BACP DSTR-20 adjustment

[Frank Raia]

I finally was able to hook up my DSTR-20. Adjusted the delay in the cp500 so its doesn't look like a bad godzilla movie, lol. Green light stays green while playing. film travels smooth. Error rate is always 5. No matter what reel.
Im sure finding 69T test film is impossible.
So how can I decrease my error rate?
Yes I use Film Guard.
Yes I have an oscilloscope.

[Ryan Gallagher]

Error rates of 5 are pretty typical for vintage prints. As long as you are not having frequent fail overs to optical there may not be much room for improvement?

Depending on the print we often see 4-7 but then every now and then we'll have a great print that runs in the 2-3 error range.

If via the scope you have adjusted the waveform peak voltage, and done what you can for the best focus on the data waveform... assuming it is staying central and steady and not moving all over the place, you might be there already. You also want the data waveform to have a relatively horizontal response across the peaks.

We have a CP650 here so someone more familiar with the CP500 will have to chime in if using WinDRAS or DRAS is possible to monitor the SRD.

Aside, 69T is not "really" needed for digital tuning, it is mostly for optical level adjustment (but it is something you should look for to keep the optical happy), the later versions of 69T did include the digital data as well. With digital it either reads within it's error correcting range or it or it doesn't, and the volume level is baked in. Really any print/trailer with SRD can be used, keeping in mind that the SRD will track differently print to print.

[Ryan Gallagher]

That said if you want more explicit advice, I'd post a picture or video of the data waveform on the scope so we can judge.

[Frank Raia]

Thanks Ryan. I will take pics of the scope for sure. I kind of thought the print age would be a factor, but was hoping not.

[Ryan Gallagher]

Thanks Ryan. I will take pics of the scope for sure. I kind of thought the print age would be a factor, but was hoping not.

More so with Acetate prints... cause the shrinkage will cause alignment drift. But I have plenty of poly prints come through our booth that exhibit equally variable tracking print to print. There is some variability in the manufacture of the prints too.

Do you have the pin probe to BNC adapters?

When I finally got a "permanent" scope connection solution going it involved these items:

2 total: Pomona 3221 pin probe to BNC adapters
https://www.digikey.com/en/products/...cs/3221/745057

And 2 50ohm BNC cables to reach the scope on a shelf nearby:
https://www.amazon.com/dp/B0CBJGZ24S

[Frank Raia]

Ryan, Thank you for those links, I am going to order those!! I was using paper clips (dont tell anyone).

[Randy Stankey]

Try using your fingers to gently squeeze the edges of the film, just before it enters the top of the reader. If the error number goes down, add another roller in the film path, above the reader, to apply just a bit of back tension on the film.

I had the same reader at Mercyhurst and I was getting the same readings as you. When I added back tension to the film, my readings went down to three or four.

[Frank Raia]

Thank you Randy, I will give it a try!!

[Marco Giustini]

Failing the proper plugs, you can use multimeter probes. They fit perfectly in the 2mm holes and then you can clip your scope onto them. On the pins protruding from the test points.

You don't really need 69T for SRD, thought it might give you more certainty that it was properly printed, I remember it was not necessarily the best option!
Error rate of 5 for an old print seems ok to me. You can use that very print to try and tweak it and see if it improves - of course if the print was badly printed, you'll be making a "proper print" worse but I wouldn't count on a better option unless you have one of those "calibrated" prints with Azimuth and other parameters written on top - which means that they've been compared to a perfect print and you can use it as absolute reference.

[Frank Raia]

Thank you Marco, thanks for the multimeter tip!

[Ryan Gallagher]

CAT III and above MM probes are annoyingly useless for this side project. ;-)

[Josh Jones]

Grab a bunch of trailers and put them together in a reel. That will give you a good average to look for. My home setup runs an average about 3.5 on most material, but I have some tags made by fotokem for the iWerks Extreme Screen that track at 0!

JJ

[Marco Giustini]

in my 25+ years cinema experience I only had ONE print reading at zero! As Josh says, most stuff would read around 4 but 5 was also common.

[Ryan Gallagher]

Thank you Marco, thanks for the multimeter tip!

I had to check the docs. But at least Dolby DRAS supports communication with the CP500 or DA20 for monitoring SRD tracking. I assume the more modern WinDRAS would too but a similar manual is not in the archive. The software installs are in the film-tech warehouse. WinDRAS is definitely another thing to get going if you are trying to monitor/improve SRD.

https://www.film-tech.com/warehouse/manuals/DRAS.pdf

I've had the most luck with USB "FTDI Chipset" to serial cables such as these with my 650:
https://www.amazon.com/dp/B006AA04K0

Avoid the Prolific Driver ones (just more of a headache). As the serial port on the CP500 is on the rear, 6ft minimum I would expect... but you can always add USB or Serial extension cables if needed.

I've run WinDRAS 1.042 on both Windows 10 and 11 at this stage. Easy with the FTDI cables.

I've not tried to make DRAS work on modern computers. It pre-dates Windows XP and probably wants a real serial port? Some folks here have discussed using it because it has some launch flags that enable other modes that are useful for other tasks.

[Frank Raia]

Ryan, I think I have that cable. Going to download the DRAS program. Also ordered the correct scope plugs that you referenced. This weekend will run some DD reels and will post pics..

Thank you