NeXT ADB soundboard to NON ADB conversion?

Started by Rob Blessin Black Hole, May 08, 2014, 08:23:08 am

Previous topic - Next topic

barcher174

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.


Stefano

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 ?

barcher174

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

barcher174

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

Hialmar

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 :)

Hialmar

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 :(

gxs

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.

Hialmar

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.

gxs

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.


gxs

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.

Hialmar

Thanks a lot :)

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

Hialmar

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.

Rob Blessin Black Hole

Quote from: "Hialmar"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