HP 3325A Frequency Synthesizer Repair: keys, caps and PLL trouble
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- Опубліковано 23 бер 2020
- The oldie (1979) but goodie HP 3325A is a Fractional-N frequency synthesizer with 9 digits of frequency resolution to play with. But my auction-salvaged model predictably does not work. Let's make it chooch again!
The bonus Fractional-N video explains the genius principle of how the synthesis works: • HP 3325A Bonus Materia...
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And I ended up making the bonus Fractional-N video, here: ua-cam.com/video/z-50pSc_wg8/v-deo.html
You always make repairs look so easy. Oh look, it's a faulty cap. I'd still be trying to get the case open using an angle grinder.
Hey, angle grinder works most of the time ;-)
EEEEEEERRRRRRRRRR!
Slam! Klunk!
'TIME!"
"It's all in the editing, Marc."
leaves it in the final cut. 😂
The only good from the event is that we have more video of Marc now that he is in lockdown.
Thank you for including all the built-in lapses of attention!
Three milli-hertz! HP for the win.
Very interesting to see the construction of those keys - the feel (and sound) of them is highly evocative to anyone that's used HP gear of the era.
This was one of my favorite pieces of test equipment on the bench. I used it a lot on doing my design validation and of course troubleshooting. I never was much of an HP scope person but all the rest of their stuff with just bloody awesome Especially their spectrum analyzers
That’s so true. They never got the scopes right. And Tek never got the logic analyzers right...
Same here, I cut my teeth with HP for signal generators, spectrum analyzers, frequency counters and power supply's, etc, Tektronix for scopes including, the TM 500 series mainframes and Fluke for multi meters (8050A / 8060A), Weller for soldering irons and Pace for desoldering stations in the early 80's.
HP oscilloscopes just didn’t have the right zen back in the day. If you really want to be frustrated, try an old Gould ‘scope. On the other hand, I loved the HP 141T spectrum analyzer mainframe. (The square CRT bezel). I had an HP function and sweep generator on my bench, forget the number now, but awesome and so easy to use. About the only downside is it was huge and heavy!
You have no idea how much I'm enjoying your videos. They're a welcoming breeze of fresh air amidst the murky and uncertain news that is permeating right now.
Nice repair. I just love the way you're explaining things.
Oh yes, these infamous red switches.. I also repaired many of these in my similarly old counter 5370B, including broken springs.
When you couple 10MHz reference from your Cs clock to the 3325A, you'll get a really precise synthesizer, the internal XO is simply ridiculous.
Anyhow, the PLL jitter will increase proportionally with lower output frequencies, so frequencies below 1Hz are barely useable. (I got the 3325B)
Used this back in the day (HP Medical). Loved the accuracy of the generator. Very useful in verifying DSP 60 Hz notch filters (for line rejection). The video brought back nice memories of the good old H-P days; thanks!
Nice video!
I also have 3325A and 3325B in my collection, both arrived without any display (but the fan spins). When I tried to fix them, I found the problem was that the tantalum decoupling capacitors on the boards failed and shorted the power rails. Although 3325A used sealed capacitors, while 3325B used plastic ones, both of them are very easy to fail. I used a FLIR thermal camera and found quite a lot of shorted ones! In case they fail again, I replaced all of them.
These are really descent signal generators if repaired, with very low THD and very high frequency resolution. The 3325A I got has option 1 & 2 installed, which made it even better!
I own its brother, the HP 3336C, and they are wonderful machines as far as resolution goes. Worth the effort of maintaining.
NIce! I love old HP kit, I have "a few" items, and they are all lovely to work on and work with. My vector voltmeter is amazingly nice, and I would not be without my 415 SWR meter.
11:20 priceless. Thank you for that. It really is all in the editing.
We used to use HP 3764 at work and I haven't touched one since I retired 5 years ago and when Marc pressed the power button on the unit I could still hear the fan start up in my head.
Personally, I would have replaced all the major caps in the supply. The theory is that if one is bad that the others which are likely from the same batch and have been serving in the same environment are in similar condition. It's not necessary but I think it's a good idea to prevent future headaches when the others fail as we all know they will. As for the plastic pins, I find a hot air rework tool works best as you can accurately soften the plastic from a distance and gently pull it free. They can be reset equally as easy by reheating them and squishing them down with the end of the handle of a hobby knife. Don't get me wrong, this was a GREAT video. Friendly advice though for future projects, replace similar passives to the ones that fail for the stage of the supply you're working on. The only thing that's generally safe to leave is the resistors and inductors. Then again resistors can go out of tolerance if they overheat too much. I usually just desolder one leg and test them with j-clips like you used on the cap with your ESR tester. Having lived a life of having to buy things broken and fix them because it's the only way I can afford such things I've learned a lot. That's why I enjoy your videos so much. Because I gain a higher technical knowledge and the wisdom of watching as you work through things. I really appreciate it.
Given the age of my 3325a and 3336 both with the 10meg crystal ovens replacing all of the cap was a fun little job. Made for very stable output. The ( all 3 of them ) 3355a also need the cap replaced . enjoyed the video.
I have this same unit but with option 001 (high stability) and 002 (high voltage output). Works great! I also have the same counter with a HP 10811. Great video as always.
That is the perfect unit I wish I had! Good choice!
"The little plastic pins can be melted out with a soldering iron" Preferably someone else's soldering iron :-)
You can always keep a cheap one on hand for doing stuff like that, that way you don't need to worry about cleaning it.
@@BlackEpyon ya, with cheap Chinesium iron.
I just love HP equipment of this era - it just screams quality and engineering.
Another GREAT video !! Gravity will effect the crystal, wonder why they placed it on bottom so when you turn it over it will change your calibration. Keep your videos coming, TNX for all your videos !!!
Thanks for this video ... i have two defective units. Will start examining the power supply
Very interesting video it brings me back to the days when I used to repair microwave Radios...
That's a nice bit of kit! Congratulations 👍
Walked away from the computer for a second.... ran back at "Meltdown alarm".
Thanks for the video Marc.
Its always fun when the little spring strip breaks. I love spending days looking for those parts and replacing them when those keyboards break.
Actually, for all the HP equipment I have, and I do have quite a collection, I have yet to have a broken key spring. I am sure it can happen, but it’s not frequent.
@@CuriousMarc i replaced many of them when i worked for my dad years ago, luckily he had quite a boneyard and also had the forethought to buy many spares before hp put them out of production.
Great repair Marc
I usually put dead HP keyboards into dishwasher or soak them in warm soap water.
And some light oil afterwards. Worked perfectly for me, so far.
Usually, keys are just dirty and with dirt removed, they are just like new.
Of course... "I have another one actually." :-) Awesome price finds sounds like. Thanks for sharing.
Mine failed last month. It was a single cap in the power supply that had failed short, causing it to pop fuses.
Zero idea what the entire process was about, but it was just cool to watch.
I calibrated a few of these. I still love the 8640 though.
Love the older HP stuff
My unit also has a broken power switch, have to print one out for it...
Thanks for the checkout, I will have to go through my unit to check the power supply.
Cheers,
You mean the plastic power button? I don't know why, but my two units also are missing that button. It must be a disease specific to these units! I had to borrow one from another unit.
@@CuriousMarc yes, it's broken on mine. I suspect it breaks from putting the unit on its face... Or maybe just a weak point.
Should be easy to 3D print one, I should get around to modelling one and printing it...
Cheers and stay safe,
@@EngineeringVignettes Great, I'll take a couple if you ever do that!
I always replace caps in the old gear I repair for my channel, it’s amazing how many times that is all that is wrong.
Argh! A UA-cam recapper! Call the exorcist! ;-)
wow tdak sia-sia videox, jal
pesan untuk kdpanx, tingkatkan kwalitas vdeox. krja bagus
The 3325A signal generator is special in that the sin wave output has very low distortion or harmonics. This makes it great for testing HI-FI equipment.
On equipment that in new to you, and in need fo checkout, always go for the PS first. Nothing cna work right if it is not getting the voltages it needs. I am in the habit of using a Variac for anything I have a question about, monitoring the voltage and current. Nothing worse that destroying parts by rushing into a power-up.
Marc! Excellent job. However, if you adjusted the power supply for spec, you'll need to do some further steps, as at the later stage of adjustments, you'll have to set the DAC levels, which is done by adjusting the power supply, even to out of spec of the first adjustment.
This instruments is very nice, but the whole adjustment procedure is quite convoluted and there are some pain point in the design, two of them are the flat cables connecting the boards (in one of my 3325A, I simply replaced them with a header pin and ribbon cable), they have all kinds of bad contact and will create intermittent problems, which usually manifest in failing amplitude calibration or some waveforms missing.
The other is the attenuator board. The one with the yellow relays which plunges contact to the PCB is simply bad. HP replaced them in later models.
Also, even though you can specify frequency down to uHz, it has jitter and in one service manual HP even explains that you have to average readings to get the frequency resolution spec.
BTW, if you are now a time-nut, then there is no point in worrying much about the accuracy, either use an external 10MHz reference, or get Opt 001 the ovenized oscillator. I see that your device does not have it. Opt 002 is also useful, you can get 40V output up to 1Mhz with that.
Probably easier to buy an other bad device with the options than to try and find the options separate, as then you'll get all the cables and whatnot with them. Especially Opt 002 has some additional cables and shielding.
Regarding your comment on the 3325B with internal modulation source, yes, it has, but in reality is is not fun to use. The arb gen only goes up to some low frequency and you have to loop back the mod out to mod in at the rear panel. You can't simply press a key to modulate with the internal source, there is no internal connection switchable from the keypad. I can count on one hand how many time I used the modulation source feature in the 3325B.
Ah, +1 to everything you say. I just realized while doing the "bonus" explanation that the DAC is the one important analoguy-thing to calibrate to minimize phase noise.
Nice fix,... as usual with old HP gear, it's the little things like caps + switches, hardly any serious faults. Watch out for those orange tantalums, i had quite a few 1970/80's HP instruments where they had shortened.
Sometime in the 80s it became fashionable to use tantalums due to their smaller package and very low ESR. Sometimes that ESR will create very large ripple currents, causing other components to blow.
Good job Marc!
A couple of suggestions: clean the contacts on those yellow attenuator relays too. They just unclip from the board, and like the keyboard switches have wipers that contact gold pads on the pc board. They develop the same problems.
Also check the isolated supply on the IEEE board. If the caps go bad on that the machine can go crazy in strange and incomprehensible ways that might have you swearing for a week.
Thanks for the tips!
Great stuff!
Hi thanks for the video. I have the 3325B could you possibly do a video on using the instrument as I am just a novice loved the sound waves.
Well, that's an amazing piece of gear.
A low past filter on fast forward segment would be great the high pitch is quite loud
While you were all joking about using this as a musical synthesizer, that is in fact what the very first musical synthesizers were -- function generators hooked up to some external modulation voltage. And in a lot of early musical experiments, not even that. A very famous example is from the BBC Radiophonic Workshop which composed and recorded the theme from Doctor Who using nothing but function generators set at a fixed frequency, and then splicing the tape recordings together to make a melody.
Usually I just remove flat spring flip around and 180 degrees and clean contacts and put back. Works like new no clicking noises are hard to press. Do that to all HP equipment from that era as yes the click and keys hard to push is annoying at best.
Hi, the captions of function buttons came off on my Ensoniq SQ2, is there a hime way to redo the text on the front panel? Thnx!
Why have the golden contacts oxidized? As far as I know gold doesn't oxidize so what part did it?
On mine at 5 kHz - when I adjust the Amplitude DB from 0 to +7, there's no audible difference on my high freq transducers. My DMM isn't even picking up a DC or FREQ reading. What do you think ?
I'm sorry to see that the "West keys" also suffer from oxidation, much like most of the dreaded Tact Switches of the same era. But at least these are open and can be cleaned, whereas the tact switches are usually "sealed" (although some of the contact cleaner can seep in somehow, sometimes). I thought that gold isn't supposed to oxidize? The debouncing circuitry on this doesn't seem to do a good job even with the contacts cleaned up... You could always use this as a hearing test when hooked up to a speaker 😁. Anyway, thanks for sharing, Marc! Stay safe.
Pure gold doesn't bind easily with oxygen, but I doubt they'd be using pure gold.
I have the same HP that needs power supply repair. I hope I can fix that.
I have the same instrument. beautiful pice of equipement.
Did you fix the advil button as well?
oh man its 3am this is awesome!
👊😎
Greets from locked in France !
Hello from locked in California. Stay safe.
@@CuriousMarc Merci Marc, pensées pour les temps à venir...
Thanks for this video. You pointed me to What I thought was the only problem on my 3325A ... but I missed one. One of the gummed-up keys, when cleaned, revealed that it was missing the spring .... and as far as I can tell on google searches and on fleabay - they are not to be found, unless I buy an entire display board. .. SO, hive mind, does anyone have a suggestion as to where I can get (a) spring? or more than one if that is the requirement to buy/sell ? So far I am at goose eggs unless I cannibalize a working HP device ... and I don't want to do that.
So ... any comments are welcome, any criticisms or pokes at an obvious answer I am missing will be accepted and appreciated. Thanks
This question might be a bit off topic, but I am looking for a good frequency counter and found a used HP 5335A, it has the oven oscillator option installed and is not that expensive, should I go for it?
Edit: also has the option 040 (expanded HP-IB control)
Grab it! I have the HP 5334A which you can see in this episode: ua-cam.com/video/HKsjwT53yXw/v-deo.html . The oven oscillator option makes a huge difference.
@@CuriousMarc Alright, I bought it, by the way, is the 5334A just a slightly earlier/later model? The specs and available options seem kind of similar at least
Are you doing HP339A for our reference.!
That's a piece of gear Hainbach would go nuts! @Hainbach
If it was easy to remove these switches from the pcb and using a small glass fiber brush for cleaning pcb traces and the moving metal contacts of the switches the switches will renewed and will last for another 40 years but look like custom designed for one time installation and removing putting back the same switch has a lot possibilities to fail.
This is all Greek to me, but I love those keys. Click-clack! So satisfying!
If you on hi end audio audio equipment this generator a very pure sin wave that can be used for many distortion tests. CAL
"...and quite predictably, it does not work." Why I watch this channel.
Nippon chemicon cap?
Why did you re-insert the old cap that was still 'good'? I'd always toss both when they are the same age and they are out of the board anyway.
Something of that age? Absolutely.
I'm sure HP was using very good caps, but still.
Agreed. Look at the number of hours those caps are rated for. None ever says "forever."
Absolutely re-cap. On an instrument of this age, I would be tempted to replace all the power supply caps. The ripple current is usually fairly high, and you can see that on the ‘scope in this video. Died out caps due to carrying sizable AC current seems to be a failure mode I’ve seen on more than one HP vintage test equipment. Modern caps are much better - and usually smaller to boot. If you are trying to maintain appearance as well as function, the new caps may well fit inside the old cans with room to spare.
You're in there. Replace all the caps.
Finally managed to get hold of one of these, but it appears that the processor crashes during the startup sequence (FREQ, Hz Annunciator and AMPTD CAL light up briefly when powered up, display remains mostly blank and sometimes displays scrambled characters). Occasionally I was able to get it to power up correctly at least, but it would crash depending upon what entry was performed (switching from FREQ to AMPTD and back twice would cause the processor to lock up completely). The manual suggests a signature analyzer for most of the debugging of the A6 assembly (Control Circuits). My question is, would it be worth obtaining one, as it appears that a majority of the tests cannot be performed without such a device? Any information is welcome, as the 3325A that I managed to get also has option 1 (ovenized oscillator), it would be great to get it going again.
The signature analyzers are pretty cheap, so I’d recommend getting one. Your problem seems intermittent though, I’d look at simple things like power supply ripple and sockets, connectors and cabling first. Next would be memory.
@@CuriousMarc Well, it was sort of intermittent the first few times the HP 3325A was turned on, but quickly got repetitive, the Logic won't start properly anymore. Maybe an IC that was already in degraded condition, and has now failed entirely? Anyway, following your advice, the power supply appears very stable, the ripple on the +15/-15 rails is immesureably small, and on the +5, it is only about 1.5 milivolts, so that's probably not the issue. Regarding memory, are you refering to the four ROM chips (U1-U4) that are holding the machine code? Can these loose their contents too? I've heard about this problem with EEPROMs, but do standard PROMs also develop this problem?
@@fklabs6813 I was thinking RAM, if this instrument uses any (I have not looked at the logic schematics). ROMs do loose bits too. But it could be a gate anywhere. The good thing is that you were working at some point, so this is likely a single failure.
@@CuriousMarc Alright, figured that a signature analyzer would be worth it anyway, considering it is the main method of logic troubleshooting for HP gear of that era, so I purchased one. With one of these, the debugging should be pretty straight forward, as all the signatures are listed in the manual. Thank you very much for the advice! Guess I will report back once I figure that fault out.
@@fklabs6813 Good luck! Just checked the schematic, and it uses a Nanoprocessor with external RAM, the same chip that Ken Shirriff recently reversed engineered and that I debug in my recent videos here with a logic analyzer: ua-cam.com/video/KdLnEOwTO6E/v-deo.html and ua-cam.com/video/ZYRSyTe9FU0/v-deo.html . There were no signature analyzer debug instructions for my system, so I had to go full Monty with the LA. I am curious to see what signature analysis reveals.
I want to see you take on a broken 8660B.
I have done its big brother, the 8662A with a PLL fault, a long while ago, in a mere 8 videos: ua-cam.com/video/XvS2NPqUrNU/v-deo.html . Same principle, but much harder because it's in the microwave domain. Incredible engineering in that instrument!
As the owner of an Arp 2600, I approve! :)
'cus I haven't (re)watched the video yet, haven't a clue what you're on about (yet)...... but I'll give a thumbs up to any mention of the 2500 or 2600 anyway!!
Я мало что понимаю, но это очень круто!
I think you may have replaced both caps.
So, just to recap: the PSU needed a partial recap? :D
Yes, It had been incapacitated.
Dustin Sparks i want you to know that I hate you :)
AttilaSVK , No, it NEEDED a TOTAL recapping, but got shit.
The 'recappers' hahahaha. You know who you are.
I think that there is an Easter-Egg in the firmware for that piece of equipment.
So you got 2 identical caps in the same circuit, one is already failed. You replace only this faulty one, and leave it's brother inside... to prepare for the same trouble for the next owner? :)
The other cap tested good, and is not leaky either. I have a whole video for the UA-cam armchair recapping community: ua-cam.com/video/GMNQDoFpYQY/v-deo.html
@@CuriousMarc Same circuit, same make. Sooner or later it will follow its fellow. Basically I'm against these brainless "replace all caps" campaigns, but in this particular case, I would not leave it in... If one is failed, I would replace both in pair... armchair recapper, LOL :)
@@janosnagyj.9540 This isn't like the motherboards of the mid-2000's with those knockoff-formula electrolytic caps that would bulge and blow after 2-3 years of service. I've long since lost count of how many of THOSE I've had to recap. Equipment of this era, it was usually the RIFA or tantalum caps that went, and even those were after 30 years.
Gentlemen and loud equipment. I bet you felt like kids again :D
The HP gear of this era was built to last forever.
Except for the electrolytic capacitors, which never last forever.
What is wrong with a computer program?
Why not change both caps? An old device with two caps and one goes bad that other cap is high risk item.
The other one tested good and did not leak. I did not have a second high voltage cap replacement in hand either. So the combo of both saved it! It’s a lucky cap.
The other cap tested good, and the lead seals have evidently lasted 20+ years, and there's no reason to believe they won't last another twenty - a new cap may not even last as long.
Better than those mid-2000's motherboards with the electrolytic caps that used that knockoff electrolyte formula. I've long since lost count of how many of THOSE I had to re-cap. In that case, if one went, you could be guaranteed the rest would fail soon after.
No, equipment of this era, it was usually the RIFA filter caps, or the tantalums.
Watch out Kraftwerk, here comes The Curious Five!
Function generator generated music when?
Tempting...
Marc... Are you turning into "The Signal Path" ?
Hopefully not, Shahriars pace is too slow. But, he likes to explain things a lot for beginners.
Mr. Carlson would say that "all of those caps need to go".
next video: How we fixed our Titan II guidance computer in time to leave the earth
Who else is here cos they thought this was about an esoteric and obscure musical instrument?
Too easy! I'm going to have to start bidding against you on the HP lab equipment on eBay.
Uh-oh. I’m in trouble.
It's often a lot cheaper to buy stuff that's listed as "not working/for parts" and just fix it yourself. Sometimes the fix is something idiotically simple, like a fuse holder that wasn't making good contact (like that VIC-20 I picked up a few months ago), and sometimes it's a little more complex, like a cold solder joint that you need to track down. But if you're competent in this kind of thing, it's a really cheap way to pickup vintage computers and test equipment.
First and a like again! Love the Videos Marc!
Wow that was quick! You get a free high-precision synthesized fractional-N vintage Hertz.
I really appreciate the prizes Marc gives.
mmmhhh those mechanical keys sound so satisfying :)
osmelloscope -> uncle bumblef**k (AVE) is zhat yhouuuu?
This guy is so funny
*** Headphone Warning *** :-)
I learn how to make a siren 🚨
HP, Made when Americans still had some pride. Damn I miss that stuff. Your going to have some rather serious test equipment in hand when done.
As usual, we only replace bad caps, NOT all caps.
It's not leaking. No need to replace it.
Caps being caps.
Editing.... It's all in the editing... lol
Oh god, turn it off!!
Marc, mom is single .... do you wanna be my dad? :)