Timekeeping Wanted to Buy

These are timekeeping items I'm looking for.

Old Heathkit Digital Clocks
Old Stopwatches
Hewlett-Packard 2509A Digital Clock
Hewlett-Packard 59309 Digital Clock
Texas Instruments LED wristwatch
Beckman Model 905 WWV Receiver
Replacement Synchron Motor
Howard Miller Clock Parts
Manual for Chrono-Log 70,071-011 Clock
  Hewlett-Packard K79-5214L Clock
Cable for Hewlett-Packard 58532A GPS Timing Antenna
Manual for Bikron Binary Clock
Mastercrafters 191 Wall Clock
Manual for Heathkit Darkroom Timer
Manual for ESE DigiTime Clock
Manual for ESE Digital Timer
KOSMOS Bio-Clock
General Electric Clock Radio schematics

I'm interested in acquiring old Heathkit digital clocks, particularly the models with the orange Panaplex displays like the GC-1005, GC-1092A, GC-1092D and GC-1094. These are six-digit clocks (hours, minutes and seconds) in either wood grain or plastic cases with various alarm functions. The GC-1092D has a date function as well. The GC-1093 Digital Car Clock also uses the gas discharge Panaplex displays.

You can read more about these clocks here.

Other Heathkit clocks, like the GC-1000 Most Accurate Clock, the GC-1195, GC-1197, and so on would also be of interest.

  • GC-1000
    I have a GC-1000 that needs a replacement pre-programmed Mostek 3870 microprocessor, Heathkit part number 444-293-1 (sometimes noted as 444-293-01). Does anyone have any spares of this part?

  • GC-1005
    The GC-1005 uses three Beckman SP-352 two-digit gas discharge displays. Click here for more information about how these displays decay over time.

    The clock chip is a Mostek MK5017 PAA (there are variants of this IC, including MK5017AA, MK5017P and MK5017A). This is a 24-pin dual in-line package (DIP), typically white ceramic with gold-plated pins.
    Click here for more information on the chip. This is Heathkit part number 443-601.

    Spare SP352 displays and MK 5017 clock chips are also of interest, as well as CS-352 (the sockets for the displays) and Dionics chips like the DI-770N and DI-297N (the DI-770 (DI770N) and DI-297 (DI297N) are driver chips for Panaplex displays like these).

Don't worry about whether the clock is working or not. Even if it doesn't function, I can always use the parts.

Speaking of parts, I'm also interested in finding MM5311 and MM5315 clock chips, 7441 and 74141 driver ICs, and Nixie tubes to build and repair other old clocks. (I have more information about Nixie tubes here.)

If you have one of these clocks, or some spare parts, gathering dust or headed for the trashcan, please drop me a line!

Comsistent with the clock and timekeeping theme, I'm interested in early digital stopwatches that use LED (or older technology).

For instance, the stopwatch to the left is from 1973, uses Panaplex display elements and requires four 'C' cell batteries to operate.

For more information, click here.

If you have an old digital stopwatch like these that you'd like to part with, please send me an e-mail!

I'm interested in older clocks, including digital timekeeping devices like the HP 2509A Digital Clock.

If you have one of these clocks, or some spare parts, gathering dust or headed for the trashcan, please drop me a line!

From the 1968 HP Catalog:

2509A Digital Clock is a precision time source used to supply time information to the data system and initiate measurements at predetermined intervals. Time-of-day is available visually and as an electrical output. It supplies time on demand, permitting associated system to operate independently of clock. All solid-state, it features pushbutton selection of timing outputs at intervals from 1 second to 1 hour. Time reference derived internally or from external 1 pps signal. Provision for 100 kHz external reference optional. Easy manual or remote time set. BCD output. Panel height 5 1/4" (133 mm). Price: 2509A, $2,250.
I'm also interested in the HP 59309A Digital Clock.

If you have one of these clocks, or some spare parts, gathering dust or headed for the trashcan, please drop me a line!

From a description in a training manual:

The clock provides time of day and the calendar: month, day, hour, minute, and second. As the months roll by, the calendar remains correct as long as the clock has power. A built-in computer knows how many days are in each month. Only once every 4 years does the calendar require operator intervention, to set the "leap year" switch. The clock outputs calendar and time onto the Interface Bus for any desired destimation such as a data plot or printout. The clock also displays calendar and time on its LED (Light-Emitting-Diode) readout.

From Hewlett-Packard Journal, January 1975:

The Model 59309A ASCII Digital Clock gives absolute time in seconds, minutes, hours, days, and months. When connected to the HP interface bus and asked to talk, it outputs the time on the bus. A block diagram is shown in Fig. 3.

59309 Block Diagram

The Digital Clock is a precision instrument, using a 1-MHz quartz crystal resonator in its master oscillator. The aging rate of the crystal is 5 parts in 106 per year. The clock can also be driven by an external frequency standard of 1, 5, or 10 MHz. It has other features that make it more than an ordinary digital clock. With a standard 9-volt battery installed for standby power, it becomes immune to powerline transients and it can operate on the battery for as long as a full day when there is a power-line interruption (the display will be turned off, however). It can operate with any other 8-lOV dc power source through a rear-panel connector (it draws 2 mA at 8V with the display off). A companion unit, Model KlO-59992 Standby Power Supply provides up to a year of standby power using size D flashlight cells. Another useful feature is an internal memory that stores the time on command for later output. This would be used to store the time of a voltmeter reading at the instant the reading is taken, for later print out. The clock can be set by codes sent on the HP interface bus. It is thus possible to create a subroutine that automatically sets the clock on system start-up. It can also be set manually with switches that are behind a front-panel lift-up door.


I have written software to communicate with the clock using a relatively inexpensive USB-to-HPIB interface. You can read about the software and see the source code here.

Problem Unit

I have a 59309A with an odd problem. It appears to function correctly - the display shows the date and time, the front panel buttons and switches update the display, and the back panel configuration switches (at least A6 and A7) correctly control the mode (at least according to the illumination of the ADDRESSED LED).

The problem is that the display (all segments of all digits) blinks at the rate of several times per second. Pressing the PUSH TO READ button causes the display to stop blinking, but the flashing resumes after releasing the switch.

I have not connected it to an HPIB controller.

There is no 9 volt battery installed; the shorting pin is in place.

Any ideas on what to check for?

I'm looking for an old Texas Instruments (TI) watch, a TI-500. This is a mid-1970's era wristwatch that displayed the time using four red LED's when a button was pushed.

The particular model I'm looking for has an all-black case with a round red lens. A thin silver ring surrounds the lens. The lens itself has "Texas Instruments" embossed in the red plastic. This model is referred to as "Series 500."

The watch uses two AG12 coin cell batteries (equivalents are 186, 301, 386, LR43, SR43SW/W).

From Texas Instruments' history timeline:

TI's first light emitting diode (LED) digital watch featured a black plastic case and a red LED digital display. Eventually, watches of this type were reduced to sell at a suggested retail price of $9.95.

The chip design began in December 1974 for TI's first watches, which were shipped in September 1975. The LED display was illuminated by pressing a button on the side of the watch.

By 1976, TI announced it was the leading supplier in the emerging digital watch market, which was projected to grow to 18 million units that year, up from 3.5 million in 1975. The largest part of the market was under the $20 segment, and in March 1976, TI delivered the first solid-state watches to retail for under $20.

You can read the guide that came with the watch here.

I'm interested in finding a working Beckman WWV receiver. Model 905 is circa 1965.

WWV receiver

I'm looking for a replacement clock motor for a Synchron mechanism. The motor is stamped with the following:
640 110V 60CY 5W 4 RPM (UL) BL1RC 6-60

This decodes to:

  • Model Series 640
  • 110 Volts
  • 60 cycles (Hertz)
  • 5 Watts power consumption
  • Speed of 4 RPM
  • UL listed
  • BL1 means that it was shipped with a round 1/8-inch diameter shaft with nothing on it
  • 6-60 means that is was manufactured in 1960

The output gear has 21 teeth.

I have a Howard Miller Clock that's in really nice shape except the clock doesn't work. Putting in a fresh battery causes the second hand to move forward correctly but the minutes and hours hands don't progress.

I'm looking for a replacement movement mechanism to return this tabletop clock to functioning condition.

The label on the back indicates the following:

  • Model Number: 622-300
  • Movement Number: 354145E
  • Case Number: 5251
  • Dial Number: 0334

The response I received from Howard Miller was that this model was last manufactured in 1986 and has been discontinued now for more than a decade. Unfortunately, no parts are available from them.

If anyone has one of these movements, perhaps in a clock they no longer wish to keep, please send me an e-mail.

I have four identical six-digit clocks from Chrono-Log marked as model 70,071-011. There are no controls on the front, and only a single power switch on the back. Protuding from the back is a slotted card edge connector with a total of 80 connector traces (40 on each side, organized as 32 and 8 with a notch in between).

I'm looking for a technical manual for this clock, specifically the pinout specifications for the connector.

I also have a Chrono-Log 70,101-412, which is similar to the 071-011 model except for the addition of mode and setting switches on the front panel.

I also have a Chrono-Log 70,233-412, which is very similar to the 101 model except that it displays month and day rather than just a day number.

Correspondence with Chrono-Log reveals that they no longer have documentation or manuals for these 1980's-era clocks.

Here's a switch. I have an Operating and Service Manual for an HP K79-5214L 24 hour digital clock.

I'm looking for the actual 5214 device, or at least more information about it (like a picture or dates of manufacture?).

I'm looking for HP part number 58522A in any length. These cables have a 12-pin female locking connector on one end and are unterminated on the other end.

The photos here show the male end coming from the Hewlett-Packard 58532A GPS receiver.

Click here for more information.

I have a Bikron Binary Clock that appears to function (with the exception of at least one burned out light bulb), but I do not have an owner's manual or instructions.

Click here for more information.

I have a Mastercrafters 191 clock that needs a new plastic dome cover. It's a neat 24-hour motorized analog clock, but the former owner used a permanent red marker to note 4-hour intervals. I tried a couple of different cleaning methods (Goo Gone, etc.) but didn't have much success.

The cover also has a few scratches on it, so either a replacement or a good way to clean and smooth the existing one would be welcome.

This is the Heathkit PT-1500 darkroom timer. It seems to work but I don't have the operating instructions so I can't be sure.
I have an early electronic digital desk clock built by ESE Enterprises in El Segundo, California. It's model ES-10 and has the word "Digitime" on the front panel. It's built into a wooden box with a two-prong (no ground) AC cord.

As you might expect, I'm looking for a manual.

The tens-of-seconds digit doesn't light up, but the clock itself appears to keep time. Also, one of the three push buttons on the bottom appears to be missing or broken. So, I expect I'll be needing spare parts as well.

There is a mention of this clock on page 50 of Michael Robbins' book Electronic Clocks and Watches. The caption reads 'A TTL clock with seven segment incandescent display.'

An ESE (E.S. Enterprises) sales brochure from 1973 doesn't show the ES-10, so it's either an earlier product that was discontinued, or it was introduced after 1973. The closest device in the brochure is an ES 112 Digital Clock, which shows hours, minutes and seconds and has three controls (fast advance, slow advance, and hold) for setting the time. ESE also offered a kit version of this clock as well as a twenty-four hour model (the ES 124).

The brochure lists ESE headquarters as 506 Main Street in El Segundo.

Also from ESE, I have an early digital timer, model ES-572CM, but no manual for it.

The timer has a 24-pin connector on the back, for which I would like a pin-out description.

I have a Kosmos Bio-Clock calculator, which is a desktop clock/calculator combo with the ability to compute biorhythms. I need a manual for it.
I have a couple of General Electric model C4505D clock radios where the clock runs fine but the radio section does not function correctly (static, low audio output).

I'm looking for a schematic that covers this model.

Thanks for looking!

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Updated May 22, 2023