Date   

Found Option 7 board DC-508

Dallas Smith
 

Hello today,

Hope everyone is doing OK. Found this on Flea-bay - "Tektronix DC508 Resolution Multiplier and Option 7 board DC-508" - for $35 plus S/H. It took me many years to find mine. Just search the quote to find on Flea-bay. I think this is a reasonable deal. Maybe could be used in some other model's? not sure.

Dallas


Re: 475A Chop Blanking and a Theory Question

Tom Lee
 

Hi Dave,

RE: 465, 475 and 485

The 485 actually predates the other two, and is a very different animal. There was very little cross-pollination between the 485 team and the folks who did the other two. There are several nice features of the 485 that I wish were more commonly offered (e.g., a built-in fast pulse gen, and two levels of input protection that make it hard to blow up the front end). Every time the red light goes on, I know that I owe John Addis another beer, 'cuz he's just saved me from a blown scope for the nth time.

The 465 and 475 had some personnel in common, and a lot of informal collaboration. Those two scopes are similar enough that a good understanding of either of them will take you pretty far in understanding the other. Lots of stuff in common, too, making organ transplants feasible in more than a couple of cases.

-- Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 12/18/2020 16:09, Dave Peterson via groups.io wrote:
There are too many dimensions to all of this!
A) Ha-ha - ya got me! You don't have to get the first edition. It's just the sight of the red cover conjures night sweats.
B) I was looking at the Bodnar FPG. For the $$ I just have too many fundamental things to get first. Like appropriate 10x probes. Send me off into a whole other tread: vertical system calibration and circuit function. I know what I need to do, but I need two proper 10x probes to measure the preamp output. And just to have an appropriate high impedance probe just for poking around. Alligator clips and banana plugs are not appropriate tools for circuit analysis. I could spend several oscilloscopes worth of $$ on just basic bench equipment. I'm trying to prioritize and pace myself. I honestly am considering building my own FPG. Reading Leo's origin thread on EEVblog gives me ideas. Might be fun.
C) Bandwidth, math, transistors, amplifiers and filters: I want to help, but you're quite capable on your own. I also remember wanting to really grok xtor theory, and after getting into it in school I recall the mental rungs on the ladder of understanding. Again, layers on layers: discrete component topologies as applied in 1970 are not synchronous with deep sub-micron CMOS circuits. I'm not as fluent in Tektronix topologies, but I also do recognize a lot of basic BJT configurations. But then there's Tektronix's weird schematics - relative to my experience. The experienced guys on this forum will give better answers, but I'm re-learning myself and remember "the mysterious black box" that was a transistor. The BJT wiki has some really good descriptions and pictures that jive with those mental rungs. Anyway, there's BJT and FET physics, bias topologies, small signal models and analysis, frequency domain analysis, transfer functions, feedback, op-amps, ... There are a lot of facets to the things being done in these scopes. Compartmentalization and experience. Layers and layers.
D) Sorry, after playing electronic tech for 4 years in the Army: 99% of if is mechanical stupidity. But divide and conquer is the methodology, and I'd say you've got it pretty much down. Not as sexy as it seems from the outside. BTW, I just killed and resurrected my cheap Chinese function generator. I just stopped working a couple hours ago. I walked away in a bit of disgust, but after 5 minuets I went back and unscrewed the cover. After poking around online I got the courage to turn it back on and start checking some basic things - power etc. When I noticed a connector partially in it's socket. That's all it took. None of the voltage probing had anything to do with it. Just that it brought my focus to the innards of the box helping me spot the loose connector. Back in business.
E) I'm just beginning to dip my toes into the Trigger and Sweep circuit descriptions and calibration procedures. One thing I'm observing is a difference between my two scopes' triggering of chop signal observation. I want to figure out why they're behaving differently. The "working" scope has a very stable trigger, the "parts" scope is being a bit finicky. Then it occurred to me it would be helpful to see the chop signal without the blanking. Hmm. Wonder how I could do that?! Thanks to some guy on the TekScopes group I know just the transistor to pull to make that happen. Interesting.
I recall my struggle to understand BJT function, and I sense you have a mix of understanding and uncertainty. I'm re-examining the fundamentals I've gotten away from since being a CMOS jockey. If there are facets of xtor theory and operation that are frustrating you, and you can articulate them, I enjoy helping. I might say stupid things along the way, but I enjoy blundering my way into understanding. Let me know if there's something tripping you up.
F) Here's another one: 465, 475, 485. These are all concurrent designs from Tektronix. Yet they're so different in so many ways, while still being the same in a lot of ways. Did they have some mix of independent, common, and cooperative departments working on these? E.g. Your 475 ALT/CHOP circuit is so different than the 465. Why? Doesn't seem that significant a circuit to have such different designs while being produced at the same time? What's the R&D rationale behind that? Similar things with the 465 and 485 - though I haven't had the chance to delve too deep into it. Just rhetorical thoughts to share. Yet another thread/dimension. I am having fun tho!
Hope you're having fun. I got to have the day off to play today, and hope you're getting to enjoy some time off too. Thanks for sharing your thoughts and experiences. It's helping me as well.
Dave

On Friday, December 18, 2020, 03:11:18 PM PST, Jeff Dutky <jeff.dutky@gmail.com> wrote:
Because everything looks like a bandwidth measurement when all you have is a fast pulse generator I had been measuring the rise time of every scope I have to see if their bandwidth matched their specs, and before I fixed the CHOP blanking problem the bandwidth of the 475A was measuring as something like 175 MHz (rise time of about 2 ns), which seemed very wrong. After fixing the CHOP blanking problem, however, I went back and measured the rise time again, and this time I got a rise time of between 1.5 ns and 1.3 ns, which gives the bandwidth as 233-269 MHz, which seems about right for a 250 MHz scope.

I am at a loss to explain how fixing the CHOP feature could affect the bandwidth of the scope (especially since I didn't have CHOP engaged when I was measuring the rise time), and it's entirely possible that some amount of operator error may be involved, but, as I also measured the rise time of my father's 475 when I got the low bandwidth measurement for the 475A, and found the 475 to be spot on at 200 MHz, I suspect I made both measurements correctly (my notes, sadly, do not tell me enough about what how I set up the scopes to be sure).

I suppose that it's possible that another NAND gate in U340, which contributes to another part of the vertical amplifier system, also had a dirty pin that was causing a bad connection, but I don't see anything like that in the schematic. I'm much more inclined to believe that my boneheadedness (like leaving the 100MHz bandwidth limit pulled out), rather than a dirty pin on U340 was the culprit, but I'd be happy to be proven wrong.

-- Jeff Dutky








Re: 475A Chop Blanking and a Theory Question

Dave Peterson
 

Sorry all, that last response was intended to be direct to Jeff, not the whole group. Disregard.
Dave


Re: Unable to display cursors and diagnostic messages after LPVS "recapping"

 

Rogerio,

I don't actually know anything about the scope you're working on, but looking at the schematic I can see that you would not only need "activity" on pins 8-10 of U2521, but also activity on pins 2, 4, and 5 in order to have any effect on U2620 (and similar for U2530/U2630).

Have you verified that the signals from the MUX chips to the op amps are active?

Have you looked at the output from U2301 (pins 12, 15, and 16) to see if it's counting all 8 possible values?

Have you checked continuity between pins 12, 15, and 16 on U2301 to pins 9, 10, and 11 on U2521?

-- Jeff Dutky


Re: 1S1 sampling bridge GaAs diodes: What alternatives?

Tom Lee
 

Nothing says "Happy Holidays" more joyfully than soldering sampling diodes.

Enjoy!

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 12/18/2020 14:57, leonard scheepsma wrote:
Thanks everyone for all feedback/comments. A friend (also active here) managed to find 4 equal versions in his Tek vault, so I think I can slowly prepare for a party!

Merry X-mas and a Happy New Year!

Leonard




Re: 475A Chop Blanking and a Theory Question

 

Because everything looks like a bandwidth measurement when all you have is a fast pulse generator I had been measuring the rise time of every scope I have to see if their bandwidth matched their specs, and before I fixed the CHOP blanking problem the bandwidth of the 475A was measuring as something like 175 MHz (rise time of about 2 ns), which seemed very wrong. After fixing the CHOP blanking problem, however, I went back and measured the rise time again, and this time I got a rise time of between 1.5 ns and 1.3 ns, which gives the bandwidth as 233-269 MHz, which seems about right for a 250 MHz scope.

I am at a loss to explain how fixing the CHOP feature could affect the bandwidth of the scope (especially since I didn't have CHOP engaged when I was measuring the rise time), and it's entirely possible that some amount of operator error may be involved, but, as I also measured the rise time of my father's 475 when I got the low bandwidth measurement for the 475A, and found the 475 to be spot on at 200 MHz, I suspect I made both measurements correctly (my notes, sadly, do not tell me enough about what how I set up the scopes to be sure).

I suppose that it's possible that another NAND gate in U340, which contributes to another part of the vertical amplifier system, also had a dirty pin that was causing a bad connection, but I don't see anything like that in the schematic. I'm much more inclined to believe that my boneheadedness (like leaving the 100MHz bandwidth limit pulled out), rather than a dirty pin on U340 was the culprit, but I'd be happy to be proven wrong.

-- Jeff Dutky


Re: 1S1 sampling bridge GaAs diodes: What alternatives?

leonard scheepsma
 

Thanks everyone for all feedback/comments. A friend (also active here) managed to find 4 equal versions in his Tek vault, so I think I can slowly prepare for a party!

Merry X-mas and a Happy New Year!

Leonard


Re: LF: An up to date eBay price list

Michael W. Lynch
 

Any time an E-Bay or other Advertisement begins with "vintage", "rare" or "collectable" the sellers are many times clueless or greedy and have priced their items way above any reasonable value. Like the recent listing that I was looking at that showed a 465 that obviously had almost all the knobs gone AND many of the shafts were gone as well. So there was no way that this thing was even a good "parts mule" and they were asking something like $175 with "free" shipping to USA only. Sellers can ASK as much as they like, it does not mean they will get their price. I agree with snapdiode, just offer X number of $$ and leave it there.

--
Michael Lynch
Dardanelle, AR


Re: LF: An up to date eBay price list

Keith Erickson
 

I do have 1- “1A1”

Keith

On Dec 18, 2020, at 4:14 PM, David Collier <dc888@tpg.com.au> wrote:

Hi Keith,
I am restoring two 545B's and have for them one working 1A1 and two (not working?) 1S1 plugins. Would love to get at least one more useful plugin, then one 1S1 will be surplus to my requirements, unless kept for spares.

Also have a late made in Holland (with readout and fan) 7603 with two 7A18 (one with DC offset); one 7B53A, and a now surplus working 7B53AN. For this 7603 I would again love to get a fancier plugin like a nice RF spectrum analyser! This 7603 came from Canada; carriage was indeed expensive.

Regards,
David Collier
Canberra






Re: LF: An up to date eBay price list

 

Hi Keith,
I am restoring two 545B's and have for them one working 1A1 and two (not working?) 1S1 plugins. Would love to get at least one more useful plugin, then one 1S1 will be surplus to my requirements, unless kept for spares.

Also have a late made in Holland (with readout and fan) 7603 with two 7A18 (one with DC offset); one 7B53A, and a now surplus working 7B53AN. For this 7603 I would again love to get a fancier plugin like a nice RF spectrum analyser! This 7603 came from Canada; carriage was indeed expensive.

Regards,
David Collier
Canberra


Re: Unable to display cursors and diagnostic messages after LPVS "recapping"

Rogerio O
 

Thank you for the replies.

The cables I had to remove were connected to A5 (J251, J421) and to the GPIB and CTT board.
However, I have checked the all the voltages required by A5 board and they were all present and on spot.

AFAIK, a problem in the cables connected to the GPIB/CTT would not cause this problem .

Consulting the chart " Readout Troubleshooting Procedure", is a little tricky since I can't say if the messages TEST 03 FAIL 01 or TEST 03 FAIL02 were displayed (I can see only the traces, but no messages/cursors) , so I moved the case
NO CURSORS PRESENT.
In this case I should check lines RA6, CA6 , DLY REF1 and CURSOR0 which were:
RA6 - Active
CA6 - Stuck @ 0V
CURSOR0 - Stuck @ -1.3V
DLY REF 1 - sTUCK @ -1.6V

The is a bright spot which flickers in the screen (my guess is that it would be the starting point of the cursor/message display).
It moves from time to time.
Also, a message flickers every 3 min (but it is to fast to be read).

I do not understand how it is possible to have activity in pins 3 and 8/9/10 U2521/U2530 and no activity at DLY REF1 and CURSOR0 since I have already replaced U2620 and U2630.
Have they fried again?

Roger


Re: LF: An up to date eBay price list

Keith Erickson
 

I have a number of 500 series plug ins.

Keith Erickson
Wayzata, MN

On Dec 18, 2020, at 1:58 PM, snapdiode via groups.io <snapdiode=yahoo.com@groups.io> wrote:

When dealing with strangers and haggling about a price, the simple approach is simply "I offer X" and wait for the reply.

There's no need for anything else.

Anyone who has a Tek 500-series can see the value of saving on shipping, for example, or have a parts mule with a CRT...





Re: LF: An up to date eBay price list

snapdiode
 

When dealing with strangers and haggling about a price, the simple approach is simply "I offer X" and wait for the reply.

There's no need for anything else.

Anyone who has a Tek 500-series can see the value of saving on shipping, for example, or have a parts mule with a CRT...


Re: So how does this hobby work now?

Greg Muir
 

Not to harp about Jim Williams but it has been some time since I have looked through articles about him. I think this article more characterizes who he was and his love for older test equipment.
https://www.edn.com/remembering-jim-williams-5-years-later/

Greg


Re: LF: An up to date eBay price list

Roy Thistle
 

On Fri, Dec 18, 2020 at 08:55 AM, snapdiode wrote:


there aren't necessarily bargains locally
Ad says, "This quality test equipment comes with a custom rolling stand, the users manual and 40 [extra?] tubes."
By that statement I surmise, the seller is clueless, or greedy, or both. The big draw, for the audio squirrels is "tubes" and the seller appears to know it.
But who knows... I've seen people asking for far more... and very indignant towards the messenger: when their informed they're dreaming.


Re: 500 scopes n stuff

Jean-Paul
 

Dear Bill: GO FOR IT thats what we are here for!

Please include your location as many are not is USA, pickup only or will ship, conditions etc.

You can upload photos on the photos area but not attach.

We are anxiously waiting your scopes!


(:-:)

-73-
Jon


500 scopes n stuff

William Rice
 

Is there any info on how to conduct oneself if one wants to list some older Tek scopes n bits to let go of?

Is this prohibited on this list? Where can I find the rules for such please?

Thank You All,
Bill
W4MXT


Re: So how does this hobby work now?

snapdiode
 

Thanks for the thoughtful reply.


Re: So how does this hobby work now?

Greg Muir
 

Yes, eventually sources for various items will eventually dry up so sellers will try to extract as much cash as they can from selling them be it aware of the scarceness of the item or simply not having any clue as to what it is.

As I had commented in a Tek post back on the 28th of November surplus back in the 60’s and 70’s used to not be recognized by the many. In earlier days the penchant was to fabricate and get that HF rig on the air because amateur radio was a commonly absorbing hobby for the adventurous. And in those days much of the military test equipment went to scrap.

Today we are faced with people pursuing other hobbies such as those “true users” trying to afford equipping their hobby labs with more advanced (but still older) hardware plus those (curious) involved in the collection of test equipment possibly with no use in mind due to the quantity that they possess (I’m more than “curious” but still personally guilty on the collection aspect). It seems to me that the appreciation of older equipment is more-or-less based upon the age and background (education – profession) of the user with many of us older people knowing how it performs, enjoy using it and know its limitations.

To wit, we can look at people such as the late Jim Williams who led the forefront of analog circuit design whose legacy still resides in many of the components the younger generation hold in their hands (while ignoring the world around them). Both his work and home labs were peppered with older Tek vacuum tube scopes form which he extracted the performance needed to effect his future designs. It wasn’t based upon “why need such old stuff” but, rather knowing that such equipment was still a good performer for his needs even though it may have stressed the air conditioning system a bit more.
https://computerhistory.org/blog/an-analog-life-remembering-jim-williams/

Of course we can’t omit the “hunters and scrappers” who either obtain equipment merely to strip them of their vacuum tubes and throw the remainder away or those more set on gold reclamation to make a few temporary bucks. Although I don’t class them as “bottom feeders” they still put a strain on the availability of older hardware.

Appreciating the power and ease of use given to more recent “older” test equipment through ASICS and other esoteric deigned components allows us to have increased performance but at the same time the ability to repair any malfunctioning item becomes a moot point since either the cost of purchasing replacement parts or finding them to be “unobtanium” simply can turn the unit immediately into a piece of scrap.

We all have a more-or-less certain affinity for older equipment given the appreciation of the unique and very solid designs for that era, the love of vacuum tubes and totally discrete components one can put their hands on or simply the affordability of an older unit that will meet our needs.

But we must remember that many of us are of a generation that does understand older equipment and can eke every bit if performance out of it and also know its limitations. And people like us will fade with time and find fewer others to which this equipment will go. The move these days is for many newbies to buy something shiny off-the-shelf that requires little understanding (and appreciation) of how it works, use their “plug-N-play” experience and put it to use. Why bother with digging into that older boat anchor getting your hands dirty to bring it back to life with the underlying appreciation that you actually have either learned something by doing so, appreciate the hard work of bygone engineers or appreciate the effort required to keep it alive?

I think that those who treat older equipment simply as a commodity to either strip or scrap should spend a little time reading through the older issues of “Tekscope” or “HP Journal” to really appreciate the effort that was put into the design of these products. Nowadays it is very difficult to find publications like this that truly explains the innards of equipment and reasons why the designs followed the paths that they took. Today’s companies won’t divulge that information because they are more concerned about competitiveness and that holy profit dollar. You now get a “box,” plug it in and use it. It sort of takes the fun out of things. We do know what “fun” is don’t we?

Greg


Re: Tektronix 317

 

Bob- that would be great, you can email me you contact information and we can make arrangements. brockkoren@gmail.com

Thanks,
Brock

8901 - 8920 of 183698