HP 3310B Malfunction Generator

I bought this thing some 10 years ago used and it has worked ok, mainly
as an audio generator. I fired it up the other day and the upper ranges
seem to output a funky sine wave now. The 10 kHz and 100 kHz ranges
output a distorted waveform that does a direction reversal a little bit
after going negative of the midpoint. It almost looks like a rectified
sine wave, but the waveform is more than half a cycle. I don't see any
issues on the other waveforms.

I can play with the range switch and find that turning it slowly can
have an impact on the point of the waveform where the reversal occurs.
But it doesn't really feel like a switch problem. I would disassemble
the switch to see if there are mechanical issues, but it is one of those
multi-gang wafer switches with components mounted directly on it and
each gang is soldered to the board, a real nightmare to remove. This
thing was made to never break, not to be repaired.

I don't have any info on it. The circuit board has some dozens of
transistors, a couple of what are likely op amps (metal cans) and well
over a hundred passives. I don't know where to begin trying to fix
it... other than connectors and switches are the primary point of
failure. But even removing and reseating boards looks like a bear in
this thing.

Any suggestions on ways to repair this?

I saw the other thread on new units and had looked at some of the little
$8 boards on eBay. Funny that there isn't much in between the $8 boards
and the $400 boxes. I would have thought this is something that could
be done very inexpensively these days. I would use a PC audio output
but my signal is outside the 20 kHz upper limit of audio outputs.

Maybe I'll add a simple sig-gen to the prototype circuit I'm building.
Lots more than $8 of effort, but I'll know what I'm getting.

Rick

 

Caps..and power supply.

Jamie

 

Operator and Service Manual for P 3310A/B is available here:
http://cp.literature.agilent.com/litweb/pdf/03310-90003.pdf

 

Service manual here:

http://www.home.agilent.com/agilent...o&pageMode=OV&pid=3310B:epsg:pro&cc=US&lc=eng

As always, check the power supplies first.

Then RTFM

 

Not knowing the 3310 offhand, I thought for a moment you were talking
about a piece of test equipment which intentionally generated malfunctions
for testing purposes.

Hey, it's HP, who knows what kind of stuff they made!...

Tim

 

That is kinda funny.

Except for the top post.

 

Lol!

I don't care if you top post, but in this case your sig made all of my
post disappear... even better, I didn't have to snip! I'll try top
posting in some of the idiot threads that are so popular here. That
should encourage others to trim a bit... lol

Rick

 

Thanks. I'll take a look at it. I guess I'm just intimidated by the
disassembly job alone.

It doesn't really look like a PSU issue to me. I would suspect the
switches, but when I work them it just doesn't feel like that's the
problem. The unit has tons of test points so that should make it easier
to see what is going on.

Rick

 

I am not sure the age of that unit but I hope it's newer than the tube
era A LCR meter would serve you will, along with a DMM.

Oh, and lets us not for get to use a scope on the power supply for cap
ripples and possible linkage in selenium devices and maybe germanium.

Jamie

 

I have an HP 3312A Function Generator, and the manual.
The looks are quite different, but the general operation should be
very similar.
Basically, it starts with a triangle / square generator,and the sine
is created with a DFG from the triangle.
So,your sine waveform problem is due to a bad diode or resistor in
the diode / resistor chain on the polarity side where you see the defect.
I could scan and send diagrams as need.

 

I have an HP 3312A Function Generator, and the manual.
The looks are quite different, but the general operation should be
very similar.
Basically, it starts with a triangle / square generator,and the sine
is created with a DFG from the triangle.
So,your sine waveform problem is due to a bad diode or resistor in
the diode / resistor chain on the polarity side where you see the defect.
I could scan and send diagrams as need.

 

NOTE: The OP _only_ complained about the sine output, and mostly at
higher frequencies; definitely not PS oriented; prob is in one of the
DFG chains.

 

Reminds me of the Missing Pulse Generator used in the Nike/Ajax
missle test van....

 

So you would not recommend first checking the power supplies on a 40+ year
piece of test equipment before doing any follow-up trouble shooting? Even
when it is a well known fact that electrolytic capacitors that old are often
found degraded.

Oh well, whatever.

 

Hey, that is one of the "rules of thumb" for repairing any circuit fault
in my opinion. First check the supplies, then if a digital circuit,
check the clocks. They are fast, easy checks to make.

I think Robert is saying he has some insight into the failure based on
the symptoms, so maybe the PSU can be skipped this time. I will be
looking at the manual I download and if it has good info on the test
points, I'll be checking the power supplies.

Thanks,

Rick

 

Oh, how long has it been missing?

lol

Rick

 

That's the spirit! ;-)

Plus it's nice if you're just slapping something on which isn't very
relevant to quoted material. Saves time, makes it easy to read.

Tim

 

I did NOT say that; i mentioned where the problem was most likely to
be found.
Yes, it is possible that there may be one or two degraded
'lytics..even the old wet electrolytics lasted 20 years at best and even
then many could be recovered by adding electrolyte.
On old tube equipment, powering them up with a variac at zero and s l
o w l y raising the line voltage to full will allow most of degraded
'lytics to re-form and perform adequately at worst.

 

Ok, I'll bite, who is Maynard Philbrick? I thought the name was
familiar, but googling it doesn't provide anything useful, mainly
genealogy pages. I can't even seem to exclude them they are so
pervasive. Linking the name to HP doesn't do it either.

The name does sound familiar. Is that a name here?

I've mainly worked on digital stuff including state of the art (at the
time of course) floating point array processors. Analog is not my
forte, but I'm comfortable with it.

It seems I am spending more time getting a new lab setup than actually
working on anything. I cleared out some old appliances and now have
room for an 8 foot workbench which I plan to build. But before I do
that I am turning my hand router and hand saw into table tools to help
with the workbench construction. The test gear is the same way, I need
this to fix that and before I can use that I need this other thing...
I've let things slide too long.

Wasn't it Lincoln who said, "Give me six hours to chop down a tree and I
will spend the first four sharpening the axe"?

I'd prefer to use a chain saw...

Rick

 

OK then. Sorry for the comment. I miss-understood what you were implying.
And agree with your assessment.