Since there were some errors on the schematic, please refer to these values should you need recapping your vintage Ace Tone drum machine:
Recently i got a nice Altec 1592B mixer.
Each input requires a dedicated preamp/transformer module, for microphones there’s preamp, 1588B or preamp+12v phantom power, model 1588C.
I had to do a massive recapping job on the 1592B- the original caps values were all over the place-and i mean not only electrolytics-the only ones that were still measuring ok were the tropical fish and some of the lower values disc caps- though most of the electrolytics were good quality, Mallory or West Germany made, ROE (Roederstein). I replaced them all with Elnas (they seem to be the standard nowadays).
Also, the resistor after power transformer 7818 (that feeds part of the tone section, so if you have an unit that powers up but does not produce a sound, check for +18v at pin 6 of the tone board, that is linked to the power board after (out) the aforementioned 7818) was burned-clear sign that some damage had taken place. The schematic calls for a 10 Ohms resistor-i decided to put a 100 ohms substitute, much better.
Sounding good, i decided to recap also the 1588B module i have here (more are on the way, and when factory new, they were fitted with 3 modules).
After using a small screwdriver to pry the enclosure open, i took a look at this interesting blog (check it) for the schematic-i also took the time to sub the carbon comp resistors with metal film and yes-noise went down.
For your reference, here’s the resistors network:
Q1 and Q2 pinout:
If the preamp is not working, check carefully the resistors-they break easily. One immaculate looking (inside and out, the spongy filler still in good soft condition, no leakages on the plastic screen etc) 1588B i have had a resistor broken at its base, and since the components are so squeezed together it was impossible to see it-i decided to test the transistors (thats why i took the q1 and q2 pics above) since everything was looking proper-and there-i spotted the broken resistor! The preamp would still burst in noise if i knocked the mic gently on the capsule, yet it wont amplify it properly. Thats the resistor connected to ground on the white wire-a pain to desolder too.
If you must desolder stuff, be patient-these boards wont take a 300 degrees hot iron-the circuit tracks will lift if you heat them up too much-use care.
Since someone over at the Tape Operator forum has raised the warning that the power supply may have been ill designed, i am powering it using an external psu (using the battery option), 24v dc.
Terminal: from left, my battery (external psu) connections (- and +) and pinout to wire an XLR balanced jack to the output: hot, cold and ground… in the mess between high and low impedance i went with, 600 ohms, good for any mixer or recorder input. PLEASE note 2 and 3 terminals are bridged (connected) at the terminal post. The signal is nice and strong.
I will not mod this unit, i like it as it is. Nice and retro sounding.
I opened my newly acquired Akai S612..to check for spiders and animal residue from its previous owner – i was intrigued by the “cassette interface”. Mine was screwed behind a closed metal door.
I realized right away it is the same cassette port as the Commodore 64.
And yes, you can save, verify and load your samples using an old (non)trusty tape Datassette!
I sampled a sound, got some tape to record, went fast forward 004 counts on the tape counter, pressed rec and play and then pressed save on the Akai panel. Red light, it’s recording.
Counter reading 044, the Datassette automatically stopped. I rewound the tape, switched off the Akai (remember with these old machines it is better to switch them off before plugging or unplugging devices from serial ports..), on again and Load. Pressed play on tape, and yes. It’s working. Easy.
No need to buy the MD280 rack to load discs on the S612.. you just need a Commodore Datassette (clean its heads and fix azimuth before doing anything)!
When i bought it it looked like this
I decided to restore it to its original colour (or as close as i could…)
After 5 months of great fun, I had to open it up because the output went silent.
Gutshots of the Hohner Basset!
Lets start with the DIN jack that connects it to the bass amp..
Inside the white enclosure there’s a lamp and a ldr.. this assembly is the actual “percussion” section.
You press a note on the keyboard, the light goes off slowly (sustain) according to the knob position, when not in auto mode.
Ahem this means the caps have been doing their job for 50 long years! Only one of the capacitors has failed, please note- the blue valvo 100uF cap now measures 1uF!
Video showing the lamp going off when a note is keyed.
This must be a very early one, word has it that Jimi Hendrix tried one of these boxes for its big muff-like forced sustain. It is one of the earliest electro harmonix effects.
It is powered by TWO 9v batteries and so much for it “being distortion free”, it is very hissy and noisy, and colours the tone. The compression is VERY apparent and squashed.
Transistors: FS36999, the same as early 70’s Big Muffs.
The tube version Black Finger is a much different, more reliable and usable item.