Repairing a 1980s HP 3325a Synthesizer/Function Generator
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- เผยแพร่เมื่อ 14 ต.ค. 2024
- My primary signal generator died after my recent move. In this video I go through the process of how I diagnosed the problem and performed this repair.
The signal generator is a 1980's era Hewlett Package 3325a. The original list prices was several thousand dollars in the early 1980's but I picked this one up for a few hundred bucks on eBay. It has been reliable and rock-solid for years but probably failed from aging components and a mild, but intentional power surge cause by me and the switched power source I installed.
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Equipment used:
HP 3325a Synthesizer/Function Generator (the patient)
Tektronix 465 Oscilloscope
Tektronix 544A Oscilloscope
Hewlett Packard 3456A Multimeter
Thanks for the informative video. I have a dead 3325A awaiting my attention. By the way, I would be wearing my anti-static wrist strap and have the unit placed on an anti static mat, for these repairs.
Thinking that I am building and designing my circuits with DIPs modules it's always a consolation to see the 80' :D
Makes sense, did resolve my HP 3457A intermittent isolation error last year by just tightening the screws for the digital & analog boards. Found out some of them were a bit loose. Since then it works fine.
I am glad to finaly see a new video on this channel
Fine! i am a patron of rll now
It's that moment when you wonder how you subscribed to this channel, but are not unhappy that you did.
Thanks very much for posting this, you inspired me to take another look at my HP 3336B which has a very similar failure mode. Unfortunately this wasn't the issue with my unit :(
I look forward to more videos from you.
Thanks for the kind comment. Sorry to hear this wasn't the issue with your unit. Unfortunately the service manuals for the 3325A are focused on doing signature analysis which makes it hard to debug anything that isn't a simple power issue unless you have a multimeter with a signature analysis function (which I don't). I was sure happy when this was fixable with a simple cap replacement.
@@RetroLogicLaboratory Thanks, I have been keeping my eyes out for a signature analyser for this very reason :) I probably wont be able to get very far without one. the 3336B is going back on the 'to-do' shelf for now.
I am new to computers, and I can't get the lid off.
I removed the face
I removed the side screws and plastic and pulled the sides back to the set point.
I removed the screws under the plastic piece on the top front
WHAT AM I MISSING????
If the GPIB board is isolated then why would its issues affect the main board and display?
You know the whole time you were doing all of that, I was trying to tell you through the screen, "Put in all of the screws!". LOL
Thanks for walking me around the inside of your unit. I've recently added this unit to my bench. It needs a bit of calibrating .
Do you have a tech library resource for older equipment to share?
Hi, thanks for the nice comment and I hope you like your new piece of equipment. The 3325a is a great function generator and pretty easy to maintain- the one big complaint I have is that the service manual focuses on using Signature Analysis for most of the troubleshooting procedures. This requires a special and relatively rare device... Anyway, the best place for manuals is the Boat Anchor Manual Archive (BAMA) which is here: bama.edebris.com/
The HPIB section of the board has an isolated ground which is important to remember when checking the voltages.
Thanks, that's an excellent point!
I think the isolated/non-HPIB part of the board is grounded via all the screws.
Nice fix. Original electrolytic caps positioned next to heat sinks should always be prime suspects.
Good observation- I didn't really think about the heat from the regulator but yeah it makes sense it would wear out those caps quicker. I ended up checking the other capacitors on the board and they were all within spec so probably you are correct; the heat did affect the power supply filter caps.
I keep my lab gear on a power cut off as well, not to mention the reasons you have ... its just like hmm I got a handfull of 1970's to 1990's gear plugged into mains along with soldering equipment so does it really need to be live 24-7? just imagine a bang out in the garage at 4am due to a storm on old gear lol
Haha yep. Also my wife wonders if all the equipment I have is going to burst into flames at some point. So the switch helps alleviate that concern. One problem for me though is that my primary frequency standard takes a good 6 hours or so to stabilize after it gets powered up. But I guess that probably makes more sense than paying for the electricity 24x7.
Good show! I have a competing brand but it was all applicable (back to basics!). Q. I don't know how much that GPIB board and PS "meld" into the rest of the larger board, but are we saying that if you removed the 9 vac plug that you might experience the same issue? If so, that would be one InTeReStiNg one :O) Of course not being there my IQ drops 50 points.. which is not good as it's only hovering at 100 as it is. Just saying. Cheers RLL
What's with 10 months between videos?! What have you been done all pandemic?
Did you get a new camera? Quality seems really good.
No new camera, I think I just learned how to use the focus control better. :)
You lost your right audio channel about 2/3 through the video. Edit: It came back at 31ish minutes.
Thanks for pointing this out! So frustrating when I forget to mix down into mono. Unfortunately TH-cam doesn't let me re-upload the video without losing all my views so I guess I will leave this one as is.... but I'm gonna put "mix to mono" in my checklist for the future.