Is this Magicforce 68 blown?

[auato]

Hello everybody,
As per subject I loved that keyboard, but one day, stubbornly, I decided to try for a DIY customized usb cable. Although I was extremely careful to mistake wrong connections, avoid short-circuits and I've a dicrete knowladge in electronic circuits and discrete manual skills, my MF68 stopped working .
Now, as you can also see in the video https://youtu.be/jcAjcOrP8ss, it's stuck with the backlights always on and no one key responds.

I have already tried a few USB cables, and more than one computer. Unfortunately I cut off the old white original USB cable (that comes with the keyboard) to figure out if it's a problem due to the connectivity and all the usb cables replaced are some chinese cheap ones. I also tried swapping the fifth shield pole with the fourth ground pole as suggsted by @KarmaUL in a thread https://geekhack.org/index.php?topic=91493.0 or making a short-circuit each other but none of these tests solved my problem. The main chip looks like a Holtek HT68F8560.

Have you ever experienced something similar on your MF68 or any other keyboard? And do I have a chence to fix it in your opinion?

[suicidal_orange]

Does the computer see a keyboard, or at least a controller chip, when you plug it in?  Or do you get an error about a malfunctioning device?  You move back to the keyboard at the crucial moment...

The LEDs may light up if just the power is connected (at least you know that is correctly wired)

[auato]

@suicidal_orange thank you!
No, any computer doesn't see the keyboard at all. Only backlight turns on. Device manager doesn't recognize anything and you cannot hear the usual Windows chime when you plug in a new peripheral.

[Darthbaggins]

Sounds like the pin-out might be reversed on the board connection.  As Orange said, we know your power and ground are correct or else it wouldn't light up - now to get the controller to function.

[auato]

@Darthbagginsbut thanks!
on the board I didn't touch anything. I could check some pins around that chip (for example clock and powr lines and or the output lines toward the USB connector) but, in any case, I'm not sure if a replacement for that controller will be easy to find. Suspected is also a small chip labeled as D121 (in the white circle) and also other discrete components like diodes and transistors.

Next step I am going to use a hairdraier to find a clue and i'll let you know.

[suicidal_orange]

As Darthbaggins said the first thing to try is swapping the data wires in the plug, they should have little tabs you can press in then the pins slide out so no soldering needed.  If it's backwards that could fix it, if not it wont do any damage.

[auato]

I just swapped the white wire with the green one but I didn't resolve the issue. Also I tried with an hairdryer (hoping for a poor joint). Finally I checked some signals with an oscilloscope: RST (reset) is high and it is a good status (it means that the controller in not kept locked). Strangely the two pins OSC are without any signal but constantly high (maybe that's normal condition as I presume that some pins share different functions). The output for data are stuck at high level when I type any key (that's not good). The only sign of life is a square wave at 1kHz on each key -

-

[yui]

for the 2 OSC pins seems normal if it does use an internal oscillator, or if you oscilloscope impedance is too low, and yeah the scare wave seems to indicate that the chip is scanning the matrix, so good, but have you tried to see if there is a short on your connector board / cable? either with a multi-meter or by removing the keyboard and testing the daughter board alone? cause if you still have 5v on the data lines then it would make sense nothing is working.

[auato]

Yes @yui it is trying to run scanning the matrix but maybe there's another problem somewhere and presumably I realized what happened ... I noticed -and you can notice in the pic- that the wires on the small daughterboard with mini USB connector were stripped and touched accidentally one another.
 IMG_1614 2.heic (223.58 kB - downloaded 73 times.)
I restored the weldings, removed the short circuits but unfortunatly the keybord is still not recognized by the computer. Most likely the white USB wire (Data-) touched all the time the red one (+ Vcc) and maybe the green one (Data+)  touched the adjiacent white one. Checking the PCB traces I noticed that the white and green wires go through two 22ohm resistors to the microcontroller and the multimeter detects a very low resistance (3ohms while the pure leads are at 0.1ohm) or a short-circuit between them:
 IMG_1616 2.heic (570.49 kB - downloaded 71 times.)
I'd like to know if a very low resistance between green and white is normal and if not if in your opinion the microcontroller HT68FB560 is a replacable component (I don't know whether firmware is present or not and in case it is it doesn't make sense to replace this part because I won't be able to reprogram it). Anyway those two 22ohm resistors would have had to prevent a sharp short-circuit so maybe I still can go to have a look around even though it looks like impossible to find an electric diagram.
For sure those stripped wires are not due to a fault of mine but due to a poor assembly.

[yui]

from what i recall the resistance between the d+ and d- should be very high, so yeah you have a short between them, although i can't open your images (i do not know what can open .heic files). i would have a hard time though imagining that the UC would not have been protected (usb datalines should be around 2.7/-2.7 max) and even if you can find the UC you will need the firmware. hopefully the 5v short blew a protection zener or something on the board. if it is the main UC that is dead, then the most effective repair may be to rewire/retrace the matrix and convert it to TMK/QMK, but that is more the territory of SO (well most of this is, he is much better than me at this )

[auato]

sorry it was my problem with the attachments so I put them agasin in jpg.
the mini USB daughter board:

and the controller:

It would be nice if someone could confirm the impedance between green and white wire from a working MF68. Unfortunately, as I wrote earlier, I do not see other components in the middle of the connector and the microcontroller (apart two 22ohm resistors labeled RA8 and RA9 which I checked as good). So... I can thing about something inside the controller which is destroyed. About how to convert it to TMK/QMK, for me it's totally a new and unexplored area so I also need to study further the community help... where do I start to document myself about the transformation?

[yui]

to me your micro usb daughter board still looks like it does have a ton of chafed wires, that could all be causing your short, have you tried to measure from the pins with the board unplugged, i am still rather very suspicious of it and before going for a full conversion we may be able to salvage this one. and if those 2 resistors read 22 and your schematics are good then a dead short on the UC side would read 44 ohms, so it kinda rules out the UC as being the culprit and instead something before those 2 resistors.
part of me thinks that the best course of action would be to to de-solder those wires from the usb board, cut the currently exposed part, strip a bit of the insulation off, tin it before they start chafing again and solder them back on, and given the quality of the wires, maybe add a bit of hot melt glue before final assembly, as a stress relief

oh and if this photo is before repair then disregard the repairing the daughter board, if your wires do not short like that anymore i suspect that it is just trash (the usb board, either internal failure of the pcb, or connector)

[auato]

That picture was before repair. You're right about something not completely clear about impedences. Both the resistors are good (22ohm) but if I measure the impedence between Data+ and Data-  the reading is 3ohm, after resistors (or directly on the chip pin 2 and 3) is about 46ohm. This reading lets me think about the sum of two resistors + something else on the PCB traces and that the chip is still in a good conditions with high impedence between pin 2 and 3. So, the short circuit could be on the connector side (below the connector or in the inner PCB layer or on the opposite side (which I cannot see bacouse I didn't desolder the MXs). I tried to lift the daughterboard connector but it's hard to do. Has anyone got a photo of the component side? Maybe on the conponent side there is a capacior bown between Data+ and Data- which is the culprit of the issue. In the video you can see the readings and that the doughterboard is unplugged

[auato]

As suspected there is something blown between Data+ and Data- but placed on the component side and not visible looking at the soldering side. In fact today I removed the smt resistors of 22ohm to isolate the microcontroller data lines from the daughterboard connector and rebuilt two temporary rails on fly with two new 33ohm resistors which were available. Of course the wires white and green have been removed from the connector. As you can see my MF68 is still alive   
and it is still a mystery about the component which propagates the short circuit.

[yui]

a fried decoupling capacitor? reverse polarity protection diode (strange that they would think you would plug in the usb backward)?
At least now you could leave it like that, or fix it properly.

[auato]

yes, I preferred to leave it as is... frankly I don't want to unsolder all the keys. Here is the final repair (I'm just waiting for the epoxy edhesive and then I can assemble my beloved MF68). Today I am very happy and I want to thank you all of you for supporting me and especially @yui 

[suicidal_orange]

The lead/wire looks dangerously close to R81 but will be fine once glued down - good work

And @yui - I have never played with an oscilloscope and didn't know that data lines were supposed to have high resistance so I learnt things today.

[yui]

The lead/wire looks dangerously close to R81 but will be fine once glued down - good work

And @yui - I have never played with an oscilloscope and didn't know that data lines were supposed to have high resistance so I learnt things today.

to be fair, i read the usb1 norm about 10 years ago and from the electronic i know i guessed that data lines should have high resistances, especially since apple used low resistances between D+ and D- to set charge current.

[auato]

The lead/wire looks dangerously close to R81 but will be fine once glued down - good work

Yes it is and you'right it is too close ro R81 but fortunately that is enameled wire.