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 (1130)

source: msx.hansotten.com

Gallery of the repair:

Phonola NMS 8245 (MSX 2) Repair.

Defect:

• Dirty characters/graphics.
• Floppy Drive dead.

Replaced parts:

• 1 x 41464 Video RAM (U16)
• 1 x Floppy drive belt

Other:

• Frame cartridge connector fix for a easy removal of the components under the frame.

Removing the filter capacitors that are exploded inside the Astec power supply of a Apple //e.

Gallery of the repair and cleaning:

I start to saying how much i hate repairing psu switching, one of the most boring things second only to the repair of CRT Monitor, at least for me.

However this repair was made. The failure is almost certainly caused by a copious spillage of electrolyte (conductive fluid usually formed from a salt solution or acid which is located inside of the electrolytic capacitors) and a dangerous test if the machine works again after the electrolyte was leaking over the pcb.

The moral of the story is easy to figure out, a short circuit has made several deaths, a good portion of the Primary (PWM) and Secondary.

The components that have been replaced are the following:

• 1 x Electrolytic Capacitor 3300µF 16v 105°
• 1 x Electrolytic Capacitor 1000µF 25v 105°
• 1 x Electrolytic Capacitor 2200µF 35v 105°
• 1 x Electrolytic Capacitor 1000µF 100v 105°
• 1 x Electrolytic Capacitor 330µF 160v 105°
• 1 x Electrolytic Capacitor 47µF 25v 85°
• 1 x Electrolytic Capacitor 10µF 100v 85°
• 1 x Electrolytic Capacitor 22µF 25v 85°
• 1 x Sanken Hybrid Voltage Reculator Module STR 53041
• 1 x Photocoupler TLP 541G
• 1 x Overcurrent Protection Elements ICP N10
• 1 x Transistor C1815GR
• 1 x Transistor DTC114 ESA (C114 ESA)

After 1 week i have decided to replace also all capacitors of the power supply section of the computer.

Components replaced:

• 1 x Electrolytic Capacitor 3300µF 25v 105°
• 3 x Electrolytic Capacitor 5600µF 10v 105°
• 1 x Electrolytic Capacitor 2200µF 10v 105°
• 1 x Electrolytic Capacitor 330µF 35v 105°
• 1 x Electrolytic Capacitor 1000µF 16v 105°
• 1 x Electrolytic Capacitor 470µF 25v 105°
• 1 x Electrolytic Capacitor 1µF 50v 105°

Gallery of the repair:

12►

Gallery:

This is a full replacement of the power supply of the Amiga 500 with a similar one of the last generation. This type of switching power supply fits perfectly inside the case of the original psu.

The repair will not be made because this psu is very common at very low prices, i don’t waste even a second to find the multiple faults, i prefer devote to other things less common.

Commodore Floppy Drive 1541 Motherboard #1

Defect:

• IEC bus unresponsive.

Replaced parts:

• Replaced 1 x VIA 6522 (UC3)

Commodore Floppy Drive 1541 Motherboard #2

Defect:

• IEC bus unresponsive.

Replaced parts:

• Replaced 1 x VIA 6522 (UC3)
• Replaced 1 x 7414 (UA1)
• Replaced 1 x 901229 ROM (UB4)

Removed parts:

• SpeedDos adapter with the flat cable (user port bus) cutted.
• SpeedDos ROM Adapter.

Sinclair QL #1 Repair

Defect:

• White Screen (RAM problem)

Replaced parts:

• Replaced 3 x 4264 RAM

Note:

I took the opportunity to install the Minerva Rom v1.98 to identify the faulty ram. Thanks to the Minerva ROM i have identified 2 of 3 Ram failed.

• Ram Location $1F340 (IC9)
• Ram Location $3D040 (IC10)
• Ram Location $30910 (IC16)

Sinclair QL #2 Repair

Defect:

• White Screen / Black Screen / Garbage Screen / Annoying Background Sound

Replaced parts:

• Voltage regulator (7805) fault. In input we have 9v and in output 9v instead of 5v.

Note:

Incredibly nothing is exploded ;-D

Commodore Amiga 500+ #1

Defect:

• Battery Leaks.

Solution:

• Battery Removed.
• Cleaned the PCB with PCC Kontakt.

Commodore Amiga 500+ #2

Defect:

• Battery Leaks.

Solution:

• Battery Removed.
• Cleaned the PCB with PCC Kontakt.

Commodore Amiga 600

Defect:

• Where are the capacitors and the tracks ?

Solution:

• Cleaned the PCB with PCC Kontakt.
• Alternative way to install the capacitors ;-D

Commodore A500 Keyboard: Keep the useful things from the useless things.

Commodore Amiga 500 Keyboards Join & Fix.

Unfortunately from five keyboards i have made only one in a good shape and full working.

Commodore Amiga 500/600 PSU Repair

Amiga 500/600 (PSU) PowerSupply #1

Defect:

• Short-circuit and the fuse blows.

Replace parts:

• 1 x Transistor NPN 2SC3679.

Amiga 500/600 (PSU) PowerSupply #2

Defect:

• Short-circuit and the fuse blows.

Replace parts:

• 1 x Transistor NPN BU508A.

Amiga 500/600 (PSU) PowerSupply #3

Defect:

• Short-circuit and the fuse blows.
• The PCB is half broken.
• Some components have suffered of too much heat.
• The locking pins of the cover are broken.
• Dirty and Yellowed.

I don’t made the repair. I recovered what might come in handy.