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Novachord #346 Inspection & Initial Wakeup

Posted: Sat Oct 10, 2009 2:35 pm
by HideawayStudio
IT'S ARRIVED - Probably the UK's only Novachord!!!

The beast turned up at 5:30pm yesterday and we had a battle to remove it from the enormous crate before it got dark (and cold!). About an hour later my friend Patrick, my fiancee and myself successfully managed to carefully lift the top lid (quite heavy), bottom frame (heavy!), and generator chassis (Freaking Heavy!) into the house. This 70 year old, 163 tube (valve) monster weighs 1/4 ton!!

To my huge relief the instrument has not sustained any damage in transit at all!

After an evening of picking hundreds of polystyrene chips from between all of the tubes in the generator chassis (seemed like a good idea at the time!) and then going over the whole thing with beeswax and scratch cover it's really not looking bad.

The good news is that generally the sands of time have been very kind to this beast. Parts of her are in amazing condition - the front panel controls, and top wooden casing are in very good condition and the Bakelite & Plaskon keys (see note below) are practically mint and have not yellowed, chipped or cracked at all.

The bad news is that towards the end of the evening we identified the reason why the beast filled AG's house with smoke! It turns out that it's suffered an absolutely typical Novachord failure mode but was sadly not caught quick enough. There are two capacitor pairs potted in metal cans located in the pre-amp "channel" within the generator chassis. These caps decouple the HT supply and are potted in bitumen. They fail S/C and the bitumen melts and pours through the chassis holes. Unfortunately, in this case, the lack of functionality was not noticed until it was too late, as sadly Marc was away from the instrument at the time. This has led to much more serious secondary damage in the PSU chassis where, on first inspection, a prolonged dead short of the HT rail has caused at least one of the mains transformers, the supression choke, probably the valve rectifier and several resistors to fry. In short it's looking like the entire power supply, including transformers, will have to be completely rebuilt. I have a company lined up to rewind the transformers and all of the remaining parts are easy enough to get hold of - the issue is that everything will have to be very carefully noted before I remove all of the charred wiring and passives and rebuild the PSU. Assuming I can get the trnasformer and chokes rewound fairly soon this is about a months work (part time).

Here are some initial piccies of what is a truly amazing piece of vintage equipment...

The Base, Top Casing and Generator Chassis:
DW_NovaInPieces.jpg
The Front Panel Controls on the Generator Chassis in Amazing Condition for a 70 year old Beast!:
DW_NovaGen.jpg
The Novachord Keys and the Keying Circuits:
DW_Novakeys.jpg
There are some it's guts now on my Synth Guts thread..... I will be starting an official wakeup/restoration blog but I've yet to decide where to host it. In the meantime I will make a new postings on VSE on the subject.

The next step is to carefully check the tube heater transformer (a big b$astard!), remove a rather frightening chassis mains decoupling capacitor, test for any any S/Cs on the filament output and then slowly attempt to wind up all 144 tube heaters in the generator chassis. At this point I will attempt to take a decent piccy of the whole lot running in the dark :)

Note on Plaskon:

The white keys on the Novachord are made of a substance called Plaskon. Like Bakelite, this is a very early plastic. Plaskon was developed and introduced in 1931 by the Toledo Scale Company to incorporate into their weighing scales. They began with the urea compound and used cellulose as a filler. They also made a few other chemical additions to keep the material from fading (they wanted a bright white color for the scale basin). Because of the superior properties and the help of a great marketing department, plaskon soon became the plastic of choice when a manufacturer wanted an end product to be a color other than the standard bakelite brown and black. Many pre-war radios in colours other than black or brown feature casings made of Plaskon.

Re: The Novachord Has Arrived in One Piece!!

Posted: Sat Oct 10, 2009 4:57 pm
by Automatic Gainsay
It is a horrible tragedy that that much damage happened, the ONE time I happened to leave it on for any length of time, AND happen to not be in the room when the problem started. :( Were the amp tubes damaged at all? They didn't seem like they were!

However, I am absolutely thrilled that it's made it there in one piece!

Re: The Novachord Has Arrived in One Piece!!

Posted: Sat Oct 10, 2009 5:01 pm
by Mr Rich
1/4 ton eh... ok, that's heavy.

I'm totally certain that this thing will reward your troubles in the long run. Well done Sir!

Re: The Novachord Has Arrived in One Piece!!

Posted: Sat Oct 10, 2009 10:00 pm
by HideawayStudio
Automatic Gainsay wrote:It is a horrible tragedy that that much damage happened, the ONE time I happened to leave it on for any length of time, AND happen to not be in the room when the problem started. :( Were the amp tubes damaged at all? They didn't seem like they were!

However, I am absolutely thrilled that it's made it there in one piece!
Hello... Don't blame youself for this - it really is to be expected of something this age. It would have happened sooner or later anyway. Just to be clear - the fault is in the pre-amp in the generator chassis not the power amp. The power amp may well have issues but at the moment it's not a priority as I can gain a line output on a XLR connector from the centre tapped pre-amp output transformer. The speakers need reconing - another reason why the PA is not a priority for now.

I've just started to examine the power supply chassis in more detail. This really is where the damage has occured. I will need to disconnect the wiring from each transformer and choke in turn and test in isolation. I then need to replace all of it's capacitors. The resistors, bar possibly one, look and test fine. Some of the wiring is looking fairly nasty - I may well sleeve it in silicon tubing or heatshrink to improve it's looks/insulation.

I have yet to test any of the tubes but I suspect two in the preamp are fine. I strongly suspect that the HT rectifier and possibly the final power pentodes (for noise cancelling!!) on both the +270V and +70V rails are now very tired after driving such a horrible load.

I may be tempted to run the PSU chassis up using a 40Watt safety limiting bulb in series with the AC input just to see what happens. This is just about the kindest/safest way to power up suspect vintage electronics.

Power supply aside, to be honest - the more I look at this thing the more amazed I am at it's condition. It's in a totally different league to Phil Cirocco's when he first set out. The wooden case is superb which the exception of some deep scrape marks on the panel in front of the keys - I have filled these with scratch cover and polished and they don't show anything like as badly but still I would like to have this professionally repaired in due course. I've just examined and tested the expression pedal which is made up of a variable capacitor and it's in superb condition. Often these are very badly corroded and the wiring is bad - not in this case. I've just read a perfect sweep on my capacitance meter from one pedal end stop to the other. I've also just replaced the mains cord with a modern vintage look cloth covered cable in a brown/bronze colour and sleeved some of the mains cabling inside the rear cabinet for added safety. The internal mains cabling and mains switch buzz out just fine.

The Novachord Arrived in a Huge Crate Weighing 794lbs!!
DW_Novacrate_Cropped.jpg

Re: The Novachord Has Arrived in One Piece!!

Posted: Sat Oct 10, 2009 10:28 pm
by Automatic Gainsay
:::shakes head smiling:::

The Novachord couldn't be with a better person. I am SO glad you wanted it!

Re: The Novachord Has Arrived in One Piece!!

Posted: Sun Oct 11, 2009 1:53 am
by HideawayStudio
Automatic Gainsay wrote::::shakes head smiling:::

The Novachord couldn't be with a better person. I am SO glad you wanted it!
:) Thanks... she'll live again - that I promise!

346's Serial Number Plate - Note the Usage Restriction!
Novaplate_346.jpg

Re: The Novachord Has Arrived in One Piece!!

Posted: Sun Oct 11, 2009 3:50 am
by dr funk
Great stuff! I can't get over the condition of the front panel - astonishing for a 70 year old instrument. Keep up the good work - can't wait to hear it in action!

Frank

Re: The Novachord Has Arrived in One Piece!!

Posted: Sun Oct 11, 2009 4:49 am
by Ashe37
a valve rectifier?

hmmm... pics!

Re: The Novachord Has Arrived in One Piece!!

Posted: Sun Oct 11, 2009 6:18 am
by Automatic Gainsay
It's thrilling to see it sitting next to an English radiator! : )

I'm sure its owner previous to me would be delighted. : )

Re: The Novachord Has Arrived in One Piece!!

Posted: Sun Oct 11, 2009 9:12 am
by HideawayStudio
Ashe37 wrote:a valve rectifier?

hmmm... pics!
:) Oh Yes... a big bottle type too... 270 volts input at up to 175mA ie. 47 Watts of HT!!! Ouch! :?

The 270V DC HT Rail Full-Wave Rectifier - a 5V4G:
5V4G.JPG
Here is the datasheet!

http://www.r-type.org/pdfs/5v4g.pdf

Re: The Novachord Has Arrived in One Piece!!

Posted: Sun Oct 11, 2009 9:28 am
by Ashe37
awesome
and huge!

Re: The Novachord Has Arrived in One Piece!!

Posted: Sun Oct 11, 2009 10:32 am
by HideawayStudio
Ashe37 wrote:awesome
and huge!
It looks even better in the dark!! I've just tested it - this is the first tube to be tested from the Novachord and, amazingly, despite it's ordeal, it's reading good!

First Glow!:
FirstGlow.jpg
The Main HT Rectifier in Action!
First Novatube Test.JPG

Re: Novachord #346 Inspection & Initial Wakeup

Posted: Sun Oct 11, 2009 4:11 pm
by cornutt
I'm still amazed that it survived being shipped halfway around the world! Good luck!

Re: The Novachord Has Arrived in One Piece!!

Posted: Sun Oct 11, 2009 4:16 pm
by cornutt
Ashe37 wrote:a valve rectifier?
This has been mentioned in another thread recently, which I can't find right now... It provides a "soft start" for the high voltage rail it feeds, since the current comes up over a period of several seconds as the heater warms. And, reliable solid-state rectifiers weren't available back then.

Re: Novachord #346 Inspection & Initial Wakeup

Posted: Sun Oct 11, 2009 5:18 pm
by seamonkey
I was curious while following this thread, what exactly the Novachord sounded like. I remember it being referred to in the same vein as the Mellotron but couldn't remember where it had been used before.

Here are some audio demos from the Novachord Restoration Project website, I especially liked the improvisations located near the bottom of the page. One can clearly hear the individual sounds of the Novachord versus being played within an ensemble.
Very beautiful.
I'm so happy this has found a home to be lovingly restored to it's original beauty.

http://www.discretesynthesizers.com/nova/intro.htm