OSI Portable Project

[Sideburn]

I must admit I was fighting with mine to read the pulse width until I realised it was up there all along at the top of the screen

Haha I bet that will be the same case on mine too. I guess hunting it down on there will be easier than trying to do it on the old analog scope.

[ronin47]

I must admit I was fighting with mine to read the pulse width until I realised it was up there all along at the top of the screen

Haha I bet that will be the same case on mine too. I guess hunting it down on there will be easier than trying to do it on the old analog scope.

Yes, I expect it will

In addition I could adjust R57 and see the pulse width changing on mine.

[megardi]

OMG. What a beautiful build!

[Sideburn]

OMG. What a beautiful build!

Thanks your reproductions are amazing as well! https://hackaday.io/project/186956-osi- ... production

[Sideburn]

The service manual gives this as the way to adjust R57:


Screenshot 2024-05-13 at 09.03.23.png


It's what I've done for mine, getting it somewhere in the middle of the range, though I haven't yet confirmed my cassette in/out is working properly.

Just did the pulse calibration.

Didn’t get this right?

IMG_8387.jpeg (716.45 KiB) Viewed 6698 times

[ronin47]

The service manual gives this as the way to adjust R57:


Screenshot 2024-05-13 at 09.03.23.png


It's what I've done for mine, getting it somewhere in the middle of the range, though I haven't yet confirmed my cassette in/out is working properly.

Just did the pulse calibration.

Didn’t get this right?

IMG_8387.jpeg

Looks very like mine, so I think so

[Sideburn]

Thats with the pot pretty much maxxed out. If I turn it all the way up then it gets just a tiny bit wider. So 500us is about as good as I can get.

[ronin47]

Thats with the pot pretty much maxxed out. If I turn it all the way up then it gets just a tiny bit wider. So 500us is about as good as I can get.

Interesting, I can easily get up to near 600uS with mine.

[Sideburn]

Thats with the pot pretty much maxxed out. If I turn it all the way up then it gets just a tiny bit wider. So 500us is about as good as I can get.

Interesting, I can easily get up to near 600uS with mine.

And you are measuring the top of the waveform like I am?

If I max the POT out then i can get it goes to where the green arrow is (actually about half that far):

OH wait is that 600?

max.jpg (272.54 KiB) Viewed 6686 times

[bxdanny]

If you want to increase that pulse width beyond 500 microseconds, would it not make sense to increase R53 from 10k to 12 or 15k?

I'm thinking 12k would give a maximum pulse width of 550 us, and 15k would give 625 us, since the series resistance of R57+R53 would be increased by 10 or 25 percent.