Repair Sharp Memowriter EL-7000 note storage and printing device after battery leakage
In addition to calculators with BASIC and electronic notebooks, Japanese companies produced quite unusual devices in a similar form factor. One of them is shown on the KDPV after repair.
An interesting feature of the device is the way to distinguish between the letter O and the number 0. Usually, either zero is crossed out or a vertical line is drawn inside it. Here, the letter O represents the inverted letter Q. Both on the screen and on paper and keyboard.
The first thing that the author discovered immediately after opening the case: the batteries not only leaked, but leaked thoroughly. It is not surprising that the device was sold to him as malfunctioning.
And on the back of the board, the electrolyte “ate” printed conductors in a third of the area.
Neutralization of alkali with oxalic acid.
After wiping dry and cleaning with isopropyl alcohol. On the right is a soldered cable going to the processor board. Most printed conductors connected to a loop do not have conductivity. In other places, such conductors were also found. Some of the cliffs are generally determined visually: copper has disappeared, the base of the board is visible.
But for most conductors, the cliff is not visible, it turned out to be easier to duplicate them all with wires.
Done. The author borrowed nail polish from his wife and covered them with wires.
Cold soldering of one of the terminals of the reed switch. The spiral track drum moves the print head. The magnet on the drum passes the reed switch when the head is in the middle.
And the head is not alone. There are four of them. From a 16-character string, each of them prints 4 characters. The distance over which this whole tandem moves in a square decreases fourfold, and the print speed increases by the same amount.
The cartridge ribbon, of course, has dried out drastically in 38 years. But ... The
translator decided to find out the characteristics of the device and found another article. It turned out that there are still a lot of Epson ERC-05B cartridges where they are commercially available - Yandex will confirm. I wonder what modern devices they are buying for. There would be no demand - no one would sell them.
The device operates in three modes. Typewriter mode allows you to type a 48-character string, edit it, and then send it to print in the form of three 16-character strings. So you can print long texts, because when you enter a new 48-character string, it replaces the old one in RAM. In note storage mode, the EL-7000 allows you to save 8 lines of 15 characters each, and the EL-7001 - 40 lines of 17 characters. Any note can be read, edited and printed. Where the seventeenth character is printed, if 16 is placed in the line, it is not said. Finally, in the third mode, the device works as a calculator with or without printing.
But it’s more interesting, of course, to refill the original cartridge with a permanent marker.
Go through the battery compartment.
See how quickly everything worked: