Commodore VIC-20 Repair

Defect:

• Black screen … then black and white image.

Replaced parts:

• Replaced 1 x 901486 KERNEL ROM (U12)
• To fix the problem of the image in black and white i have adjusted the “RED” trimmer (C48)

Commodore 16 Power Supply Repair

Defect:

• Output voltage in short circuit.

Replaced parts:

• Replaced 1 x 4700uf / 16v Electrolytic capacitor.
• Replaced 1 x 800mA Bridge rectifier.

Atari 2600 Repair

Defect:

• The second joystick port doesn’t works properly.

Replaced parts:

• Replaced 1 x 6532 RAM-I/O-Timer (RIOT)

Commodore CBM 4032 (40 Columns) Repair

Defect:

• “Device not present” error when using the IEEE 488 port (Example Floppy Drive)
• Sometimes the computer show the prompt of the TIM monitor (Machine Language Monitor program)

Replaced parts:

• Replaced 1 x IC 6522 VIA (UB15)
• Replaced 1 x IC 6520 PIA (UB16)

This Commodore PET 2001-8C also includes a homemade Power Amplifier to hear the sound of some games that use the pin CB2 of the User Port as audio output.

Also is included a reset button and two mini-led (Red / Green) that display the data (Save / Load) when using the tape recorder.

Some photos of the Commodore PET 2001-8C:

Copyright label on the motherboard:

Some photos of the repairing and cleaning:

Commodore PET 2001 (Chicklet) Repair datassette.

Defects:

• Doesn’t load any more.

Repair:

• Replace motor.
• Replace belt.
• Azimuth adjustment.

Thanks to Manosoft for the spare parts (white datassette, the same model of the black one)

Commodore PET 2001 (Chicklet) Repair.

Defects:

• Wrong chars on the screen.
• Memory problems.

Repair:

• Replaced all MOS 6550 main ram with an 6550 Ram Adapter by xAD & Manosoft (only 2 x MOS 6550 was faults)
• Replaced 1 x MOS 6550 Video Ram with a spare one from the main ram.

Video of Galaxy Invaders with Sounds:

from Wikipedia homepage:

The Commodore PET (Personal Electronic Transactor) was a home/personal computer produced in 1977 by Commodore International. A top-seller in the Canadian and United States educational markets, it was Commodore’s first full-featured computer, and formed the basis for their entire 8-bit product line.

Read more…

Gallery:

This adapter replaces all ram installed in the Commodore PET 2001 with a 6264 Static Ram and is useful when one or more ram are faulty. These type of ram are no longer available to purchase.

NOTE: This adapter will only work to replace a chip with a part number starting with MPS 6550. They will NOT replace other RAM types used in Commodore computers other than the original Commodore PET 2001.

The original design was done by Donni of the VCF forum (Vintage Computer Forums).

Unfortunately these pcb have a design problem, below the fix which needs to be done (i always forgot to post this fix, sorry)

Download: Original printable version by Donni (1279)

Gallery:

Restoration the external case of the Micro Peripherals Ltd Floppy Disk Drive that was eaten by rust.

Gallery:

Cleaning the keyboard keys is really tedious.

Gallery:

12►

Commodore CBM(PET) 4032 (FAT40) / 8032 Cathode Ray Tube (CRT) Replacement.

The cathode ray tube was taken from the Amstrad GT-65 (Monochrome monitor)

The CRT Tube Orion 310GNB31 (Amstrad GT-65) is fully compatible with the Amperex M31-334GH (CBM 4032/FAT40 – 8032).

NOTE: The same CRT work perfectly for the computer Radio Shack TRS-80 Model 3 and Model 4.

Gallery:

Commodore 16 ASSY 251789-01 REV B Empty PCB

Gallery:

Commodore VIC-20 ASSY 251040-01 Empty PCB.

Gallery of the repair:

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

Defect:

• Blue Screen with tiny Vertical lines.

Replaced parts:

• 1 x MCM6810P (128 x 8-Bit Random-Access Memory TTL/DTL)

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

Defect:

• Blue Screen with tiny Vertical lines.
• Wave/Raster Lines.

Replaced parts:

• 2 x IC MCM6810P (128 x 8-Bit Random-Access Memory TTL/DTL)
• 1 x IC CD3236A-NL (ROM)
• 1 x Capacitor 12 pF.

Note:

In one photo you can see the curious change made in this TI-99/4A by inserting a resistor in the pitch where in other motherboards is soldered a leg of a electrolytic capacitor and then one leg of the capacitor is welded and the not the other leg.  Compliments.

Video of the defects:

Gallery of the repair:

Repair Commodore Amiga 600 (White Screen)

Defect:

• White Screen.

Replaced parts:

• 1 x LM555 (SMD)
• 1 x Electrolytic Capacitor 10uf 25v

Note:

I have thought it was a problem of RAM (U17) since i have measured oddities but the problem instead is a capacitor of 10uF, dead LM555 (smd) and some pcb tracks corroded.

Repair Philips 8220 (MSX2) Black Screen with Sound.

Defect:

• Black Screen but with sound (keyboard works)

Replaced parts:

• 2 x Fuse 250v 315ma
• 4 x Tantalum Capacitor 22uf 6v
• 1 x Electrolytic Capacitor 100uf 25v

Note:

The main problem was caused by the lack of +12 volts that power the RGB Encoder module. The other voltage of -12 volts are used only for the cartridges port (but not all cartridges using this voltage)

I wanted to do a experiment to install a standard PC drive with a adapter (34 pins to 14 pins) on a Philips 8245. I would say that it work but i have tried about 20 Floppy Drives and only 1 it works ;-D

Gallery:

Download: Philips NMS 8245 (MSX2) Floppy Drive replacement (1183)

source: msx.hansotten.com