Diagnosing a dead keyboard

[berserkfan]

I got a dead Rosewill pretty cheap. No signs of external damage to keyboard or cable. I plugged it in, and totally no response. Aquakeytester says nothing. LEDs did not light up. The much-maligned USB mini-connector is not loose.

Now I’m interested in figuring this out.

1)   How do I figure if it’s the USB mini-connector? And what do I do if it is?
2)   How do I figure out if it’s the keyboard controller? (Bpiphany has the cure if it is the controller.)
3)   What other possibilities exist?

I am not looking to save money as this is a learning project, so it's perfectly fine for me to spend more money on a Bpiphany controller than I spent on the keyboard. Most important thing for me is to learn and get some hands on experience.

[BlueBär]

I think rather something between the controller and your PC is broken than the controller itself - broken controllers tend to do some funky stuff instead of nothing at all. Assuming the board wasn't DOA, chances are high that the USB connector broke and not the controller.
Did you try a different cable? Check any traces that come from the USB connector or generally any traces around the controller area. You should try to resolder the USB connector in case a solder joint is broken. If the connector itself is broken, you could easily replace it if you find another one that fits.

[mougrim]

Yep. Try different USB cable - if you ain't luccky and it won't help, open this board up and test individual switches/PCB.

[BlueBär]

Yep. Try different USB cable - if you ain't luccky and it won't help, open this board up and test individual switches/PCB.

In this case testing the switches won't be of much use I guess, since the keyboard is not responsive at all.

[mougrim]

Yep. Try different USB cable - if you ain't luccky and it won't help, open this board up and test individual switches/PCB.

In this case testing the switches won't be of much use I guess, since the keyboard is not responsive at all.

I meant testing if PCB is in working order. But I think it almost certainly is.

[IvanIvanovich]

If the usb isn't broken, cold solder joint problem... then certainly it's the controller daughterboard. The main pcb has nothing but switch and some diodes... not much can really go wrong there beside cold joint problem.

[berserkfan]

Update:

(please see photos in OP)

I opened the Rosewill, and found no visible problem. The USB connector is firmly in place. The controller is firmly in place. I considered discarding the controller and wiring it to one of my teensies, but I have no idea what to do. Please see photo for what I have, and please tell me if I can wire this to a teensy for purposes of testing and to bypass the possibly-dead USB connector.

Right now the keyboard is still not powering up. Totally no response. LEDs do not light up in aquakeytest. Windows does not recognize this.

If IvanIvanovich is correct, the cold solder joint somewhere on the USB connector may be the reason. I don’t know much about these things, but I notice that the USB connector has five solder joints near it and these solder joints are super super close together. Is it possible that poor soldering caused them to short each other out?

Keyboard itself looks like new although the box is in pretty bad shape. I can’t tell from the superficial appearance whether this was a new keyboard that never worked because of the cold solder joints. Seller has no clue – they’re a commercial enterprise that trades these things in bulk.

Now here’s my problem. I should have no difficulty desoldering the USB connector. But if the pads are really so close together, I definitely lack the skills to resolder in the USB connector without causing big pools of solder to form and short everything out. In that case what can I do?

[BlueBär]

Yes, might be an unwanted solder bridge. If you want to resolder them make sure to use a small diameter solder and some extra flux, then it might work.

[berserkfan]

Yes, might be an unwanted solder bridge. If you want to resolder them make sure to use a small diameter solder and some extra flux, then it might work.

Any better solutions than that? I ask because I know myself well enough. There's no way I can manage 5 solder points so close to each other, regardless of diameter of solder.

Is there some way to test if the USB connector is the problem? If it isn't the connector, no point desoldering and trying to resolder it.

[fohat.digs]

There's no way I can manage 5 solder points so close to each other, regardless of diameter of solder.

All these are delicate and tricky, but it is already dead ....

Could you use a very sharp knife, or pin-point, and carefully scrape a "valley" between the joints?

Be sure to wear your reading glasses!

[BlueBär]

Is there some way to test if the USB connector is the problem? If it isn't the connector, no point desoldering and trying to resolder it.

Yes, with a continuity check with a multimeter.

[Grendel]

Is there some way to test if the USB connector is the problem? If it isn't the connector, no point desoldering and trying to resolder it.

Take the controller off and connect the bare main PCB to USB. Measure if the controller is getting 5V and GND (pinout is listed here.) If it is, the problem is most likely on the controller PCB. If it isn't, disconnect USB and follow the 5V/GND  lines from the controller to the connector w/ a ohm-meter (there are two bridges in the 5V line and six in the GND line betw. the connector and the controller.)

Edit: These are the lines to check:



Edit2: Whoa! Disregards the picture, your board has a different layout. Principle is the same tho.

[berserkfan]

Is there some way to test if the USB connector is the problem? If it isn't the connector, no point desoldering and trying to resolder it.

Take the controller off and connect the bare main PCB to USB. Measure if the controller is getting 5V and GND (pinout is listed here.) If it is, the problem is most likely on the controller PCB. If it isn't, disconnect USB and follow the 5V/GND  lines from the controller to the connector w/ a ohm-meter (there are two bridges in the 5V line and six in the GND line betw. the connector and the controller.)

Edit: These are the lines to check:

Show Image

Hey, this is a really meaty reply, thank you very much!

I don't fully get what to do, but that's because I lack basic electronics knowledge. I think I could look up some videos on electrical stuff and that might help me figure things out.

EG How do you measure if the controller is getting 5v and GND? I have a multimeter. Do I set the multimeter to measure continuity, then touch two leads to pin 18 (for Rosewill Ground) and see if there is a current?

[Grendel]

(Edited my previous post!)

Set the meter to measure voltage, touch one of the GND pins w/ the black lead and the 5V pin w/ the red lead at the same time. The meter should display 5V (or -5V if the leads are swapped.) If it shows 0, find the 5V and GND joints closest to the connector and see if the 5V are there, if so the problem would be betw. that point and the controller socket. If not, the problem is further up (connector, cable, computer.)

[Grendel]

So, does the controller get 5V ?

[dorkvader]

Since it's not being recognized by windows, your problem lies in one of the following:
cable
USB connector
PCB trace
Controller.

Before you get in there with a knife scraping up the PCB: be advised of the following: The USB connector has 5 pins, and only 4 are used. The fifth is used for a special purpose. Two of the pins are supposed to be connected (both to ground) It's hard to see, but this does appear to be the case.

I would check with your DMM to see if the controller is getting 5V as grendel says.

If all else fails, I do have a new rosewill PCB and controller that someone had me desolder switches out of. I desoldered it with braid, so some of the pads might be damaged. I can test the controller though. It might help you diagnose yours (or use for parts).

[laffindude]

All these are delicate and tricky, but it is already dead ....

Could you use a very sharp knife, or pin-point, and carefully scrape a "valley" between the joints?

Be sure to wear your reading glasses!

Best way to clean these bridges up is just add flux and use a minimally tinned iron tip. Drag up on the leads should wick away the excess solder. Though, you have to be careful on single sided board. Let the board cool for a bit between attempts.

I am pretty hamfisted and these connector isn't a problem.

[mouse.the.lucky.dog]

Before you do anything else. Did you check in "Device Manager" to see if the keyboard is detected?
That is really the only way that the keyboard is not detected. I'm a totally Linux guy now, so a windows guy would have to help with this.
Unless you want to burn a linux liveDVD/usb stick.

Next stop.  USB connector.

the pins from the picture of the PCB you have are numbered like this:

      2  4
   1  3   5

There is an extrasized pad that containes both 4&5. So they should like one solder gob.
1 is +5 and 4+5 is ground. So you should measure 5V at those two points when the keyboard is plugged in.

I think the DMM will not be sensitive enough to detect the other two signals. You could rigup an integrator http://www.allaboutcircuits.com/vol_3/chpt_8/11.html
whose output can be measured by a DMM and is the total voltage put in to the integrator. ( If you know calculus the integrator outputs the integral of the input voltage over time. )

I frankly suspect it is not the port. If it were, it would be loose. Of course if you don't check nature will rig it that you got a bum connector .

Soldering the connector is not too hard. Use flux pull away when it smokes do not add any solder to the pad unless you need to then only very very little. Use something like a third hand with a magnifying lens and look through the lens. Also use a very bright lamp.

[berserkfan]

Before you do anything else. Did you check in "Device Manager" to see if the keyboard is detected?
That is really the only way that the keyboard is not detected. I'm a totally Linux guy now, so a windows guy would have to help with this.
Unless you want to burn a linux liveDVD/usb stick.

Next stop.  USB connector.

the pins from the picture of the PCB you have are numbered like this:

      2  4
   1  3   5

There is an extrasized pad that containes both 4&5. So they should like one solder gob.
1 is +5 and 4+5 is ground. So you should measure 5V at those two points when the keyboard is plugged in.

I think the DMM will not be sensitive enough to detect the other two signals. You could rigup an integrator http://www.allaboutcircuits.com/vol_3/chpt_8/11.html
whose output can be measured by a DMM and is the total voltage put in to the integrator. ( If you know calculus the integrator outputs the integral of the input voltage over time. )

I frankly suspect it is not the port. If it were, it would be loose. Of course if you don't check nature will rig it that you got a bum connector .

Soldering the connector is not too hard. Use flux pull away when it smokes do not add any solder to the pad unless you need to then only very very little. Use something like a third hand with a magnifying lens and look through the lens. Also use a very bright lamp.

Just wanted to tell everyone, thanks for all this advice! I'm going to try out your suggestions within 2 weeks. Right now am too distracted... by other projects including my need to reprogram an awesome 80-1950 from DV.