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

Reply to
rickman
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Caps..and power supply.

Jamie

Reply to
Jamie

Operator and Service Manual for P 3310A/B is available here:

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Reply to
David & Cheryl Denslow

Service manual here:

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As always, check the power supplies first.

Then RTFM

Reply to
tm

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

--
Deep Friar: a very philosophical monk. 
Website: http://seventransistorlabs.com 
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Reply to
Tim Williams

That is kinda funny.

Except for the top post.

Reply to
WoolyBully

They left that market to Wavetek. :(

Reply to
Michael A. Terrell

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

Reply to
rickman

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

Reply to
rickman

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

Reply to
Jamie

Thanks for the suggestions, after several folks have said to check power I guess I'd better do that. But what's with the selenium and germanium devices? This thing wasn't built in the 50's I'm pretty sure. What do you mean about "linkage"? Do you mean leakage?

Rick

Reply to
rickman

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.

Reply to
Robert Baer

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.

Reply to
Robert Baer

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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.

Reply to
Robert Baer

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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.

Reply to
tm

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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

Reply to
rickman

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

--
Deep Friar: a very philosophical monk. 
Website: http://seventransistorlabs.com
Reply to
Tim Williams

Listen to Maynard Philbrick at your own risk.

HP used germanium transistors in the '60s designs, like everyone else, then moved to silicon. They weren't penny pinching, they were cutting edge designs.

You should always verify the power supply is in spec on test equipment before doing anything else. Slight errors are compounded, and can cause you all kinds of headaches including a dead piece of equipment. Start with the +/-25 volt outputs are right and have no ripple. I see no Germanium transistors listed. I see are bipolar silicon, and a few FET. The parts list is in the middle of the manual, the manual is dated 1973, and has a lot of design changes in the back and sorted by serial number groups. Unless you are very familiar with troubleshooting, you may need help.

Reply to
Michael A. Terrell

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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.

Reply to
Robert Baer

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

Reply to
rickman

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