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Reviews Categories | Tools & Test Equipment for the amateur radio work bench | Hewlett-Packard 200CD Oscillator Help

Reviews Summary for Hewlett-Packard 200CD Oscillator
Hewlett-Packard 200CD Oscillator Reviews: 3 Average rating: 4.7/5 MSRP: $20.00 or so
Description: Big, heavy, all-tube Wein bridge oscillator with a big dial on the front, makes
great audio, lowfer signal source (it should anyway) and external BFO
Product is in production.
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W8AAZ Rating: 4/5 Mar 19, 2009 19:40 Send this review to a friend
Does some things others can't  Time owned: more than 12 months
Upsides-build is great. Low distortion, I have cal'd these with measured distortion under point 4 percent or better. Has a 600 ohm output impedance but in the case of a medium or high Z load, capable of vastly more output than most solid state units. Downside-most of them have a dual custom pot in the output attenuator. This pot can get noisy. If it goes bad, there is no available replacement except from a scrapped 200CD. I tried-the dual pot is not linear or log, might be antilog or something. Try a different dual pot and it just won't adjust right. Try to get a late version that uses miniature glass tubes. Make sure the tubes test 100% good. Beware of old power filter caps failing. And don't try to get the dial cal better than about 2% error tracking, it can't be done. Use a counter if the freq. is critical. Don't fiddle with the adjustments without the proper manual for your series. Keep the geartrain lubed lightly and dust and dirt out of the big ganged capacitor. Have fun with it.
WB2WIK Rating: 5/5 Feb 11, 2005 16:12 Send this review to a friend
Long live the Wien Bridge  Time owned: more than 12 months
I had to comment after reading Alexandra's recent review of this golden oldie. They don't make 'em like this anymore. I've had a 200CD since 1973, and it was probably almost ten years old then.

Extremely low distortion, output-leveled audio oscillator good to 600 kHz. Distortion is so low it's difficult to measure (in the noise level on the HP 331A distortion analyzer) and, let's see -- I think I probably never shut mine off from about 1973 to 1980 or so, while I was doing a lot of bench work -- and it still has all its original tubes. Not to mention the original light bulbs. Oh yeah, the Wien bridge oscillator uses tungsten filaments of light bulbs in the bridge...ingenious.

NS6Y lives close enough to HP's original Palo Alto lab that she might know this is the second generation of the product that actually put HP on the map, when they sold a zillion of them to Walt Disney back in about's a famous story amongst us HP ex-pats.

ALEX_NS6Y Rating: 5/5 Feb 11, 2005 07:12 Send this review to a friend
They don't make 'em like that anymore  Time owned: 0 to 3 months
This is how electronics used to be done. This is big, heavy, ugly to all but dyed in the wool 'tronics nuts, and it will help warm up the room. It's also a really neato oscillator that puts out a decent sine wave over a wide range, and I believe the tube life/reliability is really high for these units. Can be used for morse code practice, all-around source of audio and signal up into the low end of broadcast AM band, and the "user interface" is easy to figure out: On/Off switch, big ol' dial for freq, a pot for level. Look at the dial to tell what freq you're on, mine's pretty close.

What's really cool about these is, if you have a "general coverage" receiver with no BFO, set up up next to your reciever, take a wire that goes from the pos. output on this to a few turns around your SW reciever's antenna, set up for 455 kHz, and tune around until you hear a rushing sounds on your reciever - if your reciever is one one of those Donald Duck SSB QSOs, this will make it turn into intelligible voice! It's wild! No contact with your rig necessary, a little coupling to the antenna is all you need. You'll have to re-tune a little as you change bands depending on your reciever, but it works - by using this I was able to save the $10 I'd spend otherwise on a Ten-Tec BFO kit, and it's made to endure being adjusted fairly often.

These things are cheap at hamfests, swapmeets, and on Ebay too. Electronics history is great - Electronics history that will help me get my CW copying skills back and be useful around the lab here is even better!

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