Recently I have acquired a couple of Akai VX90 synths and one of them is very weird in multiple ways.

1. It only has a Line Out at the back. No Stereo Left/Right Outputs.
2. No sustain pedal jack
3. The entire IO panel is very different in terms of layout. The silk screening hints that it was made that way at the factory
4. It has 7 RCAs at the back next to the Sampler In connector. They are perfectly aligned. The top panel is carved out nicely to accommodate tha RCAs. Looks like a factory mod to me. It is too clean to be a hack.
5. The firmware on it is V1.1 which I don't think I have heard of before.
6. There appears to be no chorus parameters available to configure
7. It is an [A][C] model similar to other VX90s in the household.

Guess which one is the weird one? They are all the same from the front! Although, if we look at the back we immediately see the differences.


Uhmmm, how do I embed scaled image previews inline if they are uploaded as attachments here?

What is this thing? By some kind of dumb luck this unit has a serial that precedes one of the regular VX90s that I have. How cool is that?! This is also very strange. One unit is obscure while the other one, being the next serial #, is totally normal. See attachments for a serial picture.

I looked up the service manual for the VX90. It seems like the [J] model was the only one that had neither a chorus PCB nor a stereo out. Okay, but this is an [A][C] model! I opened up both units for a nice visual comparison and took photos. Also noticed this v1.1 firmware EPROM. The RCAs are a typical mod that some users do to tap into the Sampler In connector to avoid using the cable. Not sure if this was done for the purposes of development or if it was a factory option. See attachments for pics of the internals of normal vs weird or help me figure out how to scale images here and I will make this post look nice!

I happen to have a couple of AX73 and VX90 EPROMs with different firmware versions. We already know that the AX73 and the VX90 have the same firmware. So I dumped the EPROMs and noticed the following copyright dates:
A-ha! So it is must be an early unit! Let's continue! The unit with the next serial has a FW v1.2a on a TMM27128 EPROM. Bone stock! This EPROM has Akai labels that I have seen in AX73s and VX90s and I doubt the EPROM has ever been changed. So... even though they are the next serials yet so different feature-wise, one has a software release from 2 months prior. Not even v1.2 from April 29! I get that anything can happen during development but it is still fascinating nonetheless.

I found a post on tumblr describing a similar unit. Although, it did not have RCAs at the back but everything else is looks to be similar to mine. Unfortunately, the unit in the post has been sold a long time ago and we cannot really compare them or learn anything about a firmware used on that one.
You can read the post here if you have an account: https://www.tumblr.com/mysynthfetish...0046/akai-vx90

Oh, by the way, I am looking for 8 tactile switches. The ones I have in one of the units do not really click. These are the unobtanium ALPS SPPQ19 which are also found in Akai S900/S950. If anyone knows how I can fix them or where I can get a replacement from, please let me know! I am getting a desperate at this point.

Loved this preset on the VX-90 called Heaven. I'm sure it was super simple but it had a vibe for sure.

Does it look like this?

https://www.soundtoparts.com/en/rola...ct-switch.html

Yes, the same type but slightly different offset on those switch case support legs. This is SPQ009G and those legs are in line with the pins.

I need the switch with case legs ~5mm offset from the pins. If I don't find anything, I will try to Frankenstein them but it's a bit too much for the price given how much it needs to be modified

they are expensive , thats true.
A few thoughts:
By cutting the 4 black plastic fasteners you can disassemble the switch , clean it and carefully reassemble using strong glue.
If you are adventurous , you can use simple tact switches like this and curve the edge into proper shape so that they fit the button caps. Or cut the "Head" from the original ones and glue it to the cheap tacts.

Does anyone have old ALPS switch catalogs? This is the right way to figure this out.

Opening up switches and/or modifying them is the last resort.

I know for a fact these switches were used in many different devices except that either nobody has ever looked outside of the music industry or are simply being quite about it. Half an hour of more intense searching brought me to avionics. Suddenly a pack of 4 switches NOS is 5 bucks. They are still not the right kind but it is getting better already.

I started this thread because I wanted to carry over my posts from Facebook groups to the outside internet so that it has better discoverability and that strange units like the one I have exist in the wild.

Found another interesting VX90-related blogpost here:
https://erichizdepski.wordpress.com/...ot-and-repair/

All known Akai AX73 VX90 firmware versions:

The same files have also been uploaded to DBWBP Synthesizer ROM Archive: https://dbwbp.com/index.php/9-misc/37-synth-eprom-dumps

Here you can find an AX73 Service Manual, board schematics, diagrams and (known) Service Bulletins scanned and processed (in high resolution).

Service Bulletins:

• MS-0009: Mute time change
• MS-0010: Detune countermeasure, VCO leak countermeasure
• MS-0017: Velocity countermeasure (also applicable to MX73).

Missing MS-0013 "ALL NOTE OFF" Countermeasure.

Akai AX73 Service manual + service bulletins: https://archive.org/details/akai-ax-73-service-manual

Akai AX73 Service Bulletins: https://archive.org/details/akai-ax73-service-bulletin

The service bulletins are also applicable to the VX90.