weird old ROM chips...

Wed Aug 31, 2011 5:14 pm   

I started working on restoring an ancient computer (Wang 2200E). Having
dealt with this computer before, I decided it would be prudent to read
out the ROM chips in case they need to be replaced again. However,
these chips don't match anything I've ever heard of. Most annoyingly,
there is no ground pin! There are 23 of these on the board, with no
inked numbers the same.

The pinout is as follows:


+5V 1 24 OE1
A0 2 23 D0
A1 3 22 D1
A2 4 21 D2
A3 5 20 D3
A4 6 19 D4
A5 7 18 D5
A9 8 17 D6
-12V 9 16 D7
A8 10 15 A10
A7 11 14 OE2
A6 12 13 nAR


Look familiar to anyone?

Thu Sep 01, 2011 5:03 pm   

DJ Delorie wrote:

Interesting! "Fascinating"

Well, the 17VDC indicates the devices are MOS - I'd look into old
Rockwell parts from the mid-70s.

Any date codes on any ICs on the motherboard? If you can identify the
year then you can use the IC Master catalog from that year to find who
made ROM that were 1K X 8. I checked the 1978 guide and couldn't find
any likely suspects, but perhaps you will have more luck searching a bit
more through.

John :-#)#

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Thu Sep 01, 2011 6:36 pm   

DJ Delorie wrote:

OK, I see the Wang 2000E/F was produced in January 1976, so check out
the IC Master for 1975 (assuming you can find one) or earlier for the ROM.

What do you mean by pin 13 "nAR"? No Connection visible? Did you do a
resistance check to common in case they used an early multi-layer PCB
and the ground plane is invisible by being in the middle plane?

John :-#)#

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Thu Sep 01, 2011 6:39 pm   

John Robertson <spam_at_flippers.com> writes:

Looks like 1978-1979 time period.

http://www.delorie.com/tmp/wang2200E-roms.html (280 KB)

(yes, the pins are *rusty*)


That doesn't sound like something that would have ended up online...

Thu Sep 01, 2011 6:51 pm   

John Robertson <spam_at_flippers.com> writes:

The schematics labelled that pin AR with a bar over it. I suspect it's
"address ready".

Thu Sep 01, 2011 6:53 pm   

John Robertson <spam_at_flippers.com> writes:

As for the year discrepancy, note the "in case they need to be replaced
AGAIN" in my original post ;-)

If the power supply loses a rail, the ROMs are the first chips to die
from it

Thu Sep 01, 2011 8:52 pm   

In article <xnmxepfqpi.fsf_at_delorie.com>, DJ Delorie <dj_at_delorie.com> wrote:

If you take pin 1 as ground and pin 9 as Vcc it's the same as the
Signetics 2600 masked ROM, but that's an NMOS part (circa 1978) that runs
on +5 volts. A couple GI ROMs from 1977 also use pin 1 and 9 as gnd/vcc.
And other GI parts use +5/-[some voltage] as "ttl compatible" PMOS.

So this is a PMOS part from several years earlier. The Signetics sheet
cross references EA4600 and EA4900. Electronic Arrays, as I remember.

Mark Zenier mzenier_at_eskimo.com
Googleproofaddress(account:mzenier provider:eskimo domain:com)

Fri Sep 02, 2011 1:57 am   

DJ Delorie wrote:

Ah, thanks, the picture helps. Certainly the date codes are from 77
through 79. The manufacturers logo "E/A" looks familiar. I'll have to
check that tomorrow in my IC Masters if I have time...figuring out the
manufacturer should enable us to find the part number.

These are masked ROMs of course.

John :-#)#

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Fri Sep 02, 2011 5:33 am   

John Robertson <spam_at_flippers.com> writes:

Of course. I was hoping I could read them out and save the data at
least. If they get toasted I'll have to figure out how to create
replacements from today's technology.

Fri Sep 02, 2011 9:13 am   

John Robertson schrieb:


Looks like "Electronic Arrays Inc.":
<http://www.elnec.com/support/ic-logos/manufacturer-description/?manuf=Electronic+Arrays>
<http://www.antiquetech.com/companies/EA.htm>

Tilmann

Fri Sep 02, 2011 10:50 am   

"DJ Delorie" <dj_at_delorie.com> wrote in message
news:xnmxepfqpi.fsf_at_delorie.com...

Maybe this page can add some information

http://oldcalculatormuseum.com/t-wangic.html

Cant find your part#'s there but still...

Fri Sep 02, 2011 10:57 am   

Also found this
http://home.wxs.nl/~janvdv/wang/wangmuseum.htm
Maybe you can dig deeper from there for more info.

Pages like these makes me num..

Fri Sep 02, 2011 2:25 pm   

Yeah, I've been though the museums some. I figured this place was an
easy first choice for finding the base part *if* it was a common part
back then, I'll try to hunt down someone who's fiddled with these parts
before, next.

Fri Sep 02, 2011 5:56 pm   

mzenier_at_eskimo.com (Mark Zenier) writes:

Thanks for the info. /me wishes stuff back then was on the Internet
already

Fri Sep 02, 2011 6:23 pm   

DJ Delorie wrote:

If you can access the data and address bus directly you could always
read the entire bank of ROM using something like a Fluke 9010 or 9100
(if the CPU is common) or even wire up an adapter so you could connect
to an Eprom reader. Schematics would help for this project!

John:-#)#

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"Old pinballers never die, they just flip out."