I received this console to made a repair and a video chip upgrade.

The repair:

The failure appeared as a malfunction of the Joystick inserted in port #1 of the console. This problem is absolutely not new to this console.

The failure is due to the 74LS541 IC which, in addition to being uncommon (it is rarely used), is very sensitive to electrostatic electricity, consequently if you try to connect the joystick with the console turned on, the probability that it will fail is very high.

I preferred to replace with a socket for both IC, one for each joystick port, because the probability of a future failure remains very high.

Video Chip Upgrade:

I would like to point out that this CBS ColecoVision model does not have native RGB video output but only RF.

It was possible to do the Composite Video mod but since in recent months the good Troy Schrapel has released on github the Pico9918 project that completely replaces the TMS9918A video chip and the Video RAM with a very low cost i decided to do the replacement.

This Video Chip are used in many consoles and computers including the CBS ColecoVision.

The Pico9918 can be configured using a different firmware to output in VGA or via SCART RGB.

I obviously chose the RGB SCART output, the installation is quite simple, you have to unsolder the TMS9918A, insert a socket and at this point you can insert the pre-programmed Pico9918 and connect the R-G-B-GND-SYNC (H/V) signals, optional you can completely remove the PCB with the RF modulator.

The wires that you see soldered directly on the ColecoVision motherboard are for the AUDIO output (purple wire) and for the 5v (orange wire) the 5v are for the RGB switching of the TV.

The connections inside the scart connector are as follows: the 5v go to pin 8 and then via a 150ohm resistor to pin 16.

Also as you can always see from the photos i put some adhesive tape on the metal cover at the height of the Pico9918, i did it only for my personal paranoia, the metal does not touch the Pico9918 but better to be safe :-D

Gallery of the repair and upgrade:

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source: github.com/visrealm/pico9918

I installed the ZOE RGB rev 2.0 interface for a friend, this interface allows you to view the images with an RGB output signal with a much better quality instead of the only output supplied as standard which is RF.

This interface was purchased by me many years ago and was the last batch of the ZOE RGB rev v2.0 that i had assembled.

After several years i can confirm that the image quality is perfect and clear.

Gallery:

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Unfortunately, as often happens, the mechanics of the ATARI XC11 cassette recorder also suffer from old age problems. The cap/block of the belt drive pulley broke and consequently, being under pressure with a spring, it popped off.

I fixed the cap on the small plastic pin of the pulley with cyanoacrylate glue, it could work forever or only for a short time, only time will tell.

Gallery of the repair:

I wanted to upgrade another Philips Videopac G7000 console and adding everything i wanted to do many years ago when i only added the RGB output instead of the RF one.

While i was doing the work of modifying the console i realized that something was wrong with the games and the RGB output, some games were missing the background color or the color was faded, other times the colors are wrong, but this defect was not present with all games and therefore it was not a wiring problem (colors are not swapped likes a problem with the R-G-B wiring).

I had never realized it and probably other people have never realized it either, because it does not happen with all the games but thanks to the Flash Multicart by Andrea Ottaviani i was able to try all the software released for the G7000 and confirm that something was not working correctly.

The problem is due to the type of RGB mod, i had taken the one from the gamesx.com site as good, that is the one that has been available from about fifteen years and that almost everyone has installed but there is another mod that is completely different and above all uses a particular pin of the Intel 8048 CPU (pin 39 [T1]).

Hesitantly i wanted to try this modification and it is actually all true, it works, now the RGB mod is perfect as for the Videopac G7200 (native with RGB output) and G7400 (Native RGB by adding the components that are missing on the PCB)

Later i discovered that this RGB mod was not born like this by chance, the scheme was designed taking inspiration from the original schematic of the G7200/G7400 where this particular CPU pin is used.

Below is the list of all the modifications and enhancements that have been made:

• RGB Mod 100% Working with a extra pin from CPU (No more missing background or colors via RGB on G7000)
• External RGB DIN Hirschmann Connector.
• Power external Switch with Power-On Light.
• Power external Connector.
• Two Joystick D-SUB external Connector.
• Replaced the original PSU with a Mean Well EPS-15-5.
• RF modulator removed.
• Simple Composite Video signal amplification circuit.
• Separate composite Video and Audio output via external RCA connectors.

Gallery of the work done:

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…and now some links:

https://forum.system-cfg.com/viewtopic.php?f=18&t=10673
https://gamesx.com/wiki/doku.php?id=av:g7000_av
https://darius-saturn.com/forum/viewtopic.php?t=8342
https://www.pimparts.fr

This interesting project by Troy Schrapel emulates the TMS9918A/29A VDP with a Raspberry Pi Pico.

I wanted to assemble and personally test the PICO9918 with the TI-99/4A using both the VGA output and the SCART (RGB) output and i must say that it surprised me a lot, the image is stable and the software works without any problems.

This VDP emulation has nothing to envy to the F18A implementation although the F18A has some graphics enhancements, improvements that however must be used by new homebrew software for TI-99.

Later i will do other tests with ColecoVision and MSX, i also thank Andrea Ottaviani for helping and beta testing for Troy Schrapel implementation of the SCART (RGB) output which was not foreseen in the first versions of the firmware.

I also point out that the VRAM used by the VDP is integrated into the emulation, so it is not needed,i did tests and removed part of the 4116 VRAM RAM of the TI-99/4A and everything worked regularly, so if you have a TI-99/4A, ColecoVision or other that has the classic corrupted graphics problems (VRAM), the PICO9918 will definitely solve the problem without having to replace one or more non-working RAM.

Brief description of the images that you can see in the gallery:

• Test with VGA monitor and with scanlines emulation enabled.
• Test with TV/monitor SCART RGB, in this case i also had to connect the 5v to the scart socket for RGB switching. The 5v go to pin 8 and then via a 150ohm resistor to pin 16, this TV/monitor without this configuration doesn’t display the RGB image correctly.

These are the computer and consoles that use this VDP:

• ColecoVision
• CreatiVision Memotech MTX
• MSX1 Computer
• NABU Personal Computer
• Sega SG-1000/SC-3000
• Spectravideo SV-318/SV-328
• Sord M5
• Tatung Einstein
• Texas Instruments TI-99/4A
• Casio PV-2000
• ColecoVision ADAM Computer
• Hanimex Pencil II
• Tomy Tutor
• Toshiba Pasopia-IQ MSX1 Computer
• Yamaha CX5M MSX1 Computer
• Telegames Personal Arcade
• Powertran Cortex

How much did i spend for each PIC9918 ?

• 2 x Strip Round 40 Gold Pin : €1.15
• 1 x RP2040 Pi Core Black : €2.69
• 1 x JLCPCB Assembled (SMD components) PCB : €7.65

More or less for each single PICO9918 complete with all components you will spend €11.49.

The price of each component also includes the cost of shipping and customs clearance.

NOTE: I forgot to write that the composite SYNC for the scart can be taken from one of the two SYNC (H/V) VGA.

Gallery:

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Download: Pico9918 (VGA/SCART) Firmware v0.4.0 (PCB v0.3) (238)

source: wikipedia github

Philips Monitor (Black) VG0060-80 Power Stage Repair, the Monitor turned off unexpectedly without any suspicious noise.

This power stage is practically identical to other monitor models, for example: Philips CM8833 and Commodore 1084, but surely there will be others that mount the same power stage.

Repair:

After removing the PCB of the power stage i took the opportunity to replace also the power switch that no longer worked properly i also replaced the exploded fuse but obviously nothing worked.

The fault was due to the TS132 transistor completely short-circuited, the diagram says that a BU806 is installed but instead a 2SC3795B is installed.

Replaced, still nothing works, i tried with the tester but i don’t find any voltage, even the 300v +/- on the capacitor C112 at this point in addition to the diode bridge (D107/D108/D109/D110) there was only the 47 Ohm 7W resistor R103 to try and in fact it was interrupted, i replaced it with a 5W one, i didn’t have a 7W one in the lab.

I used the old trick of the 100W bulb in series, in my case instead of the fuse to avoid destroying other components.

Everything worked perfectly, the bulb turned on for a minimum amount of time and then turned off and the output voltages of the power stage are all present (125v/15.8v/25.5v).

Gallery:

Download: Philips VS0060-80/CM8833/1084 Schematics (246)

The A8PicoCart is a very cheap multi-cart for the Atari 8-bit (XL/XE) which you can make at home with only basic soldering skills.

The cartridge supports the following file formats: ROM/CAR/XEX and a limited support for ATR files.

Instruction manual, firmware, gerber & STL files and other documentation can be found on Robin Hedwards github page.

You can see a short video i made click here.

Gallery:

This is a short story of the Roland MT32 Midi repair.

The MT32 MIDI interface had an annoying audio problem (you can listen to the audio files attached to this post).

It seemed like the classic problem of exhausted electrolytic capacitors, but instead it was due to the ROM ROLAND R15449121 (TC534000P) position IC37.

To replace the original ROM it would have been enough to use an OTP Eprom 27C040 which however i didn’t have in the laboratory so i used a FLASHROM AM29F040 by modifying some connections.

The filename of the file used to program the FLASHROM is “r15449121.ic37.bin” which you can find in the archive attached to this post.

Below is the documentation how to adapt the AM29F040 instead of a 27C040.

• Atmel AT27C040 – 4Mb (512K x 8) OTP, EPROM (32-pin Package)
• Amd AM29F040 – 4Mb (512K x 8) FLASHROM (32-pin Package)

Tie 29F040 WE (PIN 31) and connect to VCC (PIN 32)
Tie 29F040 A18 (PIN 1) and connect to PIN 31 on Socket or PCB

Monkey Island Audio difference before and after repair:

• Before the Repair (212)
• After the Repair (198)

Gallery:

Download: Roland MT32 (various OS and extra ROMs) (254)

source: Synth Eprom Dumps

I wanted to remake the RGB connections of my CBS ColecoVision console a bit and design a new diagram for connecting the RGB video output.

This console was sold with an external modulator (CBS Electronics Adaptateur Antenne 7466 – 6F) that converted the signal from RGB to RF and it seems a Scart cable was not provided for direct connection to the television.

The original ColecoVision D-SUB DB15 to Scart cable that i have doesn’t have the correct pinout but it works perfectly with another ColecoVision always with RGB output but with an internal encoder that converts the Y (B-Y) (R-Y) to RGB signals (PAL Secam Converter A).

This fact is really curious, apparently there are more versions with RGB output as well as RF.

I decided to remove the old RGB cable that i soldered internally about 15 years ago and replace it with an RGB cable connected to the Coleco native connector.

The problem with doing this operation has always been the D-SUB DB15 connector which must be of a certain size, otherwise it won’t fit.

Brilliantly solved using a SNK NeoGeo Joypad extension cable, where we have a DB15 D-SUB connector pre-cast in the plastic where all 15 pins are used (in theory only 14 are needed for the NeoGeo Joypad, but all 15 are connected)

I cut the cable from the neogeo joypad male connector side and soldered the wires to a Scart connector and for the Fast Switching signal before connecting it to pin 16 of the scart i used a 100ohm resistor in series, i did not use the Function Switching signal.

One more thing, the Audio signal from the console native RGB connector is very low, so i made a jumper (see photo) to bypass a resistor and a ceramic capacitor, therefore i took the audio directly from PIN 7 of the SN76489 (Sound Generator).

Of course everything works perfectly.

Gallery of work done:

The Shugart SA455-3AA is a DSDD Floppy Disk Drive (360K).

The work that has been done:

• Replacement of the Electrolytic Capacitors on the Motor PCB.
• Greasing the head sliding rods with silicone grease.
• Reconstruction of the pcb track corroded by the loss of the 10uf electrolytic capacitor.
• Replacement terminals for selection with jumpers.
• Ceramic capacitor replacement.
• General cleaning.
• Read/write test with GreaseWeazle interface.

List of replaced electrolytic capacitors:

• 1 x 10uf 25v
• 1 x 47uf 16v
• 1 x 0.47uf 50v
• 1 x 0.22uf 50v
• 2 x 22uf 25v (non-polarized)

Gallery:

Download: Shugart SA455-SA465 Service Manual (240)

I decided to replace completely the PCB of the Amiga Power Supply (312503-03) because although after replacing all capacitors 1 year ago (30/4/2023) the voltages are not always stable, especially the 5V which fluctuated between 5.2v and 6.9v.

Using a Gotek HXC drive as a floppy device has burned two USB sticks, i recovered one replacing a shorted smd capacitor.

So let’s retire the old power supply pcb and welcome to the Mean Well RPT-60B fully compatible about voltage and amperage.

I leave you the Aliexpress link.

Gallery:

The usual boring replacement of all exhausted capacitors.

Gallery:

The First Amiga Intro by Lynx/Nightfall.

It only took just under two months to learn from scratch 68k Assembler and Amiga Custom Chip registers.

Well done Lynx!

Download: Retro Love Intro by Lynx/Nightfall (376)

source: pouet.net

First of all, i thank my friend Gerben for giving me the monitor.

This is a Black and White monitor but for some reason a thin transparent film has been applied to the front of the cinescope to simulate the tonality of an amber cathode ray tube, furthermore the APF logo placed on the front of the monitor to the right of the power light is masked.

The TVM-10 APF Monitor is approximately 43 years old and was used with the Computer APF Imagination Machine I/II.

The Monitor had several functioning problems, below is the description of the work that has been done.

• Removing the colored film.
• Replacement of all electrolytic capacitors.
• Replacement of a ceramic capacitor.
• Horizontal synchronism calibration (H-HOLD) by delicately removing the wax that was melted inside the variable inductor.
• Installation of a 1uf polyester capacitor in parallel with the 1.5uf one present for width adjustment horizontal (H-WIDTH) of the image, unfortunately the ferrite core inserted into the variable inductor for manual adjustment is blocked, probably with glue, forcing is not a good idea.
• Check of the Diodes.
• Calibration using the trimmer placed on the front of the PCB of the monitor for the power supply voltage which must be 12v.
• Geometry adjustment.
• General cleaning.

Only one geometry problem remains; the image on the top left side of the CRT tends to bend slightly for about 1cm and the left side of the image is slighty rounded, problem surely attributable to some polyester capacitor or resistance that has lost the capacity/value of the time.

Needless to say i checked almost all the polyester capacitors and resistors in the horizontal section and didn’t find nothing scandalous.

The photo gallery contains all the photos i made during the repair, i take this opportunity to thank a user of the plcforum who gave me tips on how to proceed with the repair.

Gallery of the repair:

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Apple ][ EuroPlus Repair.

Defects:

• Black screen.
• Power light off.
• Keyboard does not work.

Repair:

About the black screen it was enough to press all the IC in their seat, i have removed some and cleaned the IC's socket and the IC's pins.

The Power light off, the 5v micro bulb was faulty, replaced.

The keyboard had several problems;

The keyboard connector (socket) located on the computer motherboard side was faulty and consequently are missing the -12v for the keyboard encoder PCB.

The 3 TTL chips had been replaced on the keyboard encoder PCB but 2 x 74LS04 are erroneously soldered instead of 2 x 74LS00, the third TTL was correct but not working. Replaced all.

Now everything works reasonably well, unfortunately the bad keyboard has some problems, the internal slats are warped and tend out of their seat, as a result some keys do not work correctly.

I have tried to fix and clean, but the situation hasn't improved much.

Gallery of the repair: