Upgrading Commodore A3640 CPU Card (part two)

I have replaced the CPU 060 EC version with a 060 FULL with FPU REV 1.

When using the adapter with a non EC version of the 060 you must also use a fixed version of the kickstart v3.1 with the exec.library modified to support the FPU.

Gallery of the work done:

Download: Kickstart v3.1 Exec Patch Version for 3k & 4k - Ready to Burn! (1568)

Upgrading Commodore A3640 CPU Card (part one)

Works that have been done:

• Upgrading GAL (U204 & U209)
• Socket for Oscillator.
• Overclocking.
• Replacing all capacitors (the recap was already done but for the CPU adapter 040 -> 060 was necessary use smd capacitors for the little space available)
• CPU Adapter 040 -> 060.
• CPU Motorola 68EC060

Gallery of the work done:

Commodore Amiga 4000 repair with Floppy Drive that is not recognized.

Defect:

• Floppy Drive Dead (not recognized)

Repair:

• Replace CIA 8520 (U300).

Gallery of the work done:

Commodore Monitor 1084S-P Repair.

Defect:

• Completly dead with only a loud whistling noise in background.

Repair:

• Replaced the flyback transformer (AT2079/30102) everything has started to work perfectly.
• It’s mandatory to made a calibration of the SCREEN and FOCUS with the two trimmer placed on the rear side of the flyback transformer.

Note:

A loud whistling noise indicates a bad flyback transformer (also known as an LOPT).

Gallery:

Download: Commodore Monitor 1084S-P Schematics (1211)

Commodore CBM 8032 (HP Early version [1980]) Motherboard Repair (ASSY 8032030)

Defect:

• Garbage screen.

Repair:

• Replaced 4 x 2114 Static RAM (UC4 / UC5 / UC6 / UC7)

Note:

As you can see from the photos this computer is already been repaired by a butcher. The butcher did not use the sockets after replacing the static ram ones and the pads had already suffered from the previous desoldering and soldering, probably using an unsuitable soldering station.

Gallery of the repair:

Commodore CBM 8032 (HP Early version [1980]) PCB Monitor Repair (ASSY 321448)

Defect:

• Dead. Missing High Voltage from Flyback Transformer (LOPT)

Repair:

• Replaced 2 x burned resistors of 56Ohm 1/4w (R752 / R753)

… and now let’s move on to the second defect. :-)

Gallery of the repair:

Video Composite modding:

• Removed the RF modulator.
• Removed one pin of the 3 resistors (see photo) for the video composite output, you can get a better image (contrast and color) (see photo)
• I have used the same hole of the RF cable for the composite video and audio cable.

Gallery of the Video Composite mod:

Sega Game Gear (Boxed) Full Recap.

Defect:

• Dead but the Power LED is turned ON.

Repair:

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

Gallery of the repair:

Commodore 64C (ASSY 250425) Repair.

Defect:

• Basic Screen without text and prompt.

Replaced parts:

• 1 x MT 4264-20 RAM (U24)

Gallery of the repair:

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 (1078)

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: