Archive for June, 2020

BKM-129X compatible, full size version

Wednesday, June 17th, 2020

So, latest addition to the family of BKM-129X compatibles, is a full size BNC version.

BKM-129X compatible, full size version

This is functionally quite close to the original, as it now has BNC outputs also. Since I couldn’t find BNC plugs featuring auto-termination (at a reasonable cost at least), I decided to add a switch to each signal which will either terminate to 75 Ohm, or enable passthrough of the signal to the OUT port.

Top view

It is then possible to set the switches to OFF (down) and use external terminators, or simply skip mounting the switches altogether, and add a jumper/0 Ohm resistor to the lower left two pins of each switch footprint, and then use external terminators.

The board requires the same Arduino with the BKM-129X-MCU code, directly programmed to the Arduino with a programmer (read some of my previous posts regarding this).

The MCU code is here:

The Kicad project for the board here:

The 3D printable bracket here:

Card inserted to PVM-9L2
Two 9L2s connected, bottom is the full size card (before bracket)
SNES with passthrough

Please copy, share, produce and become rich, of this 🙂

BKM-129X compatible SCART Edition

Monday, June 15th, 2020

So now after having most of the BKM-129X compatible monitors tested out properly, and some minor hardware adjustments fixed, I’ve made a spin-off of the BKM-129X compatible board, a direct SCART version with audio passthrough, and selectable mono mixing circuit.

The BKM-129X compatible SCART edition

Now there’s really not much difference to this board and the BNC version; the BNC plugs have been replaced with a SCART plug (I’ve used a Ninigi SCART, and then the two RCAs are added which feature the stereo audio passthrough from SCART. Along is a selectable mono mixing circuit, which is activated by the push button switch between the RCAs. The switch is supposed to be added between the RCAs. When pushed in, the stereo sound from the SCART is mixed to mono, when out, it is direct stereo. The mono mode is meant for monitors with audio inputs (which is always mono afaik) so a short RCA cable should be connected between the black connector and the monitor.

I’ve created a 3D printable bracket to fit in the slots for these cards, which will make everything sit flush with the monitor. The files can be found here:

Inserted into a PVM-9L2 with the bracket

So not much to it, the Kicad project along with gerber files can be found here: