Access Virus B Repair

I bought an Access Virus B desktop on 15 April 2017. This looks like a really nice Virtual Analog synth. The description on ebay said:

unit powers up, only 2 yellow lights come on on the left side of the panel, the green screen lights up as well, i tried every single push button but no difference at all,  that is all that comes on

I bought it BECAUSE it was broke and got it for $330 with shipping. This sounds promising to me and many other people wanted, so I hope it is a quick fix. So what could cause this? Wrong power supply, dead battery (CR2032), bad firmware, needs a power-on reset performed- these are all things I will explore. Maybe I’ll get lucky, or maybe I’ll resell it. After the easy checks it will be time to go inside, but first some online study!

Some threads say to change the electrolytic capacitors (22 or so) and the voltage regulators (3). I just bought a tester for ESR, capacitors, and transistors. Should come in handy.

Found some more details on exactly which cap is bad. Could it just be one? Same symptoms mentioned. The cap circled is 100uf.

From https://groupdiy.com/index.php?topic=43108.0

 

Update

The synth works! I simply performed a factory reset and played it for several hours. It sounds beautiful and everything works great. What I have noticed, though, is instability. During other efforts to play it, the synth would restart constantly. All lights would flash on and the sound would stop. There is still something wrong- perhaps temperature dependent? What I have found is the synth needs a 5-7 minute warm-up period before it becomes stable and plays well. So until it really ‘breaks’ I will leave it alone.

I did replace several knobs with big retro ones that looks really cool and make it easier to find the filter and resonance controls.

Flash Forward 7 Months

The Virus is now unstable and resets whenever a MIDI signal is applied. Time for the fix. First, open it up.

 

The sound generating board is on mounted under the control board. There are 2 ribbon cables that need to be removed in order to access the underside of the board.

 

SAFELY remove the ribbon cables

to reach the underside of the board.

I removed the suspect capacitor. It is 100 uf/25v electrolytic. The positive lead is on the left in the picture below.

Bad Capacitor Removed

Note in photo above I may have removed the left PCB pad by accident due to my soldering iron not being hot enough and pulling too hard.

I tested the old capacitor and the new one to compare them.  The bad one (on the left) has a very high ESR- over 400 times the ESR on the good one. This is the problem.

 

If you are wondering what this cool test device is, it is the Yosoo GM328 multi-function tester It test resistors, capacitors, transistors, diodes- invaluable and only $20.

Does it work?

 

And it plays!