Thursday, April 28, 2016

Korg 770 Synthesizer Troubleshooting Intermittent Pitch Problems

This is a concise, technical, and hopefully well-presented account of how to resolve an intermittent problem on a vintage synthesizer. I learned a lot, and hopefully others could as well. As with all electronics projects take the necessary precautions to prevent electrocution, injury and death.

This old Korg 770 synthesizer was having intermittent pitch problems.
Intermittent problems are the mother-of-all problems to resolve.
Like finding a needle in a haystack...
if your needle is made of glass...
and the haystack takes half a city block.

The keys to the game are four D's:
- Dumping vast amounts of time into the project
- Drawing a map (schematics, diagrams), and marking the places you have already explored.
- Discipline and persistence.
- Deploying the right tools: Voltmeter, Oscilloscope, Iron, and a good rework gun like the Hakko 808.

Other things not covered in this video I dealt with during this restoration were:
- Replaced 3 broken keys
- Re-aligned a bent keybed frame
- Replaced a broken pot and broken switch
- replaced DOZENS tiny pot metal screws that were stripping out.
- Installed a 3-prong AC Power Entry module
- Added an Earth Ground to the chassis

I would like to send special thanks to for taking to time to provide graphically enhanced schematics available. Without this I may have not been able to resolve this extremely difficult situation.

Friday, April 8, 2016

Korg 770 vs Volca Bass - Synthesizer Filter Comparison

Quick comparison of the Volca Bass filter to the Korg 770 lowpass filter. Different settings for the peak are explored.

The Volca Bass takes its filter design from the diode ring filter of the 700/700S miniKorg synths of the 70's. The Korg 770 has the identical filter design except replaces matched diodes for a diode array. Do the filters sound the same? To me they sound darn close, but you be the judge.

However the oscillators themselves sound different to me. The Volca Bass has a lot more bottom end than the 770, listen with headphones or a nice set of powered monitors.

Friday, April 1, 2016

AKAI AX73 Analog Synthesizer Ad Infinitum

In this video I share some helpful tips and info on the Akai AX73.

All synthesizer audio comes from the AX73 using all original patches. No outboard effects were used, only a few instances of the built-in chorus. Rhythm provided by a Roland TR-8. Thanks for watching. Be sure to subscribe, like and comment.