Selcom Lemon II Floppy Drive Repair and Clean.

Defect: The Floppy Drive motor spins and the LED stays on but the R/W head does not move and don’t read anythings. This is a classic failure due to incorrect insertion of the Floppy Drive connector into the male connector on the side of the Floppy Drive Controller card.

By inserting the connector moved one row externally the supply consequently go to in the wrong places and the first IC to explode in the true sense of the word is the 74LS125 (see photo).

Replaced the component, everything has started to working again.

Taking advantage of the repair, i have cleaned the inside of the LEMON II Computer and done a DUMP of the EPROM, i also cleaned and lubrificate the mechanical parts of the Floppy Drive.

Gallery of the repair:

Download: Selcom Lemon II ROM EPROM Dump (890)

Autopsy:

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The computer Lemon II is a “perfect” clone of the Apple ][+ (Apple Europlus) produced in Italy by different companies, Selcom, Jen, Belton and Lemon Italy.

The mainboard was a copy almost identical of the Apple ][+, differ from the original for a few details, such the use of EPROM instead of ROM.

The contents of the ROM was slightly modified to remove any reference to Apple. So the boot screen that show “Apple II” are replaced with “Lemon II”. The Lemon II was therefore not only a computer “compatible” like the original, but a real clone.

The computer won the fame of 100% software compatibility, feature that will determine the commercial success.

This text was taken from the homepage of computerhistory.it and translated in English language.

Playing at Montezuma’s Revenge:

Lemon II at work in a school laboratory:

source: computerhistory.it leganerd.com

I have received a Lemon II computer (Apple ][+ / Europlus Clone) in a good cosmetic condition but with a serious problem at the keyboard, here below defects and repairs that has been made.

Cleaning comparison (before / after):

Gallery of the repair:

Defects:

• First problem: When a keyboard key is pressed is always displayed the same character, in this case the character “O”
• Second problem (which i have only noticed after solving the first one): The keyboard works correctly, all characters are displayed in the correct way, but sometimes the character displayed does not match with the key pressed. Example: when pressing many times the letter “I”, after a while is displayed the character “Y” and after a while it show the right character “I”.

Components Replaced:

• 2 x 74LS191 (UP/DOWN Counters)
• 1 x SMC KR2376-ST (Keyboard Encoder)

I have to thank my friend Luca that called me to inform me that there was still a piece of the SMC KR2376-ST available in the store.