Antares 2 – Kolafon

Antares 2 is a rare breed. This Synth was developed in Czechoslovakia in 1979 by VURT (Research Institute of Broadcast and Television) and only few prototypes were ever made. There was one small batch manufactured (<10 pieces) before the project was finally retired.

There were few issues with this particular piece. Mechanical problem with one of the keys and associated damage around the key J wires.

Major problem were the capacitors. I had to replace both the dried up electrolytic caps as well as metalised paper caps and ceramic caps which absorb moisture over time. Following the  cleanup of all the pots and switches as well as full recap Antares sprung back to life.

I’m giving special credit to the mechanical construction of this piece, all the electronics apart of keyboard itself are in one metal enclosure. This can be tilted upwards to allow for better access to the controls.

More pictures are little history in Czech language can be found here.

http://czechkeys.blog.cz/0912/syntetizer-antares-ii

All the electronics are in 5 modules and use gold plated high quality connectors. The entire PCB section can be also tilted and secured in place using thumb screws allowing full access to all the components.

Real joy to work on.

Trace Elliot GP 11

This preamp was humming and some of the graphical sliders worked as a noise generators rather then equalizer.  Also the two momentary switches were bad. I couldn’t find the exact momentary switch so i had to modify the switch cap slighty to fit modern replacements.

Re-cap and upgrade of main filter cap from 2200uF to 15000uF resolved all the PSU induced hum and one of the transistors in the graphical equalizer actually had a small crater where the silicon chip used to be inside of the plastic casing. It was interesting that the transistor was still working-ish but it was acting as a noise generator.

Vermona E-Piano

E-Piano was a bit more complicated repair compared to the Vermona string synth. PSU had dried up filter electrolytics and one of the earth wires fell off.

Following a pot cleanup all was working well except tremolo.

See the unusual but very reliable slider pot

I noticed some of the electrolytic caps were getting warm due to ESR. After the replacement piano was quieter with less strain on the PSU however the tremolo generator still wasn’t oscillating.

Both of the transistors were OK, all the surrounding resistors as well, electrolytes were replaced so the only culprit left were the foil capacitors and indeed once replaced by small electrolytic caps (the only 470nF I had in my spares drawer) tremolo sprung to life. I managed to later replace electrolytics with foil polypropylene condensers and tremolo was much nicer and more stable sounding afterwards.

Korg Poly 61

This Synth came to me following a damage suffered during transport. Joystick was loose /broken and it wouldn’t turn on or even when it turned on it would just display nonsense and wouldn’t react to any of the presets.

The core of the issue was a semi shorted battery and the spring clip from the joystick wedged under one of the PCB’s causing short of some sort.

With battery and the offending spring clip removed all sprung to life and worked just fine when presets were loaded.

I managed to glue the joystick together, but I sourced replacement module in the meantime.

 

Vermona Piano Strings

 

Vintage synth from Eastern Germany, you can smell the communist era inside of it. Very typical earthy smell of brown PCB boards. All it needed to bring back to life was thorough cleanup of all the keyboard contacts and slider pots.  After an hour and a half with compressed air and IPA it’s back in business.

Slider pots are actually very good design, fully open accessible and designed to be cleaned, sadly I forgot to take picture.

The way this one sound is just pure filth, it’s harsh…….

 

Tascam Portastudio 424

 

Another day, another field repair, this time on multi-track cassette recorder.  It took me a while to locate, PCB had a hairline crack all around the ground plain pad  where the input power connector was located.

Half an hour job from start to finish.

 

Vermona Automatic Drummer

Very quick in flight repair of non functional Vermona drummer in the mid of the recording session.

Fuse holder in the PSU section was so corroded it stopped working.

srubbed it clean temporarily to let the session continue and later on I’ll replace the PSU caps and solder new fuse holder in.

Audio Repairs Synthesizer Repairs Synth Restoration