Electronics > Repair
CH341A Serial Memory Programmer Power Supply Fix
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flachyjoe:
The chipset is CH341B 406725D24
Tantratron:
It seems lot of CH341x variants after all  :)
Ian.M:
Ch341B shares a datasheet with CH341A: http://bitsavers.informatik.uni-stuttgart.de/components/wch/_dataSheets/CH341DS1.PDF
and has exactly the same power pin specifications and I/O voltage levels.

If with the jumper removed, you still have >3.3V signal levels when idle on the SPI pins (1-4 of the  same header as the jumper), or have 5V on pin 28 (Vcc) of the CH341x IC (corner nearest board edge and ZIF socket), you need to do the mod.
flachyjoe:
3.332V at the 2 places so it's good.  :)

Thank you two!
Tantratron:
Hello @Ian.M and @flachyjoe

First question to Ian because I'm bit confused or lost plus I'm not native english so I did not fully understand what exact voltage test, what pins should be done


--- Quote from: Ian.M on November 16, 2024, 11:36:05 am ---If with the jumper removed, you still have >3.3V signal levels when idle on the SPI pins (1-4 of the  same header as the jumper), or have 5V on pin 28 (Vcc) of the CH341x IC (corner nearest board edge and ZIF socket), you need to do the mod.

--- End quote ---

There should 2 tests, one with the jumper installed and then with no jumper, correct ?

As mentioned earlier, I've bought from amazon the CH341A programmer board. Wether the jumper is installed, I do have always +5V  on these pins: CH431-28 ZIF-1 ZIF-2 ZIF-5 and ZIF-6. By ZIF here I mean, the socekt plug dedicated for 25XX then on this same connector, I always have +3.3V on ZIF-3 ZIF-7 and ZIF-8

What do you mean by 3.3V then what do you mean by 1-4... do you mean 5V, do you mean pin measurement voltage between ZIF-1 (CS) and ZIF-4 (GND) ?


--- Quote from: flachyjoe on November 16, 2024, 12:33:52 pm ---3.332V at the 2 places so it's good.  :)

--- End quote ---

Second question for flachyjoe, can you detail exactly what places (which pins) did you get 3.3V ?

You said to purchased on eBay in France this model https://www.ebay.fr/itm/324505422583 . The picture and title of the french eBay-vendor shows CH341A but you said the item in your hand has CH341B. Do you confirm it has 3.3V on all ZIF pins and Chip-28 so you do not need to make any modification ?

Third and last question to Ian,

When reading the beginning of the thread started in 2017, I see that you modified and edited part your post #3

I do not know what was the description to modify back then, I just want to make sure that the easiest way to modify and make sure no 3.3V flash chip to be fried consists to do this re-wiring No track cuts, just lift pin 28 (easy because its near the board edge with nothing in the way) and run a wire from the lifted pin across to pin 9, and on to the 3.3V regulator output.

Thank to take time clarifying your posts so it will safe. The reason I ask is first I'm not native english, second the thread has been going with 5 pages with other modifications so I prefer to really have say a 2024 final update.

Albert

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