FS: DT-90 DRAM Memory testers (64k, 256K, and 1meg chips)

["Robert L. Doerr" <rdoerr@bizserve.com>]

Many of the Apple II, II+, IIe, and II gs use DRAM memory.
For those of you doing repair work I have a few memory
testers that you might be interested in.  These are the
only testers I know of that effectively test DRAM chips.
Unlike some of the universal programmers which have simple
function tests for DRAM (if they test them at all) these
testers will test DRAM chips at rated speeds and can test
how they operate when powered under a marginal voltage
supply.  If you think you have memory problems then this
can really help.  It allowed me to find several chips that
would work ok under normal circumstances but would fail if
the voltage was too high or too low.  I was able to weed
out all the chips that were bad or questionable leaving
me with the ones that would work in almost any conditions.

The features of the DT-90 RAM Tester:

1) The DT-90 can test 64K x 1, 256K x 1, and 1Meg x 1 DRAM's
(Dynamic Random Access Memory IC's).

2) It can test at "read access times" from 60ns to 200ns.

3) Alternate read/write test patterns of "1010" and "0101"
are automatically run to all device addresses.

4) Vcc MARGIN tests can be selected allowing read/write
function tests to run at three voltage levels.

5) A "CYCLE" switch allows continuous testing.

6) Test immediately stops upon detecting a read error.

7) LED indicators are provided to indicate: TEST RUNNING,
TEST SUCCESSFULLY COMPLETED, TEST STOPPED ON ERROR, DRAM
Vcc level (HI, LO, or normal 5V).

8) 16 & 18 pin "ZIF" Zero Insertion Force test sockets are
provided for DRAM's being tested.  A picture of their old
ad and a link to the PDF of page one in the documenation.

http://www.robotswanted.com/pictures/dt90.jpg
http://www.robotswanted.com/pictures/dt90.PDF

These units were featured in the May 1991 Radio Electronics
Magazine.  Although they only have sockets for testing 64K,
256K, and 1meg DRAM chips I was able to make an adpater for
mine that allowed me to test the 4116 chips too.  I would
expect that it would not be too hard to make adpaters for
others as well.

http://www.robotswanted.com/pictures/4116adpt.JPG
http://www.robotswanted.com/pictures/4116adpb.JPG

These have been discontinued and unavailable for quite some
time but I was able to obtain the last of them.  I got them
since I needed one myself but I thought I would offer the
extra's for sale.  These are not in a case but they are
working units (except where noted).  You can put them in a
case if you wish.  They come with complete instructions and
schematics.  All that you will need to make them work is a
9vdc 300ma adapter for power.

$65 - Fully working unit w/docs (couple avaiable)
http://www.robotswanted.com/pictures/Dt90frnt.JPG
http://www.robotswanted.com/pictures/DT90back.JPG
http://www.robotswanted.com/pictures/dt90schm.JPG

$40 - Working unit (tests 64K & 256K chips) w/docs (1 available)
Same as above but missing ZIF for 1meg chips

$15 - NEW Blank PCB with Dead unit for parts (Build your own!)
http://www.robotswanted.com/pictures/dt90prt1.JPG
http://www.robotswanted.com/pictures/dt90prt2.JPG

If you want one let me know.  First come first served.

Regards,

Robert

rdoerr@home.com

--
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Robert L. Doerr (MCNE, MCP, A+)
26308 Cubberness
St. Clair Shores, MI 48081
Tel: (810) 777-1313 
e-mail: rdoerr@home.com
WEB Site: http://www.robotswanted.com
"Keeping Personal Robots alive!"
Heathkit HEROS (Jr, 1, & 2000), Androbots, & MAXX STEELE.
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