Novachord #346 Inspection & Initial Wakeup

[HideawayStudio]

OK this is where it all starts to get pretty grim. The PSU in this beast has been horribly overloaded due to a dead short in the potted decoupling caps in the pre-amp channel. After very careful inspection today I have determined that the main 270V HT transformer has a dead short circuit across it's primary - AG - surely this must have blown a fuse somewhere in your house?? The supression choke on it's secondary has got extremely hot but might just have survived. The wiring around this area of the chassis was in a terrible state, mostly charred and wax has run out of the transformer windings and glued the whole lot together. Worse - when you try separating the wires the insulation falls off!

Since the safety of the instrument is reliant on the PSU working correctly I've decided to strip back the entire thing back to a naked chassis and rebuild it.

The Horror surrounding the 270V rail HT Transformer:

The Grizzly Transformers & Unhappy Chokes:

The Tube Sockets:

[Automatic Gainsay]

I'm sure a number of people are saying "oh, here we go..."

While I am a fan of Phil Cirocco's work, and he plainly did amazing work on his Novachord restoration...
The admittedly lovely and lovely sounding thing he has made doesn't exactly sound like a Novachord. In his desire to remove all of the aged parts and redesign parts which no longer worked or didn't work the best way, Phil created a sort of new version of the Novachord.

ThIs Novachord, the one you're watching Dan bring back to life, did not sound like that... and I suspect it won't sound like that when he's done.

It is definitely difficult to recreate the Novachord in the exact way it was originally created due to the fact that it was made of components which are no longer available. As a technician, you have the choice to try to exactly recreate the device, or you have the choice to clean up, replace, and improve the device. Of course, there are varying degrees between the two, but Phil's work was pretty much all the way to the latter (including a number of complete redesigns).

If people would like to hear what an actual Novachord sounds like, I would encourage them to listen to the bounty of old recordings on the internet. From those, you'll get an idea of the general sound that the device actually creates. Of course, these recordings don't demonstrate how the device will sound when it is played in a modern context. When I owned this one, I absolutely loved opening and closing various filters in the midst of performance (can be heard in the Automatic Gainsay song "Beautiful" during the second verse)... and you're not going to get that sort of stuff from the original recordings. However, you will get a better representation of the original timbres.

I wish I had been able to record more with the device, but it was impossible because the tuner pots no longer accurately tuned the oscillators. Of the three recordings I made with the Novachord, the song "Beautiful" had me sampling every note and performing realtime "tweaking" to a metronome. The other two feature the Novachord in its out-of-tune state. I should post those somewhere.

Anyway, it's heartening to see such interest in the Novachord!
Perhaps it'll prove inspiring to a certain admin whom I contacted in 2002 or so about including the Novachord on a certain vintage synth website.

[Automatic Gainsay]

- AG - surely this must have blown a fuse somewhere in your house??

While it filled my basement with a dense, acrid white smoke, I don't recall that it blew a fuse! Of course, that house did actually USE fuses (instead of breakers), and I often put higher load fuses in place in the basement... so that might explain it!

[Ian S]

Some parts of that look in amazing condition for its age (others sadly don't!), but my first thought when I realised where it had come from & gone to was "the shipping must've cost a fortune!"

[HideawayStudio]

- AG - surely this must have blown a fuse somewhere in your house??

While it filled my basement with a dense, acrid white smoke, I don't recall that it blew a fuse! Of course, that house did actually USE fuses (instead of breakers), and I often put higher load fuses in place in the basement... so that might explain it!

Marc... Just to put your mind at rest, I've no intention of a strip down of the main generator chassis - that would be sacrilege! Provided the rebuilt PSU produces the specified voltages it will have no effect on the timbre of the instrument since it only produces stable DC voltages. Since the Novachord is so very full of tubes the PSU loadings are high and thus I don't want to take any chances - not least since another spectacular failure in the PSU could have damaged the generator itself.

The Array Of 144 Tubes in the Divider Channels is Impressive!

[madtheory]

Are you going fully restore the PSU, or do you plan to use a modern PSU instead?

[HideawayStudio]

Are you going fully restore the PSU, or do you plan to use a modern PSU instead?

I am rebuilding the entire PSU chassis to original spec. Today I have uncovered the sheer horror that used to be the 270V HT transformer!! Having removed the end caps (Marc close your eyes!!) it's obvious this baby must have come very close to causing a full blown fire. I now see why so many of the wax caps melted under the chassis. I don't think I've ever seen such a badly burnt out transformer. It's innards fell apart like something at the bottom of a fire grate. The suppression choke has an interesting blow hole in it and charcoal round it where something fairly spectacular has happened too.

I have spent this evening carefully pulling the termination wires out of the windings and measuring the copper wire with digital calipers. I have determined the wire spec for all of the tappings.

The good news, and for other Novachord owners!, is that I have found a company (Majestic Transformer Company in Poole, Dorset, UK) that will build both HT transformers and the choke from scratch to the original specification using modern materials for very reasonable money. These will be given drawing numbers and hence, from that point on in theory, other owners will be able to order safe new transformers for their beasts. The transformers will also have primaries wired for selectable 120 or 240 volt 50/60Hz operation. The transformers will be ready in about 2 weeks. In the meantime, I'm going to completely rebuild the rest of the PSU chassis.

HT Transformer #1 (The Sheer Horror!!!)

Measuring the Gauge of the Wire Windings on HT Transformer #2 (The Better One!):

The Repainted Chassis and Choke End Caps:

[cornutt]

Wow, I can smell that from here! You've undertaken quite a job. Good luck with that.

While it filled my basement with a dense, acrid white smoke, I don't recall that it blew a fuse! Of course, that house did actually USE fuses (instead of breakers), and I often put higher load fuses in place in the basement... so that might explain it!

Could be that not all of that smoke was coming from the Novachord...

[b3groover]

Dan, may I just say that you're the man?

[balma]

Of course, these recordings don't demonstrate how the device will sound when it is played in a modern context.

That's my biggest curiosity. Since I heard about this Novachord, I have heard dozens of World War II documentals , Gone with the Wind,old recordings, etc...

It would be really interesting to hear an old instrument, wich records have 50/60/70 years, being played by a modern producer. Mostly of these recordings are already affected by time.

How can this old beasty synth, be combined and find a place between modern devices?

What kind of sounds will be recreated, by a different mind from those years,on a different musical context?

This could be a nice example of how we limited ourselves by the tendences of our contemporary music. I wonder if any of first persons who played the novachord on its first days, stills alive today, and what he would think after hearing a modern performance....

BTW Novachord is "he" or "she"???

[HideawayStudio]

BTW Novachord is "he" or "she"???

Hmm - definitely a "she" but she's got thighs like a rhino!

I'm Told that Still Having an Original Rare Panel is after 70 Years is Very Rare

[HideawayStudio]

OK... today's delights...

I've spent much of the day preparing for the PSU rebuild itself...

This morning was spent finalising the details for the new "cloned" mains transformers. Between the transformer company and I we've determined that the originals were somewhere in the region of 80Watts a piece. From the 270Watts a Novachord consumes (burns??) when a PA chassis is not fitted 110W is gobbled up by the heater transformer in the generator chassis alone!! This leaves 160 Watts for the two HT transformers in PSU chassis. The transformer company has now identified some laminates which are very close in dimensions to the originals - so much so that it's hoped the original end caps will fit onto the cores. The new transformers will come back in about 2 weeks.

Part of the day has been spent cleaning the wire wound resistors rescued from the PSU chassis to be reused in the rebuilt one. One of the resistors is part of an HT dropper network and has three tags ie. it's two resistors in series with a centre tap. This kind of thing was very popular in both PSU caps and resistors in the old days. There is a similar thing with a huge tunafish style !PCB! oil filled cap in the PSU which is two 4uF caps in one large metal can. This is where "deadly" pcbs are found in the Novachord but the real irony is that this cap is in pristine condition and is built to last for ever - it still reads a perfect 2 X 4uF!! I simply can't understand why the whole Novachord pcb oil contamination thing has been so overplayed. There is a pcb oil filled cap in the PA chassis and the pre-amp chassis - these are all in superb condition and could arguably be left in place (I haven't decided whether I will yet). Everything else is a mixture of wax/foil/paper or bitumen potted wax/oil/paper combo caps. It's the latter horrible item which is responsible for killing my psu, trying to kill Marc (or at least burn his house down!) and leading Phil Cirocco to think his Novachord was practically glowing in the dark with deadly chemicals!

The rest of the day has been a hard slog annotating the original circuit diagrams with my own reference designators and there aren't have any!! I then have had to identify and cross reference the resistor positions on the PSU centre tag strip with the schematic. Once identified the original resistors will be removed and replaced with modern equivalents using preferred values as, quite obviously, in 1939 electronic engineers just selected any random value they could get their hands on!! There are two caps in the PSU with a stated value of "0.0937" - how the heck they thouht this was going to be achievable in 1939 I don't know - an 0.1uF of 100N cap is definitely close enough in this application - that's only 6% off ie. well within the 10% I'd expect the tolerance of a cap to be in those days.

Anyway - all the resistors have been identified and I am expecting a large box to appear tomorrow full of high temp wire, sleeving and passives galore. I am hoping that by the end of the week the PSU, bar it's transformers, with have been rebuilt.

I have painted the end caps on the three chassis mounted HT chokes. Tomorrow morning I will carefully replace the old wire terminations with modern high temp wire and refit the end caps to the chokes and mount them on the repainted chassis. From that point on the PSU will be rebuilt. There are 12 caps and 19 resistors - it's fiddly but not really difficult. The most tedious bit is cutting each short length of wire, tinning it, and routing it from component to component.

I will try and post pictures of the PSU rebuild bit by bit tomorrow.

I know I really should be blogging this but I like the folk on VSE There will be an official blog but not until the generator is in a powerable state.

Identifying The PSU Centre Tag Strip Resistors:

The Centre Tag Strip Assembly:

The Deadly Tunafish Can Cap - Uggh Full of Deadly Tunafish Oil!:

[Mooger5]

Good job on the psu chassis!

There is a pcb oil filled cap in the PA chassis and the pre-amp chassis - these are all in superb condition and could arguably be left in place (I haven't decided whether I will yet).

Keep the vintage passive components for their sonic signature (even when placed in the psu) or ebay them for a good sum 4uF paper in oils are ideal as 1st order tweeter crossovers and treasured by japanese horn loudspeaker freaks.
Check the fieldcoils in the loudspeaker drivers as they were often used as smoothing chokes in power supplies. If the drivers are matched they´re probably worth a small fortune too.

There are two caps in the PSU with a stated value of "0.0937" - how the heck they thouht this was going to be achievable in 1939 I don't know - an 0.1uF of 100N cap is definitely close enough in this application - that's only 6% off ie. well within the 10% I'd expect the tolerance of a cap to be in those days.

They used connect a pair of insulated wires to obtain a specific value of capacitance. Connect the wires on one end only, twist them until you find the correct capacitance and trim the excess wire. 0.0937 isn´t 10n instead of 100 btw??
For the old wirewound resistors I´d use direct replacements. They´re still easy to get and are probably the inductive types really, so not much expensive.
Same for the paper caps. I see in the other restoration project they went for what look like Sprague Orange Drops. I don´t know if Polypropylene was around in early 20th Century. Probably not. It´s one of the lowest dielectric constants for audio, second only to Teflon and third to air, but by using such high-quality caps they might have compromised the original sound of the Novachord...

[Automatic Gainsay]

Wow, I can smell that from here! You've undertaken quite a job. Good luck with that.

While it filled my basement with a dense, acrid white smoke, I don't recall that it blew a fuse! Of course, that house did actually USE fuses (instead of breakers), and I often put higher load fuses in place in the basement... so that might explain it!

Could be that not all of that smoke was coming from the Novachord...

I'm not saying I put unsafe fuses in... merely those which were strong enough to handle more than a CD player turning on.
It was ridiculous how often I was changing fuses previous to that point.
Anyway, it's not like I crammed a penny in there!

[Automatic Gainsay]

This is so interesting and exciting.

Somewhere in the afterlife, there is a cranky old man smiling.