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Hunting for a Signetics 2504 for an Apple 1 Reproduction

swapple

Member
Joined
Jul 8, 2008
Messages
10
Hello All.

My Obtronix Apple 1 reproduction has a bad Signetics 2504. I built the kit a while ago, but I think I would have noticed the problem then. So I guess it got tired!

The Signetics 2504 is a 1024-bit dynamic shift register, 8-pin dip. It's used here to as part of the display control. The problem I saw was odd numbers (1,3,5,7,9,A,C,E) in every other screen column were displayed as the preceding ASCII character (0,2,4,6,8,@,B,D). Data from the keyboard was stored correctly in main RAM. It was just the video memory was displayed incorrectly.

Anyway, does anyone have a source of a Signetics 2504?

Thanks!!
Scott Austin
 

VintageComputerman

Veteran Member
Joined
May 26, 2007
Messages
661
Location
WNY
Didn't you just post this on applefritter?

I am looking into my parts collection. 20% chance I might have one. Don't hold your breath, this might take some time.

If someone could post a picture, it might be helpful.
 

swapple

Member
Joined
Jul 8, 2008
Messages
10
Didn't you just post this on applefritter?

I am looking into my parts collection. 20% chance I might have one. Don't hold your breath, this might take some time.

If someone could post a picture, it might be helpful.
VintageComputerman-- yes, I just posted on applefritter's Apple-1 forum. It's a focused and less-traveled list, so I figured I'd look here for a broader audience, hoping that noone would notice the nearly identical post. Sorry about that. Depending on the response here, in a week I may ask for help on cctalk!

Thanks for the response and offer.
Scott
 

swapple

Member
Joined
Jul 8, 2008
Messages
10
Thanks VintageComputerman,

I'm definitely looking for a 2504v. Your search was for a "7622" which I'd guess is the date code. Here's a photo of it:

http://www.vintage-computer.com/vcforum/album.php?albumid=4&pictureid=39

album.php
 

swapple

Member
Joined
Jul 8, 2008
Messages
10
On a related note (sorry to cross post):

I finally finished my Obtronix Apple 1 reproduction!

Actually, building the Apple 1 didn't take much time at all! It was the custom work on the mounting board, the curved and angled plastic leg brackets, and, and ...

I uploaded photos of it to my profile:
http://www.vintage-computer.com/vcforum/album.php?u=6611

Scott
 

Dwight Elvey

Veteran Member
Joined
Jun 21, 2003
Messages
4,753
Location
Santa Cruz
Hello All.

My Obtronix Apple 1 reproduction has a bad Signetics 2504. I built the kit a while ago, but I think I would have noticed the problem then. So I guess it got tired!

The Signetics 2504 is a 1024-bit dynamic shift register, 8-pin dip. It's used here to as part of the display control. The problem I saw was odd numbers (1,3,5,7,9,A,C,E) in every other screen column were displayed as the preceding ASCII character (0,2,4,6,8,@,B,D). Data from the keyboard was stored correctly in main RAM. It was just the video memory was displayed incorrectly.

Anyway, does anyone have a source of a Signetics 2504?

Thanks!!
Scott Austin


Hi Scott
This doesn't sound like a problem that could be cased by a serial shift
register. I'd more likely suspect character ROM or some chip related to
serializing the parallel data. A shift register would normally cuase an
all or nothing type failure.
Is there a schematic on the net for the apple 1?
Dwight
 

Dwight Elvey

Veteran Member
Joined
Jun 21, 2003
Messages
4,753
Location
Santa Cruz
Hi Scott
This doesn't sound like a problem that could be cased by a serial shift
register. I'd more likely suspect character ROM or some chip related to
serializing the parallel data. A shift register would normally cuase an
all or nothing type failure.
Is there a schematic on the net for the apple 1?
Dwight

Hi
Ok, I found a schematic and yes, one of these could cause
the failure you seeing.
Have you tried swapping it with one of the other bits and does
the problem move with the chip?
Dwight
 

swapple

Member
Joined
Jul 8, 2008
Messages
10
Hi Scott
This doesn't sound like a problem that could be cased by a serial shift
register. I'd more likely suspect character ROM or some chip related to
serializing the parallel data. A shift register would normally cuase an
all or nothing type failure.
Is there a schematic on the net for the apple 1?
Dwight

Sorry Dwight-- I could have saved you some time. I already figured it as the 2504v at fault. In short, the problem moved when I moved the chip.

Thanks for your time in this!! Esp. in light of your next post.

Scott
 

Druid6900

Veteran Member
Joined
May 7, 2006
Messages
3,809
Location
Hamilton, Ontario, Canada
Ok, I'm getting tired of looking at this thread, so, I'm going to go through my parts bins tomorrow and look for the damn things. :)

IIRC, I THINK I have a whole drawer full of them and I could never find out what they were. I COULD be mistaken, but the number sticks in my mind.
 

billdeg

Technician
Joined
Nov 18, 2003
Messages
3,872
Location
Landenberg, PA USA
thanks. I checked, I do not have either loose. Although it's small I have an IC / chip inventory on my web site. Use the search form to check. I try to keep it up to date.
-Bill
 

Ragooman

Experienced Member
Joined
Apr 27, 2005
Messages
162
Location
Pittsburgh,PA
Octopart Search Engine

Octopart Search Engine

I don't happen to have this in my parts storage, but I'm continually updating this.
http://www2.applegate.org/~ragooman/hobbies-old_computer_parts.html

I've had some good success with this search engine, Octopart
There's several places on there, sometime referred to as Parts Sharks, that have access to this part. Some can require a high minimum, but you can state your price target, quantity and see if they have a reasonable price quote.

http://octopart.com/search?q=2504V

The one Parts Agent in the results, Area51, is one that I've had good success with recently.

=Dan
 

Druid6900

Veteran Member
Joined
May 7, 2006
Messages
3,809
Location
Hamilton, Ontario, Canada
Still working on it.

I have, in the neighbourhood, of about 30,000 small parts and it takes a while just to find the BINS, let alone the parts.

Seems most of the bin labels have dried up and fallen off, so, looks like time for another inventory.
 
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