Author Topic: Tektronix 465  (Read 24751 times)

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Offline rqsall

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Re: Tektronix 465
« Reply #50 on: May 13, 2015, 05:05:00 pm »
Well done! And thanks for showing off your work... might come in handy for me one day as well  :-+ :clap:
 

Offline netdudeuk

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Re: Tektronix 465
« Reply #51 on: May 13, 2015, 05:30:31 pm »
It's always good to see someone come here with a faulty machine and get it working with the help of the forum members  :)
 

Offline tautech

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Re: Tektronix 465
« Reply #52 on: May 13, 2015, 05:50:36 pm »
We all want to know when Grapsus is going into production with these?  :-+
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Offline Grapsus

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Re: Tektronix 465
« Reply #53 on: May 14, 2015, 04:07:19 am »
Hi again,

Thank you for your comments, for sure I would never have done this repair without the help of people from this forum.

I hesitate to start a small blog to document things like this so that the info can be found more easily. The forum discussion is good when the device is being repaired but for someone who will have a similar problem years after, reading through tens of pages can be unpractical.

What diode did you use?

The diodes are kind of no-name. I bought them from the ebay seller "high-voltage-hv" who was recommended by forum members here. It just says in the description "10mA 20kV 100ns High Voltage Diode". I wanted to buy the diodes from a good brand but didn't find any on Farnell or Mouser. They only sell diodes up to 4 kV and the requirement was 12 kV.

To avert any risk of the GND and HV lead breaking off, you could have used an eye terminal and solder leads to it, if you have the room around the potted trebler. Thinking of the old stand-off PCB test point type terminal. Then a snug fitting sliding sleeve over the joint.

I agree that there are better options for ground and input connection, but I wanted to finally make this multiplier with what I had at hand. Also the original multiplier does exactly this: the input lead is directly a leg from a capacitor and the ground is just a wire with low-voltage insulation going inside the box. I secured the output wire sleeve to the box with cyano-acrylate, it doesn't move at all.

We all want to know when Grapsus is going into production with these?  :-+

I think it would be safe to wait for a couple of months to see if the new inverter works reliably in the long run. Then I'm totally ok to make other units for just the cost of the parts if it can save other Teks from the landfill.
 

Offline tautech

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Re: Tektronix 465
« Reply #54 on: May 14, 2015, 06:22:16 am »
I agree that there are better options for ground and input connection, but I wanted to finally make this multiplier with what I had at hand. Also the original multiplier does exactly this: the input lead is directly a leg from a capacitor and the ground is just a wire with low-voltage insulation going inside the box. I secured the output wire sleeve to the box with cyano-acrylate, it doesn't move at all.
I probably would have done as you have in your position.

The OEM usually does much the same, however if you have them in and out a few times the leads fatigue, even insulated cable types unless made of quality fine stranded cable.
Something to consider if you make them for others.  ;)
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Offline oldway

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Re: Tektronix 465
« Reply #55 on: May 15, 2015, 02:44:46 am »
One of these beauties...

It is worth it.

I wish you much pleasure with your 465.
 

Offline Kibi

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Re: Tektronix 465
« Reply #56 on: May 15, 2015, 05:30:13 am »
I realise that I am a bit late to the party. I have this specimen that perhaps could have helped you out with it's multiplier.





Having said that, you have done a lot of hard work which you have been kind enough to share and will no doubt help a lot of people in the future.

In your first post you highlighted that some knobs are broken. I can see that CH1's red "VAR" knob in particular needs replacement. Are there any more broken of missing knobs? I may have some if you are interested.
 

Offline Grapsus

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Re: Tektronix 465
« Reply #57 on: May 15, 2015, 07:30:56 am »
In your first post you highlighted that some knobs are broken. I can see that CH1's red "VAR" knob in particular needs replacement. Are there any more broken of missing knobs? I may have some if you are interested.

You're not late at all ! Yesterday I began cleaning the front panel and the knobs before putting everything together. I am going to post a few photos to show the damaged knobs.

You're right the worst damage is on one of the vertical VAR knobs, it's totally shattered and bits of plastic are missing so it can't be glued together. A few hours ago I sent a message to the guy from sphere.bc.ca to ask if he could send me one without $30 international parcel fees.

Another very important piece that's broken is a flexible shaft coupler that connects the timebase VAR shaft to a variable resistor deep inside the horizontal board, the plastic piece in the middle snapped and the shaft rotates without turning the resistor. I was going to salvage the coupler from the astigmatism control which is less important. But if you have one of those, that would be great !!!

There are also cracks on the vertical attenuation selectors, one trigger level selector and the small plastic pieces on the coupling selectors but I think I'll be able to repair all of these with cyanoacrylate.

All these repairs are less important than having a trace on screen, but for sure it would be better to give the scope a perfect undamaged look, it will be more pleasant to use in this way. What drives me crazy is that all this damage comes from rough handling and probably forced disassembling, like someone tried to remove the knobs without loosening the setscrews. Why can't people show some respect to old and cool gear like this  |O

Edit: I added a picture of the damaged knobs. Except for the shattered VAR knob, I think I will just carefully pour some superglue into the crack and press on the sides until it dries.  Also the pictures of a shaft coupler like the one that snapped and a rubber foot that's missing.
« Last Edit: May 15, 2015, 08:16:36 am by Grapsus »
 

Offline Kibi

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Re: Tektronix 465
« Reply #58 on: May 15, 2015, 08:19:30 am »
I would appear that I can fulfil most of your requirements. I cannot do the Vertical attenuation knobs because they were the first to get smashed. As you can see from  my previous photo that those are all bent and smashed. That 'scope was mounted in a bay using the special 19" rack mounting frame designed for these particular 'scopes. Unfortunately whoever installed it did not screw the 'scope into the frame, so when it was being removed from the bay at a height of about 35U - 40U, the 'scope slid out and fell face first onto the floor.

I have everything else though. The coupling selector plastic parts that I have are brand new out of a packet so they will not match the colour of the other lever switches on the front panel.
The "VAR" knob is slightly scratched, but should clean up OK.
All of the knobs pictured below have their grub screws.

 

Offline Grapsus

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Re: Tektronix 465
« Reply #59 on: May 17, 2015, 12:30:57 pm »
Hi again,

Here is an update about the restoration of my Tek 465. Now that the screen is working, I started to progressively reassemble and test everything. Unfortunately it has many other problems. "It's one sick puppy" as Dave would say  :-DD But those problems are a lot easier to troubleshoot.

First I had to re-attach the small chop mode transformer and several other components that have been ripped by someone who carelessly opened the case. I used rigid copper wires to reach as close as possible to the windings. Then I made a small plastic cover so that is wouldn't break again.

After that, I removed the two horizontal boards in order to access the VAR shaft coupler which snapped and replace it with the same coupler that I borrowed from the astigmatism pot. I also cleaned all leaf switches with IPA and paper. I got so fed up with having to desolder 20 wires each time I want to remove those boards that I decided to install connectors. A lot of other connections use the same standard connectors, I don't know why Tek didn't do it the first place, those wires don't carry any high-frequency signals. Now I can get the vertical board whenever I want by just soldering the trigger BNCs :)

Then I reinstalled the timing boards and the timebase selector which was a huge pain to properly align. I never used an old Tek before and this selector wasn't properly attached when I got this scope but now that it works I must say that this is the coolest mechanical switch ever. The thing is a masterpiece of mechanics with all the mechanisms to handle the two timebases and the feel and the sound of it operating is totally pornographic.

With the scope in one piece I started to see traces, but they were all jumpy and noisy. Things where getting especially bad whenever I moved or touched the device. The problem concerned both channels even in GND position. The issue was somewhere close to the CRT, so I started lightly bumping various parts of the scope until I found where it was especially sensitive. It was on the scary circuitboard that connects to the delay line and the vertical deflection plates. Fortunately my unit has the integrated circuit version unlike ModemHead's where 100 components are just soldered together in free air. I took it out and it really looked like someone with poor soldering skills took a go at it, the output wires were almost broken, so I replaced them. Then I looked for cold joints and there were maybe one on one of the silicone resistors. Also the delay line connector was in an ugly condition and its shield legs were broken not making contact with the PCB. I did my best to straighten it and solder rigid wires in place of the broken ground legs. I don't know which of these repairs did the trick, but after them the traces became very stable.

After the multiplier replacement I hadn't adjusted the HV power supply and the CRT bias so the traces were kind of thick. Not having any DMM that goes beyond 1 kV, I had to improvise an HV probe. Luckily I found a high voltage 100 Meg resistor on an old printer PCB. I used it to make a 1000x probe. It did the job and I could adjust the -2450V rail which was way off. I followed the manual to set up the CRT bias and the traces became nicer.

Remaining problems:

The 1X/10X probe lights don't work, probably the bulbs are burnt. I hesitate to replace them with LEDs.

There's something wrong with the intensity control. The knob is very hard to turn and it's very jumpy when I operate it. Also the calibration procedure often says to set the intensity on +15V with respect to a dedicated test point. On my unit this voltage only goes down to 23 Volts.

The B timebase is not sweeping. The A intensified mode works, I can highlight a portion of an input signal, but when I switch to either "MIX" or "B (DELAYED)" there's nothing on screen.

Calibration seems off here and there, I'll have to follow the complete adjustment procedure.

Various knobs cracked as described in my previous post, but thanks to Kibi and his scraped 475 I may be able to give the scope back its perfect visual aspect.
« Last Edit: May 17, 2015, 12:36:21 pm by Grapsus »
 

Offline tautech

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Re: Tektronix 465
« Reply #60 on: May 17, 2015, 12:48:36 pm »
When you get to Cal, check Dave's vid from ~20 min in:
http://www.eevblog.com/2013/08/03/eevblog-502-19-hameg-analog-oscilloscope/
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Offline Grapsus

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Re: Tektronix 465
« Reply #61 on: June 22, 2015, 01:04:59 am »
Hi again !

I think I finally finished restoring this scope. All in all, it was a nightmare to get it to a state where everything works as expected. By far the hardest repair I ever did.

I found why the B timebase wasn't working, Q1098 was dead, internally short, I replaced it with a 2N2222.

I replaced the 1X/10X bulbs with white LED and they look pretty good.

Huge thanks to Kibi for sending me replacement knobs and other mechanical parts. I reinforced the cracked range knobs with superglue. And the front panel is now good as new.

Once everything re-assembled, I found that channel 1 range switch wasn't working properly. I had to remove the vertical board again and clean all the contacts. After re-assembling, the range switch worked fine but the AC/DC selector started misbehaving. So I had to remove the vertical board for the third time to finally get everything right.  :phew:

Regarding the intensity control, I still don't know if I really have a problem. I can get both sharp/dim and thick/bright traces. But turning the intensity knob around half-way already maxes out the intensity.  The service manual says that the peak-to-peak amplitude of the blanking signal at TP1486 should be between 0 and 75 Volts. What I get is between 0 and 105 Volts. If there are any other 465 owners here, can you please tell me if your intensity control behaves in the same way or does my scope have a problem here?

On the positive side, it looks like the 100 MHz bandwidth is really there ! A fast rising edge looks even faster on the 465 than on my 100 MHz Rigol. Also my homebrew voltage multiplier still works like a charm.

Thanks again to people from this forum, it wouldn't have been possible without your help.
 

Offline GreyWoolfe

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Re: Tektronix 465
« Reply #62 on: June 22, 2015, 05:50:08 am »
Beautiful repair and restoration job.  Enjoy the fruits of your labor! :-+ :-+
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Offline tautech

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Re: Tektronix 465
« Reply #63 on: June 22, 2015, 06:30:32 am »
All the scopes that I have fixed, the Intensity can be adjusted until trace is not visible, can you do this?
Normally there is another Intensity bias adjustment to make this possible and the procedure should be described.
That presumes all other CRT voltages are correct.
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Offline Grapsus

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Re: Tektronix 465
« Reply #64 on: June 22, 2015, 06:41:37 am »
All the scopes that I have fixed, the Intensity can be adjusted until trace is not visible, can you do this?
Normally there is another Intensity bias adjustment to make this possible and the procedure should be described.
That presumes all other CRT voltages are correct.

Yes, I can make the trace disappear if I turn the intensity fully counter-clockwise. This threshold can be adjusted with an internal pot named "CRT BIAS", but I didn't even need to. My problem is the other way around, I find that even with intensity at the middle position the trace is way too bright, but I can't tell if it's normal since I've never used another 465. I'd say the useful range for intensity is around 40% of the full rotation, even with x10 mag and the fastest timebase. Maybe it is supposed to work this way, but I found it strange.

The voltages in the service manual are really useless for checking this issue because the whole Z circuit works with currents. Each module that affects the intensity (external input, blanking, A with B intensified etc.) contributes a small current and all the control currents are summed to get the final intensity value.
 

Offline tautech

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Re: Tektronix 465
« Reply #65 on: June 22, 2015, 06:55:53 am »
All the scopes that I have fixed, the Intensity can be adjusted until trace is not visible, can you do this?
Normally there is another Intensity bias adjustment to make this possible and the procedure should be described.
That presumes all other CRT voltages are correct.

Yes, I can make the trace disappear if I turn the intensity fully counter-clockwise. This threshold can be adjusted with an internal pot named "CRT BIAS", but I didn't even need to. My problem is the other way around, I find that even with intensity at the middle position the trace is way too bright, but I can't tell if it's normal since I've never used another 465. I'd say the useful range for intensity is around 40% of the full rotation, even with x10 mag and the fastest timebase. Maybe it is supposed to work this way, but I found it strange.

The voltages in the service manual are really useless for checking this issue because the whole Z circuit works with currents. Each module that affects the intensity (external input, blanking, A with B intensified etc.) contributes a small current and all the control currents are summed to get the final intensity value.
Sounds OK then.
You will need the additional intensity when using the delayed timebase, particullary "A intensified by B" if the 465 has that or similar. This is where the seemingly unneeded intensity is used.
Some scope manuals describe Intensity adjustments in this mode.
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Offline Addicted2AnalogTek

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Re: Tektronix 465
« Reply #66 on: June 22, 2015, 09:40:35 am »
that sounds about right for the Intensity adjustment knob. my 465 is the same way, and from what I understand it's supposed to be that way on these analog Teks with the delaying timebase - for exactly the reason Tautech stated. when you use the B timebase, the intensity will automatically dim in some settings and you will then need the additional 60% or so of the turn to be able to make it visible again.
 

Offline Grapsus

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Re: Tektronix 465
« Reply #67 on: June 22, 2015, 04:06:51 pm »
Ok, thank you for this insight. At least it's not another thing broken in this scope :)

I finally put the case back and now I'll start using this puppy for my circuits. I really like the feel of various controls on the front panel and the very sharp traces. Also it's my first dual timebase scope, I really enjoy using this "analog zoom" where I can highlight a portion of the signal with the intensified mode and then view the detail with the B mode.

My next repair will be a Schlumberger 5224 analog scope (100 MHz, 4 channels, dual timebase), I'll open a thread if there's something interesting or not obvious about it.
 

Offline Addicted2AnalogTek

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Re: Tektronix 465
« Reply #68 on: June 23, 2015, 02:27:29 am »
sounds like you're getting the hang of it's features a lot quicker than I did.   

That should be interesting to see inside of.   You hoping to score the one from Italy or do you already have one?    Looks like it would be a nice 4 channel analog to have for someone on a budget, or just to have.
 

Offline ModemHead

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Re: Tektronix 465
« Reply #69 on: June 23, 2015, 08:22:39 am »
Really nice job on the repair and restoration.  It looks great too.  Hope you get quite a few more years of service from it.   :-+
 

Offline Muxr

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Re: Tektronix 465
« Reply #70 on: June 25, 2015, 12:58:26 pm »
I just read the whole thread. Awesome stuff. This is why I love this forum. Nice job!
 

Offline electr_peter

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Re: Tektronix 465
« Reply #71 on: July 19, 2015, 11:29:35 pm »
Very interesting thread. Great job with restoring oscilloscope :-+

I also have Tek 465 in working condition, but it needs some care. Buttons/switches sometimes fail to operate (cleaning should help), channel 2 BNC is slightly wobbly, few dials are cracked. I am a bit worried about B sweep trigger because it does not seem to work. Otherwise all seems to be OK.

Channel two BNC is slightly loose. How is it connected internally - with a screw or solder? Do I need to desolder shield to get access to it? I am a bit worried such small repair job could take considerable amount of time :scared:

Regarding B sweep - delayed time sweep operation (with B sweep trigger set to "Delayed sweep") works fine on A, Mix, A intens, B modes without any issues.  However, when I set B sweep trigger source to something other than delayed sweep (like Ch1, Ch2, ext), nothing appears on the screen for B - B trigger seems to not trigger at all. I tried same buffered signal to B ext trigger input as Ch1 one, but had no response.
I may not be providing correct type of signal to B trigger input.
Does B trigger circuitry need specific conditions to trigger (timing - right after initial A trigger or similar) or could it be broken?
 

Offline jstwinkles

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Re: Tektronix 465
« Reply #72 on: October 24, 2015, 09:23:52 am »
Hello all,
Just wanted to say thank you for this great thread.  Bought a broken 455 a while back and finally got it working thanks to the information posted here!  It's still got some wonky business with the trace, which seem intermittent, but I'm confident that I can figure it out now that there's at least a trace to debug.

Cheers! ;D
 

Offline Addicted2AnalogTek

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Re: Tektronix 465
« Reply #73 on: November 23, 2015, 11:25:38 am »
Hello all,
Just wanted to say thank you for this great thread.  Bought a broken 455 a while back and finally got it working thanks to the information posted here!  It's still got some wonky business with the trace, which seem intermittent, but I'm confident that I can figure it out now that there's at least a trace to debug.

Cheers! ;D

Intermittent traces tend to be dirty switch contacts and dirty/bad pots. shoot some deoxit gold on the contacts
 

Offline NilByMouth

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Re: Tektronix 465
« Reply #74 on: December 10, 2015, 10:31:12 pm »
I found why the B timebase wasn't working, Q1098 was dead, internally short, I replaced it with a 2N2222.

I don't understand. In the SM I have for low S/N 465, Q1098 is a 2N3906 PNP transistor. The 2N2222 is NPN?

Malcolm
 


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