Tektronix 576 - Page 1
Forum section: electronics / testgear

author: H713
author_rank: Regular Contributor
timestamp: December 20, 2022, 04:17:42 am
content: Greetings,I recently got somewhat lucky and won a 576 (with a scope cart!) at a local auction for $190. I'm still in the "evaluation" stage of this thing. Here's the good and bad news.Good:- The HV transformer is the black silicone one, not the brown epoxy one (yay!)- Generally appears to work, with some crusty switches.Not so good:-CRT exhibits double-peaking.-No readout.Questions:1) This unit has a blank cover plate where the readout should be (see photo). Was the readout an option, or did someone swipe the readout from it for some reason?2) The CRT seems readable, but the double-peaking is definitely concerning, given that CRTs for 576s are basically unobtanium. The CRT seems largely readable, but with a lot of traces (10 steps on the step generator, for example), it does get a bit dim. Out of curiosity, how quickly does the performance of a CRT drop off at this point? Does it molder in this general state for a long time, or do they usually "fall off a cliff" at this point? More to the point: how soon do I need to start looking at "other options"?

author: jonpaul
author_rank: Super Contributor
timestamp: December 20, 2022, 05:05:08 am
content: Bonjour cher Monsieurbravo great find.Had 577 and 576 since 1980s, super machines for power electronics design and debugging.1/ CRT HV and controls may need cal, ger service manual and check all PSU,HV proceedures. Clew is you say dim with a lot of steps, thus higher beam current. Suspect weak HV trsf, mult or divider resistors.2/ move dense display eg 10 close steps, position up down left right over the screen, look for burned in areas of phosphor.3/ CRT very rare, so called replacement LCD, external digital are not practical (yet).4/ Readout is complex systems of switches, fiber optics and lamps. Your unit may have a no readout option to save cost.Plate looks like original Tektronix, see manuals for options.Bon chanceJon

author: mawyatt
author_rank: Super Contributor
timestamp: December 20, 2022, 04:11:48 pm
content: Wow, you found a 576 for $190Where was this auction?Looks in great shape, not banged up and all switches intact and it's cleanWe have an old 577 that we've been restoring, not nearly as well off as your 576, and had some issues that have been corrected and is working well now.As you probably know, check the PS and all the electrolytic caps. We had a 10uF 450V that was leaking and replaced, strangely it measured ~10uF out of the circuit!! After some troubleshooting replaced a op-amp, also needed to carefully clean all the switches with CRC Electronics cleaner.A trip to the local Ace Hardware for a few replacement knobs and such, then performed a subset of the maintenance manual cal procedure and the 577 is working nicely now!!Later we also did a calibration of the 177 plug-in to improve the display accuracy & appearance. Quite impressive how well a CRT can display a voltage current relationship and how accurate Tek achieved results even in the corners.The Tek folks of the day knew how to design analog instruments with CRTs better than anyone, they achieved very respectable precision and stable results with just modest components.For the younger folks out there studying the design of these old Tek and HP relics can provide an insight into analog design and squeezing the highest levels of performance within component limits. Very similar to analog IC design where one is faced with a fixed set of devices with limited performance, and finding ways to expand/extrapolate/enable that into impressive results, Widlar of course the absolute master of such!!Best,

author: Stray Electron
author_rank: Super Contributor
timestamp: December 20, 2022, 04:36:34 pm
content: Quote from: H713 on December 20, 2022, 04:17:42 amYou stole that one! You could get your money back in the knobs and other parts alone. I hope you got adapters, Ebayer's think that they're made of gold! There is a Tektronix mail list and the 576 is a frequent topic there. you should look into that. CRTs are available, one person in the list just bought one to replace one on a 576 that was busted in shipping. I think he's also on this forum and he will probably speak up. Also there was a CRT on Craig's list in Tampa, Florida a few months ago. I have an email from the seller if anyone needs it. He doesn't know the tube's condition and I don't need one at the moment so I didn't pursue it.I will defer to others but I think most people recommend De-oxit for cleaning the switch contacts. Also IIRC it think it was a factory option to delete the display. Take a look at some of the old Tektronix catalogs.Post the serial number of your's if you don't mind. These are getting rare enough that people are starting to track every individual machine, just like classic cars.

author: H713
author_rank: Regular Contributor
timestamp: December 20, 2022, 06:35:14 pm
content: Quote from: mawyatt on December 20, 2022, 04:11:48 pmI have a 577 that I need to "take care of" as well - it's still sitting in a flight case in my shop. That one will probably end up going to a friend (I have neither the space nor the need for two curve tracers), but it's on the list as well. As I understand it, the 577 was an attempt by Tek to stop losing money on every curve tracer they built.I always find Tek and HP equipment nice to work on - it was built to such a high standard in its day. I'll post a SN for my 576 sometime tonight.

author: David Aurora
author_rank: Frequent Contributor
timestamp: December 20, 2022, 10:55:28 pm
content: Welcome to the cool kids clubCan't help you on the screen questions (mine arrived smashed, but my replacement is immaculate so I haven't experienced the in between yet), but the no readout thing was definitely an available option. To be honest though, even after using mine for months now I barely use the readout, I'm just so used to looking at the physical knob positions on other gear. I guess it's more important for taking pictures of curves, but I've got mine connected to my computer anyway so I use that for saving plots.

author: bdunham7
author_rank: Super Contributor
timestamp: December 20, 2022, 10:59:59 pm
content: Since we're on the 576 subject, I'm still looking for an HV transformer for mine. I didn't get any responses on the .io group, perhaps I'll try again. Anyone?

author: mawyatt
author_rank: Super Contributor
timestamp: December 20, 2022, 11:44:18 pm
content: Quote from: David Aurora on December 20, 2022, 10:55:28 pmCurious, did the 576 come with some sort of external computer or analog interface? Or did you tap into the Vertical and Horizontal differential signals?Anyway, glad we found the 577 we have, altho took some effort to get up & running. We were seriously considering rolling our own which would have been a big undertaking until we found this 577.Agree, looking at the knobs works well except when you require documentation, likely the reason Tek offered the optical readout.Best,

author: David Aurora
author_rank: Frequent Contributor
timestamp: December 21, 2022, 04:36:33 am
content: Quote from: mawyatt on December 20, 2022, 11:44:18 pmYeah, I tapped the deflection plates through some basic circuitry to adapt to the outside world and now use an Analog Discovery 2 to capture it

author: H713
author_rank: Regular Contributor
timestamp: December 21, 2022, 04:45:22 am
content: Serial number on this one is B325999, and is now located in Madison WI.

author: DiN
author_rank: Newbie
timestamp: August 07, 2025, 06:03:03 am
content: Hi David!I'm new here on the forum! I would also like to use the Tek 576 with Analog Discovery. Could you help me with this here or in a private message or by email? (What hardware did you use and where did you connect it exactly?) Thanks in advance! Denes