Electronics > Repair
CH341A Serial Memory Programmer Power Supply Fix
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johnmx:

--- Quote from: panoss on February 15, 2020, 05:35:41 pm ---I 'm raising this topic from the dead :D because I also ordered this programmer but (having read this topic) I didn't understand: should I modify it as suggested or it works as is?
Without any risk of burning the IC being programmed?

--- End quote ---
I recommend to modify it.
WattsThat:
For any new players out there intending to do this mod, the OP’s bodge wire modification shown in reply #4 is done correctly. What is wrong is the original schematic, it lists C4 twice. The 104 value C4 shown on the the 1117 input is in reality C1.
rygelfievel:
I'm about to take this on and have confirmed that the programmer I bought in August 2019 has a slightly different silkscreen.  What is known as C4 that @johnmx posted with picture of his mod is labeled C3 on my programmer.  The bottom two capacitors next to the oscillator are labeled C4 and C5 on mine.  Took meter to test continuity between C3 and V3 pin and it appears to not have changed physical location.  Tested C4 with V3 pin and confirm there is no connection.

I also tested the SPI header and it is still reporting 5V for CLK, CS, MOSI and MISO.  So it appears nothing has changed in the circuit other than the silk screening.

tsdr; C4 is now labeled C3 if you want to do the mod as physically nothing has changed.
bul:
Hi!

I also ordered a black ch341a and wanted to use it on a 3.3V flash, thats still soldered in PCB. Unfortunately I fried the PCB - its dead now.
That leads me to this page and the fix thats discussed here.

Please allow me to ask some questions:

--- Quote from: johnmx on October 14, 2017, 12:29:37 pm ---One simple solution to fix this issue is to simply bypass the 1117-3.3V regulator.
I can use the hot air station to remove the 1117 and then short-circuit the input with the output.
My question is, is it safe to just do the short-circuit without removing the 1117 linear regulator?

--- End quote ---
Would that change anything? Bypassing/shorting the 1117 will still provide 5V from USB to the ch341a, right? So what was the idea behind that?


--- Quote from: Ian.M on October 14, 2017, 03:16:21 pm ---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.

--- End quote ---
So no polyfusethingies are needed? just the two little wires, and of course breaking the 5V supply?

Another Question: Are there by any chance ICs out there that need a signal Level of 5V and wont work with 3.3V, that could be programmed in this device?
If so, I would add somehow a switch at the Pin28 to switch between 5V and 3.3V to be able to choose the voltage level.

I wish you all the best and looking forward to hearing from you.

Bul

pupa:
Ok. I made the mods but not as per the suggestions in your post. First I lifted the supply pin and then broke the pin off in the end trying to fix routing of the wires. These pins are very weak without the support of the soldered joint. So I had to fix the IC's VCC connection first by grinding away the silicon carefully until I could solder a wire to the IC's VCC connection, then made a 3.3V bridge line from the VCC connection across the IC to create a track to solder connections to and thus restored the operation of the programmer. Then did a mod as per the information found on the internet to supply the Programmer VCC with the 3.3v. The  REASON why the PROGRAMMER fries some e.g. bios chips is because the CH341A chip is supplied with 5VDC on VCC originally ..... with outputs in some modes at 5V and other times at 3.3 Volt (from the on board regulator). So the safest is to make it a complete 3.3V  system for now overall.  Best would be to modify it with selector for either 5V, 3.3V or target board in circuit supply for VCC  to CH341A chip. The device is a very versatile winner, the Chinese final design not so much due to design flaws. The chip apparently have a 3.3V internal regulator or such  functions but info is lacking at best.

So in your case I think the 5V supply caused the damage. Which PCB are damaged? The programmer or Target Board?

I have no problems so far reading 5V or 3.3V chips. But in case I will just change to 5V when needed. A better way will be to make or buy a daughter interface board that plugs in the ZIF socket to convert to 5V or 1.8V circuits as required. 

See upcoming attachments  to follow. (Get message files too large >>5000KB total?)
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