Commodore 16 Power Supply Repair

Defect:

• Dead.

Replaced parts:

• Replaced Electrolytic Capacitors of 4700uF/16v
• Replaced Fuse of 250v/1A Retarded.

Gallery of the repair:

Commodore 16 Repair #1

Defect:

• Black Screen.

Replaced parts:

• Replaced RAM TMS4416 (U6).

Gallery of the repair:

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Commodore 16 Repair #2

Defect:

• Black Screen.

Replaced parts:

• CPU Socket (U2).

Note:

I took advantage of this repair to install the ic sockets on the entire motherboard and use it like a “test board” for repairs.

Catweasel Z-II Mk2 (Urine CAT Cleaning)

Defect:

• The card is not recognized by the computer.

Cleaning:

• The Catweasel has traces of cat urine that with time has crystallized causing corrosion and short circuits.  I used the KONTACT PCC & Toothbrush to clean. I also checked the continuity in holes between pcb layers and traces in general.  Now it seems to work properly.

Gallery of the repair:

Peggy Plus (Scala MD100) v1.1 Recap

This Z2 card for Amiga has a problem of audio distortion on one channel. I have replaced all the tantalum capacitors, two of them in the Audio section.

Unfortunately i could not try this card, i did consider that could be also a problem of the NE5532  a Dual Low-Noise Operational Amplifier so i preferred put it on a socket, so it’s easy to replace if it is needed.

Gallery:

Commodore 64 Repair

Defect:

• Drive access problems (IEC): drive resets but it freez with a “searching for”

Replaced parts:

• Replaced EL7416 with a 7406PC (U8)

Note:

I have also removed a nasty connector welded directly on the c64 userport.

Gallery of the repair:

Commodore 128 Repair

Defect/Missing Parts:

• Two Electrolytic Capacitors have detached and the pins are gone…
• Garbage Screen.

Replaced parts:

• Replaced Electrolytic Capacitors of 220uF/50v and 330uF/50v.
• Replaced 74LS00 (U31)

Gallery of the repair:

This computer is of a dear friend; Paolo Cognetti.

Short story of the repair:

I have checked the voltages and are correct, although a couple of capacitors on the power stage need to be replaced.

I have tried to turn on the computer and i have see immediately a problem, the screen is full of random characters, with the oscilloscope i have tried to see if i have data stream on the CPU (Z80), interrupts and so on.., nothing, it seemed completely dead, replaced.

The computer has started better then before but with some video glitches, raster lines scrolls from bottom to the top and some characters scattered on the screen. I double checked the voltages and i have realized that the 12v are gone and the 7812 warmed a lot, about 80 degrees after 2 minutes.

Almost all tantalum capacitors of 1uf and 33uF on the 12v line are shorted, i have decided to replace them all (22 pieces)

After the replacement of all tantalum capacitors and two electrolytic capacitors on the power supply stage the computer has started to work correctly but with some video problems, characters scattered on the screen, after replacing two Static RAM 2114 everything works perfectly, including the Basic Cartridge that until now had never worked.

Works that have been made:

• Fixing broken Fuse Holder.
• Fixing a cold welding of a capacitor on the power supply stage.
• Testing Voltages.
• Replaced CPU Z80.
• Replaced 12 x Tantalum Capacitors (1uf)
• Replaced 10 x Tantalum Capacitors (33uf)
• Replaced 1 x Axial Electrolytic Capacitor (470uf)
• Replaced 1 x Axial Electrolytic Capacitor (1500uf)
• Replaced 2 x NMOS 2114 Static Ram.
• Fixed the botton cover with two missing screws.
• Cleaning the top cover using only water and a sponge.

Exidy Sorcerer II Repair Gallery:

Exidy Sorcerer II Gallery:

source: wikipedia

Sinclair ZX Spectrum 128k (Toastrack) Repair

Defect:

• Garbage screen on bootup.

Repair:

• Replaced 7404 (74LS04)

Note:

• Missing one HEX Inverter between Pin 11 and 10.

Gallery of the repair:

I have exhumed my old Macbook Core 2 Duo 13″ (late 2007) to install a Linux OS (Linux Mint) but before doing this work i wanted to give a nice internal cleaning and replacing the thermal paste of the cpu.

Gallery:

Commodore Floppy Disk Drive 1541 Repair (#1)

Defect:

• Motor runs continuously.
• Loading a Program or a Directory freeze the computer.
• Misaligned.

Repair:

• Replace 901229-05 (UB4)
• Replace 7414 (UA1)
• Head Alignment.

Gallery of the repair:

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Commodore Floppy Disk Drive 1541 Repair (#2)

Defect:

• Write Protect Problem.

Repair:

• A wire of the infrared LED was broken. The problem is remove the glue and the heat shrink tube around the LED.

Gallery of the repair:

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Commodore Floppy Disk Drive 1541 Not Repaired (#3/#4/#5)

Defect:

• Don’t read anything.

These Floppy Disk Drive have the Read Head interrupted. This seems to be the most common problem in the Mitsumi (Newtronics) drives.

Gallery:

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Commodore Floppy Disk Drive 1541 Repair (#6)

Defect:

• Loading a Program or a Directory freeze the computer.

Repair:

• Replace VIA 6522 (UC3)

Gallery of the repair:

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Commodore Floppy Disk Drive 1541 Repair (#7)

Defect:

• Loading a Program or a Directory freeze the computer.

Repair:

• Replace 7414 (UA1)

Gallery of the repair:

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Commodore Floppy Disk Drive 1541 Repair (#8)

Defect:

• Motor runs continuously.
• Loading a Program or a Directory freeze the computer.

Repair:

• Replace CPU 6502 (UC4)
• Replace 7414 (UA1)

Gallery of the repair:

Commodore 64 [ASSY 250407] Repair (#1)

Defect:

• Startup screen Scrambled/Garbage.

Repair:

• Replaced the IC socket of MOS 6569 (VIC-II) oxidized.

Gallery of the repair:

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Commodore 64 [ASSY 250407] Repair (#2)

Defect:

• Garbage Graphics.

Repair:

• Replaced MOS 6569 (VIC-II).

Gallery of the repair:

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Commodore VIC-20 [ASSY 250403] Repair

Defect:

• Black Screen.

Repair:

• Replaced MOS 6502 (UE10).

Gallery of the repair:

Amiga 600 (REV1.5) badly Distorted Clipped Saturated audio Repair

This Amiga 600 has suffered several months ago serious problems of the leakages capacitors.

The amiga has worked for a period and then the sound has stopped to working with the classic distorted/clipped audio defect.

I have replaced the usual LF374 SMD with a TL084C 100% compatible and everything has started to work perfectly.

Gallery of the repair:

Commodore Amiga 500 (ASSY 312510 REV.5) Repair

Defect:

• Black Screen.

Repair:

• Replaced a 74LS244 (U35)
• I have removed a rusty part of the pcb to see if the tracks are interrupted or in a bad state.

Note:

• This Amiga has already been repaired in years past, not from me.

Gallery of the repair:

This is another nice test cartridge can help a little bit the repairs, many thanks to the author of the DIAG264 software.

Gallery:

source: diag264 blog.tynemouthsoftware.co.uk

Damn! the case Housing of the Power Supply is glued and is not a nice thing.

Defect:

• +5v is missing.

Replaced components:

• 1 x IC CA723CE (Precision Voltage Regulators)

Analysis of the defect:

• Tested the cable.
• Tested the transistor TIP41C soldered on the PCB.
• Unsoldered the transistor TIP41C and i have again tested to make sure 100% that is not died, the transistor was not in short circuit or interrupted.
• With the transistor TIP41C unsoldered i have tested the output of the IC CA723CE PIN 10 VOUT which appeared to 0V instead of +5v  while the input voltage (unregulated) PIN 12 measured +17v and VREF 6 PIN was correct.

Gallery of the repair: