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09-06-2005, 12:29 PM #1
Armed with my short list of suspect IC's, the very first one I input at DigiKey and Mouser comes up "obsolete" or "non stocking" with no mention of alternatives.
It's a TI no. SN74LS245N. Description is Texas Instruments Receivers - Transmitters and Transceivers 20-DIP Octal Bus. Am I SOL or is there a source ?
09-06-2005, 12:34 PM #2
i probably have some 245s not sure if they are dip or so however.
09-06-2005, 12:37 PM #3
Octal transceivers are very common- I'm pretty sure HCT family cmos is a drop-in replacement for LS- gotta check the datasheets at home tonight. Wouldn't be suprised if I had a compatible one in the parts drawer I could mail you- unless you're trying to find that <exact> part.
09-06-2005, 12:38 PM #4
Damn, here's one that Mouser doesn't even recoginze at all. n82s123an. Dunno who made it, but there is a big "S" on the chip. German board.
09-06-2005, 12:38 PM #5
I've got a bunch of 74 series TTL also. Send me your list and I can take a look and if so, will be happy to send you for free. Was going to throw them out. Maybe they are now going to be as useful as those guys selling vacume tubes on ebay?
09-06-2005, 12:45 PM #6
Found one reference for 82s123- hope yours isn't blown, this is a programmable part. A pin compatible one shouldn't be too hard to find- but you'll need the contents before one of us on this board can burn you a new one. Yours sounds a bit like a Philips part.
09-06-2005, 12:49 PM #7
OEM Parts in Colorado Springs has a huge selection of old IC's. You wouldn't want to see their showroom which is an old supermarket, but when it comes to older components I''ve not seen anybody with a better selection.
09-06-2005, 12:49 PM #8
74xx245's are used all over the place for data buffering, used to be common on hdd interfaces on PC mainboards ages ago... Anyway, the 74LS245 you've got is a "Low power Schottky" version, and an HCT version - or "High speed Cmos Ttl-compatible" would probaby work ok. Your 84s123 on the other hand - I'll have a root about. As for availability, I'm not sure about US suppliers - sorry
09-06-2005, 01:05 PM #9Found one reference for 82s123- hope yours isn't blown, this is a programmable part. A pin compatible one shouldn't be too hard to find- but you'll need the contents before one of us on this board can burn you a new one. Yours sounds a bit like a Philips part.
Here's the list of what I need on this one board..just need quanity one unless otherwise noted. Of all the chips the TI - SN74LS245N is the most suspect.
* N82S123AN (need quanity 2, big "S" for brandname)
* SN74LS279NDS (Motorola)
09-06-2005, 01:05 PM #10
What is the supply voltage of the 245? If it is 3.5V, you can drop in a VCX part without issue.
Big "S" is signetics. Long gone, try Phillips for a x-ref. The 82s123 is a prom. If you have a good one, I believe it should be easy enough to clone it.
09-06-2005, 01:15 PM #11The 82s123 is a prom. If you have a good one, I believe it should be easy enough to clone it.
Sheesh, never occured to me there would be programmable chips on this thing, other than the EPROM chip, which is fine. :mad:
09-06-2005, 01:15 PM #12
while we're on the subject of htf trannys...
anyone care to speculate where i might find
a motorola(or equivalent) 15001 and 15002 pair of TO3's?
(amplifier power transistors )
09-06-2005, 01:45 PM #13
DT - yes a reader will do it, but the reader has to know about how to read that device- and likewise for writing. We have a pretty studly Data I/O reader/programmer here & it does support Philips 82s123 devices. I'd be glad to read out the part for you & burn a replacement if you have one. If you have other eproms on the board, probably would be good to do them as well.
Wouldn't be suprised if there were others on the board who could help out.
09-06-2005, 01:52 PM #14
TNMG.... I may have some, I know I USED to, so I'll look when I get home.
There are a number of parts that ought to sub OK for them, however.
09-06-2005, 02:00 PM #15
I did a Digi-Key search and found several possibilities: SN74LS245N (0 available), SN74LS245NSR (non stock), and DM74LS245N (non stock). They do not stock them but can likely get them.
Mouser has: NTE74LS245 (stock) and SN74LS245N (non stock), both DIPs.
Also Newark shows them as a non stock item.
A tip whem searching for digital ICs. The common logic families and many of the less common digital ICs have been second sourced by other companies. They are the same, identical ICs, often made from the original developers masks because many government contracts required a second source for parts. However, they may not have an identical part number.
When I search for an IC, I usually totally ignore any prefix and suffix. The prefix (SN in this case) is just the manufacturer's ID for that line of products. Hence the SN indicates TI's digital line and the DM indicates the exact same line in National Semiconductor's world. The suffix usually contains information on the package. there are many suffixes that indicate the DIP outline in general and variations for different package materials like plastic, ceramic, etc. By searching for a "74LS245" I instantly got all the versions of that IC and I could find a substitute in the package I wanted. If other specs are a concern, Digi-Key and the others have links to the manufacturer's sites for full spec. sheets.
I wish mechanical parts suppliers were as well organized.
09-06-2005, 02:16 PM #16
One more thing on finding substitute digital ICs. Versions from another 7400 series family will often work. For instance, Mouser has a 74245 substitute listed. It will draw a little more current but will likely work in most circuits. You can check the manufacturer's spec sheets for any parameters that are in doubt.
One caution when doing this. Although the pin assignments were mostly the same on the various version of a chip, even in different 7400 series families 7400, 74LS, 74S, 74H, etc., there were some differences. When the first letter of the suffix if different, it is best to check. For instance, National's "W" suffixes often indicated a non standard pin-out.
09-06-2005, 02:22 PM #17
Good news on the programmable chip...I hadn't noticed before but there are 3 of these on the board with the same program number, and the 3rd one checks out fine, so at least I don't have to yank one off the good control and rush it somewhere for upload...can take my time.
09-06-2005, 02:22 PM #18
Ace Electronics In Houston buys and sells surplus electronic components, some as overbuys by OEM's and some removed from old equipment. They are at 713-688-8114. They are great people, ask for Craig.
I have no connection to them other than everytime I go there for a $2.00 part I leave with $100 in other stuff I didn't know I needed.
09-06-2005, 02:30 PM #19
How many do you want? Drop me a note at
jrr0 at bestweb.net (that's a zero, not an
'oh' in the address) and give my your
09-06-2005, 02:45 PM #20
Try nteinc.com for an alternate source for your chips. They mainly do japanese product but are the most comprehensive cross I know of.