EEVblog #695 - Mailbag Tektronix 2465 Analog Oscilloscope

[EEVblog]

Sagan & Dave take a look at a couple of Tektronix 2465 analog oscilloscopes, and compare the march of technology.
Thanks to Eric Wasatonic:
https://www.youtube.com/user/ElectronicTonic156

[con-f-use]

I swear to god Sagan looks exactly like me, when I was his age. A bit scary, actually but he's going to grow up to be a handsome lad ^^

At min 14:49 one of the diodes seems to lack a bit of solder on one leg.

[(In)Sanity]

I've got a mint condition fully functional and calibrated 2465BDM that I just love.  I still use my DS2000A series more often,  but that's just because I don't want to age the jewel of a Tek.   The ASIC's overheat without the case and the proper air flow.  Even when servicing you should have air moving over them.   I've added the heat sink to the U808 or something like that chip on the one I've got.   Great scopes.

Jeff

[(In)Sanity]

Ohh,  forgot to mention.   If that Dallas NVRAM goes..you loose ALL of your calibration.   The scope will become useless.   I've already replaced the one on mine with a brand new model,  yes they still make them.    I'm pretty good at calibrating them now,  I've done it a few times to get it perfect.   The DMM on mine was the biggest pain.   The 3457A I have was good enough for a transfer standard.

Jeff

[Gibol]

Some troubleshooting video of the newer model would be nice! I hope that you can repair one of them. They look like a decent scopes

[c4757p]

Oh boy - power's on but the fan's not. Hopefully nothing overheated.

[Howardlong]

Great scopes. I have the 2467B, same as a 2465B but with the MCP CRT for enhancing fast, low repetition sweeps. I had a 2465B for some years, and regretted selling it five years ago, so I recently bought the 2467B, when it arrived it was like being meeting a long lost twin.

I repair video would be awesome!

[guido]

You will have fun with the repairs and calibration. There is a huge thread on the forum on these scopes. Including putting a heatsink on U800. Indeed you need airflow without a case! But i've also been told that the failing of U800 has to do with the manufacturing. The older ones are made by Tek and don't fail (that much).

The 2465 is indeed missing the shielding of the PS. There is no Dallas chip, but instead there is a very early EEPROM, called EAROM. As for serial numbers, Bxxxxxx is only Beaverton. They were made in other places; the 2465 in five according to the service manual (US, Guernsey, London, Sony/Tek Japan and Heerenveen in the Netherlands). My 2465 is from Guernsey. Every location has their own serial number counting i think.

I'm not so sure i would prefer the B model.... Dallas chips that go bad (but an easy fix), leaky SMD caps destroying the pcb's, PLS logic that can loose it's content (seen it in a 2710 SA, noticed at least one of those in the video) and failing U800 chips.


 

[Fsck]

didn't someone do an MRAM or other non-battery backed ram replacement for the dallas (calling it nvram is such a lie!)?

[warp_foo]

Is it just me, or does the component at 11 o'clock to U485 @ 16:02 have an un-soldered lead?

[EEVblog]

Ohh,  forgot to mention.   If that Dallas NVRAM goes..you loose ALL of your calibration.

Not for the analog scope part though of course, that should work just fine.

[c4757p]

Ohh,  forgot to mention.   If that Dallas NVRAM goes..you loose ALL of your calibration.

Not for the analog scope part though of course, that should work just fine.

Many bits in the analog section are set by DAC, which is calibrated in software. It's only got a few pots, most of which are for nonessential things.

[guido]

Including the analog stuff. It's all calibrated in software. Even the 2465 stores calibration constants and front panel settings in the EAROM.

I have a pdf from someone on the 2465B with some common fixes. Sent me a pm if you want it. Answer will be tomorrow, it's quite late over here...

[Phaedrus]

Just a heads up, my 2465a has the same or a very similar processing board to the 2465b you looked at. And mine has main ASIC date codes of late 1986, for a model that went on sale in 1987. So it didn't take them a very long time at all to transition to the more advanced processing with SMT package chips.

[EEVblog]

Many bits in the analog section are set by DAC, which is calibrated in software.

Really?
The gain of the vertical attenuators is set by a DAC?

[(In)Sanity]

Ohh,  forgot to mention.   If that Dallas NVRAM goes..you loose ALL of your calibration.

Not for the analog scope part though of course, that should work just fine.

The analog parts are all controlled by a 12 bit DAC with a bunch of sample and hold amps.   Yes the entire scope will become useless until you re-cal it.  Well...perhaps not useless..but really messed up.

Jeff

[c4757p]

Many bits in the analog section are set by DAC, which is calibrated in software.

Really?
The gain of the vertical attenuators is set by a DAC?

No, but the gain of the preamp is. Consider - the entire front panel is scanned by an ADC - how else would the vertical VAR control work?

[(In)Sanity]

Many bits in the analog section are set by DAC, which is calibrated in software.

Really?
The gain of the vertical attenuators is set by a DAC?

No, but the gain of the preamp is. Consider - the entire front panel is scanned by an ADC - how else would the vertical VAR control work?

Actually scanned by the same 12 bit DAC acting like an ADC.   Same with the auto trigger set.   I think they used that thing in more ways that I can count.   The caps around that DAC and divider resistors are famous for leaking and throwing the reference all over the place.

[c4757p]

Yup. They definitely got their money's worth out of that DAC.

Have a look at the schematics for the input section. This isn't your standard "pile of pots" analog scope frontend.

(2445A/2455A attached as it's the only one I've got handy in PDF. 2465's similar.)

Related note: when I say entire front panel, I mean it! Those aren't encoders, those are continuous-rotation pots!

[Orpheus]

Posting to subscribe to this thread because I restored a scope of this series for my local hackerspace, but never finished calibrating it. (Some members have been using it anyway, with good results)

Anyone have a good DIY PG506-equivalent squarewave circuit? (IIRC, it calls for a 1v square wave with <1ns risetime and <5% overshoot. I'd have to look up the exact specs)

[rf-loop]

Many bits in the analog section are set by DAC, which is calibrated in software.

Really?
The gain of the vertical attenuators is set by a DAC?

There is lot of digital controls in this scope (all 2400 series analog scopes)

There is available service manual.  One version is here. If this version do not pass for version there is available very good manuals from Qservice. http://168.144.151.127/manuals/91.158.77.183/Tek_2465_Service_and_Instruction_Manual_Oct84.pdf
Chapter 5 then you know.
Also in service manual quite deeply explained how it works. (Theory of operattion, Chapter 3)

It is easy calibration using oscilloscope calibration menu and if have all needed equipments. (service mode need enable moving jumper on the A5 board)
It is real pain to calibrate if do not have suitable equipments.


Also it need note that therer is important information what also need know. So do not just open case and  jump to chapter 5 and start  cal. There is enough amount of these scopes around in markets what have burned hybrids, just because all kind of noobs think they know all how to do and manual is many times  last thing what to read - after all is loosed.

When I have calibrated these models I have used  Tek CG5011 or CG5010 etc and  external oscilloscope (yes it need also) etc it is quite easy if follow service manual  exactly including which order things need do.

[(In)Sanity]

U800 was the chip I ended up attaching a decent heat sink to.   They are a common failure point.   It's already been pointed out in this post.

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg70295/#msg70295

Jeff

[gnif]

My first scope was a 2645A that I picked up from eBay for $300 due to displaying a fault code, so I dug out the service manual and found that the code was that the Dallas NVRam battery was low... when it arrived there was no fault, and it powered up fine, it has never missed a beat! 

[coppice]

Its hard to know what to read into instrument serial numbers, as many people start counting from some kind of random number. However, many popular high end instruments, which where made for a number of years, only reached a serial number of a few 10's of thousands. The HP history site says they only made 40k of the 1740, which was made for several years and was a popular choice for those with the budget. That makes me think the 1741 (basically a 1740 with storage tube) could only have been made in the hundreds per annum. They really made some of the exotic components for these things in amazingly small numbers.

[edavid]

I've got a mint condition fully functional and calibrated 2465BDM that I just love.  I still use my DS2000A series more often,  but that's just because I don't want to age the jewel of a Tek.   The ASIC's overheat without the case and the proper air flow.  Even when servicing you should have air moving over them.   I've added the heat sink to the U808 or something like that chip on the one I've got.   Great scopes.

This is misinformation:

1. The 2465 series scopes will run fine without the case, with no overheating issue.  You are confusing them with the 2430/2440 DSOs.

2. There is no evidence that adding a heatsink to U800 reduces the failure rate (which is not that high any more, seems like most of the bad U800s have already failed).

[(In)Sanity]

I've got a mint condition fully functional and calibrated 2465BDM that I just love.  I still use my DS2000A series more often,  but that's just because I don't want to age the jewel of a Tek.   The ASIC's overheat without the case and the proper air flow.  Even when servicing you should have air moving over them.   I've added the heat sink to the U808 or something like that chip on the one I've got.   Great scopes.

This is misinformation:

1. The 2465 series scopes will run fine without the case, with no overheating issue.  You are confusing them with the 2430/2440 DSOs.

2. There is no evidence that adding a heatsink to U800 reduces the failure rate (which is not that high any more, seems like most of the bad U800s have already failed).

Good to know,  I'm however leaving the heat sink in place

Jeff

[c4757p]

2. There is no evidence that adding a heatsink to U800 reduces the failure rate (which is not that high any more, seems like most of the bad U800s have already failed).

No, but there's not much sample size to discredit the procedure either, and for the minimal effort it's definitely worth the attempt if it does do anything. The chip does run hot, which tends to accelerate most types of aging.

Though from what I've seen in the 2445/2455 (never had a 65), you seem to be right about the bad ones having mostly failed by now.

For a while, I had entertained the idea of designing modern replacements for some of the hybrids in that thing - someone else has done that too, might have been for U800. A lot of them could pretty easily be replaced with modern high-speed analog ICs now.

[edavid]

2. There is no evidence that adding a heatsink to U800 reduces the failure rate (which is not that high any more, seems like most of the bad U800s have already failed).

No, but there's not much sample size to discredit the procedure either, and for the minimal effort it's definitely worth the attempt if it does do anything.

Unless you damage U800 while installing the heatsink 

The chip does run hot, which tends to accelerate most types of aging.

It's not a normal aging issue, it's a die attach failure.  For all we know, high temperatures help it stay attached.

If a heatsink helped, you would think Tek would have added them at some point... they were certainly replacing U800s under warranty.

[SeanB]

Possibly they figured the heatsink would reduce the failure rate, but that you would have to add it with a new chip as well, as the old one would be somewhere between good and fail. Changing the few percent that failed in warranty, and then repairing at cost was probably cheaper than replacing all the chips with new.

[edavid]

Possibly they figured the heatsink would reduce the failure rate, but that you would have to add it with a new chip as well, as the old one would be somewhere between good and fail. Changing the few percent that failed in warranty, and then repairing at cost was probably cheaper than replacing all the chips with new.

If Tek thought a heatsink would help, they would have added one when they replaced U800, or when they had the scope in for some other repairs.

[(In)Sanity]

Possibly they figured the heatsink would reduce the failure rate, but that you would have to add it with a new chip as well, as the old one would be somewhere between good and fail. Changing the few percent that failed in warranty, and then repairing at cost was probably cheaper than replacing all the chips with new.

If Tek thought a heatsink would help, they would have added one when they replaced U800, or when they had the scope in for some other repairs.

I'm not sure why we are arguing about the merits of removing excess heat from a chip that runs really hot.   If we were talking about removing a heat sink then I can see it.  Perhaps a Tek employee can answer the question.   I think we should focus our attention on what could be wrong with the B version Dave has instead of worrying about a non-issue.

Jeff

[edavid]

I'm not sure why we are arguing about the merits of removing excess heat from a chip that runs really hot.   If we were talking about removing a heat sink then I can see it.  Perhaps a Tek employee can answer the question.   I think we should focus our attention on what could be wrong with the B version Dave has instead of worrying about a non-issue.

Just for fun, like all the other arguments we have here.  Anyway, U800 runs about 60C without a heatsink... hot but not "really hot".

[(In)Sanity]

I'm not sure why we are arguing about the merits of removing excess heat from a chip that runs really hot.   If we were talking about removing a heat sink then I can see it.  Perhaps a Tek employee can answer the question.   I think we should focus our attention on what could be wrong with the B version Dave has instead of worrying about a non-issue.

Just for fun, like all the other arguments we have here.  Anyway, U800 runs about 60C without a heatsink... hot but not "really hot".

Ok,  sorry...carry on.

[trackman44]

Hi Dave. I have a 1985 vintage 2445 that I fixed using parts from a second unit ( I replaced the missing U800 chip from the scrap one). You know what you always say when a unit doesn't work, check for voltages!  I replaced all the electrolitics on the PSU and downloaded the service manual and adjusted the voltages to spec and it works like a champ. Do this first and cross your fingers your vertical deflection chips are still OK!

Will

[Rasz]

different outcome after unit warmed up is a sign of dried caps, warmed up regain some capacitance and allow digital side of the scope to stay on (albeit hung/stopped). It does look salvageable

[G4ZWI]

Yep, what Rasz says,...  I picked up a 2445 for a song which was coming up with allsorts of selftest fails, hit & miss powerup etc,... after a PSU electrolytic cap replace, and set up, has given sterling service for years,.... Some custom parts are available from QService  ( on the Greek island of Rhodes)
Not cheap, but seem to stock most of the hard to get bits... I did stick a small heatsink on my U800, it has never given any trouble, but as I had the unit apart......
If you decide you don't need them, Dave, I'll send you the shipping to 'The Old dart',  I'd love em!!!!

Cheers,  Merry Christmas & a Happy New Year to you & yours,...

Fred G4ZWI

[Howardlong]

...and for those of us too lazy to fix 'em, I can recommend ebay seller f1power01 in Europe who frequently has both 2465 and 2467 in stock at what I consider to be reasonable prices (for the EU).

http://stores.ebay.co.uk/Electronique-professionnel/_i.html?rt=nc&_nkw=Tektronix&_sid=454615688&_trksid=p4634.c0.m14.l1581&_pgn=3

Last week they had a 2465B (£286) and a 2467B (about £350) they seem to be gone now, but there's a good selection of 2465A there now.

I've had both a 2465B and a 2467B off this seller. Delivery is about a week to arrive from France to The Old Dart. (BTW maybe I've lived under a rock, never heard that before).

I have no connection with the seller other than as a satisfied customer.

One comment I should add for new players is that when you first switch them on, be patient. Nothing visible happens for a few seconds. The first 2465B I bought about 12 years ago I thought was DoA until I realised impetuosity isn't a good quality to have on these occasions. Also getting the illumination right and finding the trace can take a short while particularly if you're new to the scope. Make sure you have trigger Auto or Auto Lvl set to aid this so it's continually triggering. I find myself frequently changing the trace illumination of these scopes, a feature common to all CROs to one degree or another, but I seem to have to do it a bit more on the 2465/7s.

[kevinpt]

Just a note for those inspired to hunt one of these down. The Original and A (350MHz) models of the 2465 keep the cal. data in a regular SRAM with a separate backup battery instead of the Dallas chip used on the B models. It is easier to replace the battery on these while powered up without upsetting the data than dealing with the Dallas parts. That is a positive factor in their favor. Also, the custom ICs on the older models were all made at Tek's fab and have a lower failure rate than the ones used on the early B models when IC production was shifted to an outside vendor. Apparently the issues were sorted out by the end years of production for the B's. The A's have most of the new features that the B models have except for the auto-measurement capability.

The service manual is also a good read. A whole section is dedicated to describing how they implemented the algorithm to make the 360-degree pots on the front panel act like digital encoders without a jump when the wiper crosses over the non-conductive region. They did it by using ganged pots with the wiper of one rotated 180-degress with respect to the other and switching from one to the other when nearing the gap. You don't see that sort of attention to detail anymore in instrument documentation.

[guido]

The original 2465 does not have a battery. Cal data and front panel settings are stored in an early form of EEPROM (called EAROM, electrically alterable ROM). See the service manual 

[Howardlong]

In case you're still in the market for one of these, I did a video of the difference between a 2465B and 2467B.

http://youtu.be/ZGi1Uw8l-ac

Here I dispell the urban myth that electronic engineers have to sit in darkened rooms. Well they don't if they have a Micro-Channel Plate (MCP) oscilloscope anyway.

The Tektronix 2465B and 2467B are generally identical oscilloscopes, except for the screen (aka CRT, or cathode ray tube for the younger viewers).

The 2467B CRT uses MCP technology which allows the user to easily see very small repetitive but relatively infrequent pulses. The 2465B uses a conventional CRT.

The same applies when comparing the 2465A to the 2467, where the primary differentiator between the 2465A and 2467 models was the MCP CRT. (There was no 2467A).

The test shown uses a Jim Williams pulse generator which generates a 6ns pulse every 82us or so, a duty cycle of about 1:13,500.

[edavid]

The same applies when comparing the 2465 to the 2467, and the 2465A to the 2467A, where the only differentiator between the 2465x and 2467x models was the MCP CRT.

Minor correction, there is no such thing as a 2467A.  The 2467 is closer to the 2465A than the 2465.

[Howardlong]

Thank you, I will correct that, lucky it's just words and not in the video!

[barjammar]

It was a touching moment to see young Sagan learning how to do a two-thumbs-up from his dad.  I think there is a developmental milestone somewhere for when kids learn to copy hand shapes and gestures but I couldn't find a reference tonight.  I saw Sagan again in the recent soldering of the 8 bit computer, four years later.  He reads well and has a fair comprehension of decimals, at least for solder wire thickness.  Great effort Sagan!