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Wavetek 23 croaks, anyone know of "notorious" falure areas?

T

Tim Williams

Jan 1, 1970
0
Joerg said:
Ouch! That doesn't exactly speak to the competence of the guys who
designed it. Or maybe they didn't do design reviews?

I have a Wavetek 193. Excellent generator, but then the output stage died.
Same damn thing, driving a load at high amplitude...then suddenly not
driving it.

The output stage is an AC coupled RF follower using 2N3866 and 2N5160, one
set to drive and two pair for output. (An op-amp controls bias, including
"DC" output signals.) They all have heatsinks, but TO-39 isn't renouned for
heat dissipation.

Here's a picture of the layout. Schematics are on BAMA, IIRC. This is
actually some guy's 191, which has the same main board as the 193, and looks
the same as mine used to. Now I have two ugly TO-126 transistors on small
heatsinks where the four outputs used to be. Risetime sunk to an appalling
50ns. :(
http://myweb.msoe.edu/williamstm/Images/Wavetek_191_Output.jpg

Tim
 
J

Joerg

Jan 1, 1970
0
Tim said:
I have a Wavetek 193. Excellent generator, but then the output stage died.
Same damn thing, driving a load at high amplitude...then suddenly not
driving it.

The output stage is an AC coupled RF follower using 2N3866 and 2N5160, one
set to drive and two pair for output. (An op-amp controls bias, including
"DC" output signals.) They all have heatsinks, but TO-39 isn't renouned for
heat dissipation.

Here's a picture of the layout. Schematics are on BAMA, IIRC. This is
actually some guy's 191, which has the same main board as the 193, and looks
the same as mine used to. Now I have two ugly TO-126 transistors on small
heatsinks where the four outputs used to be. Risetime sunk to an appalling
50ns. :(
http://myweb.msoe.edu/williamstm/Images/Wavetek_191_Output.jpg

The output on mine has never let me down. But somehow the transmission
blew up :-(
 
J

JosephKK

Jan 1, 1970
0
Oh yeah, it's what drives the economy these days...

If all your neighbors were like you -- fixing anything that had a pretty
simple fix when it broke, only buying new cars/computers/TVs/etc. when the old
one actually wore out, etc... what kind of economy would that be? :) Imean,
I'd like to think we'd expend all our then-extra human capital on, I dunno,
finding a cure for cancer or feeding the hungry or something, but I'm kinda
dubious how likely that'd be...

The good old USA went through the principate phase into the decadent
phase of empire rather faster than any before it. It may be that both
China and India may be on track to do it even faster. Now that is a
scary thought.
 
J

Joerg

Jan 1, 1970
0
Paul said:
It sounds like its still working, but way off frequency.

What sort of clock does it have? Perhaps the crystal is bad, or some
nearby component is causing it to go out of spec.

This Model 23 generator is very sick. The PLL works but the uC control
seems to be on the fritz. Above 1kHz where it cuts in the 2nd (faster)
AC path it's missing half the sine wave. That would be easily fixed but
there seems to be a whole lot that croaked. I had done a 12h test with
it and this thing is IMHO poorly engineered from a thermal POV. Lots of
stuff in there gets very toasty.
 
N

Nico Coesel

Jan 1, 1970
0
Joerg said:
They should start talking to their customers more. I've filled out
numerous surveys for them. From those, they could have seen that I
haven't bought a Tek product in a long time. The smart thing would have
been to pick up the phone and have a chat, ask why. But no ... so I
don't participate in their surveys anymore, makes no sense to me.

They could have found some interesting things. For example that it
doesn't make sense to sell a DSO with a paltry 4k sample memory where
Asian mfgs are already eating their lunch by providing several times more.

I agree. Yesterday I clicked on an advertisment for Tek scopes on
Farnell's website. It turns out their TDS1000 and TDS2000 series only
have 2.5kpts of memory. Even my old 2230 has more memory (4kpts). I
really don't understand why they cut back on the memory depth. The
2430 and the TDS200 series have to do with 1kpts which really cripples
the usability of a digital storage scope.

Anyway I ended up buying an Iwatsu analog/digital scope from Ebay to
replace the 2230.
 
J

Joerg

Jan 1, 1970
0
Nico said:
I agree. Yesterday I clicked on an advertisment for Tek scopes on
Farnell's website. It turns out their TDS1000 and TDS2000 series only
have 2.5kpts of memory. Even my old 2230 has more memory (4kpts). I
really don't understand why they cut back on the memory depth. The
2430 and the TDS200 series have to do with 1kpts which really cripples
the usability of a digital storage scope.

I bought an Instek GDS-2204 instead of Tektronix. 25k memory, no
nickel-and-dime games on the software (all a free download), its control
codes are public, and so on. You simply can't do serious pulse-echo work
with 4k or less. Not even have a good look at SPI/I2C/RS232 hickups.
What were they thinking when writing the specs? Or, were they thinking?

Anyway I ended up buying an Iwatsu analog/digital scope from Ebay to
replace the 2230.

Did the 2230 die? Those were from the good old days, stuff lasted an
eternity.
 
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