You can add a passive low-pass filter on the osc output. There are several sources for such... like Allen Avionics. The buffer amplifier operates at unity. The input has a pot to attenuate for fine level setting. The output is attenuated by a 600 ohm network. I don't think there is much to be gained with replacing the buffer amp in terms of noise since the resistors add to this. I haven't seen a huge reduction of distortion replacing the buffer op amp.
The newer ultra low distortion op amps seem to achieve there best distortion at levels below 3 volts rms. This oscillator runs at 7.07V rms.
The newer ultra low distortion op amps seem to achieve there best distortion at levels below 3 volts rms. This oscillator runs at 7.07V rms.
To anyone, since I don't presently have time to read through all the pages... I have two 339a units that used to work fine (meet specs on osc to analyzer). One set has all knobs damage and plastic banana jack breakage (bjb) the other set is cosmetically mint (scm). Both were unplugged for a couple of years, now I needed to use them again, and neither osc section works. No output period. Using an external osc I determined that both sets - the analyzer sections appear to be working properly.
Since the Analyzer and Osc. PS are separate, I first suspected a failure in the +/-15 supplies for the osc, but nope right up there at +/-14.8. Are there any known "failure modes" in these sets that anyone can suggest that would kill both units osc sections like this from just not being powered up? I'd welcome comments or suggestions before I start tearing the sets apart (or pulling what remains of my hair out...).
My EM = abcr100k@hotmail.com
Many thanks,
Steve
@ slbender
Well age.
Try working the pots for a while, then the switches to promote cleaning.
Grab a copy of the manual. There are test point you can check. If it still not working report what you have at these test points.
Other than this I can't think of any common problems with the oscillator. I assuming these units are stock. No mods.
Well age.
Try working the pots for a while, then the switches to promote cleaning.
Grab a copy of the manual. There are test point you can check. If it still not working report what you have at these test points.
Other than this I can't think of any common problems with the oscillator. I assuming these units are stock. No mods.
Hi Steve,
If they once worked and don't now...what davada said. Then, I'd go through it and replace the electrolytics and try again. I have two of them. redid one and just did the power supply caps and an unobtainium power IC on the second one. Number1 also had some sort of ground issue that Richard found and fixed along with a couple of mod issues I couldn't sort out.
There are two types by on/off switch: one with a push button another with a toggle. The push button is more desirable--RNMarsh.
Somewhere here there is a wiki and then a blog I did to ID the changes these guys pioneered. Some folks are profiting from this as I've seen ebay 339As for sale with the described mods.
Keep the good folks where informed with pics and numbers etc. It's a lot of fun getting this stuff going.
@Richard, I'll be ready to tackle the OSC Output filter along with cleaning up the monitor output too.
Cheers,
If they once worked and don't now...what davada said. Then, I'd go through it and replace the electrolytics and try again. I have two of them. redid one and just did the power supply caps and an unobtainium power IC on the second one. Number1 also had some sort of ground issue that Richard found and fixed along with a couple of mod issues I couldn't sort out.
There are two types by on/off switch: one with a push button another with a toggle. The push button is more desirable--RNMarsh.
Somewhere here there is a wiki and then a blog I did to ID the changes these guys pioneered. Some folks are profiting from this as I've seen ebay 339As for sale with the described mods.
Keep the good folks where informed with pics and numbers etc. It's a lot of fun getting this stuff going.
@Richard, I'll be ready to tackle the OSC Output filter along with cleaning up the monitor output too.
Cheers,
Since I can't redo it in the same post try this:
which works.... Hewlett Packard HP 339A Agilent 339A | eBay
and here is the other one: HP 239A Ultra Low Distortion Pure Oscillator - upgraded Read | eBay
And what is most strange, I thought after I spent all that time working on the 339A and then the wiki and blog I thought, ya know folks are just going to use this for their profits. Imagine that.
So much for hoping to find another affordable analyzer or oscillator again.
which works.... Hewlett Packard HP 339A Agilent 339A | eBay
and here is the other one: HP 239A Ultra Low Distortion Pure Oscillator - upgraded Read | eBay
And what is most strange, I thought after I spent all that time working on the 339A and then the wiki and blog I thought, ya know folks are just going to use this for their profits. Imagine that.
So much for hoping to find another affordable analyzer or oscillator again.
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