Texas Instruments TI-99/4A Repair.

Defect:

• Cartridges port doesn’t work.

Fix:

• Cleaning the cartridge connector (computer side) with one pin oxided.

Gallery of the repair:

Texas Instruments Modulator PHA2036 Repair.

Defect:

• After a few seconds of use the image becomes dark until it disappears completely.

Repair:

• The problem was inside the RF modulator. After removed the problem is gone. If you made the composite mod i always recommend to removing the Modulator.

Roland MT-80s Repair.

Defect:

• Working good but without sound.

Repair:

• Fixing the two solder pads broken of the bridge rectifier for the 13v.

Gallery of the repair:

Download: Roland MT-80s Service Manual (936)

Video Test:

Commodore VIC-20 (ASSY 250403) Repair

Defect:

• Black Screen.

Replaced parts:

• Replaced CPU 6502 (UE10)

2 x Commodore Amiga 1200 Recap.

Gallery:

This computer did not present the defect described, but knowing well the power supply stage of the osborne, very similar if not the same as the computer series Kaypro, i have preferred to replace the two capacitors that usually present problems.

The real problem came out as soon when i have connected the keyboard, the screen started to flash and the keyboard did not work.

Several pins of the keyboard connector are in short-circuit, i have disassembled the keyboard, unplugged the flat connector and checked the continuity of all pins and everything was perfect.

The problem is the membrane broken in more parts and probably they are some residues inside the keyboard, shaking the keyboard it sounds almost like a maracas.

The membrane of this keyboard can not be replaced because the switches that press the membrane are “hot welded” by melt the plastic, however the membrane is not available as a spare part.

I have tried with the keyboard of my Osborne One (version 1 and 2) and everything works perfectly.

Gallery of the repair:

Sega Game Gear Recap

Defect:

• Dead but the Power LED is turned ON.

Repair:

• Replaced all capacitors (Main / DC-DC / Audio)

Gallery of the repair:

Sorry, this entry is only available in Italian.

Works that have been made on this Amiga 2000:

• Replaced the power plug with capacitors inside.
• Replaced PSU capacitors.
• Cleaning the motherboard with the toothbrush and PCC Kontakt.

Gallery:

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Hanimex 2650/Arcadia 2001/GIG Leonardo (loose) Repair & Composite Video Output.

I start to say that this motherboard was not in repair but in one box of  spare parts. I have only the motherboard of this console, no external case, joystick, power supply … totally useless.

Past and present defects:

• Some time ago the two EMF coils are exploded (see the photo) maybe the capacitor was in short circuit after the two coils
• Also a capacitors near the coils is disappeared.
• Black and White video output.

Repair and Video Composite modding:

• I have bypassed the two coils for the 12v DC.
• Removed the RF modulator.
• I have cutted 3 resistors for the video composite output, you can get a better image (contrast and color) (see photo)
• Replaced a 4066 because are missing two outputs of the R-G-B signal and that’s why the image was in black and white.
• Added a temporary push button for the RESET.
• The console without the RF modulator can be powered at 9v DC and not 12v DC, thus avoiding boiling the poor 7805.

Gallery of the repair:

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Download:

• Hanimex 2650/Arcadia 2001/Leonardo Games (885)
• Hanimex 2650/Arcadia 2001/Leonardo Schematic (1613)
• Emerson Arcadia 2001 Service Manual (948)
• WinArcadia Emulator (751)

This Video Composite MOD needs some work unlike other similar consoles, you need to remove a resistor and insert a trimmer, otherwise the Video Composite output signal is really bad.

Works that need to be done:

• Remove the RF Modulator (remove it completely)
• Remove the 4.7k Resitor (see photo)
• Solder a 22k Trimmer between the resistor hole (hole side to pin 8 of the TEA 1002/PE1X) and the ground, the third pin of the trimmer is the Video Composite output. (see photo)
• Solder a wire for the Audio output. (see photo)
• Use the same hole of the RF cable for the new video and audio cable.

Before closing everything i recommend to adjust the trimmer for the best Video output.

Gallery of the Video Composite MOD:

Commodore Amiga A570 Restoration.

I have received two retro things in very bad conditions.

• 1 x Floppy Drive CD-1411
• 1 x Commodore Amiga CDROM A570

… but for now we are talking about the Commodore A570.

The Commodore A570 have serious problems that i list below:

• Outside case is very dirty, yellowed and broken in several parts.
• The Caddy Guide Tracks has been destroyed.
• Damaged screws thread.
• The metal plate under the CDROM is bent on one side.
• Many rusty parts.
• Main PCB with traces of water/limestone and rust.

Works that have been made:

• Fixed the CDROM CADDY holder, it was not easy because all the metal guides are bent, now it works.
• Main PCB cleaning on both sides with the Kontakt PCC and toothbrush.
• Cleaned and grease the two rails of the laser head.
• Cleaned the head lens of the CDROM.
• Fixed the bent metal plate under the CDROM.
• Cleaning outer casing.
• Fixed with the glue the two pins for closing the case with the screws.

Work still to be done:

• The bottom part of the A570 CDROM is very rusty, i need to sand down gently and at least give a hand of anti rust.

Aesthetically is very bad but at least works.

Gallery of the restoration:

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Video:

Texas Instruments TI-99/4A Repair (1 of 3)

Defect:

• Black Screen and deafening sound in background.

Replaced parts:

• 1 x TMS9900NL CPU (U600)

Personal note that is good for all repairs:

Repairs are done with experience and skill, if there is skill does not mean that there is also the experience.

Repairing any electronic things by desoldering everything to find the bad components is not an index of experience but only ability.

Gallery of the repair:

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Texas Instruments TI-99/4A Repair (2 of 3)

Defect:

• Garbage Screen.

Replaced parts:

• 1 x TMS4116-15 RAM

Gallery of the repair:

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Texas Instruments TI-99/4A Repair (3 of 3)

Defect:

• Man lacks his legs and miss a piece of rope in the pitfall game demo.

Replaced parts:

• 1 x TMS9929TML VDC (Video Display Controller)

Gallery of the repair:

Restored the original Amiga A1200 keyboard connector.

I don’t say anything about the fucking work done before.

Gallery:

Commodore Amiga 500 Power Supply Repair.

Defect:

• All voltages are unstable.

Repair:

• Replaced a Zener Diode 5.6V (ZD2). The Diode was corroded and broken, the cause was not the acid of the capacitors.
• Replaced a Electrolytic Capacitor 1uF 50v (C9) which under voltage don’t work correctly, thanks to the freeze spray i have find it.

All the other electrolytic capacitors have been removed one by one and tested, they are good.

Gallery of the repair: