HP Model 200CD Wide Range Oscillator - Page 1
Forum section: electronics / testgear

author: DanielSpokane
author_rank: Regular Contributor
timestamp: April 09, 2018, 02:39:08 am
content: I'm cleaning out my bench area and have this old HP Model 200CD Wide Range Oscillator that I picked up at a thrift store a while back. I don't need another signal generator / oscillator (I have a Rigol DG1022 and an HP 204C)... but I've had a hard time throwing this thing away. Any fun ideas on what I should do with it?

author: tautech
author_rank: Super Contributor
timestamp: April 09, 2018, 04:31:29 am
content: Someone will want it maybe just as a historic piece of HP gear.Power it on and check it's still roughly in spec (frequency and amplitude) and take some screenshots with your DSO then list it here:https://www.eevblog.com/forum/buysellwanted/Remember to 50 ohm couple it.

author: Tony_G
author_rank: Super Contributor
timestamp: April 09, 2018, 05:04:30 am
content: I don't have any suggestions but it occurred to me that I don't think I published the photos of my 200CD (before I sent it off to a better home).As you can see my one wasn't in anywhere as good a condition when I got it - It was from an estate sale and had clearly been sitting on a shelf for a while:Mine also didn't have the leather handle attached, though the previous owner did a good job on creating an alternative:Taking the cover off is really what it says, the entire shell of the unit removes. In this shot you can see down into the variable capacitors that control the frequency - Simple air dielectric ones, if you look closely you'll notice that one of the ceramic trimmer capacitors has broken up:Here you can see the output & power supply tubes - The cans at the back (in front fo the rectifier tube) are actually capacitors - They used to build several into one tube - You can get modern replacements custom made if you're renovating an old device:On the other side you can see voltage amp tubes and the range resistors that are part of the wien bridge in the oscillator. This circuit is apparently based on Bill Hewlett's university thesis - The first version, the 200A was bought by Disney to be used to test the sound systems for the legendary movie Fantasia:Here is the bottom of the unit - The most interesting feature here are the "Black Cat" capacitors - These seem to sell for crazy money in the guitar amp world because musicians like the sound that they bring when used in an amp circuit. From memory they're a wax covered paper electrolytic capacitor so in my opinion, no matter the sound, they should be replaced:The final shot is of a cloth tag that was originally attached inside the instrument showing that it had been sent back to HP for service in June of 1969, a year before I was born:Anyway, these are great old pieces of kit so hopefully you'll find something to do with it that gives it the respect it deserves.TonyG

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 09, 2018, 05:33:31 am
content: Wasn't the model 200 oscillator the very first product out of the HP garage?

author: kj7e
author_rank: Frequent Contributor
timestamp: April 09, 2018, 05:50:44 am
content: Quote from: Richard Crowley on April 09, 2018, 05:33:31 amYes, more info here;http://www.hp.com/hpinfo/abouthp/histnfacts/museum/earlyinstruments/0002/

author: DanielSpokane
author_rank: Regular Contributor
timestamp: April 10, 2018, 05:16:37 am
content: Thanks for the info everyone. Very interesting history. I knew there was a reason I could never bring my self to throw this away.Need to find it a good home!I'm pretty tied up with work right this moment but sometime in the next week or two I will hook this up and will take some readings.