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HP 3310B Malfunction Generator

T

tm

rickman said:
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
Click to expand...

Hey, I like all that old HP, Tektronix, Fluke, Boonton, etc. equipment. It
is still serviceable, unlike all the new stuff. And pennies on the pound.
Although it's lots of pounds.
 
R

rickman

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

I'm sorry tm, with an attitude like that, you won't be allowed to
continue posting in this group. You need to get an attitude to hang
here. Oh yeah, you need to never trim any posts too! lol

Rick
 
R

rickman

I have to admit I haven't had time to look at the schematic of this
unit, but the more I think about it, the less I think it would be the
diode function generator (DFG). That just turns the triangle wave into
a sine, right? This fault reverses the direction of the sine wave in
mid course and changes the frequency as a consequence.

But then I am not that familiar with the operation of the DFG in any
detail. If the triangle wave were to change and not go as far negative
as it should, that would produce the waveform I am describing, right?
In fact, you could consider this to be a sine wave that is clipped in
time rather than amplitude. It has a phase section clipped out of it,
maybe 210° to 330°. Without disturbing the circuit at all, the point of
clipping changes on its own a bit too. So a freq counter won't give a
stable display. I guess I should look into the time base circuit...
after checking all the supply voltages of course.
 
J

josephkk

I have to admit I haven't had time to look at the schematic of this
unit, but the more I think about it, the less I think it would be the
diode function generator (DFG). That just turns the triangle wave into
a sine, right? This fault reverses the direction of the sine wave in
mid course and changes the frequency as a consequence.

But then I am not that familiar with the operation of the DFG in any
detail. If the triangle wave were to change and not go as far negative
as it should, that would produce the waveform I am describing, right?
In fact, you could consider this to be a sine wave that is clipped in
time rather than amplitude. It has a phase section clipped out of it,
maybe 210° to 330°. Without disturbing the circuit at all, the point of
clipping changes on its own a bit too. So a freq counter won't give a
stable display. I guess I should look into the time base circuit...
after checking all the supply voltages of course.
Click to expand...

How about posting a scope trace of the wonky waveform in abse? or some
picture hosting site?

?-)
 
G

George Herold

Sorry this took me a while.  Here is a drawing of what I see.  Not
exactly like the oscope display, but shows the important stuff.

http://arius.com/stuff/HP3310B/HP3310B_malfunction.png

Note that when set for 50 kHz, the measured frequency varies around 80
kHz.

--

Rick- Hide quoted text -

- Show quoted text -
Click to expand...

Weird, I understand this is a basically analog device (Not a DDS).
Then it looks like some inverter falling out of the signal chain.
Intermitent power to some section.... maybe? Does it change if you
load down the output? Have you opened it up and wiggled things?

George H.
 
R

rickman

Weird, I understand this is a basically analog device (Not a DDS).
Then it looks like some inverter falling out of the signal chain.
Intermitent power to some section.... maybe? Does it change if you
load down the output? Have you opened it up and wiggled things?

George H.
Click to expand...

No, I haven't loaded the output. I have probed and prodded with my
fingers. I think there was a point where it had some impact. I just
haven't taken the time to look at the docs yet. I'm thinking the ramp
generator is messing up and triggering the switch to the up ramp too soon.
 
T

tm

rickman said:
No, I haven't loaded the output. I have probed and prodded with my
fingers. I think there was a point where it had some impact. I just
haven't taken the time to look at the docs yet. I'm thinking the ramp
generator is messing up and triggering the switch to the up ramp too soon.
Click to expand...

What were your measured power supply voltages? Ripple?

+25 = ?
-25 = ?
+10 = ?
-10 = ?
 
R

rickman

What were your measured power supply voltages? Ripple?

+25 = ?
-25 = ?
+10 = ?
-10 = ?
Click to expand...

I didn't write them all down, but they are all within 0.2 volts of
nominal and I don't see any ripple on the supplies.

On the other hand, the fact that the problem is only on the two upper
ranges indicates it is within the "High Frequency Level Detector". I
measured some voltages there and the lower half seems to be way out of
whack. There are two symmetrical circuits to generate what would seem
to be a reference voltage for the +-5 volt level detector. But I'm not
sure that is how it works really. According to the schematic notes,
changing the switch from the lower ranges to the two higher ranges
changes the "references" from +10 / -10 volts to -10.6 / +10.6 volts.
What?

Something else I don't get is one transistor in each half is reverse
biased, yes, the CB junction is reverse biased, but the BE junction is
also reverse biased by 6 volts! The emitter resistor is connected to
+10 volts, the collector is connected to -10 volts and the emitter is
supposed to be at +10.6 volts! What??? The transistor is a PNP and the
base is supposed to be at +16.8 volts. How is this supposed to work?
Have I forgotten my transistor notation? PNP is arrow pointing to base
which should be more negative than the emitter, right?

Anyway, the half that is whacked out has some random fluctuations that I
can see on the scope which don't appear on the supplies. I figure one
of the components is bad but I can't trace it to anything in particular.
The circuit all interacts somewhat and the "noise" signal appears
through nearly all of it.

Parts of the large schematic pages are missing. I assume somewhere they
tell you the conditions for taking the measurements, but I haven't found
them yet. They do have a troubleshooting section that clearly tells you
to look in this circuit.
 
T

tm

rickman said:
I didn't write them all down, but they are all within 0.2 volts of nominal
and I don't see any ripple on the supplies.

On the other hand, the fact that the problem is only on the two upper
ranges indicates it is within the "High Frequency Level Detector". I
measured some voltages there and the lower half seems to be way out of
whack. There are two symmetrical circuits to generate what would seem to
be a reference voltage for the +-5 volt level detector. But I'm not sure
that is how it works really. According to the schematic notes, changing
the switch from the lower ranges to the two higher ranges changes the
"references" from +10 / -10 volts to -10.6 / +10.6 volts. What?

Something else I don't get is one transistor in each half is reverse
biased, yes, the CB junction is reverse biased, but the BE junction is
also reverse biased by 6 volts! The emitter resistor is connected to +10
volts, the collector is connected to -10 volts and the emitter is supposed
to be at +10.6 volts! What??? The transistor is a PNP and the base is
supposed to be at +16.8 volts. How is this supposed to work? Have I
forgotten my transistor notation? PNP is arrow pointing to base which
should be more negative than the emitter, right?

Anyway, the half that is whacked out has some random fluctuations that I
can see on the scope which don't appear on the supplies. I figure one of
the components is bad but I can't trace it to anything in particular. The
circuit all interacts somewhat and the "noise" signal appears through
nearly all of it.

Parts of the large schematic pages are missing. I assume somewhere they
tell you the conditions for taking the measurements, but I haven't found
them yet. They do have a troubleshooting section that clearly tells you
to look in this circuit.
Click to expand...

All the conditions for the measurements are on PDF page 71, schematic 2, at
the lower right side of the page. Look for all the waveforms just to the
right of the notes section.

What you describe cries out leaky capacitor. Since it is only doing it on
the upper two ranges, that sure points to that circuit.

All of the transistors in that circuit are 2N3904 (N) or 3906 (P) so a
shotgun approach might be worth it in case it is a leaky transistor.

Take note of Note-5.
 
R

rickman

All the conditions for the measurements are on PDF page 71, schematic 2,
at the lower right side of the page. Look for all the waveforms just to
the right of the notes section.

What you describe cries out leaky capacitor. Since it is only doing it
on the upper two ranges, that sure points to that circuit.

All of the transistors in that circuit are 2N3904 (N) or 3906 (P) so a
shotgun approach might be worth it in case it is a leaky transistor.

Take note of Note-5.
Click to expand...

Thanks. My copy doesn't have complete pages of the schematics. They
are cut off at the bottom and when they span two pages there is a gap in
the middle. I think I got this from the Agilent site. Is there a
better copy available somewhere else?

BTW, to make it more viewable I rearranged the schematics a bit and
rotated the vertical pages. I see notes on page 70 of 87 and this page
also has assemblies A2 and A3 and waveforms 12 through 16. Is this the
page you mean?

It includes notes 1 through 3 which is cut off a bit. I don't have
notes 4 and 5 at all. On my page 68 I see notes, but all of the data on
the right is cut off and note 5 is missing.

Wait! I found an intact set of notes on page 77. I will recheck the DC
measurements with the settings indicated. This may bring the good
section into alignment with the schematic values, but I'm sure the bad
half will still be bad. Problem is I just don't know how transistors
are expected to behave when both junctions are reverse biased like the
schematic says they should be.

I think your shotgunning idea is good, I just don't relish the idea of
taking this thing apart, but I guess it can't be too bad. When they
have front panel switches soldered to the board it makes me twinge. I'm
probably just being overly worried, I expect it is made to be repaired
as well as assembled, unlike today's stuff.

Heck, I might want to get a second one so I can use it to make a sweep
generator!
 
R

Robert Baer

rickman said:
Thanks. My copy doesn't have complete pages of the schematics. They are
cut off at the bottom and when they span two pages there is a gap in the
middle. I think I got this from the Agilent site. Is there a better copy
available somewhere else?

BTW, to make it more viewable I rearranged the schematics a bit and
rotated the vertical pages. I see notes on page 70 of 87 and this page
also has assemblies A2 and A3 and waveforms 12 through 16. Is this the
page you mean?

It includes notes 1 through 3 which is cut off a bit. I don't have notes
4 and 5 at all. On my page 68 I see notes, but all of the data on the
right is cut off and note 5 is missing.

Wait! I found an intact set of notes on page 77. I will recheck the DC
measurements with the settings indicated. This may bring the good
section into alignment with the schematic values, but I'm sure the bad
half will still be bad. Problem is I just don't know how transistors are
expected to behave when both junctions are reverse biased like the
schematic says they should be.

I think your shotgunning idea is good, I just don't relish the idea of
taking this thing apart, but I guess it can't be too bad. When they have
front panel switches soldered to the board it makes me twinge. I'm
probably just being overly worried, I expect it is made to be repaired
as well as assembled, unlike today's stuff.

Heck, I might want to get a second one so I can use it to make a sweep
generator!
Click to expand...
See my posting "Re: HP 3310B Malfunction Generator" in a.b.s.electronic.
 
R

rickman

Print all the partial schematics and try piecing them together.
Click to expand...

That won't generate the missing pieces. In my copy of the manual from
Agilent the schematics are not complete.
 
R

rickman

See my posting "Re: HP 3310B Malfunction Generator" in a.b.s.electronic.
Click to expand...

I don't seem to have access to binary groups. My server doesn't host
them and Google Groups doesn't seem to support them either.

Thanks for the effort.
 
R

rickman

Look here:

http://www.ko4bb.com/manuals/index.php?dir=HP_Agilent

About 1/2 way down the page.
Click to expand...

Hi tm,

I was just going to post thanking DaveC for pointing me to the yahoo
group where I found info pointing me to this link. It is downloading as
I type. It is a slightly older copy, but it is much better quality and
larger, 72 MB vs. 5 MB!

Thanks for the advice. This site is a treasure trove. I will feel much
better about buying old equipment on eBay. In fact, I may work on my
oscope to see if I can get the second channel working again. I wish I
could find a source for the horizontal position pot. It has been
terribly dirty for years. I asked HP about it once and they wanted $50
for a replacement, but that was way back when I could barely afford the
scope, much less money for expensive repairs. I think I wouldn't pay
$50 now, but only because the scope is barely worth that I think.

I'll say one thing about this unit, it is a field service model with a
vertically oriented front panel. So it takes up much less space on the
workbench than the horizontal units. Why don't they use this profile
with *all* the scopes? The screen fits nicely above most of the
controls and inputs with a small panel of buttons beside the screen
(power, brightness, etc.). With today's scopes they are very thin, but
still are wide horizontally. Why not thin and taller? I guess they
might be more tipsy... Makes me want to build my own.
 
R

rickman

Join the Yahoo group for HP Test Equipment. LOTS of engrs and techs have tons
of experience with the "boat anchor" HP's. I'm sure more than one has been
down this road with your particular gen.

http://groups.yahoo.com/group/hp_agilent_equipment

Good luck.
Click to expand...

Dave,

Thanks a lot for this link. I found some discussions on this unit and
one pointed me to a more complete manual! Great suggestion!!!

Now I just need to figure the durn thing out. One of the posts I read
seems to be saying that the voltages in the manual require some mods to
the circuit and I see what they mean. Voltages on the output are -16V
when the output, as we know, should be 0 volts. I may be seeing
something similar on the high frequency circuit.
 
D

DaveC

Thanks a lot for this link. I found some discussions on this unit and
one pointed me to a more complete manual! Great suggestion!!!

Now I just need to figure the durn thing out. One of the posts I read
seems to be saying that the voltages in the manual require some mods to
the circuit and I see what they mean. Voltages on the output are -16V
when the output, as we know, should be 0 volts. I may be seeing
something similar on the high frequency circuit.
Click to expand...

Glad to turn on someone else to a great resource.

It looks like you're off and running!

Good luck.

Cheers,
Dave
 
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