. What does "BIOS READER BECOMING UNRESPONSIVE MEAN" ? Detect button greying out?! Last but not least did u try holding the power button for 2-3 min after disconnecting all power supplies to drain any leftover charge?

Thanks Dinosnore for your suggestions.

I finally figured out what was wrong. There was a short on two of the clip cables I was using - I have a third as a spare, when connected everything starting working thankfully.

Just for clarification, when I mentioned ‘unresponsive’ I meant that the device would appear to be unrecognised by Windows as though I’d unplugged the device, but clearly the Power LED was still lit (this may be a short circuit protection feature within this programmer, I don’t know). I did also check to see if any residual power was in the laptop, fully discharged before any changes were made.

Some versions, connections are upsidedown than printed image show.