Fried IC9?, possibly more issues

Discuss x0x construction and related issues

Moderators: altitude, adafruit_support_bill, adafruit, phono, hamburgers

Please be positive and constructive with your questions and comments.
rememberence
 
Posts: 9
Joined: Mon May 21, 2012 4:28 pm

Re: Fried IC9?, possibly more issues

Post by rememberence »

MMM wrote:
rememberence wrote:[
Well, i tried the ground-pin (pin20) and i got totally different voltages.
So i tried to see if ground-pin on J4 is the same as pin20 on IC3 (beeping-mode on my multimeter) and i wont get any beeping.
This is a bit tricky to explain. There *might* be a problem here but since there are so many different things that could go wrong it's not easy to say right now.

The mainboard has two different grounds: "analog" ground and "digital" ground. The "analog" ground is supplied from J4 (together with the "analog" voltages 5.33v and 12v). The digital ground is supplied from J3 (the ribbon cable) together with the "digital" voltage 5v (and various additional signals). Those two grounds are not connected to each other on the mainboard itself.

HOWEVER:


The grounds are tied together on the IOboard.

So with either J4 or J3 NOT connected you will get no continuity between pin 20 of the processor (or processor socket) and the ground pin of J4. But with both J4 and J3 connected you should definitely get continuity.
Ok!
Great :)

Another thing i was thinking about was if i have soldered in the wrong resistor somewhere, would that account for the wrong voltage perhaps? I will doublecheck the resistors just to make sure.

User avatar
mmm
 
Posts: 517
Joined: Tue Apr 24, 2012 1:51 am

Re: Fried IC9?, possibly more issues

Post by mmm »

rememberence wrote: Another thing i was thinking about was if i have soldered in the wrong resistor somewhere, would that account for the wrong voltage perhaps? I will doublecheck the resistors just to make sure.
While I wouldn't rule this out as a possibility it appears not very likely at the moment. There could be some kind of unwanted copper bridge on the PCB or something else.

Let's try a step-by-step approach.

First, disconnect IOboard and mainboard completely. Connect power supply to IOboard and turn it on. Since we want to find out if the 5v supply is working properly we're doing all measurements on J3.
If you look at the solder side of J3 (on the IOboard) you'll see that the trace coming from IC20 (the 5v regulator) connects to two pins of J3: pin 3 and pin 4. The two ground pins belonging to it are pin 7 and pin 8.
Measure the voltage there. You should get 5v from pin 3 and/or pin4 to pin 7 and/or pin8.

If that works out ok make a very thorough check if the ribbon cable and it connectors are positioned properly (so that pin 1 of the IOboard goes to pin 12 of the mainboard).
If that is ok connect IOboard and mainboard by ribbon cable only.
Remove IC2 and IC3. If other IC's are socketed in this section of the mainboard remove them, too.
Check continuity between pin 40 of the IC3 socket and pin 3/4 of J3 on the IOboard. (This is to make sure that the ribbon cable isn't faulty.) Do the same for pin 20 of the IC3 and pins 7/8 of J3 (again on the IOboard).

If that works out ok power up the xoxbox and measure the voltage between pin 20 and pin 40 of the IC3 socket. Measure also the voltage between pin 20 and pin 9.

Locked
Please be positive and constructive with your questions and comments.

Return to “Making x0x”