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.
Gallery:
Atari 2600 (4-switch units) Repair.
Defect:
Replaced parts:
Gallery of the repair:
My name is “jaundice” and my last name is “lucky”. :-)
Why “lucky”? because the battery used in this Amiga was not VARTA but GP, these batteries resist slightly to aging and release less acid.
The only defect of this Amiga 500 Plus was the Floppy Drive which did not read any Floppy Disk, the motor running slower than normal, it was enough replace a 4.7uF electrolytic capacitor to make it work again.
I thank my friend Igor for the donation.
Gallery:
This Amiga 2000 is arrived in my lab in very poor condition in April 2016, the computer has been repaired and stored in an antistatic envelope.
Tested after almost 3 years, the computer does not show signs of life.
Having no video output, i have used the Chucky DIAGROM which through a serial connection i was able to identify 2 different problems with the RAM’s.
Defect:
Repair:
Below some random photo of the repair.
Gallery:
SNK Neo Geo MV1a Z-80 Error Repair.
Defect:
Repair:
Note:
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.
Gallery:
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:
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:
Replaced parts:
Gallery of the repair:
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Texas Instruments TI-99/4A Repair (2 of 2)
Defect:
Replaced parts:
Gallery of the repair:
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Download: TI99 Technical Manual (736)
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:
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.
Gallery:
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.
Gallery:
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.
Gallery:
I received this small Black and White CRT monitor from a friend, Ciro Barile of TI-99 Italian User Club, this monitor was used as a video intercom and i didn’t know the power supply voltage, the pinout but especially if it worked.
Found the pinout and the power supply voltage i saw the image turned upside down, this because the monitor could be hooked both from top and from bottom, nothing could be easier it was enough to change the deflection yoke connector on the motherboard to flip the image.
I drilled two holes on the back of the case to facilitate access to the composite video input and power supply (12v 2A).
Pinout:
Gallery:
Another 2 x Gotek (HXC) with some Enhancements.
Enhancements:
Gallery:
Credits for the best firmware Jean-françois Del Nero.
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 can see the connection in the photo.
Good Cleaning.
Gallery:
Video:
Myarc Geneve 9640 (Replacement filter capacitors and voltage regulators).
I have replaced all the voltage regulators (7805 / 7812) of 1A with the 1.5A version and all the 22uF / 35v filter capacitors.
Will also be installed the missing heat sinks in the geneve with plastic case.
Mattel Intellivision MOD 5155 (PAL) with GSOD (Grey screen of death) Repair.
Defect:
Components replaced:
Gallery of the repair:
Download: Mattel Intellivision Service Manual & Datasheet (686)
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