Trying to tune DT40Pro

[JimBo]

I've decided to tune my DT40 pros.
They have been working sort of ok, but definitely not great as they should be.
I've put the 12/30k test patern up, scan rate set at 30k in ShowRider (I'm using my FB3), the scan angle works out at 8%.
As shown in the picture part of the blue circle is missing and it is also completely inside the square and elongated.
I can't seem to improve this at all even by dropping the scan rate down to 12k.
With it like this I can't even start tuning it. What do I need to do in order to get it to a point that I can start working on it?
I'm pulling out what little bit of hair I have left.

Jim

[Pangolin]

Hi Jim,

One tricky point about that pattern. It can't be displayed "full size", or actually, anywhere near full size when you do the adjustment. I recommend no greater than 8 degrees wide!! when you do the tuning. Otherwise, the circle just won't look right.

Best regards,

William Benner

[JimBo]

It is at 8 degrees (% was meant to be degrees).
Any suggestions?
Is there anyway of winding the pots right back and then to a kown state or anything?
Which part of the tuning is out in the pic?

Jim

[buffo]

Jim,

You need more servo gain on the Y to get the circle back. (The eliptical shape comes from having your X scanner running faster than your Y.)

Have a look at the revised version of my scanner tuning tutorial. If you have already measured the scan angle and are sure you're at 8 degrees (plus or minus), then you're ready to tune. You can ignore the part where you adjust the size of the scanned image, since you're already at 8 degrees.

Adam

[JimBo]

Cheers Adam, I'll look at that version.

Jim

[JimBo]

This may seem a silly question, but where do you adjust the scan angle with the FB3?

Jim

[stanwax]

Jim
It will be what ever changes the output scan size - you will have to work the angle out yourself - have you downloaded my chart? Search for a thread called 'something useful'.
The control isnt called scan angle as the software cannot relate to the actual angle as the scan amp gain will affect this too.

Rob

[JimBo]

Cheers Rob,
The scan angle is already at 8 degrees (measured using trig), it's just that I noticed in Adams guide it said reduce the scan angle to about 5%.
The only thing in the FB3 software that I can see is in Projector Setings and then under the "Master Size and Adjustment" tab, where you grab the tabs and reduce the size of the box.

Jim

[JimBo]

Rob, what's your experience like on tuning galvos?

Jim

[stanwax]

I have tuned various scanners inc my own CT6800's (and someone elses CT 6215's) but never had a go with the DT40's - willing to help you out though if you want - im a suckker like that

Rob