Nagard Double Pulse Generator Type 5002C


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1956 valve oscillator mayhem machine

There is little information online about this crazy doomsday device. Nagard was a UK company based in Brixton Road, London (later Surrey), who made oscilloscopes and test gear from 1949 until 1962 when they were acquired by Advance Components (I also have an Advance H1E valve signal generator). I found Nagard data sheets for the 301 Wide Band Oscilloscope and the 321 Oscilloscope, as well as the earlier 5002A model from 1956 which just seems to be missing the extra 100 Ohm outputs of the 5002C. Another website has Swedish spec sheets for all 5002 models. And that's about it at present. Please let me know if you know anything about the 5002C, or have a schematic (if one even exists).

I was lucky to acquire it on eBay for an unbelievably low price "untested". As soon as I saw pictures of it, I knew it was very special and an essential purchase. From another era, it required an old Bulgin power lead (which cost a third as much as the unit itself!) before I could even find out if it worked. A tech friend replaced the broken power switch and checked it over (applying power to old valves can cause damage if the power supply is out of spec). Miraculously he gave it a full bill of health, although he had equally little idea about what it all did.

The rear panel is completely blank, all the connections and controls being upfront like modular and test gear (power goes in the right hand side). Removing the left side panel also reveals a bewildering grid of twenty-nine calibration knobs, all labelled yet incomprehensible without documentation and a PhD in electronics. After twiddling a few, it occurred to me that I should have left them as they were rather than take things even further from "normal"...!

Nothing about this thing is normal. The quality of construction is from a different age. You can no longer buy equipment this well made. The elegant, understated design looks very classy with featherlite black text on the beautiful offwhite panel. (Modal's 002 synth surely owes a debt to this unit with its similar colour scheme and layout.) The huge dials and rotary switches are a joy to behold and excellent in use, designed for precise repeatable settings - you can really play them with tiny subtle movements causing changes that would be impossible on modern instruments with their uselessly small knobs. Just a faint touch can nudge between radically different sounds either side of a Chaos Zone - these are what I call the bizarre movable regions where an otherwise continuous sweep is interrupted by weird non-linear fractal cliffs of insanity that separate the saner foothills of expected behaviour. These zones are so narrow (zero-size really) that even with large dials, all it takes is the tenderest caress, not even turning it at all, just gentle pressure on the knob itself, and suddenly you are flung into an abyss of Uncertainty. To make things even curiouser and curiouser, these regions move about depending on the settings of other dials and switches, such that they occupy a strange non-Euclidean extra-Heliospheric Space Between Stars...

All of this is probably way out of spec, but it makes for a unique and wild experience to play around with it. As well as External and Internal Trigger, there is a very satisfying front panel one-shot button which causes a single pulse. The main three large dials govern Rate, Delay and Width of the pulse; these (and the External Trigger Level and Output Voltage Multiplier) are the only continuously variable dials, all others being rotary switches to set their associated ranges. Turning the Rate knob right round produces a rising sweep like a motorbike changing gears over diminishing pitch ranges which themselves vary oddly. Sweeping the pulse Width dial is the most cosmic of all, creating a thick, deep phasing effect. Sometimes you can play weirdly stepped harmonic series tones (albeit with some unexpected pitches too which defy explanation) that sound truly magical through a reverb. There are curious points on the dials where the signals cross over from one stable pitch to another via a dark place of static noises and aggressive analogue glitches. Even with such large knobs, the resolution is very fine, and these sudden leaps over deep chaotic chasms are like wild asymptotic instabilities on a Mandelbrot mountain range of infinite zoomability.

Inputs and outputs are on UHF connectors (often found in radio test gear) which also accept 4mm banana jacks with separate Earth for interfacing with signal generators and oscilloscopes. The output signal is so chaotic and un-waveform-like, it's hard to even tame it and catch it on the scope. One must take care when using it with modern audio gear, as the output can range from 20 mV all the way up to 50 V! The data sheet describes it as having "sufficient power to operate electro-mechanical devices such as relays, counters, etc.", which could make for some wonderful kind of sex toy! Frequency reaches from 0.25 Hz to 2.5 MHz, way beyond merely audio ranges. The pulse Width and Delay can be smoothly changed (in seven ranges) from 0.2 microseconds to 2 seconds, with no duty cycle limitations allowing pulse width to be altered continuously until it becomes a square wave.

Inside is a mad box of frogs, with huge components mounted on both the top and bottom of the chassis. The rotary switches have intricate mechanisms which turn gears in a most fascinating fashion. As well as an industrial strength power transformer, there are many, many valves; some are gigantic! The biggest ones are warm like light bulbs, others glow orange. After being on for a while, they all glow a bit more. A heavy duty fan points at three huge 3cm x 9cm cylindrical TCC aluminium capacitors, which are labelled:

     TCC
 "LECTROPACK"
 ELECTROLYTIC
    100uF
350V. PK. WKG.
TYPE CE 10 L E
CAN NOT ISOLATE

I found a half-page advert for them on Page 2 of Practical Wireless magazine from February 1958, which shows their age.

The small yet thick 240V fan is insanely loud (unusably so). Since it doesn't even point at the hottest valves, I think that a better method of cooling will be to use the eight big slow 120mm fans in the top of my rackmount cabinet above Nagard's open lid, which are ironically quieter than its single fan. So two friends helped me desolder the wires to the noisy fan, which proved very difficult to even access them. It was then a three-man lift to get the super heavy (19kg) Nagard back into the cabinet and lift the rack shelf up a few notches so that it now sits directly beneath the fans. So sadly not really a portable option for live performances :-/ Audiences will instead have to come and visit me! :-)

Luckily the outside chassis is relatively unmarked, just a few small edge scratches, hardly indicative of its sixty years of age! The military-spec thick solid metal front fascia would surely see off any attacker foolish enough to dare. I cleaned off some sticker residue and it looks great. I will add some photos when I find my camera charger, but wish I'd been able to photograph the internals before the epic struggle to mount it into the rack. And I long to get a video camera to make a demo of these extraordinary sounds. An audio-only demo would be sonically interesting, but won't make much sense without visuals showing what knobs are turning - seeing is believing.

WOW! I just plucked up courage to power cycle the Nagard with speakers on (fearing it might blow the speakers) and found it makes the wackiest startup noise!!! Unlike my solid state oscillators, which make a pleasant chirp as they fade in/out on power-up/down, the valves take a few seconds to wake up, then it sweeps a manic phase shift before changing pitch (repeatably, the same way each time) = instant Throbbing Gristle! It also reminds me of some of the alien generator sounds from the first Cluster album before they even had any synths.

The house is now full of the heady aroma of warm valves and/or vintage dust :-)


© copyright Malcolm Smith 2018-08-12 - last updated 2018-08-13 - links verified 2018-08-12