Identifying 4-Memory CW Keyer with TTL Chips, 555 Timer, and Unmarked 40-Pin IC

I have acquired what seems to be a 4-memory electronic keyer. It has four connections to the outside world, 12 volts in and ground, and pins with +3 and +8 volts always on. It contains numerous TTL chips, a 555 timer and an unidentified 40 pin ic. Can anyone help?

Geoff...can you post a pic?  (probably best if you start a new thread for that)?

Geoff,The 40 pin IC is likely to be a microcontroller of some kind. As David said, a picture (or two) would be most useful. Something that would show the outside connections and the parts...

Yes. Being assessed. The only outside connections are the 4 lines mentioned above, via a 9-way D-type.
Geoff

Geoff, thanks for the photo! Please write for us the text on the 40-pin IC. As Elizabeth Simon wrote, it is likely to be a microcontroller, but it might be a UART Universal Asynchronous Receiver-Transmitter, a pre-microcontroller pin-programmed serial-port chip from the 1970s: General Instrument AY-5-1013, National Semiconductor MM5303, Texas Instruments TMS6010, Signetics 2536, ??vendor COM-????. The over-twenty-year-old Intersil or Harris HD6402 is the newest version I know of. The 555 would oscillate at 16 times the baud rate, with 6% tolerance, so the Trimpot would set the exact frequency.
The chips are socketed and the board is perfboard, so this is likely a homebrew project. The workmanship is excellent. What text is on the front and rear panels? How do you know the unit wants +12VDC? Does it want -12VDC also?A memory keyer would require three pins besides power and ground: left-paddle, right-paddle, key-line to transmitter.

OK, the  40 pin chip says - 19-10459-01 SMC 7815F COM 2017The text on the front reflects memory keyer requirements, photo follows.Applying 9 volts to the input connnection,  found by tracing wiring around the 7805 regulator lights up an LED on the front, together with another which flashes constantly.  Increasing V+ to 12 offers no change, as far as I can detect. 

Geoff, in the front-panel picture, there is a triangular white mark in the lower left corner of the panel. Is this a manufacturer's logo or is this a spurious mark? I suspect the mark is leftover adhesive from sticky tape, but you can tell me. The lack of logo further indicates homebrew. The lettered panel indicates top-quality homebrew.Thanks for the lettering on the 40-pin IC, which I repeat here to show the locations of the text on the chip:19-10459-01   COM 2017
   SMC                    7815FMy reading:SMC is Standard Microsystems Corporation, which got bought by Microchip Technology in 2012.7815F is date code 1978 week 15.COM 2017 is part number for SMC's 40-pin UART.With power OFF, measure resistance from pin 3 to ground. I predict zero ohms.With power ON, measure voltage from pin 1 to ground. I predict +5 volts.With power ON, measure voltage from pin 2 to ground. I predict -12 volts.With power ON use oscilloscope to measure pin 17 to ground and pin 40 to ground. I predict 960 Hz squarewave on both pins.Tell us the part numbers on the five 16-pin DIP packages. I bet these are Intel 1024x1 or 256x1 SRAM's.I think your box is a memory keyer, but for RTTY not CW.

Hi Peter,

Almost 100%!
Pin 3 to Gnd, 0 ohms (Power off)

(Power on)
Pin 1 to Gnd, +5 volts
Pin 2 to Gnd, +3 volts, NOT -12 volts
Pin 17 & Pin 40, 960 Hz Square wave

5 x 16 pin ics, MK4102N-1, 1k Static RAM.

Very good! Thank you so much. I haven't indulged in RTTY for many years.

What do you  think the discrepancy on Pin 2 signifies?

Geoff

On the once-standard pre-microcontroller 40-pin UARTs, pin 1 is +5V supply, pin 3 is ground, and pin 2 is -12V on the PMOS versions and open on the CMOS HD6402. The first generation of MOS ICs used just P-channel transistors running from +5V and -9V to -12V rails, with good pullup output currents and poor pulldown currents, making for interesting interfacing to TTL logic.www.intersil.com/content/dam/Intersil/documents/hd-6/hd-6402.pdf is the datasheet of the CMOS version, and should be correct for your COM2017, except for pin 2. You might be able to find the datasheet for the Standard Microsystems COM2017 on the web.I notice that pin 2 measured the same +3V as did one of the pins on the 9-pin connector. Check (with power OFF) the resistance between UART pin 2 and that pin on the 9-pin connector: That pin might be a -12V supply pin. The +3V would result from the resistors and transistors used for serial-data level-shifting. I suggest you trace out the circuitry before applying -12V, and start with a 1000-ohm resistor in series with the -12V so you can check current drain.
UART pins 17 and 40 are clocks at 16 times the RTTY baud rate.This is a hardware-only design, so you could trace out the circuitry and decipher the full functionality. This might make a historical article for EEWeb.I first used  a UART in 1974, and last used one in 1998. It's sad to me to see them totally gone, though Richardson Electronics still has the HD3-6402 in New Old Stock.The MK4102 is Mostek's second source for the Intel 2102 N-channel, +5V only, 1Kx1 static RAM.

Geoff: I suggest you download and print out the UART data sheet and a copy of this discussion, fold the printouts together, and place them inside the memory keyer. The keyer is forty years old, and could be around for a long time. Those who inherit the keyer will thank you.
www.rogtronics.net/files/datasheets/uarts/AY-5-1013.pdf is the datasheet for one of the original PMOS versions, of which your COM2017 is a second-source. I gave the URL for the later CMOS version above.

Correction: The HD3-6402 is still available from Rochester Electronics, not Richardson.

Thank you Peter, I will do that.

Geoff