Looking for a (good) Signetics 2504

4 replies [Last post]
Joined: Feb 21 2006
Posts: 21

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?

logjam- a long time ago, you said you had a source for the 25xx chips. Are they still around?

Scott Austin

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SchwindS's picture
Joined: Feb 24 2007
Posts: 44
Here you find the DataSheet of the Signetics 2504

Here is a link to one of my favorite Apple I Website's

There you find a Datasheet of the Signetics 2504
I hope it made it easyer to find a spare part for your Apple I



Joined: Jun 5 2008
Posts: 383
May be very hard to find just

May be very hard to find just one of these parts. Looks like you need a Signetics 2504v, which some of the larger obsolete part vendors list as in stock. However they usually have high prices and require a minimum purchase of something like $300.00. It may be worthwhile entering a RFQ to a few of them to see what their actual price and minimum purchase requirements are. Another approach may be to find out if some other period device of lessor value used the same part and scavenging one of those. I have found a few vendors that stock some old and obsolete parts and sell small quantities, but none of these list 2504 as in stock. Just the same, I'll list them here for future reference for the group.

advanced components electronics (ACE) http://www.acecomponents.com/
unicorn electronics http://www.unicornelectronics.com/
anchor electronics http://www.demoboard.com/anchor.htm

Mike Willegal

Joined: Feb 21 2006
Posts: 21
Thanks for the good links. I

Thanks for the good links. I'll keep looking!

BTW, I just completed my Obtronix Apple 1 reproduction. I'll be starting a new thread in a minute.


Joined: Jun 10 2010
Posts: 1
Signetics 2504V IC


I have one of these ICs (8 pin, 300mil DIP package) if you want to purchase it for a reasonable price.

-Art Harrison