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mikro

U-Switch/Lotharek's stereo schematics/functionality

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Posted (edited)

I wanted to take a closer look at the U-Switch, following the note which @flashjazzcat left in the other thread. However I have realised that not only U-Switch is no longer available but it's gone with all its documentation (if there even was any).

 

My main question would be: is it possible to use U-Switch for more than one switching task? Right now I have a stereo switch there (U-Switch's BIN <-> U1MB's M0, IIRC) and there are only the --1-- and --2-- pins there which seem to serve more as configuration pins than inputs.

 

And while we are at it, Lotharek's stereo seems to be gone as well (so no docs available, too...) -- I'm wondering about the three pins (Sr, Bell, A4). Bell and A4 are connected in my XEGS but Sr isn't? Is there more information about it somewhere?

Edited by mikro

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2 hours ago, mikro said:

And while we are at it, Lotharek's stereo seems to be gone as well (so no docs available, too...) -- I'm wondering about the three pins (Sr, Bell, A4). Bell and A4 are connected in my XEGS but Sr isn't? Is there more information about it somewhere?

Found it: 

 

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3 hours ago, mikro said:

My main question would be: is it possible to use U-Switch for more than one switching task? Right now I have a stereo switch there (U-Switch's BIN <-> U1MB's M0, IIRC) and there are only the --1-- and --2-- pins there which seem to serve more as configuration pins than inputs.

Finally found some answers: http://www.atari.org.pl/forum/viewtopic.php?id=11691 ... so it seems that yes, one needs one U-Switch for every switching operation.

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Quite unfortunate that those devices went down the memory hole. I found some interesting uses for them, including switching an internally mounted KMK/JZ 'IDEa' host adapter entirely on and off the system bus via software control.

 

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I built my first U-Switch using through hole components from a schematic that Lotharek sent me back before he started producing them and that worked great.  Of course, his version is much smaller and cleaner, but either way they are very handy devices for all sorts of switching.

 

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On 3/16/2022 at 11:46 AM, flashjazzcat said:

Quite unfortunate that those devices went down the memory hole. I found some interesting uses for them, including switching an internally mounted KMK/JZ 'IDEa' host adapter entirely on and off the system bus via software control.

 

 

You still can find the info about U-switch, if you know where to look.

 

https://web.archive.org/web/20160314031429/http://lotharek.pl/product.php?pid=112

 

The archive.org capture has a picture of the PCB, as well as the schematic (it's pretty simple).

 

Having the ability to bring up this kind of stuff is why I don't mind donating $$$ (or £££ in your case @flashjazzcat) to archive.org.

 

You should be able to find the docs for Simple Stereo up there as well, browse to https://web.archive.org and put the URL  "lotharek.pl" into the search box on the page.  The above link is the U-switch page from March 2016, so I would start there.

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Posted (edited)

He used a 4066 quad SPST bi-directional analog switch as the basis for the U-switch. An even more versatile switching chip would be the 74HC4053.

 

74HC4053.png.6f2ee9522fd559dca60efffa94495785.png

 

i used this as the basis for Mono/Stereo switching and blanking of the color signal in the VGATE circuit on the 1088XEL and XLD. Because of it's SPDT switching most any situation can be accommodated.

 

EDIT: unlike the U-switch, no inverter is required, since the SPDT will give you both normal and inverted action.

Edited by mytek
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