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swapple
July 7th, 2008, 06:00 PM
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
July 7th, 2008, 06:22 PM
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
July 7th, 2008, 06:26 PM
OK, I at least found a data sheet.

http://www.hansotten.com/apple1/signetics2504.pdf

swapple
July 7th, 2008, 06:58 PM
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
July 7th, 2008, 07:03 PM
OK, I at least found a data sheet.

http://www.hansotten.com/apple1/signetics2504.pdf
Thank you. I have that doc-- it helped me diagnose the problem!

Tomorrow I try to post a photo of the chip. BTW, it's a 8-pin dip with the markings:
7622 (after the Signetics "S" logo)
2504V
1404A

Thanks again.

VintageComputerman
July 8th, 2008, 05:21 PM
I haven't had any luck yet but this link might help. They have 8 left.

http://64.233.167.104/search?q=cache:74uIFYySlxAJ:www.clubelec.com/en/stock.asp%3Fpage%3D182%26searchstring%3D%26substri ng%3D1+Signetics+7622&hl=en&ct=clnk&cd=2&gl=us

http://www.clubelec.com/en/stock.asp?page=182&searchstring=&substring=1

swapple
July 10th, 2008, 10:47 AM
I haven't had any luck yet but this link might help. They have 8 left.

http://64.233.167.104/search?q=cache:74uIFYySlxAJ:www.clubelec.com/en/stock.asp%3Fpage%3D182%26searchstring%3D%26substri ng%3D1+Signetics+7622&hl=en&ct=clnk&cd=2&gl=us

http://www.clubelec.com/en/stock.asp?page=182&searchstring=&substring=1
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

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

swapple
July 10th, 2008, 10:14 PM
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

Ksarul
July 11th, 2008, 04:13 AM
4 Star Electronics seems to have about 11,000 of them--but they are one of those places that usually has a pretty high minimum order. . .

http://www.4starelectronics.com/part_search/search_results.asp

Dwight Elvey
July 11th, 2008, 05:55 AM
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
July 11th, 2008, 09:16 PM
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
July 13th, 2008, 11:41 AM
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
July 13th, 2008, 07:05 PM
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
July 15th, 2008, 09:40 AM
is there an equivalent to the Signetics 2504?

Al Kossow
July 15th, 2008, 10:36 AM
National 1404

billdeg
July 15th, 2008, 01:56 PM
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
July 16th, 2008, 08:43 PM
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

VintageComputerman
July 17th, 2008, 04:43 AM
National 1404


I have a lot of National Semiconductor items. I'll recheck my inventory.

Druid6900
July 17th, 2008, 11:51 AM
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.

Chuck(G)
July 17th, 2008, 02:26 PM
I believe the MM1404AN (NSC) is also a replacement. See:

http://www.datasheetarchive.com/pdf/2417485.pdf

for comparison. There's a guy on eBay offering them for $4.95 BIN.

swapple
July 18th, 2008, 09:29 PM
I've been away for a few days (way too many hours under the kitchen sink, replacing a faucet. Picky me- I didn't want any leaks.)

Thank you all for the suggestions and the news on the 1404. For now I haven't given up on finding a (more-authentic) 2504v. I've checked out a few of the surplus inventory companies and surprise, there's a pretty high minimum purchase amount. I'm going back to these folks asking if they deal with any companies that deal in smaller quantities.

I'll let you know how it turns out.

Scott