Discussion in 'General Technical Questions and Answers' started by NG3H, Oct 19, 2016.
I am looking for a wiring diagram for the Vibroplex Model EK 1 Brass Racer.
The Vibroplex model EK-1 combined the Brass Racer (old Scotia model),
which Vibroplex acquired from Hamco Paddles of Eurica, CA and
the Curtis Electro Devices 8044 (16-pin SDIP), designed by John Curtis, K6KU.
The keyer was battery operated (cutout in PCB) with a 7.5 Volt photo battery (EP-175).
Radio Museum has the Brass Racer EK-1 schematic ($$)
Schematic is virtually same as one shown in 8044 Application Note (500 kohm speed control).
Diodes used are 1N270 (6) and 1N4001 (D5, D8)
EXCEPT for the PC board and small cutout on the left side of the wooden base
parts are same as the Triangular Brass Racer
8044 Series : Keyer on a Chip
Application Note, January 1992
Turn to pages 9 and 10 for schematic and parts list.
Martin Jue, MFJ Enterprises bought out Curtis Electro Devices in 2000.
The Curtis IC was used in numerous external MFJ keyers.
Today, MFJ offers the last Curtis version: 8045ABM at $29.95
MFJ / Curtis 8045 Series Keyer-on-a-Chip
This 28-pin SDIP is NOT plug-n-play with earlier Curtis chips.
Thank you for the information, That is helpful.
The Vibroplex EK-1 schematic diagram can be
downloaded from the radiomuseum.org
D1 - D4, D6, D7 : 1N270 Germanium Diode
Supposedly MicroSemi and NTE still sell this part.
BAT41 Small Signal Schottky is a good substitute.
Mouser stocks this part.
D5, D8 : 1N4001 : Silicon Diode
R4 : Potentiometer (Variable Resistor) is 500 Kohm, trimmer
John Curtis noted in 1991, that fir the Speed Control a reverse (lefthand) log taper is best.
Controls with this taper are not easily found, however they serve to make the speed and pitch adjustments much more linear (easy to adjust).
Vibroplex EK-1 used the CTS 201 series 15mm carbon composition trimmer.
Alpha (Taiwan) mfg. a form factor version that is close.
Q1 : 2N3904 NPN transistor
Q2 : MJE350 PNP transistor
YouTube video of Vibroplex Brass Racer EK-1 operation.
I know this is a very old thread but I just picked one of these up in pristine condition. This thread helped out greatly, especially the video.