20 Sep
2022
20 Sep
'22
2:07 a.m.
Hi,
I recently acquired a Solid State Music SB-1 from which all the chips had
been removed. I've reinstalled all of the chips (I located an SSM2000) and
I've been trying to figure out why this board crashes my computers. The
conclusion that I've come to is rather astounding. The board specifies two
74ls85 4 bit binary comparator chips to perform address decoding. The
designers of this board seem to have had incorrect pinouts for it. Every
source that I can find specifies:
B3 1 16 VCC
A<B (in) 2 15 A3
A=B (in) 3 14 B2
A>B (in) 4 13 A2
A>B (out) 5 12 A1
A=B (out) 6 11 B1
A<B (out) 7 10 A0
GND 8 9 B0
The 7485s that I was able to get have this pinout. BUT! The SB-1 is
designed as:
B2 1 16 VCC
A2 2 15 A3
A=B (out) 3 14 B3
A>B (in) 4 13 A>B (out)
A<B (in) 5 12 A<B (out)
A=B (in) 6 11 B0
A1 7 10 A0
GND 8 9 B1
I Ohm'd out the board to verify this and it matches the schematic here:
https://wiki.theretrowagon.com/wiki/Solid_State_Music_SB1
What the heck??? Did the pinout of the 7485 just arbitrarily change at some
point? Was this some competition between manufacturers? Is there any way
to get the "right" 7485?
Thanks,
Bill
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20 Sep
20 Sep
2:35 a.m.
On 2022-09-19 8:07 p.m., William Sudbrink via cctalk wrote:
Hi,
I recently acquired a Solid State Music SB-1 from which all the chips had
been removed. I've reinstalled all of the chips (I located an SSM2000) and
I've been trying to figure out why this board crashes my computers. The
conclusion that I've come to is rather astounding. The board specifies two
74ls85 4 bit binary comparator chips to perform address decoding. The
designers of this board seem to have had incorrect pinouts for it. Every
source that I can find specifies:
B3 1 16 VCC
A<B (in) 2 15 A3
A=B (in) 3 14 B2
A>B (in) 4 13 A2
A>B (out) 5 12 A1
A=B (out) 6 11 B1
A<B (out) 7 10 A0
GND 8 9 B0
The 7485s that I was able to get have this pinout. BUT! The SB-1 is
designed as:
B2 1 16 VCC
A2 2 15 A3
A=B (out) 3 14 B3
A>B (in) 4 13 A>B (out)
A<B (in) 5 12 A<B (out)
A=B (in) 6 11 B0
A1 7 10 A0
GND 8 9 B1
I Ohm'd out the board to verify this and it matches the schematic here:
https://wiki.theretrowagon.com/wiki/Solid_State_Music_SB1
What the heck??? Did the pinout of the 7485 just arbitrarily change at some
point? Was this some competition between manufacturers? Is there any way
to get the "right" 7485?
They are both right.
7485,74LS85,74S85 top pin out.
74L85 the bottom pin out. SB-1
TTL data book 1985.
Thanks,
Bill
I suspect they used the L for low input loading
for the address bus. The 74C85 (fairchild ) would be the sane
substitute for the 74L85.
Ben.
4:18 a.m.
There are a few US based Ebay sellers of the 74L85.
Tom
On Tue, Sep 20, 2022 at 10:50 AM ben via cctalk <cctalk(a)classiccmp.org>
wrote:
On 2022-09-19 8:07 p.m., William Sudbrink via cctalk
wrote:
Hi,
I recently acquired a Solid State Music SB-1 from which all the chips had
been removed. I've reinstalled all of the chips (I located an SSM2000)
and
I've been trying to figure out why this board
crashes my computers. The
conclusion that I've come to is rather astounding. The board specifies
two
74ls85 4 bit binary comparator chips to perform
address decoding. The
designers of this board seem to have had incorrect pinouts for it. Every
source that I can find specifies:
B3 1 16 VCC
A<B (in) 2 15 A3
A=B (in) 3 14 B2
A>B (in) 4 13 A2
A>B (out) 5 12 A1
A=B (out) 6 11 B1
A<B (out) 7 10 A0
GND 8 9 B0
The 7485s that I was able to get have this pinout. BUT! The SB-1 is
designed as:
B2 1 16 VCC
A2 2 15 A3
A=B (out) 3 14 B3
A>B (in) 4 13 A>B (out)
A<B (in) 5 12 A<B (out)
A=B (in) 6 11 B0
A1 7 10 A0
GND 8 9 B1
I Ohm'd out the board to verify this and it matches the schematic here:
https://wiki.theretrowagon.com/wiki/Solid_State_Music_SB1
What the heck??? Did the pinout of the 7485 just arbitrarily change at
some
point? Was this some competition between
manufacturers? Is there any
way
to get the "right" 7485?
They are both right.
7485,74LS85,74S85 top pin out.
74L85 the bottom pin out. SB-1
TTL data book 1985.
Thanks,
Bill
I suspect they used the L for low input loading
for the address bus. The 74C85 (fairchild ) would be the sane
substitute for the 74L85.
Ben.
5:27 a.m.
And I thought shipping to Australia (opposite side of the planet) was
expensive.
Shipping from the US to Canada should be dirt cheap as mail can move via
trains not air freight.
$75 shipping for an IC is crazy no matter what the destination is (except
maybe Mars).
Tom
On Tue, Sep 20, 2022 at 12:51 PM ben via cctalk <cctalk(a)classiccmp.org>
wrote:
On 2022-09-19 10:18 p.m., Tom Hunter via cctalk
wrote:
There are a few US based Ebay sellers of the
74L85.
Tom
But most ebay sellers, from the USA seem to sell a item for $6.00 and
$75 shipping to Canada. China $2 and $3 shipping. With Covid all
shipping is several weeks.
Ben.
6:54 a.m.
Ben, I buy lots of stuff from eBay US sellers and most are willing to check/fix shipping
costs.
If not then I use a drop-box service where the item is shipped to Oregon, and then
reshipped to me for a not too horrible cost.
Lastly, I’ll be back at my shop in Burnaby in a couple of days and can check my inventory
of TTL chips - might well have your 74L85, and postage is pretty cheap within Canada. I’ll
try not to hose you too badly on the chip cost!
John :-#)#
On Sep 20, 2022, at 5:52 AM, ben via cctalk
<cctalk(a)classiccmp.org> wrote:
On 2022-09-19 10:18 p.m., Tom Hunter via cctalk wrote:
There are a few US based Ebay sellers of the
74L85.
Tom
But most ebay sellers, from the USA seem to sell a item for $6.00 and
$75 shipping to Canada. China $2 and $3 shipping. With Covid all shipping is several
weeks.
Ben.
22 Sep
22 Sep
4:55 p.m.
On 2022/09/19 9:51 p.m., ben via cctalk wrote:
On 2022-09-19 10:18 p.m., Tom Hunter via cctalk
wrote:
How many do you need? I have one or more of 74LS85, 74C85, 74HC85, and
7485...
Email me directly with which version you prefer. These are all NOS
parts, not pulls.
John :-#)#
--
John's Jukes Ltd.
7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
Call (604)872-5757 (Pinballs, Jukes, Video Games)
flippers.com
"Old pinballers never die, they just flip out"
There are a few US based Ebay sellers of the
74L85.
Tom
But most ebay sellers, from the USA seem to sell a item for $6.00 and
$75 shipping to Canada. China $2 and $3 shipping. With Covid all
shipping is several weeks.
Ben.
7:21 p.m.
On 9/22/22 09:55, John Robertson via cctalk wrote:
On 2022/09/19 9:51 p.m., ben via cctalk wrote:
The ICs that you've listed as having (74LS85, 74C85, 74HC85, and
7485) aren't what the OP needs. The 74L85 is a different animal with a
different pinout from the chips you've listed.
--Chuck
On 2022-09-19 10:18 p.m., Tom Hunter via cctalk
wrote:
How many do you need? I have one or more of 74LS85, 74C85, 74HC85, and
7485... There are a few US based Ebay sellers of the
74L85.
Tom
But most ebay sellers, from the USA seem to sell a item for $6.00 and
$75 shipping to Canada. China $2 and $3 shipping. With Covid all
shipping is several weeks.
Ben.
2 Oct
2 Oct
2:05 p.m.
For anyone that might be interested, I was able to get some 74L85s. After installing
them
(and chasing down a misbehaving 7400) I was rewarded with a fully functional SSM SB-1.
Bill
-----Original Message-----
From: Chuck Guzis via cctalk [mailto:cctalk@classiccmp.org]
Sent: Thursday, September 22, 2022 3:22 PM
To: cctalk(a)classiccmp.org
Cc: Chuck Guzis <cclist(a)sydex.com>
Subject: [cctalk] Re: 7485 chip history??? (Solid State Music SB-1)
On 9/22/22 09:55, John Robertson via cctalk wrote:
On 2022/09/19 9:51 p.m., ben via cctalk wrote:
The ICs that you've listed as having (74LS85, 74C85, 74HC85, and
7485) aren't what the OP needs. The 74L85 is a different animal with a different
pinout from the chips you've listed.
--Chuck
--
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On 2022-09-19 10:18 p.m., Tom Hunter via cctalk
wrote:
How many do you need? I have one or more of 74LS85, 74C85, 74HC85, and
7485... There are a few US based Ebay sellers of the
74L85.
Tom
But most ebay sellers, from the USA seem to sell a item for $6.00 and
$75 shipping to Canada. China $2 and $3 shipping. With Covid all
shipping is several weeks.
Ben.
20 Sep
20 Sep
3 a.m.
On 9/19/22 19:07, William Sudbrink via cctalk wrote:
Have a look at the 74L85 (not LS). it's one of those oddities that
some of the "L" 74 series logic have different pinouts than the
standard/LS/S/H/F/....
One notable aspect is that it's possible to wire-OR the L series
outputs--something that you don't want to do with the others.
--Chuck
Hi,
I recently acquired a Solid State Music SB-1 from which all the chips had
been removed. I've reinstalled all of the chips (I located an SSM2000) and
I've been trying to figure out why this board crashes my computers. The
conclusion that I've come to is rather astounding. The board specifies two
74ls85 4 bit binary comparator chips to perform address decoding. The
designers of this board seem to have had incorrect pinouts for it. Every
source that I can find specifies:
B3 1 16 VCC
A<B (in) 2 15 A3
A=B (in) 3 14 B2
A>B (in) 4 13 A2
A>B (out) 5 12 A1
A=B (out) 6 11 B1
A<B (out) 7 10 A0
GND 8 9 B0
The 7485s that I was able to get have this pinout. BUT! The SB-1 is
designed as:
B2 1 16 VCC
A2 2 15 A3
A=B (out) 3 14 B3
A>B (in) 4 13 A>B (out)
A<B (in) 5 12 A<B (out)
A=B (in) 6 11 B0
A1 7 10 A0
GND 8 9 B1
I Ohm'd out the board to verify this and it matches the schematic here:
https://wiki.theretrowagon.com/wiki/Solid_State_Music_SB1
What the heck??? Did the pinout of the 7485 just arbitrarily change at some
point? Was this some competition between manufacturers? Is there any way
to get the "right" 7485?
Thanks,
Bill
--
--Chuck
Sent from my digital computer
781
days inactive
793
days old
9 comments
5 participants
participants (5)
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ben -
Chuck Guzis -
John Robertson -
Tom Hunter -
William Sudbrink