Vintage Digital Clock Circuits

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mediatechnology
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Vintage Digital Clock Circuits

Post by mediatechnology » Sat Oct 11, 2014 2:57 pm

In this thread we flash back to the 1970s and vintage Digital Clock circuits.

Etsy has some very cool retro designs using wood, Nixie tubes (or the Russian equivalents), LEDs, vacuum fluorescent and my favorite - 7 segment LED bars in Mason Jars made to look like giant Nixie tubes.
Some retro clocks use modern PICs with GPS time-setting, others dedicated 70s-era ICs or discrete logic. https://www.etsy.com/search?q=nixie%20clock

My focus for now will be to post vintage datasheets.
I find that the most obscure and seemingly worthless data sheets gets the most hits.

The first data sheet is the Cal-Tex Semiconductor CT7001: https://proaudiodesignforum.com/images/ ... ock_IC.pdf

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Cal-Tex CT7001 Driving Sperry SP-151 Gas Discharge Display

Another relatively obscure Digital Clock IC is the American Micro-Systems AMI S1736 designed for liquid crystal displays.

AMI S1736 Digital Clock IC data sheet: https://proaudiodesignforum.com/images/ ... C_1972.pdf

An earlier copy of the data sheet included the internal logic diagram of the AMI S1736.
It's not often you see a gate level internal logic diagram...

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AMI S1736 Digital Clock IC Internal Logic Diagram

AMI S1736 Logic Diagram in large format: https://proaudiodesignforum.com/images/ ... iagram.jpg

LCDs at the time were very expensive.
My brother designed and sold a clock using the S1736 that drove the Fuji Minitron 3015F incandescent displays.

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KA Electronics "Time Machine" Digital Clock Kit Circa 1972 Using the AMI S1736 and Fuji Minitron Displays

The schematic for the KA Electronics clock showing the AMI S1736 interfaced to Minitron displays is here:
https://proaudiodesignforum.com/images/ ... n_1972.pdf

My Heathkit clock uses gas discharge displays from Sperry.

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Heathkit GC-1092A Digital Clock Schematic Using the Mostek MK5017 and Sperry SP-352

Large Heathkit GC-1092A DIgital CLock Schematic: https://proaudiodesignforum.com/images/ ... -1092A.jpg

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Sperry SP-152 SP-352 SP-332 Gas Discharge Displays

I scanned this Sperry Information Displays Clock Display Catalog from 1973.
It's got pin outs for the SP-151, SP-152, SP-332 and SP-352 display modules.
https://proaudiodesignforum.com/images/ ... g_1973.pdf

Sperry also published several Digital Clock Application Circuits:
https://proaudiodesignforum.com/images/ ... s_1973.pdf

SP-151 MM5311 Interface
SP-151 MK-5017 Interface
SP-352 MK-5017 Interface
SP-151 AMI SP1736 Interface
SP-151 MK5017 Automatic Dimming
SP-151 AM/PM Drive
SP-151 MM5314N Interface
Power supplies
SP-151 MM5370 Interface (Preliminary)


The Mostek MK50250 Clock IC

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Mostek MK50250 Digital Clock Application Circuit Driving A Common Cathode LED Display

Mostek MK50250 Data Sheet: https://proaudiodesignforum.com/images/ ... _Clock.pdf


An Aircraft Digital Cabin Clock using the MM5314

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An Aircraft Digital Cabin Clock using the MM5314, Byron Kirkwood, Kirkwood Associates, March 1973.

An Aircraft Digital Cabin Clock using the MM5314 pdf: https://proaudiodesignforum.com/images/ ... d_1973.pdf
https://ka-electronics.com

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mediatechnology
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Re: Vintage Digital Clock Circuits

Post by mediatechnology » Fri Jan 30, 2015 8:39 pm

Surplus Sales of Nebraska is offering a National NL5441A Nixie Tube with Socket:

Image

https://www.surplussales.com/Bulbs-Inca ... a-kit.html
https://ka-electronics.com

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Re: Vintage Digital Clock Circuits

Post by JR. » Sat Jan 31, 2015 4:13 pm

Remember when that was hard? Didn't they later start using wrist watch ICs to make clocks?

I had to build a clock into my programmable thermostat... Just count zero crossings from the mains power and divide down.

JR

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Re: Vintage Digital Clock Circuits

Post by mediatechnology » Sat Jan 31, 2015 4:46 pm

My Amperex Z-1000 (Nixie) clock using Motorola RTL MC7XX-series logic was my first adolescent electronics project.
The hard nut to crack (then) was detecting "13" and forcing "1" back into the counter. (It was a 12 Hr clock.)
With a perfect 60 Hz timebase I still lost a few tens of milliseconds a day.
Line noise added a few back.
The MM5314 and affordable 7 segment LEDs were sent from heaven.

Surplus Sales of Nebraska also has the Sperry SP-352 displays right now.
If you go to Etsy you can find some very cool-looking retro clocks.
I saw one that had a seven segment display made from huge LED bars that were placed in inverted Mason jars to look like giant Nixie tubes.
https://ka-electronics.com

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Re: Vintage Digital Clock Circuits

Post by JR. » Sat Jan 31, 2015 6:59 pm

Yup I remember when digital design was using counters and 7 segment LED displays... The Loftech TS-1 used more current for the 5V digital counters and display than the analog side.

Slickest discrete digital design I did was a 100 segment vacuum fluorescent peak/VU meter,, this was back before the TS-1 for a big dog console meter bridge and got dropped after Loft got out of the console business. The clever part was the log conversion for the display in decibels. I basically ran a counter from a fixed clock, but gated the counter off when the exponential decay of a RxC crossed the rectified audio level and tripped a comparator to stop the counter.

More logic was involved to drive the 100 segment display. As I recall it was organized as 10 banks of ten so I had to multiplex it 3x. First for full tens of the VU bar display, then the fractional partial block of VU, then the single Peak value. I never confirmed the linearity (logularity) of the meter over its; 100 dB display range, but the first prototype worked fine. If it was a little off at -70 dBu I doubt I'd get complaints.

Another of my regrets, that I (we) never got it into production, that was one slick meter using my original peak.VU patent back in the '70s.

JR

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Re: Vintage Digital Clock Circuits

Post by mediatechnology » Sat Oct 20, 2018 7:57 pm

Some pics of recent vintage clock restorations.

Sometime between 1969 and 1970 I became interested in building a digital clock.
I was about 12 at the time and began sketching clock circuits using J-K flip flop dividers.

I am "clock boy." :ugeek:


My brother had some surplus RTL (resistor transistor logic) ICs mounted on circuit cards.
I was able to buy some Amperex ZM-1000 "Nixie" display tubes and some Fairchild BCD to Decimal HV driver ICs.
The ICs are mostly MC790P J-K flip flops, some MC789 inverters and a couple of misc gates.
All-in-all there are 19 ICs. (One is underneath on a Veroboard).

I wanted a small display so a multiconductor cable was used to link the "base" logic unit to the display head.
The display sat on my headboard with the clock stashed under the bed.

This was my first major electronics project.
Looking back on it almost 50 years later I realize the logic design was pretty solid.
The execution sucked - but hey - it was my first project and I was 12.
My Dad gets credit for the solid walnut case.

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The clock display unit has three Amperex ZM-1000 "Nixie" displays. The hours "1" is a long neon.

Image
The clock base unit uses 19 RTL (resistor transistor logic) ICs mounted on individual plug-in cards.

Image
Most of the ICs are Motorola MC700-series RTL. A CMOS IC was installed "dead-bug" sometime in the 1980s due to failure.

Once I got a couple of Heathkit clocks I retired this unit.
It sat under my father's workbench for years absorbing sawdust, oil and dryer lint.

Sometime in the late 1980s or early 1990's I began phase one of the restoration replacing the 2N3055 regulator with a LM317.
An RTL IC failed and I had to cobble a dead-bug CMOS chip.
I later gave up because I realized it had become an unreliable pig.
The edgecards had became flakey and I didn't want to clean them and the receptacles.
The clock set in the garage and was later moved to the basement.
I decided, almost 50 years later to rescue it.

It took a can of Blue shower, a can of duster and a re-cap to bring it back to life.
Glad I did though.

The clock I restored before this one was an LED clock based on an MM5314.
The solid walnut case was one of my brother's from his "Time Machine" clock kit.

Image

This particular MM5314 was so pretty I had to photograph it.

Image

An early 1970's clock using scrounged LEDs and an MM5314. The "before" photo:

Image

The restoration primarily involved replacing the awful Molex socket strips with a real machined-pin socket.
I had to scrounge for more LEDs since some had bad segments.
The LEDs were then soldered directly to the PC board.

So what does my 2018 clock look like?

Image

The whole logic box is replaced by an Arduino Nano and a TinyRTC.
The display is single-wire WSM2812 RGB.
My how things have changed...

If I can find the schematics of the Ameperex RTL clock I'll post it.
I had to repair it from memory.
https://ka-electronics.com

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