What are these components (Atari STE schematics 'DL1' 'L403') ?

[sporniket]

Hello,

I am capturing the schematics of the video circuitry related with the generation of the video composite signal (i.e. around the MC1377 PAL/NTSC encoder).

In situ, that's this part (taken from my series of shots of my motherboard) :



There are 2 components that I cannot define completely : DL1 and L403

2021-06-05--02--schematics-excerpt.jpg

What I could infer so far, thanks to the datasheet of the MC1377 :

• L403 seems to be a passband filter, consisting of tuned coils. The datasheet has a sample application circuit mentionning such device from TOKO. And I could find somewhere some kind of catalogue/datasheet that look alike the component on my motherboard and with the same number of pins like suggested by the schematics. But I could not find any other details, namely the frequency range, from the marking on the component.
• DL1 seems to be a "Delay line" (there is a builtin symbol on kicad too). Again, nothing about the delay introduced, and I got nothing by looking for further data using the marking.

Here are the marking that I have on those components on my motherboard.

2021-06-05--01--what-are-these.jpg

So my questions :

• Please confirm that L403 is a passband, and DL1 a delay line ; or please teach me if I'm wrong.
• What are the parameters of each of those two components ? And it seems that it depends of the target system (PAL or NTSC).

Thanks in advance.

[exxos]

Maybe check all the service manuals to see if there's actual part numbers listed for therm.

[sporniket]

Yes @exxos, I could find some data in the STe field service manual.

For the record :

• L403 - part C100210 - Coil variable 24uH
• DL1 - part C100209 - Delay line 3.58MHz

[sporniket]

I have a last question about DL1 (the delay line) : does it follows a standard packaging (case dimension and most importantly the pinout ) , and which one ?

For L403 I could find some mechanical drawings from various manufacturer that I can follow to create a matching footprint.

I am not so lucky with DL1, I can't find any old enough datasheet/catalogue from Mitsumi (the brand engraved on the component) and it seems that each manufacturer has its own form factor...

I can only guess, looking at other motherboards without this component that the footprint looks like two footprints of L403 (without the shield) side by side. But the pitch is finer than L403.

[exxos]

You will probably have to measure and build your own part lib for it. I had to do that a lot with the remake boards. But I never bothered with the RF stuff.

[sporniket]

That's my plan, and the more data I have, the more information I can put in the schematics regarding those 2 components, for people looking for replacement parts. (of course if I ever remake a STE motherboard in the future, I will certainly ditch that part, too).

[czietz]

Note that these two parts are almost certainly custom-made for Atari. The delay line even has an Atari part number on your photo: C100213. Thus, I guess it's hard to find an exactly matching replacement, unless it's a "pull" from another Atari. I mean, it's clear what these parts are doing; therefore, one could redesign the circuit with off-the-shelf parts. But then again, who is going to bother with the RF modulator nowadays.

[sporniket]

Note that these two parts are almost certainly custom-made for Atari. The delay line even has an Atari part number on your photo: C100213.

I recently had a hunch, and you confirm it. Anyway right now what I would like to know is whether the form factor used for this custom component form factor is somewhat normalized. I mean, I want to believe that at least the manufacturer (Mitsumi) customized a generic component from its catalog. It would be better if it could have been something used accross manufacturer like "TO-92" for transistors.

I have no such problem with variable coils, I don't have a package name, but I find lot's of datasheets and technical drawings, like this one that I found this morning : http://www.gekade.com/downloads/to_conscheme.pdf

I mean, it's clear what these parts are doing; therefore, one could redesign the circuit with off-the-shelf parts. But then again, who is going to bother with the RF modulator nowadays.

I know, but I can't help feeling frustrated.

[tzok]

3.58MHz is a color subcarrier for the NTSC, but the delay line should introduce a... delay, and its nominal parameter is the delay time, which, for the NTSC, should be 63.5us. PAL color burst frequency is 4.43MHz and PAL 1H delay line is 64.0us.

That's the theory... but you'll find answers for your questions in the datasheet of the MC1377 video modulator circuit.

Filter is TOKO 166NNF–10264AG.

Delay line is DL122301D–1533 (400ns).

Clipboard-1.png

[czietz]

Filter is TOKO 166NNF–10264AG.
Delay line is DL122301D–1533 (400ns).

... in the datasheet, yes. But not necessarily in the STE. We (or at least I) don't know what Atari chose. The delay line has to compensate the group delay of the bandpass filter. I.e., it ensures that chroma and luma signals are delayed by the same amount of time. Thus, if Atari's filter design has a different group delay than the Toko filter from the datasheet, their delay line has a different value, too. (That's what I meant with "it's clear what these parts are doing".)

As for the packages: instead of searching for ancient datasheets or drawings, it might be quicker to just measure the footprint of the parts.