Wavetek 273

On Mon, 21 Nov 2011 22:36:33 -0600, Vladimir Vassilevsky wrote:

> Tim Wescott wrote:
> 
>> Anyone got any mileage, manuals, rumors, etc. of the Wavetek 273 signal
>> generator?
>> 
>> A customer is testing a PLL that I designed.  The PLL is designed to go
>> into the far sub-Hz bandwidths, and they're having trouble getting it
>> to lock onto the 15kHz signal from a Wavetek 273.  I've got it running
>> off of a crystal oscillator divided down and made into a sine wave, and
>> it's perking along quite happily at a bandwidth of 1/50th Hz. They
>> can't run it at a bandwidth below about 5Hz.
> 
> What is your PLL acquisition bandwidth?
> 
>> All I can find for that signal generator are places selling manuals,
>> and a picture of the front panel.  It has a digital readout and appears
>> to be synthesized -- yet it's actual performance doesn't seem to jibe
>> with the performance my customer is seeing.
> 
> The 1e-5 is too much of accuracy expectation for the off-the-shelf MCU
> grade crystal; not mentionning 1e-6. You can reliably count on 1e-4.
> 
>> So I'm wondering if its broken, or if it's just a multivibrator
>> oscillator behind a dolled-up digital panel, or what.
> 
> Add a discriminator to your PLL or use a frequency-phase detector to
> assist the initial pull-in.

I'm not talking about acquisition, that works just fine (it starts with a 
discriminator, then switches to a wide-open PI filter once the phase 
stops hopping around, then when the phase settles in it stops down the 
gain to whatever the preset value is).

The problem is holding lock -- they can't get it to stay locked unless 
the bandwidth is above one or two Hz, while mine stays locked just fine 
on my 12.5kHz crystal derived signal.  Since this is very symptomatic of 
the signal generator not being in good shape, I'm thinking in that 
direction.

I suppose they could have issues with their processor crystal -- but it'd 
have to be exceedingly sick.

-- 
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

On Tue, 22 Nov 2011 00:56:03 -0600, Tim <tim@seemywebsite.please>
wrote:

>On Mon, 21 Nov 2011 22:36:33 -0600, Vladimir Vassilevsky wrote:
>
>> Tim Wescott wrote:
>> 
>>> Anyone got any mileage, manuals, rumors, etc. of the Wavetek 273 signal
>>> generator?
>>> 
>>> A customer is testing a PLL that I designed.  The PLL is designed to go
>>> into the far sub-Hz bandwidths, and they're having trouble getting it
>>> to lock onto the 15kHz signal from a Wavetek 273.  I've got it running
>>> off of a crystal oscillator divided down and made into a sine wave, and
>>> it's perking along quite happily at a bandwidth of 1/50th Hz. They
>>> can't run it at a bandwidth below about 5Hz.
>> 
>> What is your PLL acquisition bandwidth?
>> 
>>> All I can find for that signal generator are places selling manuals,
>>> and a picture of the front panel.  It has a digital readout and appears
>>> to be synthesized -- yet it's actual performance doesn't seem to jibe
>>> with the performance my customer is seeing.
>> 
>> The 1e-5 is too much of accuracy expectation for the off-the-shelf MCU
>> grade crystal; not mentionning 1e-6. You can reliably count on 1e-4.
>> 
>>> So I'm wondering if its broken, or if it's just a multivibrator
>>> oscillator behind a dolled-up digital panel, or what.
>> 
>> Add a discriminator to your PLL or use a frequency-phase detector to
>> assist the initial pull-in.
>
>I'm not talking about acquisition, that works just fine (it starts with a 
>discriminator, then switches to a wide-open PI filter once the phase 
>stops hopping around, then when the phase settles in it stops down the 
>gain to whatever the preset value is).
>
>The problem is holding lock -- they can't get it to stay locked unless 
>the bandwidth is above one or two Hz, while mine stays locked just fine 
>on my 12.5kHz crystal derived signal.  Since this is very symptomatic of 
>the signal generator not being in good shape, I'm thinking in that 
>direction.
>
>I suppose they could have issues with their processor crystal -- but it'd 
>have to be exceedingly sick.

---
Why not lend them your generator and let then check their Wavetek
against it?

-- 
JF

"Tim Wescott"  wrote in message=20
news:UO-dnWjQxr-9f1fTnZ2dnUVZ_hmdnZ2d@web-ster.com...

> Anyone got any mileage, manuals, rumors, etc. of the Wavetek 273
> signal generator?

I've been searching on eBay for a function generator and I will soon =
receive=20
an HP3312A which I bought for $80. In the process I located and =
downloaded=20
quite a few manuals, but I did not come across the 273. I found manuals =
on=20
the 275 and the 278 =
(http://www.bitsavers.org/pdf/wavetek/278_Jan90.pdf),=20
and perhaps the 273 is similar.

Another resource that has quite a few manuals, including the 275, is:=20
http://bama.edebris.com/manuals/wavetek/275. But not the 273.

As you probably found, there are manuals for sale, such as this one for =
$75:
http://www.bpbsurplus.com/lc/cart.php?target=3Dproduct&product_id=3D17788=


or here for $55 (or $25/week rental):
http://www.labx.com/v2/spiderdealer2/vistaSearchDetails.cfm?LVid=3D381082=
5

I found three of these for sale on eBay, as low as $399:
http://www.ebay.com/itm/Wavetek-273-Synthesized-Programmable-Sweep-Functi=
on-Generator-0-01Hz-12MHz-/130605653318#vi-content

I don't have much experience with synthesized waveform generators, =
except=20
long ago the company I worked for (EIL) made a frequency test set for =
line=20
voltage frequency relays (50-60 Hz and 400 Hz), where the waveform was=20
synthesized using a D/A converter and a binary counter. But IIRC it used =
16=20
pots which were set to the sine function and CMOS multiplexers were used =
to=20
produce the output. This was around 1980, and perhaps EPROMs were =
relatively=20
new. Now I am building a waveform synthesizer with three-phase output, =
using=20
a PIC and a USB connection for selecting the waveform shape, frequency,=20
amplitude, phase, and duration.

Using such a method it is theoretically possible to produce a waveform =
of=20
arbitrarily low frequency, by using step-wise adjustment of output to=20
whatever precision is desired, although most DACs are limited to 14 or =
16=20
bits. For your purpose of phase locking, I wonder if it is a problem of=20
sensing the zero crossing or a particular signal level. My experience =
with=20
phase angle meters showed that waveform distortion of sine waves made it =

difficult to get accurate readings, and symmetry and DC offset were=20
particularly critical.

I have had some experience with the 74HC4046 PLL, but mostly at power =
line=20
frequencies trying to read 60.000 Hz with a 1000:1 multiplier. I do =
recall=20
some problems with stability and noise, but this was also almost 30 =
years=20
ago.

Good luck!

Paul
www.pstech-inc.com=20

On Nov 21, 6:43=A0pm, Tim Wescott <t...@seemywebsite.com> wrote:
> Anyone got any mileage, manuals, rumors, etc. of the Wavetek 273 signal
> generator?
>
> A customer is testing a PLL that I designed. =A0The PLL is designed to go
> into the far sub-Hz bandwidths, and they're having trouble getting it to
> lock onto the 15kHz signal from a Wavetek 273. =A0I've got it running off
> of a crystal oscillator divided down and made into a sine wave, and it's
> perking along quite happily at a bandwidth of 1/50th Hz.
>
> They can't run it at a bandwidth below about 5Hz.
>
> All I can find for that signal generator are places selling manuals, and
> a picture of the front panel. =A0It has a digital readout and appears to =
be
> synthesized -- yet it's actual performance doesn't seem to jibe with the
> performance my customer is seeing.
>
> So I'm wondering if its broken, or if it's just a multivibrator
> oscillator behind a dolled-up digital panel, or what.
>
> --www.wescottdesign.com

No wavtek 273 knowledge,  Sorry.  Does your customer have another
signal generator?  I was comparing different digital signal
generators, triggering the 'scope off one DSG and watching the  square
wave crossing of the other.   This cheap Protek DSG would have a hic-
up, every second or two.  Maybe they could check out the 273 with a
similar method.

George H.

Tim wrote:


> The problem is holding lock -- they can't get it to stay locked unless
> the bandwidth is above one or two Hz, while mine stays locked just fine
> on my 12.5kHz crystal derived signal.  Since this is very symptomatic of
> the signal generator not being in good shape, I'm thinking in that
> direction.
The Wavetek 273 appears to date to about 1980.  So, it is about 30 years
old, maybe more.  It would be no surprise that the power supply filter caps
are shot, and the whole instrument is running with lots of ripple.
It may also be that some tantalum caps have croaked somewhere in it.
That is about the vintage where the sick tantalum syndrome shows up.

Jon

On Tue, 22 Nov 2011 11:13:35 -0600, Jon Elson wrote:

> Tim wrote:
> 
> 
>> The problem is holding lock -- they can't get it to stay locked unless
>> the bandwidth is above one or two Hz, while mine stays locked just fine
>> on my 12.5kHz crystal derived signal.  Since this is very symptomatic
>> of the signal generator not being in good shape, I'm thinking in that
>> direction.
>
> The Wavetek 273 appears to date to about 1980.  So, it is about 30 years
> old, maybe more.  It would be no surprise that the power supply filter
> caps are shot, and the whole instrument is running with lots of ripple.
> It may also be that some tantalum caps have croaked somewhere in it.
> That is about the vintage where the sick tantalum syndrome shows up.

That's about the vintage where tantalum caps were widely regarded as the 
Coolest Caps in the World.  Given that the 1980s was the period when I 
was coming of age as an engineer, the whole "tantalum cap == good thing" 
mantra is stuck in my brain; I have to regularly dislodge it.

-- 
www.wescottdesign.com

On 11/22/2011 12:00 PM, Tim Wescott wrote:

>
> That's about the vintage where tantalum caps were widely regarded as the
> Coolest Caps in the World.  Given that the 1980s was the period when I
> was coming of age as an engineer, the whole "tantalum cap == good thing"
> mantra is stuck in my brain; I have to regularly dislodge it.
>

After seeing what a failed tantalum cap did to a board in a graphics
display system, and hearing a few other horror stories, I avoid them
like the plague.  I have had to replace many of them in various systems,
especially test gear that is used for a few months and then put in 
storage until the next time it is needed.  That is a disaster for the
old Tantalums, that intermittent usage.

A friend overhauled a Schlumberger communications analyzer, and it had
dozens of failed tantalums in it.  He just replaced them all.

Jon

On Tue, 22 Nov 2011 01:55:17 -0600, John Fields wrote:

> On Tue, 22 Nov 2011 00:56:03 -0600, Tim <tim@seemywebsite.please> wrote:
> 
>>On Mon, 21 Nov 2011 22:36:33 -0600, Vladimir Vassilevsky wrote:
>>
>>> Tim Wescott wrote:
>>> 
>>>> Anyone got any mileage, manuals, rumors, etc. of the Wavetek 273
>>>> signal generator?
>>>> 
>>>> A customer is testing a PLL that I designed.  The PLL is designed to
>>>> go into the far sub-Hz bandwidths, and they're having trouble getting
>>>> it to lock onto the 15kHz signal from a Wavetek 273.  I've got it
>>>> running off of a crystal oscillator divided down and made into a sine
>>>> wave, and it's perking along quite happily at a bandwidth of 1/50th
>>>> Hz. They can't run it at a bandwidth below about 5Hz.
>>> 
>>> What is your PLL acquisition bandwidth?
>>> 
>>>> All I can find for that signal generator are places selling manuals,
>>>> and a picture of the front panel.  It has a digital readout and
>>>> appears to be synthesized -- yet it's actual performance doesn't seem
>>>> to jibe with the performance my customer is seeing.
>>> 
>>> The 1e-5 is too much of accuracy expectation for the off-the-shelf MCU
>>> grade crystal; not mentionning 1e-6. You can reliably count on 1e-4.
>>> 
>>>> So I'm wondering if its broken, or if it's just a multivibrator
>>>> oscillator behind a dolled-up digital panel, or what.
>>> 
>>> Add a discriminator to your PLL or use a frequency-phase detector to
>>> assist the initial pull-in.
>>
>>I'm not talking about acquisition, that works just fine (it starts with
>>a discriminator, then switches to a wide-open PI filter once the phase
>>stops hopping around, then when the phase settles in it stops down the
>>gain to whatever the preset value is).
>>
>>The problem is holding lock -- they can't get it to stay locked unless
>>the bandwidth is above one or two Hz, while mine stays locked just fine
>>on my 12.5kHz crystal derived signal.  Since this is very symptomatic of
>>the signal generator not being in good shape, I'm thinking in that
>>direction.
>>
>>I suppose they could have issues with their processor crystal -- but
>>it'd have to be exceedingly sick.
> 
> ---
> Why not lend them your generator and let then check their Wavetek
> against it?

Not a bad idea, except that it's cobbled together on a protoboard, and 
they're several hundred miles away.

-- 
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

Jon Elson wrote:
> 
> Tim wrote:
> 
> > The problem is holding lock -- they can't get it to stay locked unless
> > the bandwidth is above one or two Hz, while mine stays locked just fine
> > on my 12.5kHz crystal derived signal.  Since this is very symptomatic of
> > the signal generator not being in good shape, I'm thinking in that
> > direction.
> The Wavetek 273 appears to date to about 1980.  So, it is about 30 years
> old, maybe more.  It would be no surprise that the power supply filter caps
> are shot, and the whole instrument is running with lots of ripple.
> It may also be that some tantalum caps have croaked somewhere in it.
> That is about the vintage where the sick tantalum syndrome shows up.


   I have always refused to use any Wavetek junk at any place I've ever
worked.


-- 
You can't have a sense of humor, if you have no sense.

Tim a écrit :
> On Tue, 22 Nov 2011 01:55:17 -0600, John Fields wrote:
> 
>> On Tue, 22 Nov 2011 00:56:03 -0600, Tim <tim@seemywebsite.please> wrote:
>>
>>> On Mon, 21 Nov 2011 22:36:33 -0600, Vladimir Vassilevsky wrote:
>>>
>>>> Tim Wescott wrote:
>>>>
>>>>> Anyone got any mileage, manuals, rumors, etc. of the Wavetek 273
>>>>> signal generator?
>>>>>
>>>>> A customer is testing a PLL that I designed.  The PLL is designed to
>>>>> go into the far sub-Hz bandwidths, and they're having trouble getting
>>>>> it to lock onto the 15kHz signal from a Wavetek 273.  I've got it
>>>>> running off of a crystal oscillator divided down and made into a sine
>>>>> wave, and it's perking along quite happily at a bandwidth of 1/50th
>>>>> Hz. They can't run it at a bandwidth below about 5Hz.
>>>> What is your PLL acquisition bandwidth?
>>>>
>>>>> All I can find for that signal generator are places selling manuals,
>>>>> and a picture of the front panel.  It has a digital readout and
>>>>> appears to be synthesized -- yet it's actual performance doesn't seem
>>>>> to jibe with the performance my customer is seeing.
>>>> The 1e-5 is too much of accuracy expectation for the off-the-shelf MCU
>>>> grade crystal; not mentionning 1e-6. You can reliably count on 1e-4.
>>>>
>>>>> So I'm wondering if its broken, or if it's just a multivibrator
>>>>> oscillator behind a dolled-up digital panel, or what.
>>>> Add a discriminator to your PLL or use a frequency-phase detector to
>>>> assist the initial pull-in.
>>> I'm not talking about acquisition, that works just fine (it starts with
>>> a discriminator, then switches to a wide-open PI filter once the phase
>>> stops hopping around, then when the phase settles in it stops down the
>>> gain to whatever the preset value is).
>>>
>>> The problem is holding lock -- they can't get it to stay locked unless
>>> the bandwidth is above one or two Hz, while mine stays locked just fine
>>> on my 12.5kHz crystal derived signal.  Since this is very symptomatic of
>>> the signal generator not being in good shape, I'm thinking in that
>>> direction.
>>>
>>> I suppose they could have issues with their processor crystal -- but
>>> it'd have to be exceedingly sick.
>> ---
>> Why not lend them your generator and let then check their Wavetek
>> against it?
> 
> Not a bad idea, except that it's cobbled together on a protoboard, and 
> they're several hundred miles away.
> 

Bad idea indeed!
You'd have a lot of jitter on the parts' arrival time...


-- 
Thanks,
Fred.