Shared Projects

W9AC Drake R4 AF Board

W9AC Jensen Mic Isolation Transformer-XLR

About

It’s a well-known fact that certain MSX2/2+ computers have a so-called “HIC Board” - the special “Hybrid IC” daughterboard that is mounted onto the MSX computer’s motherboard and provides certain functionality. This functionality is as follows:

• converts RGBS signals to composite video
• pre-amplifies and buffers audio
• mutes audio at startup and on pause to prevent clicks
• mixes all audio inputs
• amplifies and buffers the cassette interface signals
• buffers cassette interface’s relay operations

This board is known to be installed in the following MSX computers:

• Sony HB-F1II
• Sony HB-F1XD
• Sony HB-F1XV
• Sony HB-F1XDJ
• Sony HB-F1XDmkII
• Panasonic FS-A1mkII
• Panasonic FS-A1F
• Kawai KMC-5000 (Panasonic FS-A1F OEM)

Normally, the board works just fine, but there’s a problem with 3 electrolytic capacitors - they leak and damage the board, sometimes beyond repair. Fixing the leaked boards is difficult as some components can separate from the corroded solder pads, some tracks can be corroded under the CXA chip resulting in the board’s malfunction.

The original HIC board’s schematics and layout can be found here: http://elec-junker-p2.blog.jp/MITSUMI%20EMC-NX0039_REV02_PU.pdf

HIC Board’s Redesign

Taking into account all the above listed problems, it was decided to clone the HIC board and at the same time add the following improvements:

• use a better and commonly available encoder chip CXA2075
• add s-video output capability
• try to get rid of the original 4069UBF chip’s dependency
• make the HIC board detachable

It was also desired to get rid of the 2 special components: IMN10 and FMW1, but they appeared to be still available for purchasing, so they remained on the redesigned board.

During the redesign there appeared a few problems. The 4069UBF chip from Toshiba was used by the original engineers as an amplifier, so the board’s audio and cassette interface operations were dependent on certain features of that chip. When trying to replace this chip with similar ones, for example 74LS04 or 74HCT04, the audio functionality was crippled. The only possible replacement appears to be 74HC04 with 68pF capacitor added between pins 3 and 7 (GND). See the “74hc04_fix.jpg” image in the Pics folder.

The optional resistor R35 should not be installed unless the cassette input circuit doesn’t work as desired.

Where to buy parts

At the time of this readme’s creation the parts are available from the following sellers:

• pin headers (male and female): https://www.aliexpress.com/item/4001122376295.html
• CXA2075 encoder: https://www.aliexpress.com/item/33020885081.html
• 4069UBF: https://www.aliexpress.com/item/1005002494421415.html
• 68uH inductor: https://www.aliexpress.com/item/1005002963165525.html
• LMV358M amplifier: https://www.aliexpress.com/item/4001116443945.html
• 68pF trim capacitor: https://www.aliexpress.com/item/4000222152928.html
• 2SA1037 transistor: https://www.aliexpress.com/item/1005002503421569.html
• 2SC2411 transistor: https://www.aliexpress.com/item/1005004568437670.html
• IMN10: https://www.aliexpress.com/item/1005004322498640.html
• FMW1: https://www.ebay.com/itm/325038640119 or from Wierzbowsky (RBSC)

The resistors and capacitors 0805 and 1210 form factor can be ordered from any reasonable seller.

(experimental and as yet untested)

This is a differential buffer for connecting cheap voltmeters (for example: https://amazon.com/CenryKay-4-5-30v-Digital-Display-Voltmeter/dp/B08PB5NDMC) to the individual sticks of a Honda hybrid car’s IMA battery pack. The battery pack of a Honda hybrid car has 120 NiMH D-cells arranged in 20 sticks of 6 cells each. The cable running from the battery pack to the BCM (Battery Condition Monitor) has voltage sense taps for every two sticks. We tried attaching ten of the cheap voltmeters to these sense lines. The voltmeters have only two wires, which are used for both sensing the voltage and powering the meter. The problem is that it seems the taps are not tied directly to the battery – there must be some sort of current limiting resistor in each wire. The current drain of the voltmeters is enough that it changes the voltage read by the BCM, which throws a hissy fit and shuts down the hybrid assist system.

Here are some pictures from our first attempt: https://www.insightcentral.net/threads/yet-another-ima-problem-post.130739/page-2

This experiment uses a high impedance differential amplifier to read the voltage across each pair of sticks, and translate that to a ground referenced voltage with enough drive to run each voltmeter. The maximum voltage that might come out of the battery is less than 200 volts with respect to ground. The maximum differential across each pair of sticks is around 19 volts. The buffer that reads the highest stick pair might see inputs at full charge of 184 and 165, with a difference of 19 volts. With these inputs, the buffer would output 19 volts, referenced to vehicle ground, with a drive of around 25 ma to drive the voltmeter.

QSPI flash board for SAM9x75 EVK. Beta release.

MVP2 interface

Transistor Radiosonde Balloon Telemetry Transmitter Board Version 2.

Based on the ©1964 design of project #27 from 103 Simple Transistor Circuits for a “Telemetering Transmitter” but added 2nd channel TX control, and filtering for 27 MHz un-licensed ISM Band. Using mostly period technology - keeping BJT only NPN Si types vs. PNP. The only “modern” component added is the white LED Beacon. Definitely overdone.

More details on Github and my site: Project27

Low Frequency filter board for Hafler DH-110 preamplifier to replace C19, C119 capacitor assemblies

Breaks out the SiLabs MINI-S 2x5 debug interface to a standard ARM SWD 2x5 interface and a header with UART TX and RX. A 0 ohm resistor can be used to route either SWO or UART-TX to the ARM SWO pin.

http://frotz.net/projects/silabs-debug-adapter/

Davis ISS Receiver with TFT LCD Display. Uses Moteino with 915MHz RFM69 module.

Simple Transistor Balloon Payload Transmitter Board Version 1. It is a “Modernized” Project #27 from 103 Simple Transistor Circuits ©1964 using NPN Si Transistors vs. the original’s PNP Ge transistors. This was originally intended to be a balloon payload that transmits temperature info on the 11-meter or 10-meter bands. For scale the battery holder is a AAA cell.

PIC Programming adapter. Ver 4 with hole revisions to accept ZIF socket up to 20 pins