The HP Original for sale

The 200C isn't the original 1939 model. It was the last tube instrument HP sold (CRTs and PMTs apart) and was in their 1985 catalogue. (Yes, I have one.) ;)

Cheers

Phil Hobbs

Wow, that late? I'm trying to think of other 1930s era industrial designs that had such a long life cycle. GG1 locomotives? Iowa class battleships? GM straight six?

Not '30s, rather '40s, but B52s are still flying and from what I gather, they'll be flying another 30 years and perhaps longer. There are three generations of pilots who have flown the same bird.

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** That was the 200A - see full manual with schem:

FYI:

Since my mid teens, I have owned a fairly similar oscillator - all valve using a large, dual tuning gang from an old radio.

A 30:1 reduction, worm drive is fitted to the gang which is fitted inside its own steel box. Means the unit works perfectly with the cover off.

A pair of 6AM6s (aka EF91s) operating as triodes form the oscillator, amplitude is stabilised by an R53 glass bead thermistor. A single 6BQ5 is used as a cathode follower for low Z output.

Has three ranges, covering from 18Hz to 22kHz.

The original metalwork and basic circuit was built by staff at the Kodak factory at Coburg in Melbourne as a low frequency oscillator for motor drive, it originally used a large, dual gang WW pot.

I fitted the tuning gang and other bits to make it a general purpose audio oscillator including square waves using a 12AT7 wired as a Schmitt trigger.

I still have it and gave at a major overhaul a couple of years back.

.... Phil

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** Well there is the DC3 with many flying examples.

But the 6L6 beam tube takes the prize since it has *never* been out of mass production since 1936.

..... Phil

B52s have an expected ~90 year product lifetime, 1950s to 2040s.

DC3 / C47 from Douglas Aircraft.

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-TV

The manual mentions a rackmount model - I'd never heard of that! Google only turns up an image of a rackmount "200CDR" which looks to be a later product with a significantly different design

Tangentially related - the audio sine wave oscillator I've been using for several years is a solid state box labeled "LofTech"; manufactured by "Phoenix Audio Labs, Manchester, CT".

It's mostly full of LM13600s and TL074s with date codes from the middle of 1986. I don't have a THD analyzer so I can't say what its specs are now in that regard; visually at least the sines it puts out look math textbook perfect on a scope. The brochure claims a maximum THD of 0.5%

Unfortunately frequency stability isn't good - it's very drifty with time and temperature; sometimes 3-5 Hz up and down over time just sitting in a shop at room temperature, which is annoying. The brochure scan online doesn't say anything about drift specs so I don't know if that's normal for the product's design or if it should be serviced.

I managed to find a schematic:

And I've probably got one, too. :P

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** See link:

The unit has a single pot that sweeps the audio band, assuming it is a carbon track type, frequency stability WILL be poor. Firstly, the track has a large tempco plus the wiper will have some drift after setting. So it is not faulty.

My bench oscillator use a dual gang WW pot with hundreds of turns plus it only covers a decade range. A rotary switch choses which one of five starting at 2Hz. Drift is very small.

The all valve one I mentioned also has low drift, once it fully warms up, as the frequency determining bits are an air capacitor and MF resistors.

.... Phil

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** The schem shows a form of VCO with a linear to log converter - reminds me a lot of a Moog Synth.

It will drift with temp etc ....

..... Phil

Still waiting to see your list!

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

Got it, thanks. Probably time to invest in something a little better.

Engineers probably worked for years to design clever "DCOs" which frequency-locked analog oscillators to a temperature stable reference clock, divided down under microprocessor control.

Now musicians want the drift back. The drift sounds "organic."

Way before microprocessors, there were "top octave generators", strings of dividers running off a strategically-chosen crystal.

They were too accurate, so they sounded thin.

Cheers

Phil Hobbs

The 200CD was the last all tube instrument that HP made. "The HP200CD was a serious competitor in the HP longest product life contest. It remained in the Hewlett-Packard Test and Measurement catalog until 1985, a full 33 years which is rare in the electronics industry. Last, but not least, the 200CD was the last fully vacuum tube instrument produced by HP." There were some later instruments that still contained a few tubes. I don't recall the numbers.

Only one? I've got eight HP catalogs:

Most catalogs have been scanned and are available online at: (2.2MB) (32MB)

The first catalog (1943) has some info on the 200C and 200D oscillators:

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

I'm pretty sure CD and I were both talking about having an HP200C, not just the catalogue. Mine is actually the slightly newer 200CD, which was the last tube model they made.

Cheers

Phil Hobbs

They're currently being refitted with modern turboprops.. Basler.

Beautiful aircraft!

--sp

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Best regards,  
Spehro Pefhany

I think I'm right in saying the only HP sig gen I have is an old analogue one (probably Wien Bridge internals) that only covers 10hz to 512Mhz IIRC. It's a joy to use because it's so simple, unlike some of the others which require considerable re-familiarisation with every time I break one of them out in anger. This wonderful simplicity is why it gets used more than any other sig gen I own unless its limited range makes it unsuitable for the task. Sorry, Phil, but that list will probably never get written; I just don't have enough time to itemise everything.