[HELP] Powers On but Not Recognized - DZ60 KBDFans

[thelastangel_0]

I bought this PCB for $1 and I’m trying to revive it. I attempted ISP flashing using a Pro Micro, but it didn’t work. Then, a friend checked it and suggested that the issue might be with U3 (UL23 SOT23-6), but replacing it didn’t help either.

Now, I’ve purchased a new ATMEGA32U4-MU to replace the original microcontroller. However, with a bit more knowledge, I checked the capacitors near the MCU and noticed that some might be damaged. I want to replace them, but I’m unsure about their exact values.

ChatGPT suggested that some should be 100nF and others 10µF, but I’d like to confirm. Could anyone help me identify the correct values for C4, C1, C5, C6, C7, C8, and C10?

Thanks in advance!

[ncrowl]

Test:
 -type "dmesg -w" as sudo on a *ux -terminal
 -pull the usb -cable, disconnecting the keyboard, and insert it again. Take note what the terminal identify it as (my is "DZTECH DZ60v2")
 -to flash/reset it, hold in reset (on my under the spacebar, your card have different layout) while insering the usb-cable. The message on the terminal should be different, atmega.. something. Aah here is more notes and the firmware https://github.com/qmk/qmk_firmware/blob/master/keyboards/dz60/readme.md (not sure thats ur card though)

an atmega mcu can work without crystal clock,, may hookup serial thou to com. Looks on the picture someone already took a shoot with serial.com on you board,

[thelastangel_0]

(if measured in-circuit, these may not be entirely accurate):

C4, C5, C9 → ~(5.35kΩ)

C6, C7, C8 → (8.24kΩ)

I also tried measuring capacitance, but most of them read 0, except:

C1: 1.120µF (~1.1µF)

C10: 470pF

Diode Mode:
C1 and C10: fine

C4, C7, C6, C5, C9 and C8 Leak Value

I understand that no one can tell me the exact values for this closed-source PCB, but I asked because I’ve seen many discussions about ATMEGA32U4 (-MU) capacitor configurations. For example, some mention that Teensy does it differently from the ATMEGA32U4 datasheet recommendation, and others suggest values based on similar boards (e.g., "I know that D01 is a 1N4148W diode... As for C0, just guessing, but as it’s likely the voltage buffer for USB, 4.7µF to 10µF...").

So, any guidance on typical capacitor values for this MCU would be really helpful. Or, if anyone thinks the issue might be something else causing the board not to be recognized, I’d appreciate the insight.

[ncrowl]

(if measured in-circuit, these may not be entirely accurate):

C4, C5, C9 → ~(5.35kΩ)

C6, C7, C8 → (8.24kΩ)
...

? only voltage values can be measured in-circuit.

The 2 capacitors for the crystal-clock are 12-22 pF, they basically never breaks, is on pin XTAL1 & XTAL2 on the mcu.

One could probably use your friends "Pro Micro" to wire up a keyboard.
(or any mcu with USB host mode)

Its an mcu used by Arduino, also atmega, so there are tons of other forums.

[thelastangel_0]

Is the C4 capacitor in my board one of the two capacitors for the crystal clock (Y1)?

You mentioned that the capacitors for the crystal clock (XTAL1 & XTAL2) are typically 12-22 pF and rarely fail. Based on the PCB design and component labeling, would C7 also be related to Y1, or is it serving a different purpose in this circuit?

[zegonix]

before changing anything it is usually a good idea to try and identify the problem. as ncrowl already suggested, i would try to measure the voltages on the plugged in board. i would start with the usb and supply voltages on the voltage regulator, and continue with the vcc and ground pins of the mcu. if you have access to an oscilloscope i would take a look at the clock signal (measure on the components connected to y1) and if that doesn't show any errors i would check the uart lines.

about the capacitors.. usually there are 100nF at every vcc pin and a 1uF between regulator and chip, just before branching to the vcc pins. at the regulator one would often use a 100nF on both sides and a 10uF on one side (can't remember on which though). but check the manual for the chip in question to see the manufacturers recommendation on the values.

[ncrowl]

Is the C4 capacitor in my board one of the two capacitors for the crystal clock (Y1)?

You mentioned that the capacitors for the crystal clock (XTAL1 & XTAL2) are typically 12-22 pF and rarely fail. Based on the PCB design and component labeling, would C7 also be related to Y1, or is it serving a different purpose in this circuit?

dono what the other 2 capacitors do, take a peek at the GH60 schematics:
http://blog.komar.be/wp-content/uploads/2013/02/gh60_revC_2016-06-02.pdf
(cant find schematics for "DZ60" but think its similar, guess 1 or more are needed to stabilize main -voltage -rail, and then something to get AD-converter, -if thats in use..

But your "Pro Micro" is good? same mcu

[thelastangel_0]

Oh, and my "Pro Micro" board, which uses the same ATMEGA32U4 chip, is working fine, by the way.

I'm going to ask my friend who helped me at the beginning if he could check everything you're mentioning since he does have an oscilloscope.

what do you think about unsoldering the capacitors to test them? because I'm not sure if installing the new ATMEGA32U4 might cause it to burn out or something.

Just so you know, I'm really just trying to figure out what's wrong before I start swapping anything around.

I measured the values of literally everything:

Resistor Readings:

RCC1 & RCC2: 5.1 kOhms (0402 package)
R31 to R17, R46 to R33, R60 to R48,R76 to R62, R87 to R77: 0.994 kOhms

R1: 0.994 kOhms (Looks like this might be a repeat, assuming it's the same as above)

R2: Nothing showing up here (SMD 220)

R3: 22.0 Ohms (SMD 220)
R4: 8.86 kOhms (SMD 010)

R00, R01 (Assuming these are also 0.994 kOhms unless different)

So, next up I'm planning to check out the capacitors, the crystal Y1, and Q1 (the 9926A).
Any insights or advice you can offer on the missing reading for R2 or the idea of checking the capacitors would be greatly appreciated.

[ncrowl]

Oh, and my "Pro Micro" board, which uses the same ATMEGA32U4 chip, is working fine, by the way.
..
R2: Nothing showing up here (SMD 220)
..
So, next up I'm planning to check out the capacitors, the crystal Y1, and Q1 (the 9926A).
Any insights or advice you can offer on the missing reading for R2 or the idea of checking the capacitors would be greatly appreciated.

dono.. but check that you dont have a short -circuit, between "+" and "-" ("vcc" and "gnd", or the "1st" and "last" pins on your com-port). you can probably power the board from your "Pro Micro" on these pins.