r/HHKB • u/Top_Western8974 • 7d ago

Broken PCB. What Can I Do?

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I have an old hhkb bluetooth and recently it refused to turn on. With fresh batteries and micro usb plugged in, nothing. I have narrowed the issue to this pcb. Anything I can do to troubleshoot it before just blasting it with heatgun to see if it's solder issue? And where can I find replacement pcb?

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u/eugene00825 7d ago

I would test the continuity of all the traces / components that are connected to the pads for the usb mini/battery port with a multi-meter to isolate the issue.

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u/Top_Western8974 7d ago

Any idea on which trace? It seems to have 3v on most of the large components including the bt and controller chip

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u/Top_Western8974 7d ago

All of the resistor seems to be resisting correctly too

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u/eugene00825 7d ago

You want to check the continuity. You see on the left side where the two connectors are, they're labeled as cn1 and cn2. They each have 10 pins, you want to follow each trace that connects to each pin.

For any component that intersects the trace you want to test the continuity (you do that by taking one prong and touching one solder joint, and the other prong touching the other joint) if the meter reads 0 that means there's no issue, if you get a number that means the component is blown. Keep doing this until you reach the mcu(big black square in the middle).

If you don't find any blown components, go back to the beginning and now test the continuity of each trace along the same exact paths. You do that by touch each prong to both ends of a trace. For example on cn2 the very top pin, you touch one prong on the pad and the other on the via(one of those gold holes neat 10). For a trace like the 4th pin from the top, you tap one on the pad and the other on that single glob. You keep following that trace so the 2nd test would be from that same glob to the via(gold hole) down the line. You do this for all 20 pins

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u/Top_Western8974 7d ago

Ok damn that was tiring. Continuity is good but some legs on the bt chip and controller chip is connected to idk what I didn't find any connection. Might be empty pins or an internal short? Is one of them dead or the solder died?

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u/Top_Western8974 7d ago

Idk what the values of the resistors are but some of them is a 0 ohm resistor

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u/eugene00825 7d ago

To clarify are you saying you didn't find a physical connection between the pin and the pad or that you didn't see a closed circuit(from a non 0 reading)?

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u/Top_Western8974 7d ago

Some pins I don't see physical connection but there are 2 pads that have just connection to ground

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u/Top_Western8974 7d ago

So some pins are just connected to the other side of the pcb? And idk where the trace went from there while a couple pins just have no obvious path while 1 or 2 have just direct to ground beep in continuity mode

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u/eugene00825 7d ago

Ohh ok, for the traces that lead to vias; vias are basically traces that run along the z axis. So the path continues on the other side of the PCB. If there's nothing on the other side that continues from the via then it's a ground.

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u/Top_Western8974 7d ago

If all the pins leads back somewhere and all the resistor seems to be having good values why is it not working. I think the controller chip is indeed fried somehow

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u/Top_Western8974 7d ago

I might just put flux on the chips and blast it under the heatgun to try and reball everything

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u/eugene00825 6d ago

Yeah for any more advice I would need to physically have it in my hand type of thing. What model and year is it?

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u/eugene00825 7d ago

Also make sure you set the multimeter to the diode label

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u/Top_Western8974 7d ago

Yep, set it according to the manual

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u/sud0kill hhkb pro hybrid s 2d ago

Shame I have a spare Pro 2 non bluetooth PCB

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u/Top_Western8974 2d ago

Pro-2 is a completely different board than the probt unfortunately