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Antique Radio Technical Forum
Cal-Tex CT7001 chip

Posted by Edd on 07/18/2007 22:09

Ohhh Tayyyy ! Looks like I officially now have in mine hands ...one each.... virgin CT7001 chiperooski, resplendantly complete, with its 28 brilliantly, gold flashed pins.

The parts foraging also refreshed my demential infarcation of the identity of the other mentioned mystery clock chip......... which was..... the many more pinned Mostek 5017 or 6207 series of clock chips.

As per your problem experienced, on the missing of digit 1....looks like you would be OK up until the 9th day of the month, at which point you need the initialization of D1 display digits info !

Upon further review of the INITIAL data sheet I posted , I see that the support devices have been replaced with 21st century parts....especially with that '360 being used for interfacing with the '7001's output.

If you were building to the original Fairchild data sheet, I would assume that you were merely using a cleaned up and shaped 60~ input for the units clock timebase, vice the CMOS divider chain that the first data sheet showed.

Next, when you look up to the top right corner area and refer to the CMOS data level shifting, instead of the string of CMOS hex inverters, your unit, was in all probability.... using the 75492 and 75491 series of separate segment and digit drivers IC's for interfacing to a common cathode LED type of display. I still have some of those also.

I am posting the original Fairchild data sheet in case you don't have it to refer to anymore.

Fairchild.......[ Datter Sheet]

One other thing to think about in the initial troubleshooting:

If you will look at the bottom left corner where I have two red reference boxes for you to see the fact that if the leading digit of the calendar display ...digit one....was giving you trouble, consider this.

Take note that at the left box there is the transistor Q2 whose job it is to BLANK out the first digit of the calendar display until the day count exceeds 9 by the cutting off of the digit drive to the second section of IC4 at pin 3 by the signal being shunted to ground via Q2's Coll-Emitter junction.

Hmmmmmm now, I just wonder if that transistor was avalanching C-E on you ?...thus being the cause of your specific problem, and not the clock chip at all.

73's de Edd

(Just like youse guys mentioned, relevant to some persons / sites having IT problems...that "reliable" blue line sourcing just went south and I had to second source !)

::::Sir Lewis:
::::Eeeeeew-Weee...seems like that was an old LSI whose Sugar Daddy was Fairchild...but repackaged and marketed by Cal-tex, et al.
::::..heck....even Radius Shackamus had 'em.
::::I was building up digital clocks from RTL logic (thats pre DTL and TTL !) waaaaay back in the mid-late sixties ..but just the basic clock/ counter no further logic
::::subdivison for days/ mos nor additional using of an X-OR comparator decoding for the alarm function. It was like Star Wars to
::::anyone that viewed a unit at that early date..viewers just stood there...mesmerized.... as the seconds ticked off.
::::I later utilized the National 54xx series when the prices dropped down on them.
::::Do you "KNOWS" that your chip is bad ?...beee-cuzz you..(or palsy)... inadvertanly let a wide meter probe do a bridge
::::between pin #1 and 2 or, are some of the functions or displays being "buggy". BTW...that OLD of a unit is a potential candidate for high ESR developing in your units PS's electrolytics and bypassing electrolytic functions, if erratic operatives are produced.
::::That chip uses quite a bit of ancillary chips doing support and interfacing. Specifically in its time base referencing and doing level
::::shiftng in its output interfacing. Are they free of fault ?
::::I certainly believe that I do have a prime , virgin chip like you need....if not it is the one other series of chips with many more pins on it,
::::and another manufacturers answer to the market.
::::Will do a check in my components storage area tomorrow....not on premises.
::Sir Edward:
::Did you happen to find an old NOS 7001 chip? I would rather deal with you than some stranger on Ebay.
::Dadadididit didididadh dadidit dit
::didadidit dit didadah didit dididit
:Not that it may ever be of any help but I believe the Cal-Tex clock IC carried a Radio Shack number of RS1756.

Cal-Tex CT7001 chip 
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