HP 3300A Vintage Function Generator Repair
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- Опубліковано 23 лип 2024
- The HP 3300A I featured in the previous video needed a little TLC. Here is the video of the repair and adjustment of this great analog function generator.
Companion video on the HP 3300 series oscillators: • Vintage HP Function Ge...
Companion video of the HP 3310A calibration: • HP 3300A Vintage Funct...
Chapters:
00:00 Problems with my HP 3300A
01:42 Principle of operation and schematics overview
03:41 Overview of the inside of the instrument
07:50 Power supply adjustments
09:08 We hit a snag!
10:42 Chasing the fault
15:42 Found the bad component in the oven?
18:30 Second issue found and fixed
19:43 Late revelation, and ultimate fix
22:43 Sinewave shaper explanation and adjustment
27:37 All fixed! Bill an Dave would be proud.
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That's not a MOSFET, just a JFET.
No, it's an actual MOSFET. [EDIT: Oh no, big fail. I'm wrong and Alex is right, it's a JFET. See more details below]
@@CuriousMarc Huh. It's drawn as a JFET, and I know HP used to like to use them for analog switching in those days.
@@CuriousMarc Wow, OK. The schematic symbol was a JFET though?
Maybe I am mistaken. In the service doc they say it is a MOSFET, but maybe not. A JFET would make more sense given the time period. Let me do some research.
@@CuriousMarc I could be wrong too, maybe schematic symbols hadn't standardized yet.
I was a metrologist in a calibration lab back in 1976 and I worked on lots of this vintage HP equipment. The edge connector issue was around back then too. In the 1980's we called it "green gold" and discovered it is a fuzzy crystal growth on the contacts that pushed them apart. From what we could tell there are micro cracks or pits in the gold plating exposing the underlying metal plating. When exposed to oxygen, water in the air and current, the crystals would form from the corrosion and push the spring contacts open.
What you need is a gas tight connection at the contacts. Now days we have contact lubes like OX-Guard anti-oxidant compound or other dielectric greases like Rykon lube. These seal out oxygen from the contact points greatly reducing the green gold problem.
Is that the Jim Harmon of the HP bench briefs fame?
Read so many of those in my day.
Some mighty fine troubleshooting Marc! :^)
The master himself. Thanks for stopping by!
Good lord that thing is exquisite inside!
It is, Mr. Electro-Rabbit, it is. Your HP 200 isn't too shabby either!
For those amazed by the triangle shaping into sinusoid using diodes: There is even a much simpler way to do it, just using a JFET, two diodes and 3 resistors. I wonder, how that circuit could compare in performance with the diode shaper. Maybe a time for a test ;)
The November 1965 edition of the HP Journal provides a comprehensive description of the HP3300A design philosophy and capabilities, including the plug-ins. The author is Design Leader, Robert L. Dudley.
Thanks! I had not found it before. The HP Journal is the best!
I can't believe how good those 28 segments per period approximate the sine wave
Very cool. I used to work at a university that decided to throw out tons of old equipment that was in storage, they literally dragged it all outside one of the buildings and a truck made several trips to collect it all to scrap.
Myself and a colleague managed to salvage a lot of gear before it got trashed, we were filling every square inch of our vehicles as well as stashing more in our lab to take home later. There was everything from function generators to decatron computer racks. I scored several working tectonix 500 series scopes in near mint condition. There were spectroscopes, scientific balances and even some old light microscopes. I couldn’t believe they were just chucking this stuff out.
We saved a lot of gear but it was still sad to see the rest getting thrown into a dump truck.
Marc, always a delight to see you dig into a piece of vintage HP gear, brings back so many good memories; my favorite videos on your channel!
Thanks for a well done video. When you show the electrolytic caps I can hear Mr Carson in my head "these caps all have to go" :)
Hm, balance still isn't quite on? The even harmonics of square and triangle should be zero -- assuming it was set for 50% on the front panel of course. (Typically only the first so-many even harmonics can be zeroed, and the rest creep up regardless of adjustment; this is due to imbalance in the rise/fall edges, or the corners thereof. Very subtle, close-up stuff, nothing to worry about.) Quite satisfying seeing the sine shaper do its magic!
Or the balance of the diode shaping bias isnt correct (my suspicion) - there were separate trimpots for the positive and negative diode bias.
I live vicariously through your amazing exploits. Thanks so much for taking the time to create such wonderful work
Awesome video! I've been looking forward to seeing the repair of this thing!
Great video! Be careful if you suspect there is asbestos in the oven, I'm sure you're well aware of the danger!
I never get tired of seeing the beautiful HP workmanship!
This video is a piece of art
Been really enjoying watching your series of videos, particularly the Apollo Guidance Computer restoration, Marc, so please keep the videos coming.
I bought a 3300A, no plugin, at a yard sale in 1991. It was $18, all I had in my pocket at the time. I was able to have one of the engineers I worked with send it through the cal lab on a one time only test & calibration. Old HP is great gear. Also have the newer HP test oscillator that's on your bench.
When I watch you one-handing the metal screwdriver when tweaking those trimmer pots, I get a shiver down the spine.
Only a matter of time,
lol
Great video. I have a 334A distortion analyzer but I don't think it works that well. I tried it a little when debugging my home-brew audio amps. I am not nearly as proficient as you are, just a part time hobbyist, so to get through the amount of analysis and debug you do in one video often takes me months, with a lot more clumsiness along the way. I also have an HP239A oscillator and an HP654A oscillator which is twitchy, and no amount of contact cleaner has freed the front panel buttons which like to stick. Another work in progress I had to put away due to other more immediate things. I repaired both my 3582A spectrum analyzer (bad opto isolator) and my 35660A (bad 339 comparator in the smps and some lightning damaged memory chips), by far those instruments are the most fun to use when looking at my audio amp because they show the harmonics. this was a very fun video to watch
Wow that sine generator circuit is absolutely brilliant!!!!
Excellent content, thanks Marc! It is a good motivator - it makes me work harder through stuff I have on my workbench at the moment, in order to get to restore my 3310B sooner. I have also recently bought a non-working 8640B signal generator, full of delicious nicotine dust. But that will have to wait a bit.
Great video and nice repair. I'm currently repairing an HP 8165A Signal Source that uses a similar diode sine shaper in one of the PLL loop outputs to feed a balanced mixer and one that uses five differential amplifiers in the main VCO output to convert triangle waves into sine waves. You have to love the solutions the HP engineers came up with!
Just love these. The vids and the vintage. Thanks
i just love your videos marc! thanks i learned a ton of stuff via this video!
In a few days I ll have exactly this device delivered to me. I am very curious how it will perform. Thanks for this video
Way way back when I was a bench tech, I loved my HP gear, the best.
Interesting seeing inside one of these things. I didn’t know HP started out making function generators. My first experience with them was those “RPN” calculators that all the structural engineer interns I worked with at the time were using (early 90s).
Love the song "Fat Bottomed Sine Waves" by Queen
I'm guessing that the second-harmonic you can see on the HP Analyzer is most likely caused by some residual asymmetry in the Sine-shaping circuit, since second-harmonics, and even-order harmonics are caused by waveform asymmetry.
Interesting timing since Friday I've started restoration of my HP 6111A power supply which has been designed in the same time period as the HP 3300A. Thanks for sharing the interesting content!
Those low cost HP power supplies in the all plastic cases were good electronically, but the plastic cases break or shatter into little pieces at the slightest tap. I've got 6112, 6114.
@@acmefixer1 Do you mean 6212/6214? Since all the 6112A style power supplies are rack mount with sturdy aluminum cases
That diode network sine shaper is cool, I kinda want to make an audio wave generator based on this topology now.
I'm glad this got enough votes for you to make the video!
Nicely explained, thanks for sharing :)
very nice work!
Great video!
I wonder if that insulating hard foam is starting to deteriorate with age and off gassing some corrosive stuff? Rest of the boards were pristine, so it seems not a problem of storage environment.
I was just going to comment that. I'm sure that's whet happened. It was probably either soft foam originally that hardened, or hard PU foam but that is also able to outgass corrosive stuff as it ages. I have seen corrosion around deteriorating foam pads in various electronics over the years.
probably, cyanide is an offgas product of some polyeurothane foams so its entirely possible its cooking itself, though if that is asbestos, you have other problems
@@AsbestosMuffins asbestos is only bad if it breaks. As long as it's intact it's entirely safe. Although it is likely the foam contains asbestos, almost everything heat insulating did up until the late 1980s
Good point...
“We’ll get to see what’s inside - I’m sort of curious” No wonder whatsoever, considering your channel name! Haha. That had me
Laughing!
Excellent tear-down and failure analysis. The ICL 8038 works pretty much the same as the HP3300, but latter has a more precise sine-shaper, by having seven instead of 5 segments. That's a nice reminiscence of the 8038 circuit for me. Anyhow, you could better have used the PULSE WIDTH A function, than the TI A->B, as you could deal with the square wave signal for symmetry alignment, I think. Or get the hp5335A, instead, which has a DUTY CYCLE function.
The ICL8038 was quite a big deal back when it was introduced, being the first highly accurate single-chip function generator, even if it tends to be a bit glitchy. I believe the bugs the editor in Jazzpunk want you to kill are ICL8038s?
Beautiful hardware. Gold plated traces. Made for precision and durability, not so much to cost.
Nice repair job on a well-designed piece of gear. I love those gold-plated PCBs. They don't make them like they used to. Gotta pay for quality... and HP, among others like Tektronix, Rohde&Schwartz or Fluke, were in the top tier, weren't they? :)
I recently built myself a Function Generator using an XR2206 IC, they are pretty handy little devices, the only problem with my XR2206 Function Generator is that the square wave output is very high output and can't be adjusted with the output level control, so I need to make some mods to the circuit so that the Sine, Square, and Triangle wave outputs are fully adjustable in level, there's also a TTL Square wave output that has a fixed 5V PP output level too, great for use as a clock-signal, I did a basic electronics course at uni a few years ago and some of the stuff you get to service in your videos are quite fascinating.
Metrology was my favorite course at my uni of technology, 32 years back.
Funny way to make a sinus from triangle, looks really like the old icl8038 transistor arrays.
Back in those days ... they came with some nice tricks.
Nice explication
Wow, capacitors from TRW and Sprague. Your function generator is ready to go to space.
excellent
MIDI to IEEE488 using Pyvisa!!! I bet you would have a whole orchestra!!!!
The 2nd harmonic content hints at some slight AM modulation of the output signal, no?
It's a diode ladder filter! They sound cool in synths!
Marc, Thanks for doing these videos, they are really interesting and informative. I have always wondered how they worked. I don't know if you do requests, but I would love to see how the ebay XR2206 function generators compare to the HP units.
Nicely made HP function generator and repair. I guess the corrosion on the transistor cans and leads is caused by the insulating foam of the current source oven. When this old material begins to deteriorate, it emits aggressive chemicals. Maybe you should replace that stuff to prevent further damage to the circuit board?
Huh? Marc is curious about how the HP has a fat bottom ? That’s uhm. Ok? I’ll just keep watching. It’ll be an excellent video once again.
Tektronix FG504 works similarly - triangle generator with switching current sources and diode sine-shape circuit.
I always remove and clean the card edge connectors, they often give trouble.
Out of interest I was looking at the circuit diagram. On channel A the amplifier seems to be lopsided in its drive current capability. Q5, the upper transistor can pull the output up very strongly and I presume that is why it is mounted externally. On the negative excursions though Q6 would not have the same pulldown capability as Q5. What’s the reason for this?
1:55 You really shouldn’t put yourself down like that. 😉 😂
that is pretty on the inside
Does that frequency counter have a Duty Cycle measurement mode? Would have been really convenient instead of having to switch between high and low period. I only have two small ones and they don't have a Duty Cycle mode.
Those sounds are very reminiscent of the soundtrack to Forbidden Planet ("composed" by Bebe and Louis Barron) which was created using ring oscillators. Apparently, the circuit design was rudimentary to say the least - after an unknown time the circuits would let out the magic smoke, so it was never possible to exactly re-create the sounds once this happened. This lead to the Barron's habit of recording everything they did, just in case.
Errie, that opening sound, seemed to be straight from the film "The Forbidden Planet"
I borrowed it from Hainbach, with his permission. Definitely done using similar means.
Any idea why a Fluke 8300A is so much more expensive than an HP 3478A?
Can you talk more about the oven inside please.
I recognized that 5334B. I've got a 5335A on my bench.
Hello, I'm sorry if this is a little off topic, but I recently acquired a Leader LSW-330 Sweep Marker Generator. I've been looking for a user manual for that device (Leader LSW-330) but have not had any success. Any assistance would be greatly appreciated. Thank you
Might i ask, where do you find decent quality schematics as i am looking for the HP 311A schematic however the only i found is pretty much unreadable and i cannot even open pdf's from keysight
When the manuals are not available or of poor quality online, I usually buy them on eBay and scan them in hi-res, then post them on my website and on the internet archive for everyone.
the oven may feature asbestos insulation always good for some fun.
You adjusted the beast when the top cover plate was off.... The oven will make a big difference to the rest under a metal plate.
super interesting repair and cal... 😃 there are several videos on 5.5, 6.5, 7.5 digit multimeters that are impressive until 4 or 5 of them are side by side and hardly any of them read alike , kind of close so what is the purpose of high resolution? how would people like NASA know which one is the absolute value Keithley vs Fluke and the like? 🤔
You get it calibrated at a metrology lab. Or at least, you calibrate it using references you got from said lab.
It's because their instruments are not calibrated properly, or they don't use the right leads. My two high precision voltmeters do agree for all digits.
that makes makes me feel better, thanks
Ohhh Van
Would be nice if this was shot in 4k when looking at the tiny text on the schematics.
I was thinking that maybe if you matched the two current source transistors you would have gotten better results
Not for this circuit. Matching transistors is what you do for a differential pair. This is not a differential pair arrangement.
My mother is an expert with currants in the oven for functions. She agrees that if any of the contents are bad, it can affect rise times and if really bad, don’t be surprised if a saw turns up at the function. I asked if it could be rectified and she said it would almost be a SIN.
the inside looks Like a Braun Radio ^^
What is it's maximum output voltage spec?
Quite a bit. 35Vp-p into high impedance, 15Vp-p into 600 Ohms. Most likely the 15V into 600 Ohms of the 3300A is aimed at testing tube audio circuits. The 3310A can even do 15Vp-p into 50 Ohms.
Hello i own one but cant find a power cable. Could you please tell me what kind of plug it is ?
They have a code name but most people call them an oval power cord. There are always some on eBay, just not cheap. The other solution is to replace the socket with a modern IEC power cord.
@@CuriousMarc thanks !, i was trying to avoid that but since im on a budget ...
@@emilienlesage947 That’s a very acceptable modification, HP themselves sometimes have the two versions as they abandoned the oval socket in later production.
@@CuriousMarc Alright thanks will do so !
what about a 2N2222
Maybe watching this will give me the nerve and the initiative to fix my old, probably not really worth fixing because it was pretty basic even when new, analog Tek scope...
As per shango66's UA-cam channel, those dome top transistors are notorious for failing (in his case, not usually in test equipment but in vintage transistor radios).
I'm wondering how you eliminated the capacitor that's being used to create the triangle wave from being a problem? Any leakage would have caused an imbalance in the charge/discharge cycle.
It would be fun to see a THD measurement on the 8566. It's got one of those built in programs to measure that.
It does? How do you get that going?
@@CuriousMarc They're called "DLPs", downloadable programs. I just did this on an 8566B but danged if I can find the spot in the 2.5K of unsearchable manual pages! Maybe it's on the pull-out instructions on the bottom of the instrument. It could be that they were erased? Not sure, but they ought to be in ROM.
Sort of curious… Marc?
11:15 Sus indeed.
That way of generating a sine wave is cheating! ;) After the great legacy making a perfect sine using Wien bridge in 200 series, this is just cheating.