All posts by Tom Virostek

I haven’t posted in quite some time. The usual excuses apply: work, family, lack of motivation. However I have had numerous requests for a solution for the CEM5530 IC. I designed such a board back in 2000, and the bare PCB’s sat collecting dust in a drawer until somebody mentioned that I had some of them. Within a few weeks all 30 boards were gone (including the ones in my two Prophet VS’s).  I had re-done the design as a 4 layer PCB to make it even smaller and the latest batch are built and assembled by a factory (instead of being hand assembled by me). The price of the boards is 50.00 each plus shipping.

The DSM-1 project has stagnated a bit. However I will be revisiting it soon.

The DSS-1 kits are almost sold out. As of today there are two left. I won’t be making any more until after the DSM-1 kit is done, the new DSS-1 kit will be based on the DSM-1 kit.

The new 5530’s getting ready for wave soldering at the factory:



My move to the new house is complete, so I’ll begin manufacturing DSS-1 kits shortly. I expect them to be ready by end of March. There are 20 kits left at $250 each. As always, installation by a professional service center is strongly recommended.

EDIT: The new kits have arrived! The PCB assembly company did a great job. There was a bit of a delay due to some components I forgot to order.


I’m at work, sick as a dog, replacing the mounting bolts of our surround speakers in our mixing rooms. I hope everyone is having a relaxing and enjoyable holiday, and maybe even making music with their favorite synths!!

When I get a minute or two I’m finishing up my final batch of OB-Mx voice boards that I started building over 6 years ago. I put them on hold since I didn’t have any CEM3374’s or CEM3382’s to finish them. But thanks to John Leimseider in Canada, and Vintage Planet, I’m going to have another 12 voice OB-Mx to play with.


I have just recieved a shipment of ASR-10 SCSI boards, so if you’re interested send me a message with the contact form and let me know your PayPal address if different than your regular e-mail. The price is 299.00 USD plus shipping (10.00 USA and Canada, 15.00 rest of the world).

I’m having my boards assembled at a factory now, instead of building them myself, so once I’m sold out it takes longer to get new ones.

Here’s a short summary of where I’m at with my current projects. I’ll be moving (finally) and won’t be set back up until mid December at the earliest. That means that once the existing stock of kits is sold out, there won’t be any more until early next year.

DSS-1 upgrade: 7 kits available now, another 20 after the new year. After that I’m going to focus on the DSM-1 upgrade.

ASR-10 SCSI kit: 30 being built, expected availability 11/15/2013

ASR-10 Digital I/O kit: 15 available. Still have to figure out the rack ASR problem with overheating.

EPS-16 SCSI kit: 20 available

Prophet 3000 memory expansion: being beta tested. Basically working but having some issues with memory test giving false errors.

Prophet 2000 memory expansion: Not started, but I think Wine Country Productions have them in stock

Korg DSM-1 upgrade: Being researched, I’ve got the code around 30% disassembled and commented. After that I have to decide which microcontroller I should use.


I’ll soon be moving to a new house, and until then I’ll be suspending work on all projects. I’ll have some upgrades available in limited quantities. Also, I’m currently preparing to have all my board assembly done by another company. I’m just not able to keep up with the backlog of orders.

I’ve also sold out of the modified DSS-1’s. I won’t be selling any more of these myself, but I have several sources that can modify a stock one for you. I have around 25 kits left, and after that there won’t be any for a while, as I’ll be focusing my efforts on the DSM-1. Please feel free to submit ideas and enhancements.

The Prophet 3000 memory upgrade will need some more R&D. It’s passing some tests and failing others. I’m not sure yet if it’s an issue with my board or the P3000, but it seems like the additional DRAM chips need to be buffered similarly to the original DRAM chips. Have to dig out the logic analyzer and see what’s going on.

I’ve completed another batch of DSS-1 upgrade boards, but they tend to go pretty quick, so let me know if you’re interested. Also, I’ve just received another 30 boards for the ASR-10 SCSI upgrade. I’m now looking into having them assembled by another company. The reason for this is twofold. First, having the boards assembled on an assembly line is more reliable than hand soldering. Second, I currently only have 2-3 hours a week to do any sort of PCB assembly. Each SP-3 board, for example, takes almost 2 hours to assemble start to finish.

I’ve also had a couple of requests for the SP-4 SCSI board for the TS-10 and TS-12. If I have enough requests (more than 10) I’ll look into making those too.


Last night, I got the boards for the memory expansion module for the Prophet 3000. I built a couple up and they work! All four banks check out in both the Voice chip and DMA chip tests. One of my P3000’s (the rev B, with the I-627B already installed) is having issues with bank 4 when tested with the DMA chip. The Rev B unit had the RAS signals switched around so that you could get two banks of memory without needing the upgrade board, the downside being all of the track cutting and jumpers. The rev A unit (which most P3000’s are) is working flawlessly with both the I-627B daughterboard and the memory expansion board. It works fine with the 3.0B OS, not so much with the WCP1.6A OS. So, there’s a bit of a catch-22: If you upgrade to the I-627B and 8 Meg, you may not be able to use SCSI, but if you stay with the I-627A, you can’t expand the memory. Once more testing has been done, I’ll contact Wine Country and see if they can modify the OS to work with both SCSI and the I-627B. The existing SCSI implementation is pretty limited, as far as I can gather: You can’t actually format the drive on the P3000, it has to be pre-formatted on a Mac with OS 7.x (who even has one of those these days??). The actual problem with WCP1.6A is with loading some floppy disks, so maybe SCSI will work – once I can get a properly formatted drive.

Pictures to follow….

I just got the boards back from PCBcart for the I-627 transition board. I’ve built one prototype, and will test it this weekend.

The website has moved to a new host, so there may be some interruptions over the next few days as I sort things out.

UPDATE: Things appear to be working OK now.

UPDATE 2: The adapter works perfectly!! However, I still have to test it with the expanded RAM module which is still a few weeks away. Currently I only have 1 bank of memory installed.

Over the last few months I’ve had several DSS-1 boards sent to me for repairs following unsuccessful modifications. So, I’ve decided to change my policy regarding upgrades. Going forward, I will only support installation by an authorized service center. I only have time to either build the boards, or do repairs and installation, but not both. And it ends up being just as expensive to have the boards repaired as it is to send them to a service center in the first place.

Contact me for a list of people that I’ve authorized to perform the upgrade.