Vintage Oscilloscopes & Computers

[Hugo Holden]

Recently I repaired a vintage scope, a UK made Telequipment D52. While not the most amazing scope in terms of bandwidth around 7MHz. it does have some interesting qualities when fitted with the long persistence CRT, that make it behave like a storage scope. Also, unlike most dual channel CRT scopes, it is a true twin beam CRT , usually "dual trace" is done using a single beam CRT with either ALT or Chop modes, which can introduce some interesting artifacts, unless you are aware of them. Older scopes can have applications in aspects of computer repairs. Though most people would probably go for a modern scope or a digital scope. I wrote up an article about repairing the D52, it had some interesting "self Cracking" resistors, and I noted that Telequipment instrumentation appeared on the control panels in the famous Gerry Anderson's TV series the Thunderbirds, all done with giant Puppets.

https://worldphaco.com/uploads/REPAIRING%20THE%20AMAZING%20TELEQUIPMENT%20D52%20DUAL%20BEAM%20OSCILLOSCOPE.pdf

 

[Chuck(G)]

I recall working with a Tek 564 storage scope back in the day. It was very frustrating, particularly when dealing with high-frequency events--the stored trace could be very dim. But it was the only scope that could store a trace (actually 2).

I still occasionally pull out my 465 scope on its cart. There are some tasks that are just easier with an analog 'scope.

 

[NeXT]

I'm both too poor and too stubborn to invest into ANY modern-ish digital storage oscilloscope (one of these days I dream Keysight is gonna come knocking with one of their "youtube creator-grade" scopes...) so I actively continue to use analog scopes for debugging and other assorted tasks. I have tried using storage modes but most of my tubes are too heavily used for the storage modes to be all that usable.

 

[Quagmire]

I recall working with a Tek 564 storage scope back in the day. It was very frustrating, particularly when dealing with high-frequency events--the stored trace could be very dim. But it was the only scope that could store a trace (actually 2).

I still occasionally pull out my 465 scope on its cart. There are some tasks that are just easier with an analog 'scope.

Back in my post Navy cal lab days (Raytheon), we primarily delt with the US Navy on a contract basis. The shipboard electronics shops, which we supported, had Tek scopes for the most part and some H/P storage scopes. H/P storages scopes had about a 9" circular storage CRT which had fairly good persistence in the store mode. The H/P's were difficult to work on and had very small diodes in the timing circuits which were hard to locate let alone test. This was all prior to digital and solid state phase-lock circuits were just coming into their own.

 

[Zare]

My high school had to kick the old stuff sometime, but I didn't think of it when I was supposed to, only recently...
I'd really like to recover a good old 100-200 MHz scope, digital ones aren't cheap at all.

 

[Hugo Holden]

My high school had to kick the old stuff sometime, but I didn't think of it when I was supposed to, only recently...
I'd really like to recover a good old 100-200 MHz scope, digital ones aren't cheap at all.

The scope I would recommend is the Tek 464 (or 466). These are fantastic, I have three of them (I went nuts over them) They can store for very long periods and its easy to photograph the display. In non storage mode they are a beautiful performer, so its better to have the ability to store in the scope, even if you don't use it much. The construction quality is unmatched by any modern scope.

The thing is, and here is what most don't know, certainly ebay sellers don't appear to be aware of it at all:

The truth of it is not in clearly stated in the manuals either (there are two different service manuals), unless you can read between the lines and inspect the scope's interior and test them out with leveled sine wave generators. After serial number B200000 and up, Tek make a massive upgrade to the 464 scope, though curiously did not change its manual specs or its model number. Though in the later manual it did say the vertical amplifiers were 100MHz..or better.

Tek completely re-designed the Vertical amplifiers and went to a Gilbert Cell front end, in a custom Tek chip. (this had large advantages including a very easy invert for channel 2). Also they upgraded to panel LED's and altered the front panel artwork making the scope change easy to recognize externally at a distance, but still is was said to be a 464 model scope.
(compare the photo I have attached to many other 464 scope images on the net)

Now the manual specs in both manuals say the 464 is a 100 MHz scope implying, perhaps, that its vertical amplifiers are -3dB down at 100MHz. While I don't have the earlier 464 versions to check (I insisted on the updated versions for myself), I can promise you that the late model 464 is perfectly flat to 150MHz and only -3dB down at 160 MHz. I have Tek leveled sine wave generators to test & calibrate them.

And here is another surprise; the Tek 2465B is a 400MHz rated scope. But Tek could have marketed it as a 650MHz one. Because it is flat to well over 400MHz and only -3dB down at 650MHz and 6dB down at 760MHz, it is astonishing. Mind you my scopes are all in perfect calibration. I have attached 5 test images

Also, though I don't have one to check, but apparently some time in the past I read that an ebay seller/repairer found this out; the 2465A that was rated by Tek as a 350MHz scope was actually flat to over 400MHz on testing, so the seller started to re-badge the 2465A's as 2465B's because he had 2465B badges. He said that Tek made an error and he found them out. Still I didn't like that much because the two scopes were a little different inside and I don't think the bandwidth of the A model was as good as the B, and passing one off as the other is not ethical. Also accusing Tek of making a mistake, well that is bordering on Blasphemy, because to me at least, Tek were the Gods of scopes who always, historically at least, delivered more than they promised.

So it seems in the old days, Tek and Telequipment, both significantly under-rated the bandwidth capabilities of the vertical amplifiers in their scopes. That sort of under-spec-ing doesn't happen any more.

In any case, I suggest that you get the late version of the Tek 464 (like the one in the attached photo, you will fall in love with it and never sell it). I wrote an article on these to help calibrate them:

https://www.worldphaco.com/uploads/TEKTRONIX_OSCILLOSCOPES.pdf

 

[Quagmire]

Way back in the Tektronix tube type o'scope era, the Tektronix mil-spec maintenance manuals were arranged to really help the military service technician. They featured a tiny 'wizard', complete with pointy hat and robe in the manual's page margin, along with tiny foot prints which would lead you to another relevant troubleshooting page. Very clever.

 

[Hugo Holden]

Way back in the Tektronix tube type o'scope era, the Tektronix mil-spec maintenance manuals were arranged to really help the military service technician. They featured a tiny 'wizard', complete with pointy hat and robe in the manual's page margin, along with tiny foot prints which would lead you to another relevant troubleshooting page. Very clever.

Clever, I wonder ?

Tek and many other instrument makers had to "play along" especially with military contracts, in that they were expected to provide such fault finding charts.

The whole notion of it was completely flawed at the basic logic level. The fault finding charts were 95% useless and not worth the paper they were written on. The problem was, they were based on "imagined faults" that might occur in an instrument. But, like Horatio: there were many more faults that could occur that were not imagined in their Philosophy.

The result was that nearly all of those charts and the Wizard pointing to the likely culprit, ended in a dead end.

Part of the issue with the whole idea that you could guide a Technician like a Chimp through a fault finding exercise, was predicated on the notion (by management) that the Technician cannot think for themselves. Or perhaps if they did it should be discouraged.

In the military the notion was prevalent, in that people "followed orders" and would never question them (even when they were plainly stupid) The idea that a Technician might have to think for themselves, analyse a problem, then formulate a hypothesis for themselves and test that with their examination, to repair an instrument, was not only "unappealing to management" but an affront to their perceived superiority. Imagine that , if a subordinate actually had to possess analytical thinking and make unique decisions?

The reality is though, to effectively repair a lot of electronic equipment, especially more complex mixed Analog and Digital circuits seen in devices like Tek scopes, it requires a high level of electronic knowledge, experience and analytical thinking, to say nothing of patience and care. These latter two qualities, mostly being sadly missing, in places such as Scope Calibration Houses, that claimed they were scope Experts. Believe me, I have seen the damage wrought on Tek scopes in some of these ISO certified Houses.

 

[Quagmire]

Clever, I wonder ?

Tek and many other instrument makers had to "play along" especially with military contracts, in that they were expected to provide such fault finding charts.

The whole notion of it was completely flawed at the basic logic level. The fault finding charts were 95% useless and not worth the paper they were written on. The problem was, they were based on "imagined faults" that might occur in an instrument. But, like Horatio: there were many more faults that could occur that were not imagined in their Philosophy.

The result was that nearly all of those charts and the Wizard pointing to the likely culprit, ended in a dead end.

Part of the issue with the whole idea that you could guide a Technician like a Chimp through a fault finding exercise, was predicated on the notion (by management) that the Technician cannot think for themselves. Or perhaps if they did it should be discouraged.

In the military the notion was prevalent, in that people "followed orders" and would never question them (even when they were plainly stupid) The idea that a Technician might have to think for themselves, analyse a problem, then formulate a hypothesis for themselves and test that with their examination, to repair an instrument, was not only "unappealing to management" but an affront to their perceived superiority. Imagine that , if a subordinate actually had to possess analytical thinking and make unique decisions?

The reality is though, to effectively repair a lot of electronic equipment, especially more complex mixed Analog and Digital circuits seen in devices like Tek scopes, it requires a high level of electronic knowledge, experience and analytical thinking, to say nothing of patience and care. These latter two qualities, mostly being sadly missing, in places such as Scope Calibration Houses, that claimed they were scope Experts. Believe me, I have seen the damage wrought on Tek scopes in some of these ISO certified Houses.

Hugo you've taken a rather sever tract on this. I've been involved in electronic repair for most of my working life and have never thought of myself as a chimp when using a Mil-Spec Tek manual which had the Wiz at the edge of the page. It was more or less considered "cute" in a joking manner The cal lab that I worked for was top notch and supported the Amphib Navy at Little Creek as well as NOB Norfork. The technicians were not chimps and must have possessed certain high level service school completions to qualify for a position. The manuals were merely a reference and the schematics were very accurate. The Wiz was merely an accent, not an instructor. Your take makes it look like cal lab was able to "hire off the street" be cause of the Wiz in the tech manual and no expertise was required. The manual's scope and content were detailed in the Mil-Spec. That was the standard and it was adhered to to the letter.

 

[alpher]

Amazing, quick question. I also have a few scopes an sg503 leveled sinewave generator, but always used the R&S signal generator to check the bandwidth and calibrate, what is the difference between decent signal generator like SML01 and sg503? Is the level being kept to much better standards in the sg503?

 

[Hugo Holden]

Hugo you've taken a rather sever tract on this. I've been involved in electronic repair for most of my working life and have never thought of myself as a chimp when using a Mil-Spec Tek manual which had the Wiz at the edge of the page. It was more or less considered "cute" in a joking manner The cal lab that I worked for was top notch and supported the Amphib Navy at Little Creek as well as NOB Norfork. The technicians were not chimps and must have possessed certain high level service school completions to qualify for a position. The manuals were merely a reference and the schematics were very accurate. The Wiz was merely an accent, not an instructor. Your take makes it look like cal lab was able to "hire off the street" be cause of the Wiz in the tech manual and no expertise was required. The manual's scope and content were detailed in the Mil-Spec. That was the standard and it was adhered to to the letter.

You misunderstood my remarks completely, and thought the worst. I never said the Technicians were actually Chimps, far from it. They were mostly often the thinking and insightful ones and smarter than any in management roles. You must know that yourself I would hope.

It was the management systems that controlled them that assumed that they were utilities to follow orders, and that the technicians required (mostly useless) fault finding charts to shepherd them through a fault finding process. As I wrote, it was the notion that management had about the Technician's abilities and that complex electronics failures could be reduced to simplistic charts (which I assure you they cannot) that was the problem, that ended with the directive to produce such charts, which mostly do not lead to a resolution of a real world fault.

 

[Hugo Holden]

Amazing, quick question. I also have a few scopes an sg503 leveled sinewave generator, but always used the R&S signal generator to check the bandwidth and calibrate, what is the difference between decent signal generator like SML01 and sg503? Is the level being kept to much better standards in the sg503?

The SG503 has an internal feedback controller (as does the SG504, which goes to 1GHz) to make 100% sure that the actual voltage level presented to the scope is perfectly stable, regardless of the frequency.

If you get any standard signal generator, it cannot be used to check a scope's bandwidth because the output level (amplitude) changes with the frequency because of the changing impedance of the load or the properties of the generator itself.

In the case of the SG504 which goes to 1GHz, they monitor the amplitude right at the BNC male connector on the cable with a leveling head where it plugs onto the scope. In the case of the SG503 which only goes to 250MHz, they do it at the BNC output connector on the SG503 itself. In both cases there is an LED warning indication if for some reason the feedback loop fails and the signal goes out of level.

I don't know anything about an SML01 though, or if it had amplitude leveling ? If it does it may well be ok.

 

[Quagmire]

You misunderstood my remarks completely, and thought the worst. I never said the Technicians were actually Chimps, far from it. They were mostly often the thinking and insightful ones and smarter than any in management roles. You must know that yourself I would hope.

It was the management systems that controlled them that assumed that they were utilities to follow orders, and that the technicians required (mostly useless) fault finding charts to shepherd them through a fault finding process. As I wrote, it was the notion that management had about the Technician's abilities and that complex electronics failures could be reduced to simplistic charts (which I assure you they cannot) that was the problem, that ended with the directive to produce such charts, which mostly do not lead to a resolution of a real world fault.

My original quip up in #7 was about a simple "Wiz" image on the edge of a "Mil-Spec" Tektronix service manual and you pounced on it. It had nothing to do with management or poorly trained techs or chimps. Speaking strictly for the US Navy folks, and Naval techs who have ever worked in a calibration facility or Intermediate/ONR/Depot level maintenance facility can attest to that. There was nothing wrong with those DoD Mil-Spec manuals and the repair/cal procedures were vividly outlined. As far as management goes, if you were in a civilian cal lab which held government a contract, and you didn't perform, you were out. Maybe things were/are a little different in your part of the world.

 

[Hugo Holden]

My original quip up in #7 was about a simple "Wiz" image on the edge of a "Mil-Spec" Tektronix service manual and you pounced on it.

My remarks basically apply to troubleshooting charts and the concept behind them, your Wiz icon may have nothing to do with these, I'm not sure.

Generally, troubleshooting flow charts are practically useless and most technicians worth their salt know this, certainly for scopes for actual repairs but it applies to many other equipment with multiple mixed analog and digital sub systems, VCR's etc etc. But maybe there are versions of the manuals for scopes which I have not seen, secret ones only the military had that are more insightful. However, I have been repairing scopes and other similar complex equipment for many decades and have not found an instance yet where any fault finding flow charts were of any significant help leading to the fault's diagnosis. Basically they slow down a deductive process, stop you thinking for yourself and send you down a garden path to a blind end in practically every case, unless you are very lucky, in that the imagined fault scenario such as a simple power supply failure or obviously failed part has occurred and in those simple cases if you have studied the equipment & know to do initial basic tests first on the power supplies and reset systems etc you won't need further help.

Tek scope manuals though are very good at providing waveforms and circuit voltages and these always aid in the repairs.

Here are just a few examples: The Tek 2465B scope has a number of troubleshooting charts and not a single one of them has been of any use repairing the 2465B scopes I have. For example, the chart's creators never imagined a Tin Whisker linking two tracks together causing a new circuit configuration, or the multiple electrical effects of leaked electrolyte from surface mount capacitors on the CPU board. Or leaked electrolyte on the PSU board. I have written numerous articles about these issues. The Tin whisker problem affected the main board, and there was a professional Tek scope repairer in the USA that had a pile of main boards all deemed un-repairable from this issue, they never found the cause, presumably they followed the flow charts and came out empty handed.

A good example; the other day one of my Tek 464 scopes failed. The signs were that the CRT's beam suddenly went badly out of focus, the brightness control failed to fully extinguish the beam but was partially working, the vertical position controls appeared to have limited range but were still working and the horizontal retrace was visible too (not blanked) and the H scan length shortened a little. This suggested a multi-system failure in both the CRT's high voltage support circuitry, the Vertical Amplifier's DC conditions and the Time-base too. The initial logical conclusion being that "it must be a power supply problem" common to those three systems. A quick check on the power supplies revealed all was normal. No troubleshooting chart could have predicted the cause. When a problem like this crops up, you have to put your thinking cap on. The question to ask is; what could cause three systems to simultaneously malfunction, that was not the power supply, could another common factor be the cause? After thinking about it, there is one system in that model scope which modifies the three affected systems together, the Beam Finder circuitry. After investigation, I discovered the cause of the fault was that just one of the contacts in the beam finder changeover switch was not making a proper connection.

We shouldn't get onto the topic of scope Cal labs. The damage I have seen from some. Typically they scrape off calibration stickers with screwdrivers and scratch the paint, and then cover it with the new sticker. Mostly inside the scope subject delicate parts to extreme forces, over-tighten screws and use the wrong sized screwdrivers damaging the screw heads, and on top of that don't do a patient and accurate calibration sometimes either. I know because I have checked the calibration on scopes relatively freshly out of some cal labes, and its not ideal in some cases. Because of this I bought all of the required Tek generators and calibrate my own scopes and won't let anyone else near them. Plus it is less risky for the scope not having to ship it to a cal lab. I don't know about my part of the world doing things differently, but with my own scopes I value them, treat them with respect and care and insist on perfect calibration.

 

[Quagmire]

My remarks basically apply to troubleshooting charts and the concept behind them, your Wiz icon may have nothing to do with these, I'm not sure.

Generally, troubleshooting flow charts are practically useless and most technicians worth their salt know this, certainly for scopes for actual repairs but it applies to many other equipment with multiple mixed analog and digital sub systems, VCR's etc etc. But maybe there are versions of the manuals for scopes which I have not seen, secret ones only the military had that are more insightful. However, I have been repairing scopes and other similar complex equipment for many decades and have not found an instance yet where any fault finding flow charts were of any significant help leading to the fault's diagnosis. Basically they slow down a deductive process, stop you thinking for yourself and send you down a garden path to a blind end in practically every case, unless you are very lucky, in that the imagined fault scenario such as a simple power supply failure or obviously failed part has occurred and in those simple cases if you have studied the equipment & know to do initial basic tests first on the power supplies and reset systems etc you won't need further help.

Tek scope manuals though are very good at providing waveforms and circuit voltages and these always aid in the repairs.

Here are just a few examples: The Tek 2465B scope has a number of troubleshooting charts and not a single one of them has been of any use repairing the 2465B scopes I have. For example, the chart's creators never imagined a Tin Whisker linking two tracks together causing a new circuit configuration, or the multiple electrical effects of leaked electrolyte from surface mount capacitors on the CPU board. Or leaked electrolyte on the PSU board. I have written numerous articles about these issues. The Tin whisker problem affected the main board, and there was a professional Tek scope repairer in the USA that had a pile of main boards all deemed un-repairable from this issue, they never found the cause, presumably they followed the flow charts and came out empty handed.

A good example; the other day one of my Tek 464 scopes failed. The signs were that the CRT's beam suddenly went badly out of focus, the brightness control failed to fully extinguish the beam but was partially working, the vertical position controls appeared to have limited range but were still working and the horizontal retrace was visible too (not blanked) and the H scan length shortened a little. This suggested a multi-system failure in both the CRT's high voltage support circuitry, the Vertical Amplifier's DC conditions and the Time-base too. The initial logical conclusion being that "it must be a power supply problem" common to those three systems. A quick check on the power supplies revealed all was normal. No troubleshooting chart could have predicted the cause. When a problem like this crops up, you have to put your thinking cap on. The question to ask is; what could cause three systems to simultaneously malfunction, that was not the power supply, could another common factor be the cause? After thinking about it, there is one system in that model scope which modifies the three affected systems together, the Beam Finder circuitry. After investigation, I discovered the cause of the fault was that just one of the contacts in the beam finder changeover switch was not making a proper connection.

We shouldn't get onto the topic of scope Cal labs. The damage I have seen from some. Typically they scrape off calibration stickers with screwdrivers and scratch the paint, and then cover it with the new sticker. Mostly inside the scope subject delicate parts to extreme forces, over-tighten screws and use the wrong sized screwdrivers damaging the screw heads, and on top of that don't do a patient and accurate calibration sometimes either. I know because I have checked the calibration on scopes relatively freshly out of some cal labes, and its not ideal in some cases. Because of this I bought all of the required Tek generators and calibrate my own scopes and won't let anyone else near them. Plus it is less risky for the scope not having to ship it to a cal lab. I don't know about my part of the world doing things differently, but with my own scopes I value them, treat them with respect and care and insist on perfect calibration.

Were talking apples and oranges here. The Tek scopes that I'm talking about were tube type and there were no printed boards to work with back then. Everything was wired. The "Wiz" was there to simply point you to a continuation in the manual. It was more or less a reminder - it didn't do anything. This was the 50s into the early 80's. So, where you around then?

 

[Hugo Holden]

Were talking apples and oranges here. The Tek scopes that I'm talking about were tube type and there were no printed boards to work with back then. Everything was wired. The "Wiz" was there to simply point you to a continuation in the manual. It was more or less a reminder - it didn't do anything. This was the 50s into the early 80's. So, where you around then?

Yes, I was at least from the late 1960's onwards, I always wanted to get a Tube based Tek scope, but I never had the opportunity to get one here in AU.

Due to the additional size and weight, the only scopes I could have shipped to Australia were post 1975 vintage and mainly solid state types.

However, I have many documents from Tek on their Tube scope creations. One of them, by Gerald Eastman in 1969, outlined the idea of a black level clamp. I wrote about this interesting design, invented by Tek, but used by Conrac, described on page 25 of this document:

https://www.worldphaco.com/uploads/The_1987_Vintage_Avionics_Conrac_Video_monitor..pdf

Tek always managed to come up with interesting and creative circuitry to support CRTs.

 

[Quagmire]

Yes, I was at least from the late 1960's onwards, I always wanted to get a Tube based Tek scope, but I never had the opportunity to get one here in AU.

Due to the additional size and weight, the only scopes I could have shipped to Australia were post 1975 vintage and mainly solid state types.

However, I have many documents from Tek on their Tube scope creations. One of them, by Gerald Eastman in 1969, outlined the idea of a black level clamp. I wrote about this interesting design, invented by Tek, but used by Conrac, described on page 25 of this document:

https://www.worldphaco.com/uploads/The_1987_Vintage_Avionics_Conrac_Video_monitor..pdf

Tek always managed to come up with interesting and creative circuitry to support CRTs.

Right after I retired from the service, I worked full time for Raytheon. One of the fellows who used to work for me, hired me. He was a graduate of the Navy's special test equipment calibration school in Denver, CO. We worked 'time study' and it was a great job with zero pressure. Our mission was to repair all of the stuff that the shore based and shipboard based repair facilities screwed up. And believe me, there was a ton of it - enough to keep our facility going 24/7. Once we repaired a unit then the certified cal school people would sign-off on it as QC. Cal stickers would be affixed and in most cases it was annual. You would see, for example, a freq counter come in that was manufactured by Monsanto, a chemical and fertilizer company of all things. But, it was Mil-Spec, they won the contract bid and so it didn't matter. We would find the power supplies were the first place to look in all most all of the stuff. Scopes could be tricky but there was so much talent in the shop that everyone shared their expertise. This was the late 70's. Tektronix was the 'Cadillac' of scopes IMHO. The 455 comes mind as it was new technology solid state and the workhorse of the fleet. Best wishes from me and the Wiz.