The BKM-68x is an RGB / Component video input card for the A-Series BVM's. It is the only option
for getting RGB into an A-Series (cards from other models are not compatible) and they are extremely rare and
The BKM-68x cards are both hard to find and very temperamental to use. Many consoles seem to
have sync issues with this card, as the A-Series BVM's don't have the "VCR Mode / Automatic Frequency Control
(AFC)" that the previous BVM's offered, which cleared up a lot of the horizontal problems. At the moment
(very early in the testing stages), it looks like using an Extron 580xi might be a good
compatibility fix, however more information needs to be collected as to why the 580xi helps the
sync, as well as other methods of forcing compatibility.
Many of us are also testing every option possible to find a way to get 240p signals into the
A-Series BVM's without using the BKM-68x at all. Our efforts have mostly been futile, but we'll keep trying so
that maybe someday, A-Series BVM owners can have cheaper alternatives for RGB inputs into their consoles.
XGA was nice enough to donate both the operational manual and
the service manual for the 68x:
The first video is an overview of some of the common problems of the 68x, as well as possible fixes and
alternative input options. The second tries a possible fix and explains more about what the horizontal
sync issue actually is. I hope to soon have a follow-up video with more information, as I still need to
test PAL consoles and component video.
Many A-Series BVM owners are searching for alternative ways to get a 240p RGB signal into the
monitor without using the BKM-68x. At the moment, the only solution found ads one frame of lag and only outputs
480i (as demonstrated in the 1st video above). Any other solutions will be posted here.
VCR Mode / AFC & Why it's
needed for the SMS:
Here's some screenshots from the D-Series BVM manual, explaining what VCR mode
Another description provides a more technical description of the issue that Automatic Frequency Control will
correct: "It will also occur when the receiver is operated from a signal which does not have
horizontal slices in the vertical sync block." Apparently, the Sega Master
System doesn't have horizontal slices in the vertical sync block, which explains the root cause of the
issue. Without AFC, or a way to re-generate the horizontal frequency (such as by using a 580xi), the
SMS can never sync to a BKM-68x.
Here's a link to detailed pictures of the board itself, in case anyone's interested
in the actual circuitry: https://mega.nz/#!R1sFCZpQ!vxTkUyGhEe4fDaJ8nfUp5vyVETV6JhBlwVNy-KYX7g0
BKM-68X maintenance menu:
XGA also provided a guide on how to access the maintenance menu of the 68x itself, which isn't in the
manuals. Also, the main A-series maintenence password is 53415.
This is how you access the BKM-68X maintenance menu and also the options that are available (I don't believe
these options are listed any either of the operation manual or service manual for either the A20F1 or the
BKM-68X). If anyone has any suggestions on what options to enable / disable to get it to sync properly with
consoles like the AES, please speak up.
1) Press the MENU button and select "SYSTEM CONFIGURATION..."
2) Select "MAINTENANCE..."
3) Enter the password 53415 and press enter
4) Select the "BKM-68X..." option
Page 1 options
Page 2 options
Page 3 options
Well, that's it for now. I'll update this page as soon as there's any more information on the best ways to
make all consoles compatible, as well as any possible workarounds for the 68x.
Here's links to the main Service Manual
Page and the main RGB Monitor page. Also, feel free to check
out the main page for more retro-awesomeness.