[sdiy] Retarded function generator - Agilent 33220A

[Nicholas Gregorich]

I never had the Vpp problem that the original poster has [I almost  
always use the HiZ output mode] but all of the 33220As at school have  
the broken softknob problem! You have to spin the knob backwards to  
move up in value. Its terrible!

Nick.

On Apr 20, 2007, at 11:08 AM, jays at aracnet.com wrote:

> Charles,
>
> I'm pretty familar with the 33220A. On a daily basis I have a hate  
> relationship with one on my desk. If I were looking for a signal  
> generator I would avoid this one. Granted some of my problems with  
> the unit are with the GPIB/PI implementation which most people here  
> wouldn't use.
> 1) Soft knob crapped out a month out of warrenty. Costs about 1K to  
> fix.
> 2) The only reliable way I can control it externally is with the  
> GPIB interface. The network and USB interfaces are marginal.
> 3) Some important features can not be controlled over the GPIB/PI  
> interface and have to manually be tweaked.
> 4) Some of the waveforms aren't as good as they should be.
>
> There probably is a very simple explination why this happens. Check  
> the termination of the 33220A which is at Utility | Output Setup |  
> Load. Switching between 50 ohm and hi-z termination screws with the  
> output level. Having it set to 50 ohms with 10V output and driving  
> a hi-z input will probaly give you about 20V out. That or just  
> changing the termination can change the output voltage. This is not  
> a unique feature for this signal generator. There are a number of  
> other ones that do this also.
>
> Jay S.
>
>
> Charles Bisaillon wrote:
>
>> Hi, I would love to get your opinion on this one,
>>
>> I remember having unexpected low level problems when we were  
>> presenting the
>> capstone modular project. Well, I recently learned from a  
>> classmate that the
>> function generator I used to design the whole synth actually  
>> outputs twice
>> the voltage selected. I remember setting it daily to 10Vpp and  
>> using it
>> instead of my 10Vpp VCO. I went back to check verify this and he  
>> was right,
>> set at 10Vpp, I get 20Vpp at the output. How can someone design  
>> such a
>> stoopid thing?
>>
>> Anyways, this means that all of my module's inputs, unity gain, clip
>> circuitry, headroom, etc, are designed to receive twice the  
>> voltage that
>> they will operate on. On the other hand, all my outputs are designed
>> properly and yield proper levels (provided you get a proper input,  
>> which in
>> this case is 20Vpp). It's such a pain, even my 1V/oct is actually  
>> designed
>> for 2V/oct...
>>
>> I now have a choice to make: Raise the VCO outputs to 20Vpp  
>> instead of 10Vpp
>> and the ADSR to 10V instead of 5V, or go back to the breadboard  
>> and redesign
>> the VCF and VCA? I would love to get your opinions on this.
>>
>> Thanks
>>
>> Charles (I hate electronics)
>>
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