Sega SC-3000 Repair

Defect:

• The graphics of the games is not displayed correctly.
• The BASIC cartridge does not work.

Replaced Components:

• 2 x MCM4517-15 RAM (IC12/IC13).

Note:

I have replaced the two RAM MCM4517-15 with a classic RAM 4164 (also used in the Commodore 64) paying attention to short-circuit the pin 9 and 10 of the 4164 RAM.

The MCM4517-15 RAM are 16,384 Words x 1 bit while the 4164 is 65,536 x 1 bit, both are PINOUT compatible except for the pin 9 which in the MCM4517-15 is not used while in 4164 is A7.

This “tricks” to short-circuit the pin 9 and 10 instead of using a resistor of pull-down is also used in some coin-op arcade boards that use the same RAM.

Gallery of the repair:

Mattel Intellivision with ZOE RGB (Limited Edition)

Why is Limited Edition?

Because i have made these works:

• Shielded cord Male MiniDIN Scart (cable length: 2,5 meters) also the cable that connecting the female connector MiniDIN to the PCB of the ZOE RGB is shielded.
• Female connector MiniDIN installed in the RF signal output hole and strongly fixed.
• Removed the RF Modulator.
• Installed a electrolytic capacitor in series of the output audio.
• Minimized the flat that connects the ZOE RGB with the Intellivision Motherboard.
• Installed the metal cover on the solder side of the motherboard.

Gallery:

12►

The TI 99/4A Flash ROM Cartridge, or FlashROM 99 for short, is a cartridge for the TI 99/4A home computer that allows for running ROM cartridge images stored on an SD card.

The FlashROM 99 supports ROM-only images of up to 32K that use the write-to->60xx bank switching scheme. It will not work with programs using GROMs or CRU-based bank switching. The cartridge does not require the Peripheral Expansion Box and runs on both PAL and NTSC consoles.

FlashROM 99 is released as Open Source Hardware under the CERN OHL license and the GNU GPL license. Both hardware design files and firmware sources are available on GitHub.

The project homepage is hosted at GitHub.

Gallery:

Download: FlashROM 99 SD Card (1200)

source: endlos99.github.io/flashrom99 ti99iuc.it

Texas Instruments TI-99/4A – Navarone’s Widget Multi Cartridges Fixed.

Works that have been made:

• Annoying short circuit under the cartridge connector on the slot 3 between the pins: 4,6,8,10

Texas Instruments TI-99/4A – Alpha Lock Joystick Fix.

This mod fix the problem of the alpha-lock key that need to be up or down when you are using joysticks.

The instructions for the Alpha-Lock Joystick Fix can be found here

Texas Instruments TI-99/4A – CPU Overclocked at 3.58mhz

This project allows you to increase the speed of your console from 3mhz to 3.58mhz. It might not sound like a big increase but this is a 20% increase in speed and it is easily noticable.

The instructions for the CPU Overclock modding can be found here

Gallery:

Texas Instruments TI-99/4A – Internal TMS5220 Speech Synthesizer.

The instructions for the internal assembly of the TMS5220 Speech Synthesizer can be found here

Gallery of the works that have been made:

It could be better!

I had severals problems with the free space inside the TI-99/4a, maybe i have put too many things … but everything works perfectly :D

Texas Instruments TI-99/4A – 32k Internal Expansion Memory + Status LED + Reset.

Works that have been made:

• 32k Internal Expansion Memory.
• Switch for disable the Expansion Memory.
• Reset Pushbutton switch.
• Bi-Color LEDs to display the status of the internal memory expansion 32k. (ON = Green / OFF = Red)
• Replaced the resistor for the LED from 2.2k to 220 ohms.

Gallery of the works that have been made:

It could be better!

I had severals problems with the free space inside the TI-99/4a, i had to remove one side of the metal part, the biggest problem is the internal 32k expansion which is not very well done, there is no a way to secure it inside … but everything works perfectly :D

Texas Instruments TI-99/4A – F18a (FPGA Based TMS9918A) Installation.

Works that have been made:

• Installation of the F18a and removal the tape connector to make a opening for the vga connector.
• The metal cover is no longer used.
• RCA 2 DIN Homebrew Adapter to use the audio output after installing the F18a on the TI-99/4a.

Gallery of the works that have been made:

Repair Commodore 64 (ASSY 250407) 1 of 6

Asserted defect:

• Sometimes works, sometimes not, check solder.

Fix:

I state now that this Commodore 64 has been socketed.

The work done is not bad but was better clean up the remaining flux around the pcb pads, the eye wants its part.

The defect occurred twice on 55 switching on and off (i counted them)

In one of these two times i have noticed the problem that was missing the CPU Output Clock on the solder side pad. I redid the solder and fixed the socket pin and everything worked again.

I also noticed that one of the eight RAM it was warmer than the other, but working, i have decided to replace it. I don’t exclude that this operation has only fixed one of the problems, the other might to be the power supply that i don’t have.

I have twisted several times the PCB on itself, i dropped down at least 10 times on the table and leave power on for four hours, now i  can exclude solder problems.

In the photos you will see a PLA 906114 (U17) that for some bizarre reason have solder it on the socket, really curious.

Gallery of the repair:

Repair Commodore 64 (ASSY 250425) 2 of 6

Asserted defect:

• Black Screen.

Defects found:

• Missing the Composite Video Signal.
• Black Screen.
• Missing Audio.

Repair:

• Replaced 1 x MOS 8701 Clock Generator (U31)
• Replaced and Socketed 1 x MOS 906114 PLA (U17)
• Replaced 1 x MOS 6581 SID (U18)

Gallery of the repair:

Repair Commodore 64 (ASSY 250407) 3 of 6

Asserted defect:

• Black Screen.

Defects found:

• Black/Garbage Screen.

Repair:

• Replaced and Socketed 1 x MOS 906114 PLA (U17)

Gallery of the repair:

Read more…

PPI Super Sketch for Texas Instruments TI-99 Repair.

Defect:

• The cartridge is not recognized by the TI-99/4A.

Repair:

• Replaced 1 x 74LS139 (U1)
• Replaced 1 x 74LS30 (U2)

Note:

The repair of the Super Sketch cartridge was quite simple, in the first time i thought a problem of the ROM but instead the failure was the two IC U1 and U2, which should do the work of the Bank Switching.

To remove the two IC i have preferred to cut the pins and then remove each pin because i know very well this type of PCB and also lowering the temperature there is a risk that the pitches come off.

Gallery of the repair:

Easy replacement of the Commodore Amiga Mouse push-buttons.

Gallery:

ORIC-1 Repair [1 of 2]

Defect:

• Garbage boot Screen and then another Garbage screen (see photo).

Repair:

• Replaced 1 x CPU 6502 (IC5)
• Replaced 1 x RAM HM4864P (IC12)

Gallery of the repair:

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ORIC-1 Repair [2 of 2]

Defect:

• No audio.

Repair:

• Replaced 1 x Electrolytic Capacitor interrupted of 220uF 10v (C1)

Gallery of the repair:

Commodore 64 (ASSY 250407) Repair

Defect:

• Black screen and a noisy background sound .

Repair:

• Replaced 1 x MOS 906114 (PLA) U17
• Replaced 1 x MOS 6581 (SID) U18

Commodore Amiga 500 (ASSY 312510) Repair

Defect:

• Garbage boot Screen (see photo).

Repair:

• Replaced 1 x FAT Agnus 8371

Gallery of the repair: