The Last Project

I picked up an old Arp Odyssey recently.

Arp Odyssey

It was one of those snap eBay purchases – a synth listed just moments before with a Buy-It-Now price that seemed unusually low. I’ve made a lot of those types of purchases in the last couple years. It all started with an Oberheim OB-1 that I got for $300 (plus the seller wound up throwing in a semi-functional SH-101 for free). I’m not a gambling man (or at least casinos and lottery tickets don’t really phase me), but the thrill of that split-moment decision became a little addictive.

I began watching eBay listings in most of my spare moments. I bookmarked the page of newly-listed analog synths and made a habit of routinely checking it. I’d check in the grocery aisle, on the L, at a stop light, or during breakfast. Checking at a rate of about a dozen times a day, a good deal seemed to show up every two to three months. Sometimes I was a little trigger-happy and wound up with a purchase I wished I could take back. But once I got a TB-303 for $150. That was certainly the high point, heartily nudging out the OB-1 snag from its gloried throne. I’ve bought two Minimoogs, a Matrix 12, an AKG C414, a Roland RS-09, a TR-808 and probably a few other odds-and-ends using the same technique.

Sometimes the items are in pretty-much perfect shape (like the 303 or 808). But most of the time, there’s a lot of repair work needed. The two Minimoogs required re-bushing the keyboard, heavy cleaning, some moderate electronics repair work and, for one of them, a new wooden case. The OB-1 had some filter issues but, more alarmingly, actually had a piece of the case sawn off. I ultimately had to find a local welder who specialized in aluminum welding. The Odyssey falls into this later category of synths. It’s in sad shape. Like the Minimoogs, the uneven keys are a tell-tale sign of needing new rubber bushings. A couple of the sliders are snapped off. The case seems to be missing all but one lonely screw. I believe it powers on but I think the seller claimed that it “makes funny sounds”. For an analog synth, that could mean anything from “totally broken” to “works like usual”. For the price, it’s probably still worth all the work. But lately, repairing broken down gear feels like all I do anymore.

This blog is actually a nice illustration of how I feel at the moment. I started it out in that great blog tradition of just wanting to meander about the subject and share what I’ve been up to. I thought I’d perhaps post semi-completed songs or talk about what excites me about certain pieces of music. Instead, the blog has veered deeply into the subject of my latest gear acquisition, and how I’m in the midst of repairing it.

So I’m trying to take a step back from repairing synths. And more broadly, from buying synths. And perhaps even getting rid of some synths. I suppose that calling the Odyssey “the last project” was a bit melodramatic. I still have a number of items that I intend to fix up (I’m looking at you, Lexicon Prime Time). But I’m trying really hard to stop this behavior of gear acquisition. At least for a little while.

Bit One Mission Successful

I’ve had a broken Crumar Bit One synth sitting around for about a year now. This last week I finally got it fixed up and it’s already on its way out the door (courtesy of eBay).

Crumar Bit One

I bought this from a guy in Chicago last summer. I was heading to Chicago for an old roommate’s wedding and I noticed the synth on Craigslist. I emailed the guy and we started trying to figure out the logistics of meeting up. Apparently I mentioned that I was in Michigan and he immediately grew very cautious and said that the synth likely wasn’t worth driving down to Chicago solely to see and that it had a few problems. I told him I was heading that way anyway and left a little early to make a slight synth detour.

Everything was fine, but occasionally a note would sound sort of weird. The seller wasn’t a keyboard player and wasn’t really sure what was going on. I noticed that this was only happening to every sixth note, and it sounded like the filter simply wasn’t being applied. The Crumar uses Curtis chips for its filters, so I hoped that maybe one of the chips was just bad. I figured out which Curtis chip was tied to the faulty voice and tried swapping in another chip but the problem remained. At that point I got busy with other stuff and the synth sat around all winter. Resolving to finish it up, last week I got it back out and opened it up.

Bit One - Workbench

I don’t have an electronics background and I feel like I’m over my head whenever I start poking around at the circuits. But I’ve watched my friends Kris and Jon (both gentlemen who have a much stronger grasp on electronics theory) troubleshoot circuits and I’ve gleaned that sometimes it’s better to just try to follow your gut, and swap parts out for a true empirical test. I think I’ve erred on wanting to conclusively prove that a resistor or diode was bad before I replaced it. Sometimes it’s better to just have a hunch and then test out that hunch. So in this case, I started measuring voltages around the Curtis chips and found that the voltages coming out of a couple op-amps were far different than all the others. I’ve seen old 70s vintage op-amps fail a couple times in other synths, so these seemed like worthy suspects. A quick trip to Radio Shack and I had two new op-amps installed.

Sure enough, that fixed the filter issue. Apparently one or both of these guys were bad:

The Culprits

I cleaned up a few more little things on the synth and then listed in on eBay. It’s a cool synth and I like it. But these days I’m trying to focus on using my Matrix 12. I’ve trying to narrow my focus a little, so I need to thin out the herd a little. Hopefully this will find a new happy home somewhere!

Hello Mr. Roland Sampler, please meet my friend Mr. Color Monitor

Tonight I experienced my Roland S770 sampler in full color, and it was deeply satisfying.

Roland S770 Color

First, a little story, and then I’ll try to give more of the technical details at the end:

Some of the old Roland samplers from the 80s have the luxurious option of a monitor output. On my sampler (the S770), there is both an RCA plug (for monochrome composite video) and a mysterious 8-pin DIN plug that supposedly would provide color video. Getting the monochrome RCA output to work is pretty easy, but I really wanted the color output. I already tried once to wire up a converter and failed miserably. Well, tonight was different.

After my initial failure, I decided to actually order the right parts and do a better job of wiring everything up. I bought an 8-pin DIN plug from Mouser (part 171-0288, to be exact) and picked up some different transistors. I set aside the breadboard and actually soldered everything together this time. The 8-pin DIN plug was a major pain, and the whole thing probably took me a couple hours. I’m very slow at soldering.

I plugged everything in and fired up the sampler with great anticipation:

S770 progress

I guess it was progress, but it was still pretty unusable. I felt a strange confusion of joy and disgust. After checking everything over a couple times and finding it all right, I honestly didn’t know what else to do. But at the same time, I had to admit that I was getting some sort of signal, so the theory behind the whole operation was pretty sound.

I went back and poked around on the circuit board, paying close attention to the wires that fed the horizontal sync. I replaced the transistor but found that the video display was still slanted. I began to lose hope. And with that, I also began to lose caution. At one point I disconnected the little yellow wire that fed my horizontal sync line to the monitor and was connecting and disconnecting it from its transistor. I’m sure that’s a very bad thing to do. At one point I accidentally brushed it against another leg of the transistor and the signal immediately snapped to attention. It was perfect! I was somewhat stunned.

I checked the schematics and found that my “fix” was definitely not in agreement with the official circuit. I didn’t really care though. I wired it up with the wire now touching the other leg of the transistor, plugged everything back in and quickly declared victory before it could stop working:

A happy Roland sampler

This has been a lot of work, but it’s really nice to have the color output. It adds something special to the whole Roland S770 experience. Here are a few more pictures, and then I’ll try to explain whatever technical details I can remember:

S770 Screen 1

S770 Screen 2


Technical Details from Someone Who Just Thoroughly Undermined His Electronics/Circuit Credibility:

The surest way I could find to hook up to Roland’s RGB output is with an old CGA monitor. If you’re in Europe, SCART is supposedly an option. However, I have no idea what SCART is and I’m not in Europe. Also, I happened to have an old CGA monitor laying around the house, so I went with that option. I’m using the super-old IBM 5153 monitor. Folks have reported success with various Commodore or Atari monitors also, but this IBM monitor is all I had. CGA monitors aren’t nearly as common as they once were, but I’m sure they can still be had for very reasonable prices if you watch eBay for a little while. I never see them at thrift stores anymore, sadly.

Information about the Roland sampler video format is scant but not impossible to find. In particular, this thread gave me some hope that it was possible to build an adapter to convert from the Roland output to a CGA input. In particular, they talked about a schematic. I studied the schematic long and hard, through it was a bit blurry. Then one day while I was flipping through my S770 owner’s manual, I found the exact same schematic in the back. So to help anyone out, here are some higher-resolution scans of that video schematic info:

S770 Video Diagram Wiring

Roland S Sample RGB schematics

As I mentioned, I bought the 8-pin DIN plug from Mouser. It feels a little cheap, but it did the trick and I didn’t initially see many alternatives for good 8-pin DIN plugs. The schematic drawing mentions a mysterious “DTC 11 AFE” transistor. I took the advice on that afore-mentioned thread and went with the more common BC550. That worked fine. For the cable, I just lopped off the ends of an old printer cable and used eight of the wires inside. Unlike CGA monitors, old printer cables are in ample supply at the thrift stores. I got the female D-Sub-9 connector for the CGA monitor to plug into at Radio Shack.

That thread mentioned not needing the 1k resistor for the vertical sync. I tested both with and without this resistor and found that it didn’t make a difference, so I left it in.

However, here was my change to the circuit that proved critical in getting it to work with my adapter. I have no idea if this is applicable to other monitors, but I know it was needed for my IBM 5153. Instead of connecting pin 4 on the DIN plug (the “H” line on the schematic) to the base of the transistor, I basically bypassed the transistor and just wired the straight into pin 8 on the CGA monitor’s D-sub connector. I’m not sure what I did there, but I’m not going to argue with a nice-looking color display on my monitor.

The only thing that isn’t working well is the horizontal offset on the screen. It’s just a little too far to the right, probably by about half an inch. Unfortunately, my monitor doesn’t let me adjust this. I’m not sure if there’s something I can do to the circuit or if I’m just stuck like this. However, it’s still very legible and I’m tired of working on the circuit instead of actually using the sampler, so I think I’ll just let this horizontal offset issue slide.

Anyway, here’s the final product. Please ignore those three op amps on the side. They were the beginnings of another project on that circuit board from years ago and I was too lazy to unsolder them. Despite several hours of soldering, it’s pretty messy, and it still looks pretty crappy. But I’ll throw it in a little case and forget about all that while I happily use the new color display on my Roland sampler.

S770 video converter

The Jupiter and the Quadra: brothers of another color

I just got back from Ohio where I was visiting my friend Jon, hanging out in his studio, hunting for Wurlitzer pianos at the thrift stores and trying to bargain at the antique store for a bag full of old Maxell high-bias XLII tapes. Good times all around.

I had also brought my Arp Quadra project down to show Jon. I bought this synth about a year ago from a friend of a friend in Chicago. It needed some TLC. Instead, I opened it up, tore it apart, and then neglected it for about nine months. Note: that’s an extremely effective way to lose lots of little synth parts. Anyway, I managed to replace a couple faulty parts and successfully put it all back together for the trip. I’d been telling Jon about it for a while and was excited to show the work-in-progress.

Unfortunately, my repair job fixed one thing but appears to have messed up the CV control on the keyboard. So we didn’t really get to try it out very much. While we were carrying it back upstairs, we paused next to Jon’s Jupiter 8 and I realized how many physical similarities these two synths share. Ok, I guess it’s just color and size.

Quadra and Jupiter

Aside from that, they couldn’t be more unlike one another. The Quadra is an American synth made shortly before Arp’s downfall. The Jupiter is, of course, from Japan. And although Roland had been around for a few years, the era of the Jupiter 8 is when Roland was really beginning to hit their stride. Arp was going down, and Roland was shooting up. The Quadra was a massive flop, the Jupiter 8 became a legend used by every respectable band.

Quadra closeup