What are these circuits? Mimo Genius II - Page 1
Forum section: electronics / beginners

author: ReeseRiverson
author_rank: Newbie
timestamp: February 04, 2016, 06:26:07 pm
content: I have a Mimo Genius II here that I would like to diagnose a little bit, or at least figure out what's going on here. It has a CGA/EGA input on a 9-pin D-Sub terminal. When I opened it up, I saw some circuits I couldn't make out what they are.On the picture I attached, they are labeled RM11, RM12, and RM13 on the PCB right behind the connector. They are 8 pin circuits with the numbers 103 on them. I couldn't find any information online regarding what "RM" stood for, and I really couldn't find any schematics.Basically this thing recognizes the sync signal coming from my IBM 5150's CGA output, but there's no image displaying. When I run my Tandy 1000 on EGA, it's missing a lot of color information. Whites were blue/light blue, and on a game, it was just blues and a green color showing. I'm wondering if, for some reason, it's not getting the primary RGB signal. EGA has a secondary RGB signal. Which is what allows it to retain backwards compatibility with CGA. The specs on their site show CGA/EGA to be well compatible, but I am not sure what's going on.http://www.mimoenterprises.it/wp-content/uploads/2012/11/GeniusII1.pdfSo my first thought, is to diagnose it, but it'd help to know what these circuits are in particular.Any help is greatly appreciated, thanks!

author: AF6LJ
author_rank: Unknown
timestamp: February 04, 2016, 06:29:19 pm
content: They look like resistor networks. to me.Just a package with some pull up resistors inside.

author: ReeseRiverson
author_rank: Newbie
timestamp: February 04, 2016, 06:38:21 pm
content: Quote from: AF6LJ on February 04, 2016, 06:29:19 pmWould it be possible they use those to combine signals together? It appears they have these hooked to both the primary RGB and secondary RGB together (regarding the EGA pinout).These signals are not analog, they're TTL based from my understanding for both CGA and EGA.

author: Mickster
author_rank: Contributor
timestamp: February 04, 2016, 11:35:21 pm
content: AF6LJ has indicated what they are already - resistor networks, also known as resistor arrays and in this case, Bourns calls them Chip Resistor Arrays:http://www.bourns.com/products/resistive-products/chip-resistor-arraysThe "103" indicates the resistance value, in this case 10K Ohm per individual resistor.There are 4 in each of the arrays in your image.If you need to know the 3-digit codes on resistors, you can look here:http://www.hobby-hour.com/electronics/smdcalc.phpDon't know for definite, so I am simply guessing that the 'RM' designation on the silkscreen probably stands for 'Resistor Module'.Regards.

author: miguelvp
author_rank: Super Contributor
timestamp: February 05, 2016, 07:13:26 am
content: CGA and EGA have TTL level signals for color.CGA has Red, Green, Blue and Intensity applied to all RGB.EGA has Red, Green, Blue and Intensity per color component (so intensity for Red, Green and Blue are separate)That port is the CGA/EGA connector, so it's applying the per color intensity to the color channel in question, so a 2 pin R2R DAC in essence.The video processor might require analog, so that's there to combine the Red and Red intensity together and the same for the Green and the Blue.