Play Meter

An easy-to-build
Gottlieb prom tester
By Jim Calore
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Gottlieb Prom Tester
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This easy-to-understand , easy-to-
build Gottlieb Prom Tester will detect
any memory failure due to bad
addressing or incorrect data outputs
in seconds .
This is done by comparing the
suspect prom with a known good
prom . The results are known im -
mediately!
This will certainly be an invaluable
piece of test equipment to add to
your shop . It eliminates guess work
and will find heat related failures
also .
CIRCUIT EXPLANAT[ON
A 555 timer chip, employed as a
free -running oscillator , serves as the
master clock . The output of this clock
is fed into a chain of counters to
obtain the prom addresses.
By addressing both proms sim-
ultaneously , their respective outputs
at any address should be identical.
The error detecting circuit will pick up
any difference , stop the clock , and
activate the error lamp.
If the prom under test is good , the
test cycle lamp will activate and the
test will automatically start again . The
reset switch will start the addressing
from zero count.
If you suspect a heat problem , just
led the prom recycle continuously
until its operating temperature is
reached .
CONSTRUCTION
This circuit can be built easily on a
4 1 h-by 6 -inch circuit card , available
in most electronic stores . [t would be
advisable to use sockets for all the
[C's . For the prom sockets use
low-insertion type sockets to facilitate
easy removal .
All [C's used are common , easy to
obtain , and inexpensive .
NOTES AND MODIF[CAT[ONS
The clock circuit can be adjusted
for a slower scan rate by increasing
the valve of the resistors and! or the
capacitor on Pin 6 .
The error LED will be activated
when the tester stop-go switch is in
the stop position . This checks the
LED before running the test.
PARTS LI ST
IC ' s
555
7493
7486
7402
7408
1
3
1
1
1
PLAY METER . March. 1979
Sockets
8-PI N
1
l 4-P IN - 6
18-P IN - 2
Lo-in s ertion
Resistors
470
3
270
1
lK
4
LEDS
2
(Green, Red)
CAPS
. 01
2
Switches
1
Togg le
Push-Button
1
Misc .
---
Hook-up Wire
Circuit Board 4 ~ " x 6"
Provid e +5V and GND Taps
57