Reading Discs

[SteveH4263]

Does anyone have a photo of where too hook the multimeter leads too the pot? I have a multimeter and a newbie when it comes too this stuff. So what do I need to do to measure the resistance on the multimeter? How do you keep the leads on the points to measure resistance?

[Raen]

A multimeter is not really mandatory for the job, you can just rotate the screw with a screwdriver and go by trial and error.

Some say that you need to rotate the screw to the right, others say to the left, others that you can't rotate the screw either way too much or you will burn the laser, etc, but what others say isn't always true.

I've calibrated the lasers on my Dreamcasts a few times - different GD-ROM drive versions; and they all appear to have a mechanism on the screw that makes it possible to be rotated 360º without any problem, that it'll just return to the initial position - if you rotate it too far from the "read zone", the laser will enter a "dead zone" where the disc will spin too slow or too fast and the laser won't be able to read it, even though he tries.

The usual conception is that tweaking the potentiometer will rise/reduce the voltage output to the laser head, making it able to read past scratches, dust, etc, but there's also the idea that is supported by some tech savvy people, that tweaking the potentiometer adjusts the voltage output to the DC motor that spins the discs, and not to the laser head itself.

While I can't be certain about this, because I never dealt with a multimeter onto the GD-ROM disc mechanism PCB, from my experience this is what actually happens, as only the disc spin mechanism suffers behaviour changes and not the laser head, which continues to work as usually does.

Imagine a clock, from my experience, the "read zone" is comprehended between 10 and a half and 1 and a half or so - rotating the screw and placing its pointer (usually a red dot or a bigger indentation) pointed to a direction other than that area, will just make the disc too slow or too fast as I've told.

You can go by trial and error as most people do (rotate screw, place disc, hold the lid lever and see if the game launches, if not, redo the process until it does - its just a question of fine movements sometimes), but if you really want to use a multimeter to be sure, I don't know which voltage/resistance values you must be looking out for, as I don't even know what voltage input the GD-ROM drive takes from the Motherboard/PSU pins.

As for the process itself, there are numerous videos on Youtube, just search for "Dreamcast laser calibration" or something like that

[Wulffee]

Once you hit that dead zone where the drive stops spinning dial it back the other way and keep trying its just like the other poster said its like a butter zone in which the laser will only work in. I have ruined a launch system laser i tried to repair but out of all the other DCs I have that was the only one. Also tidbit dont even hookup the av cord keep the top off and power up holding the back latch down for the disc to spin if you dont hear that high pitch beep for the disc to load try and try again to tweak it till you do. It is very simple to do for anyone. Good luck hope you fix it. Also almost forgot check the other post I have posted on about this Meguiars Car Stuff called Plastix another member suggested cleaning the laser with it with que tips, works like a charm I would do that before you tweak the pot.

[SteveH4263]

Well that didn't answer my question about the pot. I have done the above. I want to know how to use a multimeter to read the resistance on the pot and how to keep the leads on the pot? Help please.

[Paspie]

Well, I finally got round to ordering another Dreamcast. The new (to me) unit is in almost flawless cosmetic condition, but I have the same issues as when I bought the first one: some discs work, some won't.

There doesn't seem to be any correlation to the condition of the discs themselves. One of the non-functioning games has one the most undisturbed surfaces of my collection. However, this is an opportunity to get my repair job right because the laser unit is still calibrated to factory spec. I'll probably try the headlight 'resurfacer' mentioned in another thread, which should bring some life back to the lens.

[krssn]

Post deleted because apparently Paspie thinks an answer on how to use that multimeter is unwanted at this point.

So yeah, you wanna know how to use a multimeter on the laser, you're gonna have to ask someone else.

[Paspie]

Checking the timestamps for posts, especially when responding to them, always helps.

[krssn]

Checking the timestamps for posts, especially when responding to them, always helps.

Does it matter?...

I'm sure there's other people who might be interested in this also.

It certainly beats not answering his question, posting misinformation, or resurrecting old threads with rather pointless posts and then whining about someone answering a 3 month old question...

[Paspie]

Checking the timestamps for posts, especially when responding to them, always helps.

Does it matter?...

I'm sure there's other people who might be interested in this also.

It certainly beats not answering his question, posting misinformation, or resurrecting old threads with rather pointless posts and then whining about someone answering a 3 month old question...

This is my thread, I can do whatever the **** I want with it. And that means you're not going to argue about whatever I say is not productive, you're going to accept it.

My last post was made with the mindset that people could comment on it if they wanted to...I wasn't anticipating a response from the start.

[krssn]

No worries. I took the explanation down.

Hope you're happy with your thread now.