All posts by Tom Virostek

Johan Sahlberg has had some ME-16 expansion boards manufactured, based on a design I did that never saw the light of day. If you’re interested, contact him directly at f_l_y_h (at) He has a very limited quantity available.

Work progresses slowly on the DSS-1 upgrade. However I have almost completed the design for the new processor daughterboard.

I’ll probably end up missing the 2017 self-imposed deadline unless a miracle happens.

I just looked at the date of the last post, and it’s been well over a year. Everyone has been asking when the DSS-1 and DSM-1 upgrades will be available. To be honest there hasn’t been a lot of work done on them recently. There are several reasons for this but mostly I’ve been too busy with house renovations, family, and work. Also the new microcontroller I had planned on using was more than 18 months late (it was announced in January 2015). I have finally received some samples and will start work on it soon, time permitting. I don’t expect the upgrades to be available until the end of 2017.

As for the other projects, the ASR-10 SCSI boards are still available, as are the CEM5530 replacement modules. The EPS16 SCSI boards are sold out. I haven’t decided whether I will do another batch of them since I would rather use the time for the Korg upgrades.

People often ask how to order boards from me. What I need is your PayPal email address and your shipping address, so I can send an invoice. I only ship on weekends now as I can’t get to the post office during the week.

All of the equipment posted for sale has been sold. I’ve also stopped buying, repairing, and reselling synths as I have no time to do it and there is minimal financial return.

Nothing much new to report. School is back and my daily commute to work is 90 minutes again. Combined with the 10 hours per day, six days per week work schedule, guarantees that nothing much will be getting done for a while. The ASR10 SCSI card issue has been resolved. Supplies of the EPS16 SCSI card and DI-10 digital audio interface for the ASR-10 are running low. I’ve added a bunch of new items on the gear for sale page. I’m trying to clear out some of my less used gear.

I’ve contemplated designing a conversion kit for the ASR-10  to go from a VFD to an LCD (purple screen). Looks like they used a device with an external EPROM to emulate the functionality of the old display controller so it’s technically feasible. The only question is whether the newer LCD displays will physically fit in the space. I’d just have to get a hold of a purple screen ASR or at the very least a purple screen ASR display board. Might work with the EPS /16 series as well.

We’re having a hot, muggy summer in LA this year. I’ve been spending more time in the pool than in the workshop. However I have had a bit of time to start preparing my ASR10’s for sale. In doing so, I made an unfortunate, albeit interesting discovery.

I had made a clone of the SCSI board (model SP-3) for the ASR-10. The first batch I did used the same SCSI controller as the original board, an AM33C93 from AMD. For the second batch, I had found some Western Digital WD33C93. The EPS16 SCSI board had used the Western Digital version, so I figured everything would be cool…unfortunately not.

I had done most of the testing on a first-run ASR-10 with a mainboard dated 1992. All the testing with the second batch of SCSI cards was good. However the past week when I was preparing another ASR10, I found some issues. Although it would boot from a SCSI drive, the ‘change storage device’ and ‘copy OS to drive’ would give ‘file operation error’. Long story short, the ASR10 in question had a mainboard dated 1993 which had been redesigned. The newer mainboard did not like the WD33C93, but was happy with the AM33C93. In fact the AMD version worked properly with all revisions.

I did a bit of research and found that the WD versions had several revisions; the latest being 00-08. The chips I used were a mix of 00-04 and 00-06 which were reported to contain various bugs, although I was not able to get the specifics on what was affected. Apparently the AMD version was equivalent, or derived from, the 00-08 version of the WD controller. Perhaps the first generation ASR mainboard was designed to be compatible with the WD controller, and once they switched over to AMD, this compatibility was removed…

So…for anyone who bought the SCSI board with the WD controller (it’s the only square chip and has WD printed on it), I’ll happily replace the board or just the SCSI controller. Contact me and I’ll get it sorted out.

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.