Tektronix 2465B oscilloscope teardown

[razberik]

The seller obviously didn't really know what he was selling since his reply to me asking for probes was "please explain what probes are and where I can find them".

Use word "cables". "Cable" is more explaining that "probe".
Quite funny in situations where "cables" are more valuable than the instrument itself.

[cheeseit]

I got similar deals on a Tektronix 2440 and 7854 which apparently sat in storage for many years and were in excellent condition.  Later I hunted down a front cover for the 2440 so it remains clean and protected.

The 2nd and 4th channel (I think) did show a bit of noise when the scope was cold but that went away after warming up.

Warming up usually results in better performance from aluminum electrolytic capacitors so this might indicate that they are at the end of their useful life.

I am fussy on exactly which 2465 series oscilloscopes had problems with leaky surface mount aluminum electrolytic capacitors but I do not think the early and late ones did but it is still worth checking.

The readout and traces shimmers a tiny bit randomly from time to time. Otherwise everything appears to work fine but I haven't yet done much testing.

Check to see if this is just an artifact of the beam multiplexing needed to display the readout by disabling the readout.  Sometimes the readout will momentarily synchronize with the sweep to produce visible artifacts.

I was thinking electrolytic caps warming up too so great that you mention this. And this one unfortunately does have leaky surface mount caps but it still haven't caused that much damage.
I will look into the part about beam multiplexing and synchronization. Thank you!

The seller obviously didn't really know what he was selling since his reply to me asking for probes was "please explain what probes are and where I can find them".

Use word "cables". "Cable" is more explaining that "probe".
Quite funny in situations where "cables" are more valuable than the instrument itself.

Cables might have made more sense to him but I would expect him to answer that there is a power cord included.. I don't know about the probes being more valuable than the instrument but it sure was a nice bonus having a working 2465B thrown in when purchasing probes. I'm thinking of selling it once refurbed and perhaps use the money to finally buy a modern scope. I've been wanting a Rigol 1054Z for a while.

Update:
Just a few images for now since I'm of to bed but I've taken the case of and it looks both good and bad. Good because it is really clean, and bad because the surface mount caps have leaked. The damage is not that bad and some scrubbing with alcohol and a brush should take care of it. This is my first time removing corrosion like this so I will have to read up on it using this thread. I thinking replacing the affected resistors and caps, or what? I will at least remove the other components to scrub thoroughly.

I have some side-by-side images of this 1993 next to my 1989 vintage, if anyone is interested? There are a few differences, besides the obvious A5 boards, like different bodges and such.

Corrosion:




The U800 has a strange concave and roughed up mark. Is this a sign that its been cooked? I hope not and would think that it would be convex and not working if so, judging by its looks.

[Old-E]

Taking a scope break –

While still curious about where the upper frequency limit is, I’ve had daydreams of actually seeing 500 MHz displayed.   The 2465B is rated for 400 MHz, which is quite respectable.   But the scope spec’s say it will display 500 MHz!

To find that upper limit, thought I would use my Baofeng handheld radio as a signal source.   This is one of the many slightly different variations of the well known UV-5R which is spec’d up to 520 MHz.   Tested this one to find the upper limits and was pleased to see it top out at 570 MHz.   So that should do well in finding the upper limit of the scope.

The connection was made by simply hooking the scope probe onto the insulated antenna and pressing the transmit button.

Plan was to start out at 570 MHz, then reduce the frequency until the scope was able to lock on to it.   But the scope locked on to the first test at 570 MHz.   And everything was very stable at that frequency.   Wow!

Next test was to see how the frequency readouts worked.   Pressing the delta V & delta T buttons displays the vertical cursor lines that indicate frequency.   For this test the cursors were spread over 10 cycles which read 57 MHz, which = 570 MHz for the waveform.   And again, all was stable and reading correctly.   See photos below.

Repeated the test using the 10x button and adjusted the cursor to cover just one cycle.   And again, everything was stable and accurate.

Then I let the scope determine the frequency by pressing the lower red “HELP” button followed by the channel 1 button.   And as can be seen in the 3rd photo, it easily read out the frequency as 576.9 MHz, while the Baofeng can be seen indicating570.000 MHz on the top indicated frequency, which amounts to a 1% error.   Wow again!

While these frequencies are impressive, they say nothing about the voltage levels that have rolled off quite significantly.   And the scope probe I used was only rated for 100 MHz.   But the same argument could be made for signals at 400 MHz where the scope gain has rolled off by 3 DB, plus probe losses.

The only bad news here is that I still don’t know where the upper frequency limit is.   But, that’s ok, I’ll take what is until I find a higher frequency signal source.

[cheeseit]

Taking a scope break –

Very interesting - I hope you find a higher frequency source!

Update

Now that Christmas is over I finally found some time to continue work on my second 2465B. It cleaned up real nice, except for the BNC's. I took the front panel out and disassembled it and then washed the face plate in warm water and soap. The buttons were washed and then whitened with hydrogen peroxide. The image below doesn't really do it justice but they are gray now, not that brownish-gray like before.
As a pleasant surprise both the implosion shield and the blue filter cleaned up nice too and has hardly any scratches, only a few tiny ones that are only barely visible when viewed from certain angles and in the right light. Combined with the generel cleanliness inside and lack of dust on the fan and on the boards, I'm inclined to believe that the low number of hours on and power cycles are indeed true and haven't been reset.


What unfortunately didn't just clean up is the badge, which is a minor annoyance for now, and the BNC's. It looks like the plating on the BNC's have been eaten through by corrosion. They of course work no problem but their appearance bothers me. The image below is after polishing them once. I would like the scope looking mint if I resell it, so, I've found a source for somewhat cheap (NOS I think) BNC's but am wondering if desoldering and replacing them will affect anything? It's heating up the associated components twice after all. Or are they salvageable, and if so, using what? I've used what I had, which is a product called Silvo, that has worked fine before.




I've started recapping the power supply with the components I had in stock using my new ZD-915 - what a joy it is to finally have a desoldering station. My TL866 has arrived so now I await the arrival of an order from Mouser so I can finish recapping and replace the DS1225Y with FRAM.
Doing this I found some more corrosion, this time under the four 250µF 20V caps on the A3 board. All four have some black gunk around the positive lead but it fortunetly didn't spread that far and cleaned up nicely using a glass fiber brush, alcohol and q-tips. No visible damage after it has been removed.

[Old-E]

Very nice looking scope cheeseit!   Thanks for sharing.   It's amazing what a little soap & water or other cleaners can do.   Certainly increases the perceived value.

My scope arrived very clean inside and out, except for the BNC's that are tarnished.   like yours, they all work just fine, but some cleaning would help the appearance.   You said you used Silvo to clean the BNC's.   Is that a silver polishing compound?

Interesting that you used hydrogen peroxide on the knobs which might brighten mine up too.   Never heard of using it for that.

Your BNC's appear to be pitted, which probably means there is nothing that can be done to fill in the pits.   Appears that your scope may have been stored in a higher humidity environment.

Also have been wanting to suggest that you replace the 4 electrolytic caps on the A5 board ASAP, because they leak, as yours are just starting too.   C 2965 appears to be corroding the adjacent screw head.   Mine was worse and an adjacent IC, U2890, had absorbed the acid which caused it to fail.   Thought those IC's were totally sealed, but this one had a corroded interior when I opened it up, along with signs of corrosion on the exterior solder connections.   So where the corrosive gases migrate to, can be a challenge to forecast.   Other board connections were thinned, but still ok.   Also replaced several other suspected components adjacent to those cap's.

[lordvader88]

why does this thread have some many views/replies for some random scope ?

Anyways I own a Tektronix 2430A, got it for a decent price (I guess) on fleabay, but as it turns out CH1 has a big problem in the vertical gain. But all and all good enough for now.

[tautech]

@ cheeseit and Old-E
There's some good restoration tips in this sticky thread including polishing BNC's.
https://www.eevblog.com/forum/repair/vintageclassic-renovation-techniques/

[cheeseit]

@ cheeseit and Old-E
There's some good restoration tips in this sticky thread including polishing BNC's.
https://www.eevblog.com/forum/repair/vintageclassic-renovation-techniques/

Thanks, don't know why I forgot about that sticky and I remember seeing robrenz fantastic results and thinking that would come in handy sometime. I will try to find what he used but what about replacing the BNC's, I know how to do it but will it affect anything?

why does this thread have some many views/replies for some random scope ?

Because it is a great scope.

My scope arrived very clean inside and out, except for the BNC's that are tarnished.   like yours, they all work just fine, but some cleaning would help the appearance.   You said you used Silvo to clean the BNC's.   Is that a silver polishing compound?

Yes it's primarily for silver polishing but also works on gold, aluminium and chrome. I once gave it a try on some BNC's that were tarnished and it worked great. I'll try some other products but they do appear pitted and had green oxide spots so I think they are too far gone for just polishing.

Interesting that you used hydrogen peroxide on the knobs which might brighten mine up too.   Never heard of using it for that.

It works wonders. Google whiten yellow plastic and you'll find many guides but it's basically about submersing it in a 3%-10% solution and exposing it to UV. Many just place it out in the sun but I've found that using a desk lamp lowered down over the glass jar that I use works great. The LED bulb I use and the little heat from it is enough. I just stir it vigorously from time to time to remove the bubbles that form and rinse it once it looks nice. The aluminium inserts in some of the knobs on the 2465 is not a problem in a low solution but other metals very much react in hydrogen peroxide so remember to remove the set screws.
Some suggest using a UV-sealant afterwards might be a good idea.

Also have been wanting to suggest that you replace the 4 electrolytic caps on the A5 board ASAP, because they leak, as yours are just starting too.   C 2965 appears to be corroding the adjacent screw head.   Mine was worse and an adjacent IC, U2890, had absorbed the acid which caused it to fail.   Thought those IC's were totally sealed, but this one had a corroded interior when I opened it up, along with signs of corrosion on the exterior solder connections.   So where the corrosive gases migrate to, can be a challenge to forecast.   Other board connections were thinned, but still ok.   Also replaced several other suspected components adjacent to those cap's.

I have new caps on the way for exactly that and plan to desolder the adjacent passives and IC's and clean it using brushes, white vinegar, water and alcohol. I'll replace the passives where the solder looks dull and perhaps a few of the 7400 logic IC's but the damage doesn't look that bad so I hope that a thorough cleaning is good enough.

[tautech]

@ cheeseit and Old-E
There's some good restoration tips in this sticky thread including polishing BNC's.
https://www.eevblog.com/forum/repair/vintageclassic-renovation-techniques/

Thanks, don't know why I forgot about that sticky and I remember seeing robrenz fantastic results and thinking that would come in handy sometime. I will try to find what he used but what about replacing the BNC's, I know how to do it but will it affect anything?

That would be up to you. Sure if you want her looking like new then replace them, personally I wouldn't bother.
Grab the part # and have a search in Sphere's stock:
http://www.sphere.bc.ca/test/tekparts.html#catalog

Why I say I wouldn't bother is because when I tried to find BNC replacements that are an exact physical match it can be hard work but the one for this Tek could be a common part and easy to find.
BUT then you have to install them......maybe the scope has to come into many pieces to gain access to the solder joints............nah if they're functional I'd leave them be.

[cheeseit]

Thanks again. I will try polishing it some more, this time using another polishing agent and some buffs on my Proxxon. I already have ordered some BNC replacements though, at €9 a pair, just in case polishing isn't good enough and I can't live with it. I take it that replacing them doesn't pose any problems, apart from quite possibly being a bit laborious.

Man, that Sphere site just takes you back to the bad old days of mid 90's internet..   They do however have a lot of great stuff.

[tautech]

I take it that replacing them doesn't pose any problems, apart from quite possibly being a bit laborious.

It could be worse than just laborious, especially the Gnd connection pins. If the Gnd plane is substantial, as it likely will be as to not fuse if a connection is made that makes a Gnd loop, then desoldering the BNC Gnd pins will require an iron with good thermal mass. These can be tricky but not impossible with a good iron and is one of the reasons why I said if they are functional just leave them be.

[Old-E]

lordvader 88
"why does this thread have some many views/replies for some random scope ?"

How many analog scopes are there that have all these features, and can display more than 570 MHz?

[Michael Lloyd]

I have a number of Tek scopes, including a 2465B and 2467. My favorite is a 545B but that's another era. The 2467 is in storage and the 2465B is on the rack and I use it. How concerned should I be about the battery?, tant's and, electrolytics?

[tggzzz]

I have a number of Tek scopes, including a 2465B and 2467. My favorite is a 545B but that's another era. The 2467 is in storage and the 2465B is on the rack and I use it. How concerned should I be about the battery?, tant's and, electrolytics?

The infamous mains X/Y film caps can be "entertaining" when they fail; in my 2465 a series resistor rapidly dissociated itself and took some of the PCB prepreg with it.

The control board caps are also infamous for venting their spleen over nearby components. Seen that in my 2445B.

A protection against battery failure would use the test routine to examine the nonvolatile memory's contents, and to make a video as you step through each location. Then, if necessary, you could reprogram another memory with the old calibration constants.

[Michael Lloyd]

I have a number of Tek scopes, including a 2465B and 2467. My favorite is a 545B but that's another era. The 2467 is in storage and the 2465B is on the rack and I use it. How concerned should I be about the battery?, tant's and, electrolytics?

The infamous mains X/Y film caps can be "entertaining" when they fail; in my 2465 a series resistor rapidly dissociated itself and took some of the PCB prepreg with it.

The control board caps are also infamous for venting their spleen over nearby components. Seen that in my 2445B.

A protection against battery failure would use the test routine to examine the nonvolatile memory's contents, and to make a video as you step through each location. Then, if necessary, you could reprogram another memory with the old calibration constants.

I've been hesitant to touch the 2465B and 2467 but I'm thinking about recapping the PSU as a precautionary measure. Maybe the control board too (now). I'll look into running the test routine

[med6753]

I have a number of Tek scopes, including a 2465B and 2467. My favorite is a 545B but that's another era. The 2467 is in storage and the 2465B is on the rack and I use it. How concerned should I be about the battery?, tant's and, electrolytics?

The infamous mains X/Y film caps can be "entertaining" when they fail; in my 2465 a series resistor rapidly dissociated itself and took some of the PCB prepreg with it.

The control board caps are also infamous for venting their spleen over nearby components. Seen that in my 2445B.

A protection against battery failure would use the test routine to examine the nonvolatile memory's contents, and to make a video as you step through each location. Then, if necessary, you could reprogram another memory with the old calibration constants.

I've been hesitant to touch the 2465B and 2467 but I'm thinking about recapping the PSU as a precautionary measure. Maybe the control board too (now). I'll look into running the test routine

I recommend you consider recapping the PSU. I recently did my 1985 vintage 2465 DMS and it fixed a drifting issue with the DMM and Counter/Trigger option boards due to a low +5VDC that originated from the Inverter board. This voltage was not part of the group that can be checked on the main board at J119. The attached chart from the Tek Yahoo Group lists all the caps that should be replaced.

If your A5 Control boards are SMD you should seriously consider changing the caps. They are known leakers and will damage the board. The older pin thru hole boards (such as mine) are much less prone to issues and in fact mine is all original.

 

[Michael Lloyd]

Thanks for the parts list. Everything is ordered. $30-ish for a little peace of mind.

A protection against battery failure would use the test routine to examine the nonvolatile memory's contents, and to make a video as you step through each location. Then, if necessary, you could reprogram another memory with the old calibration constants.

I haven't found a test routine that shows the NVRAM contents. It passes the tests I ran with the ?T/?V menu selection but no data is displayed. From what I've read the battery doesn't warn you when it dies...

[Bryan]

I haven't found a test routine that shows the NVRAM contents. It passes the tests I ran with the ?T/?V menu selection but no data is displayed. From what I've read the battery doesn't warn you when it dies...

I believe it is Exercisor 2 test that displays the calibration data.

[Michael Lloyd]

Much appreciated. I checked the service manual and was able to figure out how to retrieve the cal data. I video'd it and put it on YouTube. I don't know if it's useful for anyone else. If it is I'll post a link.

[Old-E]

Mic. L.
There has been some fairly detailed entries in this thread, over the past year or two, on saving and transferring the digital calibration data for your scope.   it would be good to publish your experiences here too for all those interested.   Many of these improvements / restorations are laborious.   But the scope one ends up with is quite good.   

[med6753]

Thanks for the parts list. Everything is ordered. $30-ish for a little peace of mind.

A protection against battery failure would use the test routine to examine the nonvolatile memory's contents, and to make a video as you step through each location. Then, if necessary, you could reprogram another memory with the old calibration constants.

I haven't found a test routine that shows the NVRAM contents. It passes the tests I ran with the ?T/?V menu selection but no data is displayed. From what I've read the battery doesn't warn you when it dies...

Good deal.  When you get ready to replace the caps on the Regulator and Inverter boards do NOT do a mass remove then go back and do a mass install. There are minor differences between the 2465, 2465A, and 2465B. Plus there are discrepancies with the board lettering and the schematics which Tektronix never fixed. Doing a mass replace then install will result in aggravation and magic smoke. Do one or two caps at a time and compare value, orientation, and voltage rating as you replace them. Granted that's inefficient but it will be accurate.

Also you'll notice that C1110, 1111, 1113, 1114, 1115, 1116 have all been "upgraded" to 330uf. I followed that recommendation and everything works fine.   

[Bryan]

Much appreciated. I checked the service manual and was able to figure out how to retrieve the cal data. I video'd it and put it on YouTube. I don't know if it's useful for anyone else. If it is I'll post a link.

Wish I ran the test and recorded the data before replacing my Dallas. Something went wrong and I lost all the calibration data. @#$*$*($. Why don't you go ahead and post the link

[Bryan]

Good deal.  When you get ready to replace the caps on the Regulator and Inverter boards do NOT do a mass remove then go back and do a mass install. There are minor differences between the 2465, 2465A, and 2465B. Plus there are discrepancies with the board lettering and the schematics which Tektronix never fixed. Doing a mass replace then install will result in aggravation and magic smoke. Do one or two caps at a time and compare value, orientation, and voltage rating as you replace them. Granted that's inefficient but it will be accurate.

Also you'll notice that C1110, 1111, 1113, 1114, 1115, 1116 have all been "upgraded" to 330uf. I followed that recommendation and everything works fine.   

Good advice and take lot's of pictures of your board before recapping. There is either a error on the Tek schematics or a error on the board silkscreen for one of the caps and the polarity is reversed. Can't remember which cap, but best to replace one at a time so you don't miss it. Also note that some boards have one extra bi-polar electrolyte's where the replacement list only shows one. Think it's the later revisions, so best to order a extra or two.

[peter-h]

Hello everyone!

I have a 2465B which I bought about 10 years ago, refurbished by a firm which used to sell new and used Tek gear - Hesing Technology in the UK (disappeared some years ago).

It's been working great until a few days ago. The front panel has basically packed up. The LEDs are mostly illuminated although many appear at a low brightness. The rotary switches work fine, pressing the buttons which activate what sounds like range switching relays does create the right relay clicking noises, so it almost looks like it is just the LEDs which are not being driven correctly. But I also notice that the AC/GND/DC/GND/DC selection on each channel doesn't seem to work, so some of the momentary buttons seem to have also acquired only a partial functionality.

I have been doing hardware/software development since the 1970s and have download the service manual mentioned in this thread. And I have read hopefully all of this great thread but can't see this issue mentioned. So while I can start with the service manual, to get me started faster, has anyone here come across this issue before?

I do have another scope - a cheap 25MHz DSO - and various DVMs I can use.

Page 461 (front panel troubleshooting flow chart) seems relevant. I entered the Exerciser 01 mode and all the switches and pots are getting picked up. However, I can't find anything in the manual on the switch codes referred to on that page. Also the four 2-digit hex values seem to change in a funny way. Hard to describe without doing a movie but pressing a given switch once registers on the switch code display (in the first two groups), pressing it again registers too (this time in the second two groups) and subsequent presses don't change anything. This may well be right but it's not what I would expect from a keypad scanned in the usual matrix way. Why the two button presses?

But definitely every switch and every pot does work, so maybe the input mode selector issue is either imaginary (the CRT display doesn't show everything) or there is a separate issue.

The LEDs clearly don't work. I will have to check the items referenced there. The attached image shows that nearly all the LEDs are lit up to some extent.

Has anyone come across this before?

Many thanks for any input!

EDIT: I found table 6-17 for the switch codes. It doesn't suggest that pressing a switch twice should change anything on the switch code display...

[james_s]

The first thing I would do is check all of the power supply rails. A dead or off-spec output can cause all kinds of issues.

I hadn't seen this thread yet but those are some great pics. That scope, like most Tek gear is a work of art. I have a lot of respect for the guys who designed this stuff. Wonder if those hybrids could be replicated by modern SMD components on a small PCB?