Saturday, 31 January 2015

Conn Min-o-matic Rhythm Drum Machine

I picked this up very cheaply. Might be fun to mod.
If anyone has the schematics for this drum and is willing to share I'd be eternally grateful.

 I think this dates from 1966 - all analogue goodness with discrete components.

pretty simple to use with only 9 push buttons and 2 knobs global volume and tempo frequency - See more at:
 A drum machine can't get much simpler than this. Nine pattern buttons & two knobs for volume & tempo.

 There are 5 sounds: kick, snare, conga, Hihat, claves, metronome click.

Sadly there are no seperate outs
If you do decide to mod this please be very careful. Once the cover is removed you run the risk of electric shock. This will KILL YOU.
Rear mounted tone control, 1/4" phono output jack & Hi / Lo output level selector.

This is not the simpliest drum to mod. The Rolands & Korgs tend to seperate their PCBs into PSU, rhythm & voice sections. Not so here. Everything is on one PCB.

The PSU is here. Be very careful !!!

There are 6 pattern presets: Waltz, Ballad, Foxtrot, March,Teenbeat, Latin, metronome.

Here is some info about C.G.ConnInstruments
There are 6 pattern presets, no possible variations except the Double Beat function:
- Waltz
- Ballad
- Foxtrot
- March
- Teenbeat
- Latin
- metronome - See more at:

Socceroos - Football's Asian Champions of 2015

Roland (Rhythm) TR-77 & Bentley (FR-8L) Rhythm Ace Drum

The TR-77 was Roland's very first drum machine. It was released in 1972. TR stands for Transistor Rhythm. As it is Roland's first drum machine, its place in the history of Roland and indeed in Electronic music history, is assured.

Officially named the Rhythm Tr-77, it was in reality a updated Rhythm Ace  FR-7 &/or FR-8L
The FR-7 appears to be very very rare (In fact I have never seen one in real life or even a photo). More common is the FR-8L  To make things even more confusing, in the UK, the FR-8L was  re-released as the Bentley Rhythm Ace and in the USA she was sold as the Hammond Auto-Vari 64.

 the Hammond Auto-Vari 64

1972 was the foundation year for Roland, who also released in the same year, the TR-33 & TR-55. The 77 was Roland founder's (Ikutaro Kakehashi) baby as he migrated from the old company, Ace Tone. The Tr-77 became Kakehashi's flagship product. 

Here are the TR-77 & the Bentley Rhythm Ace ....... united once again.
The differences between the two machines appear to be small, however they do sound different. The Bently/FR-8L is also slightly shorter than the TR-77.

The TR-77 has two additional patterns (the Western & the 6/8 March) over the Bently.
and also a Samba 1 & Samba 2 rhythm. The Bentley has only 1 Samba Rhythm.

The Bentley has 5 faders for Volume,Tempo, Cymbal/HH/Maracas, Guiro, Snare, Bass Drum.
The TR-77 has 6 faders for Tempo, Fade Time, Volume, Bass D, Snare D, Guiro & Hi-Hat/Cymbal/Maracas.

As you can see from the pics above, these drums were designed to sit on top of an organ.
The wood finish and the built in music stand indicate their designer's original intentions.
However, I think they are the warmest sounding drums I have. I really dig them.
The voices are generated by "tuned resonance" type circuits. Though neither has the kick of a 808, there is a smoothness to both that I truly love.

The Bentley Rhythm Ace (FR-8L)

Both also have that lovely start/stop metal bar that can be seen on their extreme left.
Why don't more drums have this?

The Roland Rhythm TR-77

The Roland Tr-77 Rear

 TR-77. Start, High Impedance & Low Imp outputs.

Here is a interesting video where a Roland TR-8's handclap is routed to an individual out and then run into the Footswitch stop/start of the TR-77. This allows the TR-77 to start and stop on command via an audio signal. The handclap on the TR-8 were placed on steps 1 and 14 of the sequencer and the TR-77's tempo was hand-adjusted to match. 


Both the TR-77 & Bently FR-8L have no sync abilities without modifications.
Nor do they have seperate outs for the individual drum sounds.
 The Bentley Rhythm Ace FR-8L rear

Bentley FR-8L

Bentley FR-8L
These drums are ripe for modding.
Here are some links to start you on your modding and/or circuit bending way.
3. Burnkit2600 TR-77 mods (trigger inputs, External clock Sync,Tone Mods).
4. Warren Cann from Ultravox  (his experiences modding the TR-77)
5. CircuitBenders (FR-8L & the TR-77)
6. Circuitbenders (Tr-77 External Power conversion to reduce hum & background noise)
7. Bently Rhythm Ace with Buchla & Euro (using a envelope follower to sync)
For more info on the history of Roland Drum Machines click here

Friday, 30 January 2015

Korg PS 3200 & Volca Beats.

I just love mixing up my Korgs.
Here we have a old 1978 Ps-3200 & a modern Volca Beats.
They are sequenced via a Doepfer Dark time.

My thanks to Paul for tweaking the gear. I'm currently waiting for the Korg SQ-1 and when it's here I'll definitely upload more videos.

The Dark time uses the V/Oct standard.

The CV design of the MS-20, MS10, and the PS-3200 always used the Hz/V standard.

This provides excellent pitch stability, however it also limits the number of the step sequencers that are able to correctly control the PS3200. The Dark Time is working well in this instance as it's using midi, not CV and gate. My PS-3200 has been midified.

And yes, GATE OUT Polarity (+ polarity vs - polarity) and SYNC IN/OUT Polarity ie, + (rise), - (fall) can also be a problem  

Korg uses S-Trigger ("short circuit trigger", sometimes called "negative trigger"). This involves keeping the voltage high, and then shorting the trigger circuit whenever a note is played.

The Dark Energy uses a positive trigger which is also called V-Trigger  or "voltage trigger". This method involves keeping the voltage low (around 0 V) and producing a fixed positive voltage to indicate when a note is played.

As a descendant of the SQ-10, the SQ-1 supports the Hz/V standard so it should enable me to perfectly control the MS-20 or MS-20 mini and the PS3200.
Until then, the Dark Time is doing fine.

Flying Fox - Jodhpur - India

What a great way to see the fortress of Mehrangarh in Jodhpur, India.
Flying over these magnificent battlements is so exciting.

Zip 6: The Magnificent Marwar (300m) You fly over two lakes an land on the tip of a fortified tower that rises 30 metres out of Ranisar Lake.

Battlements of Rajasthan

 Flying Fox - cable - over Mehrangarh Fort.

The medieval "Blue City" of Jodpur.

Thursday, 29 January 2015

TKB Build - 4 - main PCB - Semi-conductors

*** Click here for the TKB Build Index ***
The diodes (6x 1n4148) are already in. Transistors & integrated circuits to go.
The main board uses 10 transistors:
One PN4250 & nine PN5179. (my vintage TKB uses nine EN5179s)

 This is a pic of a vintage EN5179.

Today the PN5179 and EN5179 are very hard to get, so they have been replaced with the more common 2n3904.

The PN4250 is unchanged from the original.

There are 9 types of ICs used on the main board.
These are:

1. LM324N. We need 4 of these.
     Mouser #: 512-LM324N    
     Manufacturer: Fairchild Semiconductor
     This is a quad Operational Amplifier.

2. 4042. We need just one of these
     Mouser #: 595-CD4042BE   
     Mfr. #: CD4042BE
     Manufacturer: Texas Instruments
    This is a CMOS quad clocked D-type latch.
For more about latch circuits click here:

 3. 4050. We need 3 of these
      Mouser #:     595-CD4050BE    
      Mfr. #:     CD4050BE
      Manufacturer:     Texas Instruments
     This is a non-inverting hex buffer.
Some info on buffers:

 4   4051. We need 3 of these.
      Mouser #:     595-CD4051BE     
      Mfr. #:     CD4051BE
      Manufacturer:     Texas Instrumen
      The CD4051B is a single 8-Channel multiplexer having three
       binary control inputs, A, B, and C, and an inhibit input. The
       three binary signals select 1 of 8 channels to be turned on,
      and connect one of the 8 inputs to the output

5. 4069 - We need two of these.
      Mouser #:     595-CD4069UBE    
      Mfr. #:     CD4069UBE
      Manufacturer:     Texas Instruments
      The 4069 contains 6 CMOS inverter circuits.

     For more info click here:LOGIC INVERTERS

6. 4081 - We need two of these.
     Mouser #:     595-CD4081BE     
     Mfr. #:     CD4081BE
     Manufacturer:     Texas Instruments
     This is a Quad 2-Input. AND Gate.

For more info on Gates click here: LOGIC Gates
7. 4516 - just one is needed.
    Mouser #:     595-CD4516BE    
    Mfr. #:     CD4516BE
    Manufacturer:     Texas Instruments
    Desc.:     Counter ICs Binary Up/Down

8. 4520 - We need just one.
    Mouser #:     595-CD4520BE   
    Mfr. #:     CD4520BE
    Manufacturer:     Texas Instruments
    Desc.:     Counter ICs Dual Binary Up

9.  MM74C150
     This is a 16 line to 1 line Multiplexer
      Datasheet info

Part 5. Pot boards.
*** Click here for the TKB Build Index ***

Wednesday, 28 January 2015

TKB Build Notes - Index - The Human Comparator Kit

TKB Build Notes - Index - The Human Comparator Kit.
This is the main Index for the build notes for the Serge TKB (Touch Keyboard Sequencer).
Many thanks to Zthee (The Human Comparator) for making this build possible.

I'm documenting my experiences as I put the TKB together to help me trouble shoot in the future .
Hopefully, this will also help others in their quest to build the TKB & more importantly, to learn the
Art of Electronics & of Electronic Music.

1. Pics of the kit before starting.
2. Some pics and info of a vintage TKB.
3. Starting the build - main PCB -  resistors, diodes, headers, caps, etc.
4. Main PCB - Transistors & ICs
5. Pot boards.
6. The Touch Keyboard (Installing the LEDs)
7. Front panel assembly.
8. Wiring up the touch keyboard
9. Installing the S2 & S3 Ribbon cables.

This index will be updated as the project progresses. 

The official build notes of the Human Comparator 

The original build notes for the TKB kit from the 1970's are here: 
Official modifications to the TKB from the1970's are here:  
Intro to the Serge Modular Music System

Muffs has a great thread here:
Zthee's previous project was the TTSH (Two Thousand Six Hundred).
This is a clone of one of the greatest synthesizers of all time, the mighty ARP 2600.
My build notes for the TTSH are here:
TTSH Build Notes

TKB Build - Part 3A - Main Board

TKB - Touch Keyboard Sequencer - Build Part 3 - Main Board. (Resistors, Caps, etc).

*** Click here for the TKB Build Index ***

Before we begin there are some preliminary pics of the PCB

I'll start of with least temperature sensitive components such as the IC header sockets, resistors & diodes.

Mouser #: 571-5103308-3
Mfr. #: 5103308-3
Manufacturer: TE Connectivity
Desc.: Headers & Wire Housings 16P 2 ROW HEADER LP
These modern headers connect the Main PCB to the rest of the keyboard. In vintage TKBs, the headers used were slightly different:

Notice the silver arrow which is used to check the header orientation.
Vintage TKB headers.

Back to the Modern PCB: 

Looks like the four 22pf caps on the left need to be swapped for 100pf.
According to one of my tech friends, you can experiment a bit here. Serge used 82-100pF,
but you could even go as high as 220pF. Apparently the caps are filtering some unwanted noise from the clock driving the keys, and 100pF suppresses it OK. ....but even higher values might do a better job. The only problem is - go too high and it might start to slew your signal… ????

I'll def do some experimenting with this. (Many thanks to my friend for this advice).

Looks like the surface mount 100n caps need to be soldered to the underside of the PCB across pins 5/4 & 11/10.  of the  LM 324s --- SEE PIC BELOW

The LM 324 is a low power quad Op-Amp

There are 5 surface mount 0.1uF / 100nF caps to solder to the underside of the PCB.
The soldering points are a bit tricky to see at first. They lie across two of the LM 324s -  pins 5/4 & 11/10.
and underneath the LM324 just below the MM74C150

The SMD caps lie under the three LM 324s on the top right

Almost finished the easy part ... soldering the resistors, diodes, caps & headers..
I think its a good time to stop and compare this board to a vintage TKB main board. This one is a unrestored TKB -- also from the late 1970s.

Notice the bud box below is self powered.... in fact it has two PSUs, and was once part of a much larger system.

 Top pics of the main TKB PCBs (vintage on left)

The underside of the PCBs.

*** Click here for the TKB Build Index ***