5 silver pots on the Turbo Duo pcb?

[Platinumfungi]

I've looked right over them forever but I just got to thinking....five adjustable pots on the pcb have to be good for something.....? They're all fairly close together in the front right quarter of the pcb (on the top). I figure I'll start screwing around with them if no one knows.

Thanks for any info!

[kattare]

Bumping an ancient thread, I hope that's ok.

I have a PCE Duo I'm working on that has defied me for a while now.

The behavior is that after pushing RUN, it will spin up, and the laser will try to focus, but after a few clicks and whirs (CD spins really fast for a bit) it spins down and I get the "Please set disc" error.

I've replaced the laser assembly with a new HOP-M3, but the behavior is the same, even after playing slightly with the pot on the assembly itself.  Which leads me to believe the pots on the pcb need some adjusting.  Question is... what pot?  Which pots are for the focus, which are for the tracking, which are for the spindle, etc?  They don't seem to be labeled on the board and all I have in terms of test equipment is a simple meter.  (Man, I'd love to get a good scope, but I'm about 4 weeks away from a probable layoff.)

Taking it a step further, has anyone here done in-depth diagnosis of the possible focus/tracking/power issues specific to the duo pcb?  Or has anyone ever had access to a service manual?  I'd love to put together some step by step troubleshooting docs.  Especially since as these things age, there's going to be more and more of them in need of "love".

Cheers.

[blueraven]

"Please Set Disc" error in orange right?

I had that same error last month with a broken unit. The laser turned out to be very dirty (previous owner was a turbo gamer and turbo-smoker), which I cleaned with compressed air and a q-tip with glass cleaner, and then I had to re-set the laser back to the origin position. I used a small screwdriver and slid it along the track back to the left, lubricated the track with some grease, and after 2 attempts the duo booted the disc.

Sorry in advance if this doesn't help.

[kattare]

Blueraven, appreciate the input.

Before I replaced the laser assembly I did try to clean up the old one.  (q-tip w/ alcohol)

With the new laser, I'm pretty sure that it's not getting focus.  I just have no idea which pots are the focus gain and focus offset and no idea how to pin down which pot is which.  There's probably some series of steps you can take on a functioning system, tweaking one pot at a time, to figure out which pot is which, but I don't have that good of an understanding of the laser pickup system overall.

Fun times.  ;-)

[Game-Tech.US]

Before I replaced the laser assembly I did try to clean up the old one.  (q-tip w/ alcohol)

Fun times.  ;-)

Have you done a complete cap replacement yet? Maybe if its not getting correct power it wont load correctly?

[kattare]

I haven't yet... My next step is to transplant the entire mechanism from it into a working system.  If the mechanism all checks out, then I'll go the cap route.  I'll keep you all posted.  ;-)

[Charlie]

My notes on TurboGrafx 16 Duo may help:

VR101 = E/F balance
VR102 = Focus Offset
VR103 = Track Gain (Track error level)
VR104 = Focus Gain
VR105 = VCO

Charlie

(Maybe this data should go into the repair section?)

[kattare]

Damn Charlie, that stuff is GOLD.  Thank you!

[kattare]

Hey Charlie,

Following up - Any idea what/where the testpoints might be?  ;-)

Have you done a bunch of duo laser repair?

Cheers.

[Charlie]

These measurement points may help.

VR101 = E/F balance, pin 13 of U101
VR102 = Focus Offset, pin 18 of U101
VR103 = Track Gain (Track error level), pin 45 of U102
VR104 = Focus Gain, pin 48 of U102
VR105 = VCO, pin 30 of U102



Charlie

[kattare]

Following up...

I was able to get a bunch of the 100uf and 47uf caps replaced in this unit.  You could pretty much tell which ones needed replaced, they were all corroded around the connections.  After replacing a bunch of caps, it was able to play music cd's on the inner tracks no problem.  With Charlie's pot data I was able to take that a step further and got it reading first the full music cd, and finally with some fine tuning I got it to read a few different CD-R's.  Very nice.

Thanks a TON for the assist!

[Platinumfungi]

Great work guys As far as I know this is the only useful discussion about the pots I've ever seen!

I think it would be a great addition to the forums if one of you guys, or anyone who's willing and experienced, could make a short "Repair Guide" thread about how to adjust the pots for beginners. Just describing what each pot will alter in non technical terms so everyone can understand.

[kattare]

Made a new generic repair guide-ish thread about this and other things...

Unfortunately this kind of stuff really fits much better into a wiki or something similar.

Some of these repair threads have some real gold buried 10 pages into 'em.  It's just hard to find.  ;-)

[Charlie]

Check around, you are not the first to suggest some sort of repair manual.  And you are also right in the "gold" buried in a number of these threads.  I'm hoping someone will actually sit down and begin to collect the various pieces of info (based on the various consoles) and put them into some sort of useable form.

By the way, as I mentioned in another post, if you can tell us what caps you actually replaced (by number), I may be able to tell what their function is.  This info would of course be useful for the manual.

If I may suggest, it would be an additional help to measure the voltages at the measurements points.  This would help others who may need to adjust the pots; there would be less trian-and-error.

Thanks
Charlie

[blueraven]

By the way, as I mentioned in another post, if you can tell us what caps you actually replaced (by number), I may be able to tell what their function is.  This info would of course be useful for the manual.

A great idea, it may shed light on various problems by showing how each of the caps affect audio/video/performance of the unit! By describing it sequentially you could probably successfully diagnose a few other viewer's past problems.