#170 Tektronix 465 review and troubleshoot Part 1 - Page 1
Forum section: electronics / repair

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 23, 2018, 12:20:12 pm
content: I finally got my own Tektronix 465 oscilloscope. I have been searching for many years to get one that I could work on and get back running.This unit was giving to me from a anonymous viewer.I am going to do a series on repairing and aligning this old piece of Tek history.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 23, 2018, 04:05:52 pm
content: This is a bit interesting.After just playing around with the controls I got the below waveform.In channel 1 or channel 2 mode separately I only get a dot on the crt.When pressing both channel 1 and 2 together I get a trace.It is only control by channel 1 volts/division. Channel 2 has no effect.I may should had put this video on the repair forum.

author: AF6LJ
author_rank: Unknown
timestamp: June 24, 2018, 11:31:00 am
content: This should be a good thread, lots of Tek 46x fan-boys and fan-girls out there.With that waveform from the calibrator on the screen, when you push the trigger view button and rotate the A timebase trigger level what do you see???If you see the normal trace and can move its position on the CRT at least you know most everything on the left side of the CRT is okay.

author: bd139
author_rank: Super Contributor
timestamp: June 24, 2018, 11:56:23 am
content: Sounds like the channel switch array is dirty. You can give it a squirt with switch cleaner from the top. Had similar trouble on my 465.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 24, 2018, 04:21:22 pm
content: Quote from: AF6LJ on June 24, 2018, 11:31:00 amAgreed, these are fantastic old scopes.Yes I can move it around bt doing what you asked.Found a few more interesting issues while working on the scope.I have had several emails, and messages stating I have the trigger mode set wrong. I do agree with that but it is the only way I could get anything on the display.I will be posting some screenshots later today of the progress and working on part 2 of the repair.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 24, 2018, 04:22:43 pm
content: Quote from: bd139 on June 24, 2018, 11:56:23 amThis is something I have not done yet and was waiting to finish part 2 of the video.I do believe that some of the problems are in dirty contacts and controls.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 24, 2018, 09:31:24 pm
content: Here is a few screenshots of current state. On the trigger board I found a diode that was cracked. It is D517. I looked up the Tektronix part number but could only find it was a signal diode.I just removed it and tacked in a 4148 for testing.As you can now see I have trace on channel 1 with the trigger mode set to auto.Channel 2 as well.I now have the probe attached and this is the resulting wave form. Either sweep or trigger issue.I can grab the time base or any other control on the right side of the scope.As soon as I turn or push I loose trace.Really does not matter what control I play with on the right hand side I will loose trace. Perhaps it is time to remove boards and give the controls a good cleaning.Also wanted to add that turning the unit off then back on restores the trace. Trigger knobs also have no effect.

author: AF6LJ
author_rank: Unknown
timestamp: June 25, 2018, 06:34:31 pm
content: Cool, progress.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 25, 2018, 09:29:20 pm
content: Quote from: AF6LJ on June 25, 2018, 06:34:31 pmThanks.There is more.I pulled the trigger/sweep boards and cleaned the switch contacts.Then removed the cover from the time base cam and cleaned all the contacts.I put the unit back together and tested it.I can now get trace on channels 1 and 2 using the calibrator.So this is better progress than I thought.Still at times the trace will vanish.It is also unstable.

author: AF6LJ
author_rank: Unknown
timestamp: June 25, 2018, 11:06:52 pm
content: So it looks like, at this point you are left with just a few fussy controls to deal with.

author: tautech
author_rank: Super Contributor
timestamp: June 25, 2018, 11:26:50 pm
content: Quote from: Radio Tech on June 23, 2018, 04:05:52 pmYou still can !For you as the OP, there's a button/icon at the bottom left of the page called Move Topic, use it !All about this feature here:https://www.eevblog.com/forum/blog/what_s-this-move-topic-icon-all-about/

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 26, 2018, 12:20:30 am
content: Quote from: AF6LJ on June 25, 2018, 11:06:52 pmLooks like that may do it. I have to order the caps to replace the ones needed. May even replace those tantalums also.But it is good to see life come back in this old classic.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 26, 2018, 12:21:18 am
content: Quote from: tautech on June 25, 2018, 11:26:50 pmCool!I did not know this was a user feature in this board.Thanks

author: Old Printer
author_rank: Frequent Contributor
timestamp: June 26, 2018, 01:25:55 am
content: Quote from: Radio Tech on June 24, 2018, 09:31:24 pmAre the right side controls that blank the trace mounted to the same board? If touching any of them have the same effect, it sounds like a broken trace/cracked solder joint etc. Either somewhere on the board, or a place where the board makes a connection to something else. I would guess that pressure on the board in different places is disturbing an intermittent connection or cracked joint. I have a nice 475, but have not been in it for some time so I don't recall the right side board setup.

author: AF6LJ
author_rank: Unknown
timestamp: June 26, 2018, 01:31:19 am
content: Quote from: Radio Tech on June 26, 2018, 12:20:30 amGood deal.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 26, 2018, 04:27:35 pm
content: Quote from: Old Printer on June 26, 2018, 01:25:55 amYes there are many connections between the trigger / sweep board to the time base board. All the connections run through the main pcb via connectors.See pictures of what I am finding on these connectors and the solder on the trigger l sweep board.

author: AF6LJ
author_rank: Unknown
timestamp: June 26, 2018, 05:46:19 pm
content: Someone has been in there, and left a level 1.5 mess.

author: bd139
author_rank: Super Contributor
timestamp: June 26, 2018, 05:54:25 pm
content: Looks like “someone was asleep at the tek factory” to me. I’ve seen that a couple of times. Even forgotten solder joints.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 26, 2018, 07:55:07 pm
content: I think you both are correct lol.I pulled the A trigger hold off control out. Took it apart. This is a dual function switch, Rear is a dual switch. Front is a variable resistor. I was able to clean the switch with some DeoxIt. How ever the variable part is sealed. So drilled a very small hole into the body and was able to inject some D100L into it with a needle.Put it back together and things are working much better. I still have the trace fade away issue but noticed something else. When connecting a probe to the unit the display would blank. Turn it off and back on restores trace. Even a jumper just touching the outer shell of the jack will cause this. Sounds like a faulty ground somewhere. More digging to do.A moment ago I was able to connect a function gen to channel one and 2. After watching for a moment I saw the traces flicker. Bright, dim, then out and come back. I also noticed the lights in the volts per division dim down. More power supply issues also.So the saga continues. I am happy to see it work when it does. I have recorded most of this on video.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 27, 2018, 12:26:34 pm
content: So here is a question for you 465 guru's.I pressed the trigger view switch and only notice the rear set of contacts open.The front set remains closed all the time.Is this normal and only works in certain models? Or is the switch broken in a way?I am searching through the manual to see if I can find the drawing of this.

author: bd139
author_rank: Super Contributor
timestamp: June 27, 2018, 12:58:05 pm
content: Front set are bandwidth limit. Pull the trig view control out and it should open the front set.

author: AF6LJ
author_rank: Unknown
timestamp: June 27, 2018, 01:00:36 pm
content: Yup....

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 27, 2018, 01:10:07 pm
content: DUH.Had a Homer Simpson moment.Yep that did the trick.Got to clean those now.Anyway thanks.Still thinking I have a ground issue in the 5 volt area. I really need to get to some other things today but the curiosity is killing me.

author: bd139
author_rank: Super Contributor
timestamp: June 27, 2018, 01:26:16 pm
content: Always worth tightening up all the mounting screws on the 465. Surprising number of weird things can be cured with that simple step.

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 27, 2018, 05:00:47 pm
content: I had one of these with a fault stored for a long time. Saw this thread and decided to give it a last chance. In my case the problem was the filtering cap for the +5V line, a 5000uF 25V cap. These seem pretty low quality electrolytics. Found laying around a couple of 50V 2200uF and put them in parallel.That made it, working fine now.

author: bd139
author_rank: Super Contributor
timestamp: June 27, 2018, 05:04:21 pm
content: I've got the same caps in mine and it's fine after 44 years. You win some and lose some. They're pretty good quality. I suspect they will die at some point.

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 27, 2018, 05:14:54 pm
content: Quote from: bd139 on June 27, 2018, 05:04:21 pmI assumed they must be bad quality because this particular scope hasn't been used much, tube trace is very bright as well as graticule. Also I found others complaining about the same, something to be aware of anyway,https://www.eevblog.com/forum/repair/tektronix-465b-oscilloscope-repair-77721/msg1075640/#msg1075640

author: bd139
author_rank: Super Contributor
timestamp: June 27, 2018, 05:28:21 pm
content: Anything above 20 years is pretty good IMHO used or not.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 27, 2018, 05:44:05 pm
content: Quote from: bd139 on June 27, 2018, 01:26:16 pmAgreed. One of the first things I did. They can always be problematic.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 27, 2018, 06:07:20 pm
content: Success atlas! I have thew triggering fault and trace fade out solved.So what was to problem you ask?I will tell you.It first started out with the power supply rails as you saw in the part 1 video. Do not ever assume that you have a certain circuit working right. I should have know better that that myself.I decided it was time to start back with the basics. Remember that transistor I replaced in the video? Q1558 which is a 2N2222. I noticed it was running very hot. To the point you could not touch it. So I went back and isolated every circuit from the 5 volt rail. Transistor was no longer hot. Thinking it has to be another circuit I tested the resistance on each. Found nothing out of the ordinary. I then went back and checked the voltage on the 5 volt rail. It was over 7 volts. I checked Q1556 and showed a short between base and emitter. Q1556 is a MPS U45 darlington transistor. All I had on hand was a TIP120 Radio Shack transistor. in out is different. So wired it in. I now have 0.23 volts. Tracing back to U1554 I found errors in the voltages. So replaced U1554 MC1458.Trigger now works, stable waveform, can calibrate channel 1 and 2.And trace no longer disappears.As you can see channel 1 with function gen connected.Channel 2 on calibrator.Next step now is to start the restoration.Replace all the caps electrolytic and tantalum. Replace m bodged in parts. Then align the unit.What a ride.

author: bd139
author_rank: Super Contributor
timestamp: June 27, 2018, 06:19:47 pm
content: Nice job

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 27, 2018, 06:27:50 pm
content: Quote from: bd139 on June 27, 2018, 06:19:47 pmThanks!I am please to see it working correctly now. This will also give me some time to play around with this scope and get to know it better. Then when the parts arrive I will start on the restoration.Really should have went back and looked at those power supply rails a second time. Sure would have saved a few steps.

author: AF6LJ
author_rank: Unknown
timestamp: June 27, 2018, 08:27:36 pm
content: Nicely done Buddy.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 29, 2018, 10:37:47 pm
content: Quote from: AF6LJ on June 27, 2018, 08:27:36 pmSorry Sue, Been very busy and missed this. Thanks for the comment.I am loving this scope. Really a nice performer. I do plan on getting part 2 uploaded sometime soon.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 11, 2018, 10:14:28 pm
content: Part two of this repair.We now have a fully working scope, so we will have a part 3 of the restoration.

author: AF6LJ
author_rank: Unknown
timestamp: July 11, 2018, 10:35:44 pm
content: Oh Goodie, something to watch after supper.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 12, 2018, 12:20:34 am
content: Quote from: AF6LJ on July 11, 2018, 10:35:44 pmI hope you find it entertaining.I found the issue about 30 minutes after I uploaded part one. But that would had made for a 15 minute video. So drew it out a bit.Enjoy your supper.

author: tggzzz
author_rank: Super Contributor
timestamp: July 12, 2018, 08:08:09 am
content: Quote from: Radio Tech on June 24, 2018, 09:31:24 pmHave a look athttps://www.eevblog.com/forum/repair/renovating-an-early-tektronix-475-oscilloscope-a-few-random-hints-and-tips/Similar symptoms, may or may not be the same cause.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 16, 2018, 12:31:03 am
content: Quote from: tggzzz on July 12, 2018, 08:08:09 amGood information. Thanks for sharing.

author: med6753
author_rank: Super Contributor
timestamp: July 20, 2018, 06:56:48 pm
content: I viewed your videos with great interest in that I also have a Tek 465/DM44 that I'm in the process of restoring. And the issues I've had are quite different from what you had and I'll share what I found so far. (It's not done but real close)This 465 came my way a few months ago from a Ham who was selling most of his equipment. I noticed right away that it was in pretty poor shape and had apparently been stored in a damp environment. But the price was right and I decided to give it a shot. First thing I did when I got it home was give it a good cleaning. I got it to the point where it looks decent but you can still tell it's lead a rough life.First attempts at power up did not go well. Line fuse blew immediately. I found the +15V supply solid short to ground. Tantalum caps C4498 and C891 were shorted. At that point I just replaced the ones I found shorted. Future plans are a massive tant cap change.But this did not fix the supply issues and the line fuse continued to blow immediately. The +110V supply was shorted to the +55V reference supply. Extensive carnage here. VR1515 and CR1514 shorted. R1517 burnt. And finally Q1516 and Q1518 shorted. Once all the parts were replaced the scope finally powered up but with a very weak trace.Once I adjusted the +55V reference to nominal, adjusted the HV to spec, and set the CRT bias the trace intensity is now normal and bright. Applied test signals to channel 1 and 2 and it was immediately apparent that there were issues with both attenuator switch decks on the vertical board.Both Volts/Div switch decks were extremely noisy and it was apparent that I would have to pull the vertical board to clean them. It was not fun pulling that board and disassembling the switch decks. But once I got it back together Channel 1 was fine but now I had no trace at all on Channel 2. After a lot of troubleshooting and head scratching it turned out to be nothing more than dirty transistors sockets. Dexoit worked wonders here. Channel 2 trace was restored but still had issues with the attenuator not tracking correctly.More troubleshooting and found the cause. Channel 2 X10 attenuator assembly is shorted. I have a new one on order. Plus new BNC's for both channels. Channel 1 BNC is very worn and intermittent and Channel 2 BNC has an internal short and randomly switches by itself from X1 to X10.Here's some pictures it currently pending replacement of the attenuator and BNC's. I also spray painted the case which really helped to clean it up. And finally, I'd like to thank fellow member bd139 for his suggestions/help in troubleshooting.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 25, 2018, 01:09:31 am
content: Great job on the repair!Looks pretty good to me. You had a bit of work on that one. But now it has come together and another fine unit saved.Well done.Mine is working pretty good and when I get time I will restore it back to spec and give it a good alignment.Thanks for sharing your information.

author: med6753
author_rank: Super Contributor
timestamp: July 25, 2018, 09:14:18 am
content: Thanks! My plans this 465 are the same as yours. Once I get all the issues repaired I'll be doing a complete calibration. I've already calibrated the volts/ohms portion of the DM44 and it came into spec.

author: AF6LJ
author_rank: Unknown
timestamp: July 25, 2018, 03:07:51 pm
content: Looks good