Texas Instruments TI-99 Power Supply Repair.

Defect:

• Missing 16v (AC)

Repair:

• Replaced the Thermal Fuse with one of 125° 2A (see photo).

Gallery of the repair:

DigiLog FD-2064 (C64 Floppy Drive Clone) Repair.

Defect:

• The Floppy Drive don’t read anything on the Floppy Disk (The reading led light is always off and the Head doesn’t move)

Repair:

• Replaced a 74LS10 IC.

Other:

• Dump ROM (EPROM)

Gallery of the repair:

Download: DigiLog FD-2064 ROM (658)

After many years i have decided to made some improvements to my Sinclair ZX Spectrum 48k Issue 2.

Below what has been done:

• Replaced the obsolete 7805 voltage regulator with a modern and performant one that heats up much less; the TRACO Power 2450 (DC / DC Converter)
• Replaced the ULA Ferranti with a fully compatible FPGA solution (vLA82 designed and created by Charlie Ingley). Again it does not heat anything.
• Replacement of all electrolytic capacitors.
• Rework of an old Composite MOD with a more performing one.
• Replaced the Membrane and the bioadhesive to fix the keyboard with hard keys.

Gallery:

Atari 2600 JR (version without RF Modulator Box) PAL Composite Video Mod for my friend Charlie.

Gallery of the work done:

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source: blog.tynemouthsoftware.co.uk

Defect:

• Background noise (AC) and doesn’t reproduce sound from the cassette.

Repair:

• Replacement of two electrolytic capacitors of 22uf and 100uf  (see photo)
• General cleaning.

Gallery of the repair:

When you remove a chip with the screwdriver you have to be careful to lift the chip from the socket and not the socket from the PCB :lol:

That said and after bridged the broken pcb track of the GTIA and replaced a failed RAM the computer started working properly.

After the repair i have also make a improvement of the S-Video signal (XE series support the S-Video output).

This simple mod replaces/adds some resistors and capacitors that in the XE version are wrong for a perfect S-Video signal.

The instruction can be found in the link at the end of this article.

NOTE: The description of the STEP 4 is incorrect, it’s not Q2 but Q3 and in the STEP 5 is not Q3 but Q2.

NOTE2: Obviously after assemble the computer i have noticed the “B” key was stuck, the key piston have a crack, after replace it now the button work properly.

Gallery of the repair:

12►

Download: Svideo Atari 130XE Mod (741)

This is the same article of the previous one “Floppy Disk Cleaner” with the only difference that i have used a ALPS mechanics.

I have also connected the RED Led throught a 680 ohm 1W resistor to the 12v line.

Previous post:

Why throwing away a Commodore Floppy Disk Drive with a broken head it could become a great gadget to clean Floppy Disks.

How to do ? just disassemble the entire part that controls the movement of the head including the head itself.

The power supply used is 12v with at least 1A, you must connect the positive to the BROWN wire and the negative to the BLACK wire of the motor control PCB.

Good Cleaning.

Gallery:

This computer has kept for many years my BBS “Hidden Power / Nightfall HQ” up until closing, previously the BBS ran on the Amiga 1000 … then A500 and A2000.

I also publish two historical photos of my “BBS Room” where you can see this Amiga 3000 running.

I give a brief description of what was done and what i did today for this computer.

• Year 2001 i have removed the battery and one of the two SCSI Harddisks that was dead.
• Year 2010 i have cleaned the external/internal case and published the photos on the blog.
• Year 2018 i have cleaned the keyboard.
• Year 2019 i have carefully cleaned the motherboard that was covered with a sticky layer of Nicotine (in the BBS Room peoples likes to smoke a lot)
  • Cleaned the Floppy Drive covered inside and outside by a sticky layer of Nicotine, to repair it i had to completely disassemble it.
  • Replaced the Kickstart ROM 2.04 with version 3.1
  • Removed the last died SCSI Harddisk.
  • Installed “new” 250Mb Quantum Maverick SCSI Harddisk.
  • Installed WB 3.1 and MagicWB + a couple of Demos and of course Pinball Dreams Harddisk version.
  • Replaced the WD33C93A SCSI controller chip with AM33C93A-16PC.
  • Cleaned the Keyboard pcb and replacements of the rubber pad, more than 20 keys are died.
  • Removed the Zorro BSC / Alfa Data MultiFace Card 3 (multi Serial) card and installed the Village Tronic Ariadne II (Ethernet Card)

Everything works perfectly as you can see from the photos.

Gallery:

I received as a gift… we start badly,i have recover, we are not there, i purchased, much better, yet another computer from Radio Shack that was missing in my collection.

The computer equipped with several manuals and Floppy Disk was given to me by a dude (thanks Scott) from the United States, he had written “near mint” and is this phrase that attracted me.

The Computer is a Radio Shack TRS-80 Model 4 (GATE ARRAY) therefore of last production with cathode ray tube with green phosphors.

The seller was not joking saying that it was “near mint” and working, the computer is kept very well it almost seems like it has never been used, it can be observed from the cathode tube, from the pcb of the monitor and from the flyback transformer, keyboard, External and internal Case and from the power supply, the usual ASTEC, which has never warmed up, perfect.

The warranty sticker was also intact.

Since there was nothing to clean/repair i have made some hardware enhancements and little replacements.

What i have done:

• Replacement of the 3 filter capacitors (RIFA) which i usually remove and i don’t replace.
• Converted the ASTEC power supply from 115V to 230v because this version of the power supply allows it because has a 115v/230v switching.
• Replaces the 115v power plug with a schuko.
• Various labels to identify the computer has been converted to 220v.
• Installed 64k RAM to update the Model 4 to 128k (blue wire mod as well)
• Dual ROM to BOOT from FreHD or from Floppy Drive. I have used the Jim Brain ROM-el 2364 which uses a Flash ROM (AT49F001AN) but with a standard Mask ROM 2364 pinout.
• Installed a switch for Dual ROM hidden in the ventilation slots without drilling the case.

All test are made with the FreHD interface by Ian Mavric.

Gallery:

123►

Download: TRS-80 M4 GA Dual Boot ROM (850)

This repair was done only for a personal challenge, the computer is still unstable and with several died components.

After a careful cleaning the computer presents these problems:

• TED MOS 8360R2 not working (keyboard doesn’t work) even if i replace the TED doesn’t work, TED also tested on a working C16 doesn’t work.
• PIO MOS 6529 need to be replaced. The keyboard doesn’t work.
• CPU MOS 8501 Dead.
• Joystick ports (see photo)
• Cartridge connector need to be replaced.
• Modulator without lids (Above and Below)
• The sockets of TED and CPU should be replaced.
• Other rusty pieces.

Gallery of the repair:

Commodore 64 repaired ASSY 250425 (1 of 3)

Defect:

• No Video Signal.

Repair:

• Replaced 1 x MOS 8701 R1 (U31)

Commodore 64 repaired ASSY 250425 (2 of 3)

Defect:

• Out of Memory.

Repair:

• Replaced 1 x RAM MT 4264-15 (U21)

Commodore 64 repaired ASSY 250407 (3 of 3)

Defect:

• Garbage Screen.

Repair:

• Replaced 1 x RAM MB 8264A-12 (U22)

The usual modification of a Gotek in HxC this time also with OSD (On Screen Display) support for Amiga 1200.

Gallery:

Video:

source: hxc2001.com

I have received from a friend two Sinclair ZX-81 to repair and taking advantage of the “sinclair” moment :-D i have also repaired one of my ZX-81 that is died staying off for years :-(

Two out of three ZX-81 have the ULA dead, while the third had a dead membrane and some short circuits caused by someone who don’t know how to unsolder/solder properly.

I have recovered the ULA from this last one and repaired the better one of the two ZX-81, i have also installed the Video Composite mod using the ZX8-CCB kit.

I have also repaired my ZX-81 always with the ULA dead and installed the Video Composite mod using the ZX8-CCB kit.

I thank Marco Lucarelli for giving me the Video Composite mod and giving me one of the two ZX-81 (without ULA / dead Membrane and short circuits) for spare parts.

Gallery of the repair:

I have replaced all the electrolytic capacitors of this Amiga 600 motherboard.

Gallery of the repair:

I have replaced the CPU socket of the Amiga 2000 CPU because the computer have a strange boot problems, for example: black screen.

After the replacement the problem has been gone.

Gallery of the repair: