US Turbo Duo with no power

[crakattak]

Hello all,

A friend recently gave me a Duo console. I'm using the Radio Shack Tip Q with proper polarity, sufficient amperage, and 9 volts verified using a multimeter.

I'm getting no power on the console. No LED. No CD spin up.

I open the case and get 9 volts at the mini power board, and 9 volts at the fuse, which is good. I also get various voltages around the board. Keep in mind I'm not sure what voltages I should be reading, I'm just trying to find out where it's stopping but I can't follow along this board without a schematic or some guidance.

My questions:
a) Would the 7805 regulators still allow voltage to pass if they were faulty?

b) Does anyone have or know of any diagnostic procedures or schematics for the US Turbo Duo?

Thank you in advance!

kraky

[Tatsujin]

you should get about 9 volts before the 7805 (GND to pin 1) and 5V after the 7805 (GND to pin3). check some TTL/CMOS ICs which normally you should get the same 5V at the supply Pins (always between down right and upper left pin -> e.g 16 Pin IC = pin 8 and pin 16).

[Charlie]

There should be voltage on the fuse even with the switch off.  Check that you get voltage out of the switch when it is on.

There are 11 individual voltage sources.  Many are identical voltages, just separated for isolation.


There are two 7805's in the DUO(U302 and U303). 

There is a POR (power-on-reset) chip U304. 

There is a "Go/No-go" flag via U107, that monitors the 2.5V sourced at U101 (of course, U101 needs the 5V in the first place!)

There is a 2.5V source off of the 5V source from U303 via R321 and R322.

There is a delayed 5V source from U302 at C200.

There is an 8V (approx) source off the 9V source at C323 via C305 (set by zener on C305).

There is a 4.5V (approx) source off of U302 via D501.

There is a second 5V (approx) source on C952, sourced from the 5V on U303.

Make sure you are referenced against true board ground, at negative lead of C301,C307 or C308.  Tab of 7805 can be used also if you are sure board is not burnt.

Good luck
Charlie

[crakattak]

This is phenomenal info. Thank you guys so much! Now I can go in with a lot more confidence and hopefully get this Duo live. I'll report back with results good or bad.

kraky

[Charlie]

Minor typo:
"There is an 8V (approx) source off the 9V source at C323 via C305 (set by zener on C305)."

The voltage is approx 4V on C323.

Thanks
Charlie

[Charlie]

Gee, if I knew what that meant, I could probably answer it!

Charlie

[blueraven]

There should be voltage on the fuse even with the switch off.  Check that you get voltage out of the switch when it is on.

There are 11 individual voltage sources.  Many are identical voltages, just separated for isolation.


There are two 7805's in the DUO(U302 and U303). 

There is a POR (power-on-reset) chip U304. 

There is a "Go/No-go" flag via U107, that monitors the 2.5V sourced at U101 (of course, U101 needs the 5V in the first place!)

There is a 2.5V source off of the 5V source from U303 via R321 and R322.

There is a delayed 5V source from U302 at C200.

There is an 8V (approx) source off the 9V source at C323 via C305 (set by zener on C305).

There is a 4.5V (approx) source off of U302 via D501.

There is a second 5V (approx) source on C952, sourced from the 5V on U303.

Make sure you are referenced against true board ground, at negative lead of C301,C307 or C308.  Tab of 7805 can be used also if you are sure board is not burnt.

Good luck
Charlie

Charlie,

This chart has helped out a lot, The knowledge is invaluable for the techies here. I've used it in two repairs already. Thanks. 

i want to run big boost and i also want atleast a 100 shot of nitrous what all would i have todo to the 420a to make it hold that for right now i just wanna run about 12psi on my t3 turbo but i was to have a 100shot on top of that. and also when u are turboed when should you spray it to keep the engine from blowing up?

This may be in the wrong section of the forum..... I'll answer anyway 

I'm guessing this is for a Civic, seeing as you said it was a T3 turbo. If your running a VTEC 4-cylinder, I recommend going with a 10-12 psi boost. Install a full-flow race header, 2&1/4 true duals with an H-pipe out the back, stage-2 intercooler with quad-core, replace your second-gear synchro, install a short-throw shifter, hydraulic clutch, ISN ignition coil and computer, NGK double-platinum plugs, port and polish your head, upgrade your camshaft, and put a K&N filter in (stock shape, don't use a cone). Make sure to replace your leaky gaskets when you upgrade, as the increase will also increase the overall PSI in your engine.   

The 100-shot of nitrous is a sure-fire way to blow up a 2.2 or 2.3VTEC engine with too much stomp. If you build the engine right and can shift, you don't need laughing-gas.

[Charlie]

"This chart has helped out a lot"...

You're welcome...if you are keeping repair notes for later, make sure you get my second post about the 8V/4V typo.


--------------------

Aha!  It means "car"!

Charlie

[crakattak]

After a getting the proper voltages and becoming frustrated I moved on to other projects and have come back a month and a half later to find my Duo no longer suffers from the lack of power. However, now the CD motor refuses to spin up and the Duo asks me to "set the disk". I am now going to search for this issue in the forum and see if I can figure this out. I can play Hu cards just fine. WOOHOOOO!

Thank you all very much for your technical assistance!

crakattak

[nodtveidt]

skevenna73 is a spambot. Pay it no mind.

[crakattak]

Some progress to report. Hucards are still playing very well. CD spindle is in a state of no spin. Laser does its little dance and shines it's red love just fine. Each motor in the CD portion is tested good with a 9v battery. High voltage I know, but those little buggers can handle it and confirms to me they are functional.

I believe my problem is the magnet on the lid. I can get the CD to Spin up if I adjust the height of the lid. It's very touchy but I can get it to spin up but I cannot at all get it to any games' load screen. I always get the "Please Set Disc" message. I spent about 3 hours tonight playing with pads and spacers trying to find the "just right" distance that allows it to spin up AND load. Does anyone have any experience with this issue?

[nat]

Yes.

Solution: I took the magnet out of the lid completely. You can then just set the magnet on the spindle manually before closing the lid.

[crakattak]

Hi Nat,

Thanks for the tip. So far no luck with the magnet resting directly on the spindle. There seems to be a sweet spot that's a millimeter or two above the spindle. Kinda sucks and I'm passing out. Try again tomorrow.