HP 200CD Valve (tube!!) oscillator problems?

"H and P were not that savvy at transformer design."

Maybe not, but BOTH transformers (T1 PN# 200CD-9, HF & T2 PN# 9120-0016, LF) are wired to the range switch(s). I think what you're trying to say is, the LF & HF are combined into one output, as that's how the switches are wired. Each transformer has it's own EL-86.

I love my old HP tube oscillator... I think mine's a 200AB, because it covers the audio range only, but I don't have it handy at the moment to check.

PRR mentioned calibrated attenuator sets and "gain sets." Maybe I'm an anachronism, but I use 'em. I've got two Gates stereo gain sets, as well as some H-P calibrated 600-ohm attenuator sets. I scanned the manual for the Gates gain set, which can be found here. The circuit could be DIY'd if one were sufficiently motivated. Probably easier just to hunt around for a used one, though. Gain sets are, or at least were, used by every broadcast station for their annual FCC-mandated "proofs" (proof-of-performance tests). Calibrated attenuator sets come up often on eBay. These sell for pretty cheap, usually.

I have an AB as well. A nice 4 rack space unit, it is. I wish I had a use for it. :roll:

(resurrecting thread :grin: )

I have a 200CD as well.

A question(this hit me while driving in the car today), this oscillator is capable of crankin many volts (24V AC!!). I can't think of anything I do with audio at present that would need to go so hi.

What were they building these things to test?

Regards

ju

Well---you could drive a single 6AS7 on the bench to a useful output directly if you liked. And cooking resistors, as PRR mentioned.

I have a 200CD sitting on the floor at the moment, but it's reassuring to think it's there for an emergency :green: or when I need MORE COWBELL!! errr... I mean voltage.