A Quick Peek Under The Hood...The Moog 930 Powerful Supply!

Here's a look at the Moog 930 power supply, the supply that powers the larger 35 and 55 modular systems.

This module has been on my radar for a while as a prime candidate to be refurbished. It's the lifeblood (the beating heart, if you will) of the whole system, and aside from cleaning an intermittent pot decades ago, it's never had (or needed) any other service.

At 40+ years old, it's certainly more than ready to have the various electrolytic capacitors replaced. These type of capacitors don't last forever, and even though the ones used in this supply were very high quality devices, the time had come for them to be swapped out with nice new ones, and have the entire unit completely cleaned and refurbished. I've read that you can typically expect about 10-20 years of reliable service from most electrolytic caps, so these have done very well indeed!

The supply creates 4 different voltages...+12V, -6V, +15V, and -15V. Each voltage has its own separate card complete with adjustments to set output voltage, current limit, and overvoltage trip points.

Interestingly enough, the two 15 volt cards play almost no part in the Moog 55 operation. The only thing powered by the +15 volt supply is the trigger buffer card, which just draws a few milliamps of current, and the -15 volt card is not used anywhere in the system. These are both fairly robust cards too, with each one capable of supplying 1.5 amps of current. The only use for them I could find was at the accessory connector in the back, where you would connect a Moog ribbon controller, sample and hold controller, or drum controller, and none of these draw anywhere near that much current.

In the schematics for the CP3-A mixers they are shown as being connected to the 15 volt supplies, but in the cabinet wiring diagrams and in reality they are only connected to the +12 volt and -6 volt supplies. These supplies are even brought up to the top cabinets through the cabinet interconnect cables, but unused.

 

As you might imagine, I have big plans for these supplies in a future project...

...Yes, big plans indeed...Excellent.

 

 

Although Moog put their name on this, the individual supply cards were actually made by Powertec (apparently no longer in business) and are marked on the boards as model 1607. A nice bit of kit back then, and still pretty nice even today, especially after some much-needed maintenance.

 

This is what the cards looked like before being refurbished. Although the caps looked to be in pretty good shape physically (no cracks or bulges in the rubber end seals), measuring them showed that they were at less than 50% of their rated value. Not really surprising, given their age.

 

 

I replaced them using a combination of Sprague and Nichicon high reliability capacitors. This should carry the system at least several decades into the future. While I had the cards out for servicing, I replaced the large power transistor mica insulators with new thermally conductive pads to help them transfer heat to the large black anodized heatsinks more efficiently, and run cooler.

 

Each card had the old dried up heat sink grease underneath the card mounts removed and replaced with fresh thermally conductive paste to help transfer heat from each card's heatsink to the metal chassis for better cooling.

 

Here's what a card looks like after being cleaned and refurbished with new caps.

 

 

All connector points are cleaned by being lightly burnished to remove any corrosion with a small square of 3M Scotchbrite green scrub pad sprayed with a little Deoxit D-5, then wiped clean with a soft cloth. The same treatment is applied to the screws used for the connectors as well.

 

Here's the newly refurbished cards being re-installed back into the chassis, which has been previously cleaned inside and out with Windex to remove any old heat sink grease left behind.

Now it's starting to look powerful!

 

 

I created a duplicate AC input plug to power up the supply outside the Moog 55.

This will allow me to completely test and adjust the individual cards before the assembly is returned to service inside the modular system. All of the pins of the two Molex connectors (one is AC power in, the other is DC voltages out) are scrubbed with a small stiff nylon brush and D5, then cleaned with a soft clean cloth. This will remove any built up corrosion and make sure we get a solid electrical contact for all of the supplies.

 

Here's the supply back in place, and ready to go for another few decades ( at least).

The eagle-eyed among you will note the yellow factory " birthday sticker" showing the date of the system cabinet assembly, August 20th, 1974.

Happy Birthday to an old friend.

This year (2015) it will be 41 years old, and still going strong.

The work continues...

...And the beat goes on...

...Yeah, the beat goes on...

 

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The Secret World (And Surprising Hidden History) Of The Moog 960 Sequencer!

This particular blog entry started simply enough.

As you probably already know, Moog is making a limited run of their Modular systems, including the 15, 35, and 55, as well as the Sequencer Complement B.

An incredible feat, and I could scarcely belive my eyes when I saw this announcement (and the entire Analog Resurgence from Sequential Circuits and others) at the NAMM show earlier this year. For a few moments, I worried that I was actually having a stroke, and this was what my sputtering and sparking brain was coming up with to try and entertain me in the interim...("Hey, it's actually 1974, and everything's going to be just fine, so don't freak out, OK??")

 

I saw a thread on a forum recently where someone was asking why the sequencer was so expensive ($8500). A lot of hoopla erupted after that, with people alternately trying to explain why something like this might cost what it does, and others declaring that this was nothing short of highway robbery, and they'd much rather have their brand (insert name here) sequencer which is just as good, or maybe better, and just who does Moog think they are, anyway?!??!!?

As I continued to read through this thread, I thought that maybe I should profile the 960 sequencer next, and provide some pictures showing the high level of craftsmanship and quality that actually went into creating this excellent and iconic piece of technology, so I removed it from my System 55 and started taking some pictures of it, and that's when things began to get really interesting (more on this in just a bit)...

Now, to put things into perspective, the Sequencer Complement B is actually a collection of two 960 Sequencers, mated with two 962 Sequential Switch modules, a 961 Trigger Interface module, and a 994 Dual Multiples module all contained in a beautiful solid walnut extension cabinet. A serious amount of handbuilt technology for a serious amount of money?

 

Well, back in 1974, this same setup went for $3,295, and rightfully so. An inflation calculator will show that in today's dollars, this would now cost $15,894!!!

Suddenly, the $8500 price tag begins to look a bit better...

 

It's certainly not difficult to see why these would cost what they do, given the cost of components these days that would be used, the amount of effort required to locate and procure them, and the sheer amount of hand labor that goes into creating something like the 960 Sequencer. I haven't seen one yet, but Moog claims (and I have absolutely no reason to doubt them) that they will be making these modular systems and assemblies using the same components and manufacturing techniques that they used in 1974. This is almost unheard of in this day and age, and shows their commitment to getting this reissue right...for those that can afford it, of course.

Take a look at the beautiful wiring looms that are required to connect all of the components together. This would be difficult to make if you were already experienced at making these, and did this every day, for years. Now imagine that you have to recreate this starting from scratch, and the task begins to take on some weight...there's a lot of stuff to get right.

Boards will be created from the original artwork and lovingly hand-stuffed just like in the old days, using period correct components, photo etched front panels, etc, etc.

The switches are very difficult to come by these days, and expensive, and the pots...don't even get me started on the pots!!!

Allen Bradley hasn't made these type J series pots in years, but back in the day they were considered the absolute top shelf component, Military Grade, and they were expensive even back then.

It's a testament to their quality and ruggedness that every one of them in my 55 modular is still working 40+ years later. Switches too!

The Canadian company PEC makes what I would consider to be the closest currently available replacement, and even these run around $15-$20 each.

The 960 sequencer uses 25 (!) of these.

Almost all of the circuitry that powers the brain of this system has been out of production for years. The chances of finding replacement chips for these are low, which means that they will cost many times their 1960s-1970s prices (cheap enough back then, not so much now). These are Motorola RTL chips, an early type of digital logic chip.

As you can see, the 960 Sequencer uses a fair number of them, as does the 961 Trigger Interface and the 962 Sequential Switch modules. Major Kudos to the good folks at Moog for marshalling the resources to make these incredible instruments available again. How the heck did they do it?

 

 

And now, on to the Hidden History part of today's Feature Presentation, which is already in progress...

Hey! I've owned my System 55 for 30+ years, and gleefully modded various parts of it as well as performed all my own maintenance of it, and I only now realize that I've taken certain parts of it for granted.

Even in this sophisticated system, there were still sections of it that were hand built on perfboard (!) for certain functions. My system 55 is a pretty early one, and it seems that these hand-built boards were created like this before finished printed circuit boards were available.

The CP3A mixers were built this way...

Boards that do Trigger buffering...

 

...As well as hybrids like the attenuverter for the 904 filter...a circuit board grafted to the board that power is connected to.

 

I've seen pictures on the web of other modules that were more or less hand made, and after spending time modifying and refurbishing sections of the modular many years ago, I sort of ignored these oddities.

In less than a year, Moog was building the 55 modulars with actual printed circuit boards in these locations. Here you can see these boards in a later model. Notice that the individual hand-matched 100k ohm summing resistors have been replaced with a resistor network package for both the CV summers and the CP3A mixers (those light blue rectangular packages).

 

As I was taking some close up pictures of the sequencer, this (finally!) caught my eye...

What The What??!!!?!?

I'd always assumed that this was just another factory hand built module, but as I was paying more attention to it while photographing it, I suddenly realized that this board really didn't look like any other Moog handmade boards, and looking carefully at the opamps revealed a datecode from 1976,

after the module was built at Moog, and purchased by the college.

So now, a new facet of the history of my system had been revealed...it had been modified by someone while it was still at the college!

 

The board appears to duplicate the circuitry for each of the three analog voltage outputs of the sequencer using 308 opamps (a very good opamp at that time) to replace the discrete component opamps that were being used at that time on the sequencer. This would make the output voltages less sensitive to drift with temperature changes, and make it more stable, especially for live performances where temperature changes are likely more pronounced.

 

This is what the discrete component opamps would have looked like before all the circuitry was removed and replaced with the current board assembly...

 

The quality of the work is pretty good, which is probably why it never attracted my attention before. The area where the original circuitry was has been completely depopulated, and the board was nicely cleaned to remove any flux and solder left behind...a very pro job.

 

It makes me wonder if the work was done locally by a teacher or student, or if it was shipped off somewhere to be professionally modified. There were places in the 70's that specialized in performing modifications to synthesizers, although I can't recall reading about anyone performing this particular mod. I'd love to hear from anyone who might recognize this or have more information about it!

The only things I would have done differently would be to use low drift cermet trimmers like the Bourns 3362 in place of the carbon Piher ones that were used, which would make it even more stable.

Yeah, I know...picky, picky.

Trimmers like these were certainly much more expensive and less available back in the mid 70's, and even Moog used cheaper carbon trimmers in their original discrete component version.

 

After finding this, I began to wonder if there were other mods that I had glossed over as well, so I began to look at the other modules in my system with a fresh perspective.

 

I didn't have to look far.

 

The same discrete opamp circuit was used in the 962 sequential switch, and sure enough, there was the same replacement board installed in its place, a true chip off the ol' block.

This one used a precision multiturn trimmer (a nice touch) and the same board material and datecoded opamp. These were likely modified together, and a very nice job they did of it, too!

 

Now my curiosity was up. I had another 962 sequential switch that I has gotten quite a while ago from a friend, same circuitry but a different front panel layout. This panel was the same size as the one for the power switch and pilot light in the lower right corner of the main cabinet, so I had moved the power panel to the rear of the unit, and installed the much more useful sequential switch in its place.

Looking at the board for this unit, I found this...

 

Same idea, but an even more elegant implementation...a handmade etched and drilled printed circuit board, also complete with the 308 opamp. Whoah! It's apparently a thing, I guess.

Am I the only one who doesn't know about this?

 

 

Again, some nice low drift cermet trimmers certainly wouldn't be out of place here, but there's not much else to improve this groovy little mod, which apparently, has occurred to more than one set of crafty hands...

 

 

 

 

 

 

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The Incredible Mutation (And Restoration) Of The 360 Systems Frequency Shifter

The 360 Systems frequency shifter is a really interesting and fairly rare piece of analog gear, and well suited for use with synthesizers. There are at least two different versions of this device, with the earliest ones housed in a green case...

... and the later versions, sporting some circuit upgrades, housed in a blue case.

I remember first reading about this as part of the equipment listed on the back of the excellent first album by Larry Fast/Synergy "Electronic Realizations For Rock Orchestra". You can see one of these sitting on the top of the Moog Modular 15 in his studio at that time...

 

I had no idea what it actually was, but MAN did it sound cool! FREQUENCY SHIFTER!

Larry not only helmed the many wonderful and inspirational Synergy releases, but also added his distinctive magic to albums and tours by Peter Gabriel, Nectar, Foreigner, and others. A true pioneer.

Thanks, Larry!

My unit is a very early one, I think. A look at the serial number would suggest that it might be made in early 1975, perhaps serial number 8? Maybe, maybe not.

There's quite a bit of rework going on underneath the board. This is often the case with very early boards, as mistakes are discovered and repaired to make the early units sellable. A close examination of this board showed that entire power supply was laid out backwards (!) so all the diodes and capacitors had to be installed backwards to make it work correctly. The blue jumper wires make the proper connections here and there, and parts that were either forgotten or added later to make things work correctly are soldered on back here as well. I really like the 360 logo etched into the board. If you look closely, you can see that they actually used it to connect two traces!

 

The print ad for this (thanks, Riley!!) at the time made some very interesting suggestions about the capabilities of this unit, in typical 1970's flair....

Turn a violin into flannel bass??!??!? What the what? Good God, Y'all!

Those with sharp eyes will note that the case shown in this ad isn't the same case used in either the green or the blue production versions. This picture was probably the original proto unit.

As I mentioned earlier in my blog, I acquired one of the earlier green ones along with my Moog 55, and after a few simple mods and some recalibration, I was able to use it on various projects for a number of years. I remember calling the good people at 360 Systems at the time I got it to see if I could get a schematic, and it took a while for them to actually locate one at the factory! I eventually got a huge blueprint-size schematic in the mail, free of charge. Impressive customer service!

The most useful mod to it at the time was replacing some of the single turn trimmer pots in the balanced modulator sections with 12 turn trimmer pots, to allow for a more accurate calibration (the four green rectangles at the bottom left quadrant).

 

 

Adusting these pots allows you to reduce the amount of background noise and signal bleedthrough, and with the new more accurate trimmers in place, calibrating it was much easier, and improved the performance by a noticeable amount. I also at that time upgraded the generic opamps in the audio path with quieter devices.

In use, there are some pretty interesting effects to be had from this device. As you turn the shift knob, one output shifts things upward by the frequency set on the shift knob, while the other out shifts things down by the same amount. Things can get crazy pretty quickly!

With just a small amount of shift, and the up and down outputs panned hard left and right in a mix, a beautiful chorus sound is created, different from any others. It's said that the swirling "oooh" and "aaah" background vocals on Pink Floyd's song "The Great Gig In The Sky" are treated with a prototype frequency shifter, and that's what it sounds like to me...a sort of growly, swirly wonderfulness.

 

There's also a Ring Modulator output, to create all sorts of clangy, metallic timbres. I read somewhere that John McLaughlin used one of these units in the mid 70's with a footpedal to sweep the oscillator, and that seems likely to me as well...imagine the hyper-speed metallic goodness. Go Johnny, Go!

 

 

Ring modulators were starting to enjoy some well-deserved popularity in the early 70's. Oberheim built a stand-alone effects box type device (dig those crazy graphics!!!)...

 

...and also built a slightly modified version for sale by Maestro (they look quite a bit alike, eh?).

 

Artists like Jon Lord, Joe Zawinul and Jan Hammer were soon using them on their electric pianos and organs to produce a more interesting synth-like texture and create a pitch bend effect for solos.

For many artists at the time, this often served as a gateway (or at least a sideways entrance) to using synthesizers like the Minimoog or the Arp 2600, as they became more readily available.

 

 

I loaned my 360 Systems Frequency Shifter out to a friend, who at some point apparently decided that it was now his. When I finally got the unit back, he had proceeded to remove the circuit board, discard the case, and mount it into a single rack space casing. Like most of his (always very nicely made) devices, it was basic black, and all knobs, jacks and switches were unmarked. Feh.

After a number of phone calls, I was luckily able to track down the original case languishing in the back rooms of a recording studio (thanks, Roger!), and decided that when I got the time, I would restore it to its former 70's glory. The case had faded and discolored somewhat with time, but I still loved the sheer weirdness and funky mojo of the overall package.

GREEN! It's really an underused color.

My original schematic had gone missing, but after some sleuthing, I found a copy on the internet. I'll publish it here for those who might be interested. This would seem to be the scematic for the later model blue Frequency Shifter, as it differs in some areas from the components used in my unit, and the date on the print is from 1976. It was however plenty close enough to allow me to identify all of the necessary wiring locations on the circuit board to successfully transplant the board back into the original enclosure.

This looks remarkably similar to a schematic I saw in Electronotes back then for this type of device. It's certainly possible that one might have inspired the other...

 

Some important parts were missing. The original power transformer was gone, as was the cool green illuminated power switch and original potentiometers.

This also seemed like a good time to replace the electrolytic capacitors, as they were now 40+ years old, and the rubber seals were dried and cracked. The opamps in the audio path had already been upgraded a number of years ago, and I also wanted to extend the frequencies of the shift oscillator, and provide better CV control of the shift frequencies so I could easily control it from the Moog 55 and other devices.

The original unit had line level and instrument level outputs ( just the line level outputs scaled down with a resistor divider). I thought that the panel space for the instrument level outs would be better served by making them the inverted phase versions of the line level jacks. This could make for some interesting stereo effects during shifting.

I found a transformer from Mouser Electronics that fit the same mounting holes, and was just a bit larger voltage-wise than the original. I also found a functional green illuminated power switch...nowhere near as cool looking as the original, but it would certainly do until a better replacement could be found. These were fitted, along with a new power cable and strain relief.

 

The front panel was cleaned, and the new power switch, jacks, knobs and pots were installed. You can see some of the discoloration around the screw holes, but it still looks pretty good, I think.

 

 

Adding the parts for the output inverters and the improved CV scaling would require the addition of a small board to hold the necessary circuitry, so I built everything on a small perfboard and mounted it to the inside front panel of the unit. This made wiring up the various outputs easy and kept the lead lengths short.

When I fired it up initially to take a look at everything, I found that that the transformer voltage was indeed too high. This made the voltage regulators on the main board overheat since they now had to dissipate the extra power to bring this higher voltage down to the required level at the main board.

I added a couple of small 5 watt resistors to each side of the transformer outputs to soak up the extra voltage, and secured them to the top of the transformer with some silicon rubber adhesive. This reduced the power dissipation of the regulator, and now things were running nice and cool again. I also upgraded the 12 turn trimmers to grey 20 turn trimmers, since one had gone intermittant after all these years.

 

 

 

 

To extend the frequencies of the shift oscillator, I bought a 5 position rotary switch to replace the original 3 position switch. Now I had a position below and a position above the original panel marking. I added the appropriate capacitors to the shift oscillator circuit for the two new positions, and that gave me a lower and higher shift range, as compared to the original circuit.

After a bit of wiring to connect all of the front panel controls, and some tesing to verify that all of the various circuits were functioning correctly, it was time to reassemble the board into the original case, and recalibrate the system.

 

The unit is still missing its unusual gigantic radio tuner dial to set the shift amount, but I believe that it's merely biding its time hiding in my storage space. Until it returns, I did manage to find a smaller version to keep the front panel from looking too barren.

And so here it is, in all of its Mighty Green 70's glory, its Mojo and Mighty Shifting Powers intact!

Good God, Y'all!

 

 

 

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