Atari 800XL with a missing delay line EP8212 (CO60472) Repair.

Thanks to the SRAM 64Kb Module by Lotharek, i have been able to resurrect a Atari 800XL which lacked the EP8212 delay line (CO60472) which is no longer available as spare parts.

More information of the SRAM 64Kb Module visit the lotharek site.

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Commodore A501 (REV 6C) Expansion Memory Unit Kissed by luck.

Why “lucky”? because the battery used in this Expansion Ram Unit (A501) was not VARTA but GP, these batteries resist slightly to aging and release less acid.

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Atari 2600 (4-switch units) Repair.

Defect:

• Black Screen.

Replaced parts:

• 1 x CPU 6507 (A200)

Gallery of the repair:

SNK Neo Geo MV1a Z-80 Error Repair.

Defect:

• No Sound (Z-80 Error)

Repair:

• Replacement of the Z-80 CPU in PSOP40 format.

Note:

• The error message “Z-80 Error” means everything and nothing, may be faulty the Z-80, SNK MASK-ROM SM1*, SNK NEO-D0 or also the YAMAHA YM2610.

With the Neo Diagnostics bios and with the M1 ROM burned and installed on the CHA Board of any NEO GEO cartridge, the problem can be better identified.

It is said that the error C3/00 that you see in the photos of NEO DIAGNOSTICS (write: C3 but reads: 00) is an almost assured a CPU problem, in fact, in this case it was.

The Z-80 CPU in PSOP40 format has been recovered from a failed SEGA GameGear.

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source: neogeo diag

Project born in 2017 for my SX-64++

I wanted to improve the schematics and make a PCB, the previous version was made on prototyping board pcb.

I have also added some features that i need when i will install the FPGASID in the SX-64++ and like the previous version the sidSwitcher integrates perfectly with the Overlay-64 & Keyman-64.

This circuit is not for sale. Schematics, Gerber and Atmel hex will be available soon for Download.

P.S: This project can also be used as a simple SPDT of analog audio signals. 2 INPUTS and 1 OUTPUT.

Features:

• Output for Overlay-64 (http://henning-liebenau.de/overlay64/)
• Input Push Button or Keyman-64 (http://henning-liebenau.de/keyman64/)
• Bicolor LED (SID1 GREEN / SID2 RED / SID1 + SID2 ORANGE)
• Output Mono or Stereo SID1 (LEFT+RIGHT / LEFT) / SID2 (LEFT+RIGHT / RIGHT) / SID1 + SID2 (LEFT+RIGHT / LEFT-RIGHT)
• Possibility to use the mute function.
• Jumper for configuration.

Schematics: (Prototype and Final):

The following photos are of the first version, second enhanced version, prototype breadboard and pcb.

Texas Instruments TI-99/4A Repair (1 of 2)

Defect:

• Black Screen and deafening sound in background.

Replaced parts:

• 1 x TMS 4732/2532 ROM (U611)

Gallery of the repair:

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

Defect:

• Garbage Screen.

Replaced parts:

• 1 x TMS4116-20 RAM (U103).

Gallery of the repair:

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Download: TI99 Technical Manual (896)

This Commodore Amiga 600 is arrived in laboratory in immaculate state still with the warranty sticker.

Immediately after the disassembly i have immediately noticed that were are several problems of acid released from the capacitors and dirty that affected this poor Amiga 600 and its Floppy Drive.

A decoupling capacitor it’s exploded with a pit on the PCB side, solved this problem i started to replace all the electrolytic capacitors and to clean the pcb with specific products.

After the replacement of the electrolytic capacitors, i have tried to turn on the amiga that apparently worked, shame about the distorted sound and the floppy drive that read 1 time of 100.

I had to replace the electrolyte capacitor on the Floppy Drive and soon after i looked for the fault of the audio problem that 99% is always the usual LF374.

In this case it was not only LF374 but also a 10ohm resistor that did not let the +12v to the LF374 and a short-circuited ceramic decoupling capacitor.

Components that have been replaced:

• IC LF374 substituted with a fully compatible TL084C (U15)
• 10Ohm resistor (R301)
• 330nF capacitor (C301)
• 330nF capacitor (C41)

Unfortunately the welding of the LF374 did not come very well how i like to do it but the pad are destroyed and corroded by the acid and they were about to detach, indeed the pad of the pin 2 of the LF374 was really detached, that’s why the pin 1 and 2 of the IC LF374 are connected together, they were connected via the pad.

I leave you to the photos and the video.

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12►

Video:

The Commodore-SX64 keyboard after some time isnt’t responding anymore (all or some keys). In this case, the keyboard needs some cleaning and repair.

First of all you have to disassembly the keyboard housing, pay particular attention to the screws, this plastic is very old and not of a good quality, it breaks only if you look it.

Gently remove the membrane and clean with alcohol all the metal contacts on the keyboard pcb and also clean all the contact pads on the membrane without alcohol.

Next i took some graphite in cream (Keypad Fix) to reconstruct the pads on the membrane by simply applying a very fine layer of graphite on the contacts.

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This monitor although fully functional in the video section, was missing audio. The integrated circuit of amplifying sound (TDA 2611A) was not powered.

The problem was a broken pcb track (see photo), solved this problem the sound is back.

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