Commodore Dual Drive Floppy Disk Model 4040 Repair
Defect:
- Completely dead with all LEDs lit up like a christmas tree.
Replaced parts:
- Replaced 1 x LM340K (7812) Voltage Regulator (VR1)
- Replaced 1 x 7406 Hex Inverter Buffers/Drivers (UJ6)
- Replaced 1 x 6522 (VIA) Versatile Interface Adapter (UM3)
- Replaced 1 x 6504 8-Bit CPU (UH3)
- Replaced 1 x 6502 8-Bit CPU (UN1)
Note:
The cause of many problems was the previous repair. It was replaced the voltage regulator LM340K (7812) with a LM338K (Adjustable Regulators). The two components are not compatible and have a different pinout.
Download:
I have adapted a power supply Cisco (P/N 34-0874-01) to be used with the Home Computer Amstrad CPC 6128/664 that use two voltages +5v and +12v (pinout). If you want to use this computer without the original monitor the only way is use a external power supply.
The photo speak for themselves, the modification is very simple. The only thing that i want to say, maybe not everyone knows it, the Cisco power supplies uses the STANDBY remotely, you need to connect together the ROF line with the one of two RTN (GND).
I have also added a third cable in case you want to use an external Floppy Drive.
Gallery:
Tandy Radio Shack TRS-80 Data Terminal (DT-1) Repair.
Defects:
- Some keys are dead (X – Z – DEL – ])
- Sometimes the characters typed are uppercase and sometimes lowercase.
- The DT1 Terminal doesn’t turn on the first try.
- Horizontal scan problem. The right side of the image is rolled up on itself.
- Outside ground of the CRT disconnected.
The jobs that have been made:
- Replaced 1 x 74LS138 Demultiplexer (U1)
- Replaced 1 x 74LS240 Octal Buffer/Line Driver (U23)
- Replaced almost all capacitors on the power supply side with the wrong ESR/Capacitance.
- Cleaning keyboard switches. Fortunately these switches can be opened.
- Removed the filter capacitor (RIFA)
- CRT Linearity adjustment.
- Restored the outside ground of the CRT.
Radio Shack TRS-80 Model 1 (#2) Repair.
Defect:
Replaced parts:
- Replaced 1 x CD4069 HEX Inverter (Z6)
- Replaced 1 x CD4069 HEX Inverter (Z57)
- Replaced 1 x 74LS00 QUAD 2-INPUT NAND GATE (Z5)
Radio Shack TRS-80 Model 1 Repair.
This is the second time that this computer was repaired within 2 years.
Defect:
- Video Sync issues (Horizontal Driver) and then … garbage on the screen.
Replaced parts:
- Replaced 1 x CD4069 HEX Inverter (Z6)
- Replaced 1 x MM2102 RAM (Z62)
Repair Commodore Amiga 3000 Motherboard with Battery leakage
There was once a motherboard of an Amiga 3000/25 devastated of the Battery acid where missings all the socketed components and others are unsoldered and recovered for other things.
The situation was not exactly the best one, in other words … was going into the box of spare parts.
I made the impossible, i have cleaned, scraped and rebuilt many tracks of the pcb corroded by the battery acid and i must say that with lot of patience i have repaired the motherboard giving a new life to this Amiga 3000/25 that he had no many chance to come back to work
Apple IIe Power Supply Repair.
Defect:
- Dead with clicking noise in background (This power supply works even without load)
Replaced parts:
- Replaced 1 x 200uF 10V Electrolytic Capacitor.
Removed as a precaution the RIFA filter capacitor.
Gallery:
Epson PX-4+ Easy Repair
Defect:
Replaced parts:
Removed the internal Backup Battery (RB 301) 4.8v 90mA.
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.
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:
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.
Commodore Dual Drive Floppy Disk Model 4040 Repair
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