EEPROM Eraser

Although you will stumble over programmers for EEPROMs, matching eraser units are few and far between. The small ‘hed.eraser’ solves the problem quickly and efficiently.Even after more than ten years, various Flash technologies have failed to completely supplant EPROMs. This is surprising because erasing an EPROM using a dose of UV light is tedious, while the glass window in the housing of EPROMs adds considerably to the device manufacturing cost. The Electrically erasable EPROM (EEPROM) is an attractive alternative. Just like the EPROM, it can be ‘burned’ in traditional programmer systems. Moreover, it is 100% electrically compatible with UV erasable counterparts. However, not all programming systems for EPROMs are capable of actually erasing an EEPROM, and that is why such a tool is presented in this article.

Resistors:
R2 = 12kOhm 
R3 = 270Ohm 
RN1 = 8-way 10kOhm SIL array
RN2,RN3 = 7-way 1kOhm , DIL array
Capacitors:
C1,C4,C5 = 10µ F 25V (lead pitch 2.5mm)
C2,C3 = 100nF (lead pitch 5mm)
C6,C7 = 22pF (ceramic)
C8 = 100µ F 25V (lead pitch 5mm)
Semiconductors:
D1,D3,D4 = 1N4148
D2,D6,D7 = 1N4001
D5 = BZ102 (zener diode 1.4V, see text)
D8 = zener diode 20V, 500mW
D9 = LED, 5mm, green
T1,T2,T5,T7 = BC327-40
T3,T4,T6,T8 = BC337-40
IC1 = AT90S1200-8PC (programmed)
IC2 = 7805
IC3 = 7812
IC4 = ICL7662CPA (Intersil)
Miscellaneous:
X1 = 7.3MHz quartz crystal 
8-way pinheader with 2 jumpers
S1 = pushbutton, 1 make contact (ITW)
2-way IC socket
40-way ZIF socket
K1 = mains adaptor socket, PCB mount