Open Source Sega / Gremlin G80 PSU boardset

Over the past couple of weeks; I’ve been designing a replacement G80 PSU for the Sega/Gremlin G80 Vector machines specifically for my Star Trek Captain’s Chair.

I began by using National’s WebBench to design a simulate the 5V and 12V switching PSUs which would replace the linear PSUs on the original board. IMHO; the problem with existing linears is that you’re limited to the Pd of the BJT in the circuit. That BJT leads to a lot of wasted heat in the system. Having said that; I like linear supplies as they are easy to debug and build… for less than 1A of draw.

The Transformer and diode bidges will remain. My intent it to have the board somewhat drop in place of the existing board. I say somewhat; because the power-MOSFETs will need to be bolted to the existing heat sink on both switchers. I’ll probably keep the linears for the negative rails.

I imagine one will have to drill and tap the existing heatsink with some new mounting holes for the mosfets.

Web-bench gave me the following designs:
5V >4A Switcher

12V >2A Switcher

These boards were laid out and put on a single piece of FR4 so they can be assembled as a pair. The design is currently in my BatchPCB shopping cart; waiting for the parent board to complete it’s design phase. Nothing really to write home with regarding these PCBs… I expect the 5V switcher to meet a minimum of 5A… possibly much higher. It’ll likely be limited by the 8A diode bridge on the main parent board. The 12V switcher should meet a min of 2A… probably limited by the 4A bridge on the parent board.

The main parent board is the host for the switching board pairs; and holds the audio amp(s). The main board is currently in development; I’m adding the 12V diode bridge and the final audio AMP.
12V >2A Switcher
Clearly this is an eye-chart schematic. It might be easier to look at the segaSTpsu_rev-99 .

The first notable change is that I’ve replaced the main Audio AMP #1 with a ClassD part from Maxim: MAX9742. This integrated AMP IC should provide specs better than the original discreet amp on the board. It’s configured as a bridge tied load (BTL) targeted for a 23V/V gain with a -3dB frequency of 25Hz. This -3dB frequency and gain was obtained from a spice simulation of the original discreet circuit.

Other notable changes include:

  • Q23 (2N3906) makes “pull down” pulse remover for the CPU board. In the G80 PSU; R23 and D1 make up a pulse circuit which is sent to the CPU board. The CPU board has a 555 timer which implement a missing pulse detector. If a pulse is missed; it puts the CPU into reset. If my theory holds; the 2N3906 acts as a pull down preventing pulses from reaching the 555 timer – which puts the cpu in reset. So if my switching PSUs are not in regulation; this transistor effectively provides a not-“power good” signal to the CPU.
  • U3, U4, and U5 are power good circuits / detectors. U3 is a MAX8215 which monitors the 4 main digital rails to the G80 card cage: +5, -5, +12V, and -12V. These four voltages are “compared” and if in regulation a high is placed on the OUTx lines. These four signals are ANDed together and sent to DIN where it’s “delayed” by ~200mS via C20/R12. This allows the PSUs to stabilize before the CPU is given the “OK” via Q23. U5A and U5B/A1 provide “power good” LEDs for the various power rails – to aid in quick debug of the G80 PSU.
  • U2 provide a local 3.3V linear PSU to power U5 and the pullup on OUT3 (+12V m0nitor). This was done to enable OK12P to drive !SHDN on the ClassD amp. !SHDN cannot have more than +4V driven into it – hence the 3.3V source/pullup. Idea is to prevent premature popping/clicking while the PSU(s) are coming up. The 12V should take the longest to come in regulation and it’s also similar to the VDD/VSS supplies used in the ClassD amp. Additionally !RESET (Dout/U3) drives the “mute” pin of the (SFT / U1) meaning the ClassD amp should remain muted until the “power good” signal is sent to the cpu board.
  • C32/33/L5 (and C27/24/L12) provide a PI filter to reduce vripple into the switching regulators- increasing their stability.
  • I kept Linear Regulators for the lower power rails (-5 and -12) but upgraded the regulators to the National LM2990 as they provide better short circuit protection and slightly more current (1.8A). If desired; one could “in theory” drop in the cheaper/older 79xx series  negative regulators to save costs. They are pin compatible.
  • I’ve put fuses on the +/-12V regulator inputs which are missing from the original G80 design. F6 is a resettable fuse given it’s low power and we need board real estate for other items.
  • Finally LEDs were put in parallel and under the glass fuses on the board. The theory is that if a fuse blows; the LED become a small 10ma current path and the LED lights indicating to the user that the fuse is blown. I neat debug feature if you ask me -hope it works.

I hope to complete the main board design as soon as my upgraded pcb license comes in.
Once I finish the design and validate/test it… I plan to release the design and PCBs via the TAPR open source license.

See a design error? Speak up!

Notes: Enabling NTFS on LG NAS ( N2B1 )

Jotting down some Notes for enabling the LG N2B1 BluRay NAS to read/write NTFS partitioned USB drives using new firmware and the NTFS-3G package.

  1. Flash new N2B1 firmware to enable SSH server so one can get access to the command prompt on the device:
    Tantalus’ N2B1 Firmware
    Author used N2R1 2569t
  2. Enable SSH in the web console and login into the NAS device using a SSH Client.
  3. login as root . See FAQ
  4. if virgin use of apt-get; initialize the repositories using:
    apt-get update
  5. use apt-get to install gcc compiler.
    apt-get install build-essential
  6. apt-get will fail to install libc6 library; use workaround here:

    mv /sbin/init /sbin/init.mv
    touch /sbin/init
    chmod 755 /sbin/init
    dpkg –configure libc6
    apt-get update
    mv /sbin/init.mv /sbin/init

    WARNING: If you execute the first command, you have to execute the last command, before you reboot your NAS-Box

  7. repeat apt-get install build-essential
  8. gcc -v to verify gcc compiler has been installed and is working.
  9. download NTFS-3G from Tuxera.  Author used: ntfs-3g-2010.10.2
  10. untar: tar xvf ntfs-3g-2010.10.2.gz
  11. cd ntfs-3g-2010.10.2
  12. ./configure –prefix=/usr/lib to install to the correct directory. on Author’s system; the system autoconfigured to /usr/local which caused problems during make install.
  13. make
  14. make install as root. or sudo make install
  15. you should then be able to to mount NTFS partitions using:

    mount -t ntfs-3g /dev/sdb1 /mnt/ntfs

Many Thanks to forum.NAS-Portal.org for hosting the information necessary to piece this together.

GTB Black Hole repo-ed fuse cards

While finishing up my Black Hole project; I found the need to replace my rotted fuse cards with some fresh replacments.

Before:

After:

Thanks to Jim (Gott Lieb?) on RGP for helping me figure out the garbled wording. This post has been updated with the fixed WARNING card.

I’ve made the file available in PDF form so Black Hole owners can replace the fuse cards on their machine.

These resulting PDF file is licensed under the Non-Commercial Creative Commons license.

Gottlieb Black Hole Fuse Cards

Gottlieb Open Source PopBumper Driver Board?

I just successfully; built my prototype Gottileb PBDB design and have tested them in my Black Hole Pinball project at AustinModders.com. I have decided to release this  design under to the public under the TAPR Non-Commercial Open Hardware License which indicates:

You may make products based upon this design, provided you do not make more than ten units in any twelve month period for your personal use.

The design include the recommended fixes from marvins u-fix it site including both  Power and Fire LEDs. It also features protection circuitry including a barrier diode and a resettable fuse to try an prevent damage to other devices in your machine. The Logic on this board is Low-Voltage tolerant; so it should operate in situations where +5V is low.

The design uses the more readily available and cheaper TIP120 transistor for driving the popbumper coils.

Schematics :

Click to view GTB PBDB FabB Schematics in PDF

The PCB is designed as a pair; IE you get two boards in the same foot print as the original. I designed it this way to minimize PCB cost, aid in building multiple units, and enabling the boards to be snapped apart after assembly. The board is a two layer PCB with mostly surface mount parts on the top layer to minimize PCB real estate. The TIP120 driver transistor is mounted on the bottom layer again to keep the board size low.

PBDB Fab B Top Layer w/ Silkscreen
PBDB Bottom w/ Silkscreen

For those without PCB layout tools; a set of two bare PCBs are available from the batchpcb service for under $28. You can purchase the boards from this link:
http://batchpcb.com/index.php/Products/44762

The Bill Of Materials (BOM) of a pair of boards is available from Digikey for $10.70 (as of the time of this post). A CSV file with the digikey part numbers is here: A8_PBDB.bom.csv

Here’s a package of the materials above as a single download: GTB_A8_PBDB_pkg.zip

Here are some pictures of the prototypes assembled and installed:

Edit jzitt 11/4/2010 to add batchpcb order link