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NeXT ADB soundboard to NON ADB conversion?
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barcher174



Joined: 07 Dec 2012
Posts: 556

PostPosted: Sun Nov 02, 2014 8:49 pm    Post subject: Reply with quote

I used a 150ohm resistor across the RGB VGA signals. Another thing I'll mention is that you need to use a properly shielded cable to connect from the cube to the sound box otherwise you'll end up with distorted video. The next original cables are fine, but I've seen issues with 3rd party cables meant for Apple II's.
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barcher174



Joined: 07 Dec 2012
Posts: 556

PostPosted: Sun Nov 02, 2014 11:41 pm    Post subject: Reply with quote

I did another one today:

Inside:

https://www.dropbox.com/s/m32ebg478nbvb8v/IMG_0088.JPG?dl=0

Outside:
https://www.dropbox.com/s/p1r24wt68qgrle4/IMG_0089.JPG?dl=0

Also updated the howto doc with VGA information:

http://www.asterontech.com/Asterontech/next_adb_conversion.html
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Stefano



Joined: 29 May 2014
Posts: 8

PostPosted: Mon Nov 03, 2014 12:43 pm    Post subject: Reply with quote

Just to better understanding:
For the VGA connector, I must solder ONE 150 ohm resistor, one of it's terminals soldered together to the R, G and B pins of the VGA connector; other resistor terminal soldered to the monochrome signal (the RCA plug on the soundbox).
Correct ?
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barcher174



Joined: 07 Dec 2012
Posts: 556

PostPosted: Mon Nov 03, 2014 1:20 pm    Post subject: Reply with quote

Yes that is correct. The RGB signals should be shorted with a single resistor.
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barcher174



Joined: 07 Dec 2012
Posts: 556

PostPosted: Sun Jan 25, 2015 8:09 pm    Post subject: Reply with quote

It seems Belkin KVM cables make a reasonable replacement for next original cables. I modified a 25 pin cable and see no distortion on the VGA. Here is a cheap lot on ebay:

http://www.ebay.com/itm/321444570314?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

--
Brian
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Hialmar



Joined: 27 Jan 2007
Posts: 24
Location: Toulouse, France

PostPosted: Tue May 12, 2015 12:25 am    Post subject: Reply with quote

Hello,

Could you please re-post your explications and photos from your Dropbox barcher174 ?
All the links I tested end up in 404 errors.

Thanks a lot in advance,
Patrice

Edit: my bad everything seems ok here:
http://www.asterontech.com/Asterontech/next_adb_conversion.html

Thanks a lot Smile
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Hialmar



Joined: 27 Jan 2007
Posts: 24
Location: Toulouse, France

PostPosted: Tue May 12, 2015 2:19 am    Post subject: Reply with quote

Sorry for the double post but I know have a real question:

Where can I find the mini-din 5a connector where the non ADB keyboard plugs in ?

The rest sounds easy to find.

Of course I could cut the non ADB keyboard connector and hook it to the soundbox board but it would be a pity Sad
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gxs



Joined: 19 Dec 2010
Posts: 6
Location: Belfast, UK

PostPosted: Tue May 12, 2015 3:48 am    Post subject: Reply with quote

Mouser.com has a couple of options for panel mounted 5 pin Mini-DIN sockets.

In stock part numbers are -
806-KMDPLX-5S-280
161-381/5-E

Non stock items that can be ordered in small quantities are -
490-MD-50SV
490-MD-50CV
490-MD-50PL100

I could not find any 5 pin at Farnell or RS.
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Hialmar



Joined: 27 Jan 2007
Posts: 24
Location: Toulouse, France

PostPosted: Tue May 12, 2015 5:22 am    Post subject: Reply with quote

Thank you very much.

I'm not sure those are compatible though. The NeXT keyboard as a rectangular plastic thing in the middle of the connector.
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gxs



Joined: 19 Dec 2010
Posts: 6
Location: Belfast, UK

PostPosted: Tue May 12, 2015 6:26 am    Post subject: Reply with quote

3-pin to 7-pin Mini-DIN connectors have a plastic key and slot in the plug and socket respectively. Each pin count has the key/slot in a different location. This stops incorrect mating of connectors with different pin counts.

See http://en.wikipedia.org/wiki/Mini-DIN_connector for more details.

The pictures on mouser.com and on the first page of the data sheets provided by the manufacturer are usually a random representative from the range. So although you choose a 5 pin Min-DIN the illustration may be of an 8 pin connector. The data sheets should have a "technical specification" that shows dimensions, pin layouts etc. that will give accurate information for each part number in the range.

From the outlines it looks like it may be possible to alter a 6 pin socket to approximate a 5 pin socket by enlarging the slot with a small drill and blocking off the extra pin. 6 pin Mini-DIN sockets are widely available since they are used for PS/2 keyboards and mice.
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barcher174



Joined: 07 Dec 2012
Posts: 556

PostPosted: Tue May 12, 2015 9:07 am    Post subject: Reply with quote

I like these:

http://www.digikey.com/product-search/en?vendor=0&keywords=MD-50PL100

--
Brian
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gxs



Joined: 19 Dec 2010
Posts: 6
Location: Belfast, UK

PostPosted: Tue May 12, 2015 10:26 am    Post subject: Reply with quote

I forgot about Digikey. I've never used them.

The part you mention looks to be the same as the last item on the Mouser list I posted - 490-MD-50PL100 by CUI Inc., though Digikey do have them in stock.
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Hialmar



Joined: 27 Jan 2007
Posts: 24
Location: Toulouse, France

PostPosted: Tue May 12, 2015 11:39 pm    Post subject: Reply with quote

Thanks a lot Smile

Digikey is present in France so that's very good for me.
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Hialmar



Joined: 27 Jan 2007
Posts: 24
Location: Toulouse, France

PostPosted: Wed May 13, 2015 12:16 pm    Post subject: Reply with quote

Just a small question:
In the modification as we output the HSync and the VSync separately on the VGA connector do we still need a LCD monitor that accepts Sync on green ?

Thanks in advance.
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Rob Blessin Black Hole
Site Admin


Joined: 05 Sep 2006
Posts: 587
Location: Ft. Collins, Colorado

PostPosted: Thu May 14, 2015 2:22 pm    Post subject: Reply with quote

Hialmar wrote:
Just a small question:
In the modification as we output the HSync and the VSync separately on the VGA connector do we still need a LCD monitor that accepts Sync on green ?

Thanks in advance.


I think as long as the monitor supports 2 bit gray scale it should work as DB19 connector to video chipset on mono or cube motherboards is just 2 bit gray scale. 1280 by 1024 resolution and synche on green would be for the NeXT Video Color systems only.

Best regards Rob Blessin
_________________
Rob Blessin President computerpowwow ebay sales@blackholeinc.com http://www.blackholeinc.com
303-741-9998 Serving the NeXT Community since 2/9/93
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