Problem with tunning DT40PRO

[Alex_kld]

Hi!
ihave problem,I have projector that you want to configure.
I tried to adjust his people, who had no manual. and did not know the purpose of each resistor, ie twisted them all in a row.
I downolad manual DT40 PRO and started to act In accordance with the procedure Adam Burns - Scanner Tuning Tutorial.
But in manual marked only LF DAMPING and SERVOGAIN.

after the setup procedure according to the method. still some distortion on the X axis at any angle.
Then I changed to cable from scanners to drivers, but this was not successful.

Give me advice, what my next steps? how to make adjustments in such cases?

[buffo]

Do you have the new style DT-40 amp? If so, it does not have a high frequency damping control. In that case, you can ignore the part of my scanner tuning tutorial where it talks about high frequency damping. You'll just need to balance the servo gain and low frequency damping controls to get the best image you can.

If you have the older style DT-40 amp, the high frequency damping control should be labeled. (I think it was located to the left of the Servo Gain control, looking down on the board from the edge where the pots are located.)

To tell which version of the amp you have, look to the left side of the amp. If you see a "daughter board" sticking up that has two extra pots on it, then you have the old version. This daughterboard is the notch filter, which was determined to be unnecessary and was removed in the later versions along with the high frequency damping control.

Adam

[norty303]

See this thread...

http://www.photonlexicon.com/forums/...ight=dt40+pots

Which has a link to this thread in post #5

http://www.photonlexicon.com/forums/...-s-Help-Please

[buffo]

Yeah, I looked at those threads before I posted. Unfortunately, none of the posts in those threads actually identify the tuning pots on the DT-40's.

Cruch posted a picture that might have contained the pot labels, but the link to the picture is dead now, so we'll never know.

I seem to remember that some of the later DT-40 amps had silk-screened labels on the bottom of the board for the tuning pots, but I could be confusing that with another amp design.

I'm at work right now, but when I get home I'll do some digging and see if I can find a copy of my old DT-40 cheat-sheet that Bill Benner put together for me back in 2007. (We didn't know what the pots were when he first tuned my galvos, so he figured it out on his own and wrote it down...)

Adam

[dave]

Adam: Jian still includes both the notch filter and the HFD AFAIK. Also, the pots are chained from DZ's manual.

Alex: Ill send you what I have for the most recent DT amp as far as I know. It might be that you are trying to tune by adjusting the wrong trimmers.

[buffo]

Hi Dave;

I went to the Dragon Tiger website, and this is the link to the latest DT-40 manual. http://www.dtelectronic.cn/DT-40Pro_User_Manual.pdf

If you look at the board, you can see that the notch filter is missing, and in the manual it states that the high frequency damping control has been removed.

I remember Bill Benner speaking with Jian about this idea back in 2009 or so. Bill's position was that the high frequency damping makes tuning much more difficult, and it didn't really add much to the performance. He recommended a fixed damping circuit for high frequency, and then just having servo gain and low frequency damping adjustments. From the looks of the .pdf above, it would seem that Jian followed Bill's advice.

Adam

[norty303]

Yeah, I looked at those threads before I posted. Unfortunately, none of the posts in those threads actually identify the tuning pots on the DT-40's

Look harder

Post #9 in my second link has an attachment called DT40Pro2.pdf (or something) which is a 4 page document with full schematics, and notated photograph of pretty much everything.

Not sure if I can link directly to the file, but here goes...

http://www.photonlexicon.com/forums/...8&d=1175332886

[buffo]

Ahhh... I didn't realize that the PDF that Yadda posted had more than one page. I was at work when I was looking at it, and I only ever saw the first page. Guess it was still loading the other 3! My bad... (Our Internet connection at work is notoriously slow.)

So yeah, that pdf file identifies the correct tuning pots for the original DT-40 pro amps (the ones with the notch filter) on page two, and again on page 4 in the picture. (By the way, the link you posted above works fine.)

If Alex has one of the newer amps though (the one without the notch filter), then he won't have the high frequency damping control.

Adam

[Alex_kld]

Hi!
thanks for answer.
i have this version DT40 PRO.

[buffo]

Your amp appears to be a hybrid of sorts. It's different than the original amp that Norty linked to above, and it's also different than the new version that Dragon Tiger has listed on their website.

Based on your picture, I believe your high frequency damping control is between J5 and J8 on the board. That would be the 5th pot if you start counting from the far left in the picture you posted. However, I'm not positive that this is correct. It could also be the third pot from the left, or even the 6th pot from the left, though I regard that as a long shot.

You can test this by making small adjustments to the pot while watching the test pattern. Make sure you note the original position of the pot before you start, so in case it's not the high frequency damping pot you can put it back where it was. But if it is the HF damping control, if you turn it down about 1/2 a turn, you should see some undershoot on the corners of the center square when displaying the ILDA test pattern. (Have another look at my scanner tuning tutorial for more information about undershoot on the ILDA test pattern.) Note that if it's the low frequency damping pot, turning it down will give you overshoot.

It is very important that you correctly identify the Servo Gain, Low Frequency Damping, and High Frequency Damping controls before you start tuning. If you don't know which pot is which, you will get lost very fast.

Adam