Turbo Express controlls not working

[megaman1981]

I recently purchased two Turbo Express systems.  I replaced all of the caps in both, and they both have great sound and video.  My problem is that on one of them, the controls don't work. 

I did replace the cap on the control board, so I know it's not that.  If I take the control board from the good TE and swap it with the bad one, I get the same thing, and the bad TE's board on the good TE, it works fine, so I'm assuming it is something on the main board.

When I play the racing game, I honestly can't think of the name of it, it goes to a name entry screen and the cursor starts moving around, but still no response from the controls.  Does anyone have any idea of where I should look, or what I should do?

[turbokon]

Check the tiny smd resistors near the hu6280 to see if they are still good and not damage.




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[megaman1981]

I checked them, and they all look good, and tested good.

[Fidde_se]

Sounds like something is shorted somewhere, a little stain of tin or even some electrolyte fluid somewhere, making one or two buttons behaving like they are pressed all the time.

Follow the traces coming from the keyboard connector.

[megaman1981]

Yeah, that could be.  This one, somebody had already replaced a couple capacitors, I think the ones for video, and they did a really poor job, so I replaced them all.  Maybe they messed something up when they did that.  I'll look a little deeper and see if I find anything.

[turbokon]

I had one where they damaged one of those resistors when replacing those caps. I would trace those down.


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[megaman1981]

I checked a bunch of resistors, and they all seemed fine.  There's so many, it's possible I missed some.  But there's the number on each one, and my meter gave that same number when I checked them.  There's one, labeled R723 that has a 000 on the back of it, and that's what the meter read, but it looked like one of the contacts was different than the rest, like the solder had been melted or something.  I don't know if that has anything to do with it, but I tried to melt it down hoping if the contact was broken to repair it.  It didn't change anything, so either that resistor has an issue, or it's something completely different.

[turbokon]

That 000 ohm resistor is just a jumper resistor to bypass the region check from pin 29 of the hu6280.  Check this post for the control pinout.

http://www.pcenginefx.com/forums/index.php?topic=12509.msg243169#msg243169


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[Fidde_se]

That's just a blob, an irregulation in the amount of solder, it's actually a defect by IPC standard Class 2 and 3, but in this, it will make no difference, check cheap Chinese electronics, like toys and they're practically built of it, so this isn't a problem.

[megaman1981]

I think I may see the problem.  If you look in this picture directly to the right of where it says CC10, the board is damaged from when somebody replaced those capacitors.  You can see the headphone jack is melted too.  Like I said in a previous post, that set of caps were replaced already when I got it, and not very well, so I replaced them again.  I think the connection from R719 and R723, maybe more, were damaged.  I'm sure I could bypass that bad spot if I knew where they went.

[NightWolve]

Ah, yeah, I see it, you gotta jump those damaged traces/pathways and see if that fixes it. Whoever did the cap replacement had trouble getting the old one off, he/she melted the plastic there and even damaged the PCB. The soldering iron was set to extra hot I gather as well for the PCB damage. Well, good luck!

[megaman1981]

anybody know where those lines go?  It looks like there are three right next to eachother, two from that group of resistors and a third I can't tell where it comes from.

[Fidde_se]

Take a look at this one.
http://www.retrosampling.se/Temp/Imgp0514_mod.jpg

I guess nr 1 is not damaged.

But nr 2, I cant see where that goes under the capacitor, but you might see that better if looking closer. A fair guess the hole next to the other in the other end. you can swab the bad looking part with a cottonstick and some alcohol, and you can see better what kind of damage there is.
with a "beeper" you can check for continuity between that proposed hole and the end of that bad traces as when traces are off there is a tiny piece of copper visible, and if it's not visible then scratch some until it does.

some wire and 3 and 4 is easily fixed