Hi,
I recieved the 339 yesterday afternoon. From last night and all day today it is working very well. better than spec on both generator and analyzer !!
Here is what I found to cause problems:
Ground loops -- connected to other equipment and one I had (and maybe you also) was a ac power ground pin with intermittant connection. The thd+N will be high (N) if you have grounding issues and -
your 400Hz filter does not work. So, you cant just hit the 400Hz HP filter and get rid of the grounding power freq noise.
Then the tricky problem. Due to aging of R & C values there is a problem with obtaining a null sometimes. The osc freq and the null freq can get too far apart and then you read high thd+N. You will have to use the fine frequency adjust on the front panel to be a little on the high side on some ranges and then the auto-null will grab it and give you a nice null.
From 10Hz to 20KHz, the thd is well below -100dB. Your analyzer shows max of -100dB. I touched up the trim some with my analyzer so the thd is lowest possible. At 1 KHz it is in the 120's.
You did good on the mods.
THx-RNMarsh
I recieved the 339 yesterday afternoon. From last night and all day today it is working very well. better than spec on both generator and analyzer !!
Here is what I found to cause problems:
Ground loops -- connected to other equipment and one I had (and maybe you also) was a ac power ground pin with intermittant connection. The thd+N will be high (N) if you have grounding issues and -
your 400Hz filter does not work. So, you cant just hit the 400Hz HP filter and get rid of the grounding power freq noise.
Then the tricky problem. Due to aging of R & C values there is a problem with obtaining a null sometimes. The osc freq and the null freq can get too far apart and then you read high thd+N. You will have to use the fine frequency adjust on the front panel to be a little on the high side on some ranges and then the auto-null will grab it and give you a nice null.
From 10Hz to 20KHz, the thd is well below -100dB. Your analyzer shows max of -100dB. I touched up the trim some with my analyzer so the thd is lowest possible. At 1 KHz it is in the 120's.
You did good on the mods.
THx-RNMarsh
Hi Richard,
I appreciate the update on the 339A.
Grounding pin ah ha that may be one of the gremlins...
and explain why sometime things just don't work right
as we know intermittent can be the most difficult of
troubleshooting tasks.
AND
I've learned something new again, that the Frequency Vernier
pot is to be used -- to help align the frequency and null.
And
Thou shall ignore the teaching of Ron Popeal on this, we shall not
"set it and forget it."
RATHER
We shall set it then adjust it so we align the oscillation frequency and null.
I couldn't confidently determine THD with my equipment and it is nice
to know it is not all FUBARed up.
Especially nice to know that I did good on the mods.
I never want to see that waterboard again. ; )
I appreciate the update on the 339A.
Grounding pin ah ha that may be one of the gremlins...
and explain why sometime things just don't work right
as we know intermittent can be the most difficult of
troubleshooting tasks.
AND
I've learned something new again, that the Frequency Vernier
pot is to be used -- to help align the frequency and null.
And
Thou shall ignore the teaching of Ron Popeal on this, we shall not
"set it and forget it."
RATHER
We shall set it then adjust it so we align the oscillation frequency and null.
I couldn't confidently determine THD with my equipment and it is nice
to know it is not all FUBARed up.
Especially nice to know that I did good on the mods.
I never want to see that waterboard again. ; )
339A loop-back test results -
And here is your 1000Hz (10 X 100) distortion reading with osc out to analyzer in; indicating -102dB:
THx-RNMarsh
And here is your 1000Hz (10 X 100) distortion reading with osc out to analyzer in; indicating -102dB:
THx-RNMarsh
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Richard,
Okay. Does it matter if the 1000 Hz is set via 10 x 100 or 1 x 1000?
When you input is it straight OSC OUT to DIST ANAL or do
we need to add 600 ohms resistance? I know when I tuned
it you mentioned to go straight in...when I look in the HP 339a
manual they always have 600 load on the DIST ANAL input.
It sure beats the hell out only -78 dBv. ; )
Okay. Does it matter if the 1000 Hz is set via 10 x 100 or 1 x 1000?
When you input is it straight OSC OUT to DIST ANAL or do
we need to add 600 ohms resistance? I know when I tuned
it you mentioned to go straight in...when I look in the HP 339a
manual they always have 600 load on the DIST ANAL input.
It sure beats the hell out only -78 dBv. ; )
@Sync You don't need the resistor. Keep in mind the noise goes up with source resistance.
Grounds need to be clean. The resistor is required when calibrating the unit to keep the noise down and to prevent the op amp from oscillating. Remember the max gain is 80dBFS.
The 339A is high sensitivity analyzer and susceptible to RF. Shielded cables must be used.
Grounds need to be clean. The resistor is required when calibrating the unit to keep the noise down and to prevent the op amp from oscillating. Remember the max gain is 80dBFS.
The 339A is high sensitivity analyzer and susceptible to RF. Shielded cables must be used.
What David said -- and note that the ouytput Z of the oscillator is 600 ohms, so the analyzer has a 600 ohm input load when you connect them directly. I aplogize, Sync, for not thinking of the possible frequency offset between analyzer and oscillator. By all means, use the freq. vernier as needed.
Also note that the oscillator will have its lowest THD at max output, whereas the analyzer is much less sensitive to level as long as none of the tuning LEDs are lit.
Also note that the oscillator will have its lowest THD at max output, whereas the analyzer is much less sensitive to level as long as none of the tuning LEDs are lit.
Hi Gents,
Well we can definitely say, "It is what it is."
OR
Like that baseball guy used to say, "It ain't over 'til it's over."
The most recent Super Bowl an example.
So yes, who knew?
AND
As Deming use to say, "It's unknown and Unknowable."
This leads to another question, when making/taking measurements,
does it really mater if it 1kHz? or if 1.1kHz works better because
of said alignment issues?
If we are using say looking to 20 Hz to 20 kHz range.
Well we can definitely say, "It is what it is."
OR
Like that baseball guy used to say, "It ain't over 'til it's over."
The most recent Super Bowl an example.
So yes, who knew?
AND
As Deming use to say, "It's unknown and Unknowable."
This leads to another question, when making/taking measurements,
does it really mater if it 1kHz? or if 1.1kHz works better because
of said alignment issues?
If we are using say looking to 20 Hz to 20 kHz range.
Data from mfr of such LDR used in distortion analyzers and variable gain control etc: Vactrol
They can find a sub for the ones in the 339A if you had a weak or bad one.
BTW -- there is a series R going to the LDR to control led/lamp current/brightness and thus shift the tuning R to compensate for variations.
[This series R can be played with to see if it shifts the auto-tune/sync better for all ranges. See schematic.]
-RNM
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Going backwards a little bit:
Input Amp
Was this the A4U1 on the removable board
or over on A3U100?
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@Sync -- actually, the range and multiplier settings do matter. The combo that yields the lowest osc. tuning R values is better on my 339 for both distortion and noise. YMMV.
@RichEEM, Which range & multiplier works best for you?
1 x 1K
10 x 100
HP manual has it at 1 x 1K.
1 x 1K
10 x 100
HP manual has it at 1 x 1K.
10 x 100 seems best at the moment, but I just turned it back on after being off for a while. IKt generally takes a few hours to warm up and stabilize. The 10 x 100 setting seems less finicky about the position of the freq vernier, too.
It's on the main board. Sync your unit is working well enough. I don't think yours will improve much changing more op amps.
On mine the 10 X100 works best. Has the least noise and distortion.
But as far as tuning-alignment it makes no difference.
But as far as tuning-alignment it makes no difference.
Hi,
I was ready to ship it back to you.... but i was so certain from the symptoms and my experience that you had a short under the U1 quad opamp that I just removed that socket. I found the short for you between pin 4 and 5 on the top side under the IC.... removed short and put the socket/IC back in. The 400Hz filter works fine now.
I'll ship it back soon. Attached is the new 1KHz result with all filters IN. It measures well below -100dB. Your 339A is measuring residual of about .00065% THD+N (BW = 400Hz - 30KHz). 🙂 The generator is still lower than this, however.
THx-RNMarsh
I was ready to ship it back to you.... but i was so certain from the symptoms and my experience that you had a short under the U1 quad opamp that I just removed that socket. I found the short for you between pin 4 and 5 on the top side under the IC.... removed short and put the socket/IC back in. The 400Hz filter works fine now.
I'll ship it back soon. Attached is the new 1KHz result with all filters IN. It measures well below -100dB. Your 339A is measuring residual of about .00065% THD+N (BW = 400Hz - 30KHz). 🙂 The generator is still lower than this, however.
THx-RNMarsh
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Richard,
Well I'll be.
That's not bad at all. So it is running about -105dB on the analyzer.
with the filters working. I unplugged that devise and measured
but couldn't find anything. But if it was a short on the top....
Tricky. Sometimes we just don't know...but if with think
or trust what we feel sometimes it will lead us to the solution.
Look forward to receiving it back, thank you for getting
me off the waterboard.
Cheers,
Well I'll be.
That's not bad at all. So it is running about -105dB on the analyzer.
with the filters working. I unplugged that devise and measured
but couldn't find anything. But if it was a short on the top....
Tricky. Sometimes we just don't know...but if with think
or trust what we feel sometimes it will lead us to the solution.
Look forward to receiving it back, thank you for getting
me off the waterboard.
Cheers,
339A, Back Home Again
Richard,
She made it back safely. Had a long and storied voyage.
Plugged her in and she's just humming along a tad better than
you showed in your last pic of the meter. Very stable : )
I had one or two short bouts of the ground issue...
makes me wonder if the HP339a IEC sockets might
be just a bit under sized, at least I now what to look
for when the symptoms reappear.
You given me more relief than you know from the on
going waterboarding that I've suffered through.
The short you found cleaned up the a lot of the
meter, Now I can finish what ever is left t o do on the
meter output.
As my little girl say's with the joy of a 22 month old:
"WWWWWhhhhhheeeeeee ! "
Richard,
She made it back safely. Had a long and storied voyage.
Plugged her in and she's just humming along a tad better than
you showed in your last pic of the meter. Very stable : )
I had one or two short bouts of the ground issue...
makes me wonder if the HP339a IEC sockets might
be just a bit under sized, at least I now what to look
for when the symptoms reappear.
You given me more relief than you know from the on
going waterboarding that I've suffered through.
The short you found cleaned up the a lot of the
meter, Now I can finish what ever is left t o do on the
meter output.
As my little girl say's with the joy of a 22 month old:
"WWWWWhhhhhheeeeeee ! "