Turbo Duo doesn't power up

[ClodBuster]

My Turbo Duo, which has been fully recapped last year and gave me hours of fun, does suddenly struggle powering up. Not even the LED lights up when switching the system on.

I've checked the power supply for faults. It's a Goobay universal power supply ( http://www.premium-cable.de/Goobay-Netzteil-stabilisiert-flach-ACDC-5V-6V-7V-8V-9V-10V-11V-12V-5200mA-60W_p5921_x2.htm ), the output is set to 10V DC with the correct pin assignment. No trouble here.

Last time my console refused to work, I did a simple case reassembly to fix it even if I couldn't locate the root for the problem. Maybe there was just a bad solder joint somewhere?

I'll repeat the same, but I would also like to know if there are any signs to look out for once I got the console opened up.

[Keith Courage]

First check the fuse. If that is good then check the two 7805 voltage regulators. Every common for one of these and or both to go bad. Do you own a volt meter? That's the best way to see if they are working.

[ClodBuster]

Thanks for your reply. Yes, I got a Voltmeter, this is how I tested if the power supply still had 10V output.

I'll see if I can get any useful readouts from the 7805's after checking the fuse.

[ifkz]

Look around for cold solder joints at the usual places:
=On the Duo, there is the small PCB board that the power supply end plugs into.  If I were having power issues, I would just touch up everything on that tiny board with new solder.  Suck off the old, add new (reflow), piece of cake!
=Reseat the cable that connects to the motherboard from this tiny board.
=Lastly, I would reflow each of the 7805's legs.  They (x2) generate a lot of heat, and I would think the legs could have fractured the solder over the years.  After all this I would see if it is any different and then pull the meter out.

Once, I was refurbishing a first model Playstation (the one with the built in composite on the back) and it had a cold solder joint at the power pin that was preventing it from even powering up.  Usually the fault is itermittent, like you describe, but this was completelty stone dead.  It took 5 minutes to get it up and running (and a donor PS One drive to make it functional).

I hope this helps, it is really a quick job once you have everything disassembled.  Not hard at all, even if all you have is a non-temperature controlled $7 wand    I haven't had this particular issue yet, but I hope these tips get you going again.

[ClodBuster]

Surely they'll do! Time to fire the Weller up again. Good thing these components are rather easy to reach, unlike the caps. I'll let you know if I had success.

[ifkz]

Now that I've taken one apart and really worked on it, I have nothing but respect for NEC's engineers.  It is a really nice system to work on, everything is easily replaced if needed.  Good that you have a Weller, you'll go far 

I'll keep an eye on this thread, good luck!

[ClodBuster]

So, the system is now open again and one of the first things I noticed was one of the wires to the AV port was loose. Congratulations to the previous owner who did the RGB conversion with a screw-on type DIN socket to the plastic case instead of using one that solders directly to the PCB. Nice botch job, every now and then I see wires coming loose from the pins, I'm kind of used to that look now.
Time to remove that PITA DIN socket and rather screw a DB9 socket to the rear of the console, just a la GameSX.

Unfortunately this wasn't the root of my Turbo Duo's problem.
The fuse is fine. One of the regulators (the left one) heats up excessively, while the other one stays cold. When I got the PCB out of the case and looked from the underside, I could see that the small solder joints from the "cold" regulator are looking suspiciously small and flat. Too bad I couldn't measure any Voltages directly from them, since I needed to unplug the main PCB from the small power inlet PCB to get it flipped.

I would really like to re-solder anything in that area, but at first I need to buy some more tin-lead solder tomorrow. Maybe I'll also try again getting any further measurements.

[ifkz]

Sounds like you are well on your way to a healthy Duo 

[BlueBMW]

Wellers are good... I do really like my Hakko FX-888 tho

[Bernie]

I prefer hair dryers myself.  Nice blast of heat.

[ClodBuster]

Just a humble WHS40. Nothing special, but at least it lets me use different types of tips.

@Bernie: Lol, I heard about that story, but never saw pics.

[pulstar]

Wellers are good... I do really like my Hakko FX-888 tho

The Hakko is really nice in my opinion as well.

Clodbuster, looks like you've found the area where the problem is. Hopefully it's just a dry joint and a quick reflow will sort you out.

[ClodBuster]

My poor 40 W iron isn't really up to the task of resoldering the big 'ole heat sinks, but the 7805s themselves got new solder now. I saw that the black wire at the small power input PCB wasn't attached to anything. I assume it should be attached to ground like seen on this picture:
http://www.pcenginefx.com/forums/index.php?topic=3249.0
Funny enough the Duo worked for months without the wire being attached.

I also saw my Duo is missing the HuCard metal cover, since I got it region-modded from the previous owner.

Let's see if I can get it back running tonight.

[ClodBuster]

Blast from the past.

In the meantime, I upgraded the electronics equipment of my hobby room to a Weller WS-81 soldering station, a Voltcraft LPS1153 15V/3A adjustable lab power supply and two DMMs (EEVblog Brymen BM 235 and Fluke 12E+). Makes working on electronical doodads much more pleasant than before.

Last night, I started troubleshooting on my Duo again. I set the power supply to 10V and limited the current to 1A max, and hooked it up to the Duo's power input.

I double-checked the voltage and current flow by hooking up one of the DMMs in parallel and the other one in series. Voltage was fine, but there was no current flow shown, neither on the lab power supply nor on the DMM.

Then I unhooked one of the DMMs to check for voltage between GND and some points on the Duo's PCB. The fuse was fine, it showed 10 V DC. However, the power regulators did not show any voltage. They weren't heating up, too.

Strange. I will go deeper into troubleshooting in the next days.

[ClodBuster]

Rookie mistake. Before measuring, I should have flipped the power switch on the Duo.

D'oh.

Well... There are still some odd things going on that I need to sort out before continuing with the repair work. I'll let you know then.