Author Topic: #170 Tektronix 465 review and troubleshoot Part 1  (Read 2925 times)

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Offline bd139

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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #25 on: June 27, 2018, 05:04:21 pm »
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.
 

Offline MasterTech

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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #26 on: June 27, 2018, 05:14:54 pm »
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.

I 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
 

Offline bd139

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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #27 on: June 27, 2018, 05:28:21 pm »
Anything above 20 years is pretty good IMHO used or not.
 

Offline Radio Tech

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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #28 on: June 27, 2018, 05:44:05 pm »
Always worth tightening up all the mounting screws on the 465. Surprising number of weird things can be cured with that simple step.

Agreed. One of the first things I did. They can always be problematic.

Offline Radio Tech

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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #29 on: June 27, 2018, 06:07:20 pm »
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.



« Last Edit: June 27, 2018, 07:03:24 pm by Radio Tech »
 

Offline bd139

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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #30 on: June 27, 2018, 06:19:47 pm »
Nice job  :-+
 
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Offline Radio Tech

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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #31 on: June 27, 2018, 06:27:50 pm »
Nice job  :-+

Thanks!
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.

Offline AF6LJ

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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #32 on: June 27, 2018, 08:27:36 pm »
Nicely done Buddy.
Sue AF6LJ
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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #33 on: June 29, 2018, 10:37:47 pm »
Nicely done Buddy.


Sorry 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.
 
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Offline Radio Tech

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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #34 on: July 11, 2018, 10:14:28 pm »
Part two of this repair.
We now have a fully working scope, so we will have a part 3 of the restoration.



Offline AF6LJ

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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #35 on: July 11, 2018, 10:35:44 pm »
Oh Goodie, something to watch after supper.
Sue AF6LJ
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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #36 on: July 12, 2018, 12:20:34 am »
Oh Goodie, something to watch after supper.

I 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.
 
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Offline tggzzz

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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #37 on: July 12, 2018, 08:08:09 am »
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.

Have a look at https://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.
« Last Edit: July 12, 2018, 08:14:34 am by tggzzz »
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline Radio Tech

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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #38 on: July 16, 2018, 12:31:03 am »
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.

Have a look at https://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.


Good information. Thanks for sharing.  :-+

Online med6753

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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #39 on: July 20, 2018, 06:56:48 pm »
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.   



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Offline Radio Tech

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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #40 on: July 25, 2018, 01:09:31 am »
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.
 
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Online med6753

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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #41 on: July 25, 2018, 09:14:18 am »
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.
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Offline AF6LJ

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Re: #170 Tektronix 465 review and troubleshoot Part 1
« Reply #42 on: July 25, 2018, 03:07:51 pm »
Looks good  :-+ :-+
Sue AF6LJ
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