Electronics > Repair
CH341A Serial Memory Programmer Power Supply Fix
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yunLad:
Hi to people of eevblog forum! I wish I found this thread before the damage was done, 3v3 vcc and 5v on data… oh well.

For inspiration I wanted to share my execution of the 3V3/5V mod with spdt switch on the layout @jakeisprobably traced, big thanks for that!


* Cut 3V3 track going from the middle pin of voltage regulator
* Add a capacitor to the output of that regulator just to be sure
* Lift the VCC pin, insulate with capton tape underneath and connect it to the cut ex3V3 track right next to it
* Add a spdt switch or jumper to choose voltage on that ex3V3 track
* Add a shottky from voltage regulator output to pin 9
rivest:
This version has a voltage switch but the price is a little higher:

https://www.aliexpress.com/item/4001272558261.html
RaceJay:
Hi'all,
Actually, there's a much easy way to do this fix; you just have to cut a track on the board and add a plastic jumper on pins labeled '3.3V' and '5V'. I've have successfully flashed a Winbond 25Q64FVSIG which is a 3V chip.
Cheers!
https://www.geocities.ws/racejay/ch341a/3.3V_Easy_Fix.jpg
maronz:
I've just wanted to stop by to thank the original author, and all the contributors which helped me to make up my mind.

In the end I went with the "no solder" modification as suggested by "RaceJay". Of cause I've read that V3 (pin 9) should be connected to 3.3V, but it appears that this was not required to successfully program the 25Q128 BIOS chip in my HP Folio 9480m.
beez276:
Hi,
I modded my CH341A, but I don't get 3.3V when verifying voltage.

* GND > CLK 3,18V
* GND > CS 3,24V
* GND > MOSI 3,19V
* GND > MIOS 3,18VI was able to read Thinkpad T440p's EEPROM, but is it safe to write chip with these voltages?
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