Date   
Re: Advice sought on 7934 vs 7904A mainframe

Chuck Harris
 

David DiGiacomo wrote:
....
Both the 7934 and 7904A have fans that are loud enough to be annoying
in a quiet lab.
Ok, when I read the above line, I immediately snorted! Then I realized
he was talking about the cooling fan, and not scope aficionados.

-Chuck Harris

Re: I wonder if there is much interest in vacuum tube oscilloscopes such as the 500 series

Daniel Koller
 

There's still an interest!    I have a 575 (used irregularly) and a 545 (used OFTEN).   but it just works every time I turn it on.   I haven't needed to fix it in a few years.    I completely disagree that the 500 series are useless "boat anchors" or "room heaters" .   Yes, they are bigger than a modern scope, but if you have the bench space, they are every bit as useful.   Mine are on carts.  More so, for general experimenting, there are a lot input and out put connections on the 545 made by banana jacks (on my older version).   that makes it very easy to set up an experimental setup, rather than to just monitor a signal.   It's a great scope to *use*!
  Dan

On Thursday, March 28, 2019, 7:07:02 AM EDT, Brian via Groups.Io <brianas1948=yahoo.co.uk@groups.io> wrote:

Hi everyone , I also have 500 series scopes , 547 , 2 x 549 and a 564 . I even have a 661 that still works . I like all these scopes and will hang on to them as long as I have the space as they are all reminders of my early working life as they (547,549 and 564) were all new and state of the art when I started work
Despite my liking of these I also have a number of 7000 series scopes and even a couple of TDS scopes , one of which I am attempting to repair as for me buying broken ones and fixing them is the only way I can afford any of them having retired now .

Brian

Re: I wonder if there is much interest in vacuum tube oscilloscopes such as the 500 series

Dave Voorhis
 

On 28 Mar 2019, at 01:07, John Williams <books4you@...> wrote:

Hi folks. I have been observing the topics of interest here for a few weeks, and I am not seeing much on older scopes ie before the 7000 series.
I have a 549 with Type Z, 1A2 and 1A4 plugins. I love it and it just works, though I need to do some mechanical restoration work on one of the 1A4 channels.

I also have a 564 which produces a trace and the storage works, but I need to fix the plugins.

I haven’t posted about them much because so far I haven’t encountered anything on them I felt the need to ask questions about.

I’d like to get my hands on a 575, but here in the UK they’re relatively rare.

Re: TEK 475 voltage issues.

Glen Layne
 

I'm trying to measure the +105/160 from the labeled trace. This trace with +105/160 printed on it ends on the + of C1452. So, basically, I was trying to find +105/160 on C1452. Maybe I'm trying measuring in an incorrect spot. There is an unlabeled measurement pin near Q1496 that has +142 v. The metal top of Q1497 (2n2907a) has +142v. The metal top of Q1496 is where I think I should find +110 but right not I just got 87.4 and the same at the +110 pin.

Q1497 from the parts list. My serial number is > 275000
tek part no Serial/Model
151-0301-00 XB080000

Re: TEK 475 voltage issues.

Roger Evans
 

OK, I understand the +105/+160V measurement problem! There is some screen printing on the 475 PCB near Q1490 that says '+105/160V' and it is printed on one of the PCB traces but that trace does NOT connect to the +105/160V line (and it measures about 10V!). The schematic shows a +105/160V test point but I can't find it. You can measure the real +105/160V on R1423, mine measures around 125V.

Roger

Re: TEK 475 voltage issues.

Glen Layne
 

Many thanks Roger. At R1423, I find +141.7. Now, my issue is something dragging down the +110. It's currently sitting at 87.3. If I leave the unit on, it will slowly drop even more.

Glen

Re: I wonder if there is much interest in vacuum tube oscilloscopes such as the 500 series

bill koski
 

I still have a 556 which I built my own cart for. I have it next to my test bench and use it often. I bought it with the manual for $25 at a HAM fest about 15 years ago. Other than needing a vertical driver tube (which cost me 30 bucks at the time) it has worked great. I have a bunch of plugins for it including a 1L5 Spectrum analyzer (a subject for another day that I'll have to pick the brains of the people here!) and a 1A4 4 channel plug in. Friends are impressed when I use a 2 channel in the other bay and can put 6 different traces up on the screen! Though it's only rated 50MHz I've displayed a stable 100MHz on it.
Amazing scope for its time and still quite a performer today. Plus it keeps me warm in my office on cold winter nights!!!
I also have a single bay scope that I acquired with some other equipment. I believe it's a 545B? I've not even attempted to plug it in yet. It's sitting in the wings waiting for some much needed TLC.
While we're on the subject does anyone have an extension cable for the plugins that they would like to sell so I can work on a couple sick ones?

Electromyograph EDX-1 - Based on Tektronix 5000 Series Mainframe

Wolfgang Schraml
 

Hello,
Acquired an interesting device at a recent swap meet - an Electromyograph ("EDX-1") based on what appears to be a 5000 series mainframe. I posted a few pictures in the photos section under "Electromyograph EDX-1". I did some googling but couldn't find a whole lot (other than another one of these that sold on eBay Canada not too long ago).
Haven't done any detailed assessment yet.

Just wondering if anyone has any information about this. Trying to decide whether it is worthwhile restoring.

Thank you,
wschraml, KI7PFX

Re: TEK 475 voltage issues.

Roger Evans
 

I guess it is obvious out last posts crossed and also I seem to have a different board revision from you.(serial 708886, Holland, no Q1497). For some reason the series regulator Q1496 (on my schematic at least) is a PNP so the output is from the collector not the emitter, hence the 87.4V. On my 475 almost all the transistors are socketed so can you pull Q1496, Q1490 and Q1494 and check them? If they all check OK then measure the voltage at the junction of R1486 and R1487, if it measures at 50V then the regulator is working and one or other resistor has drifted. If it measures at 87.4 *(50/110) then the resistors are OK and you either have excessive load current or something else around Q1494 is at fault.

If the scope is basically working then measure the ripple on the 105/160V line. The calibration may be out but it is just a go/no go measurement.

Roger

Re: TEK 475 voltage issues.

Roger Evans
 

Posts crossed again!

It sounds very much like you have an excessive current load on the +110V line. If you look at the power distribution diagram, schematic <11>, then the horizontal amplifier would be a good starting point, there are two loads via the 100R resistor R1267 so try measuring the voltage drop across R1267 and also check C1267 and VR1267. Also check the value of R1267, it may have overheated.

Roger

Re: TEK 475 voltage issues.

Chuck Harris
 

If there hasn't been a ripple measurement on the 110V line,
now would be a good time.

If a diode is open circuit, or a filter is very high ESR, the
ripple could be such that the regulator is dropping out of
regulation during the valleys between the peaks. This will
show up as a lower than normal average voltage from the supply.

The scope may even work fairly well under that circumstance.

-Chuck Harris

Roger Evans via Groups.Io wrote:

Posts crossed again!

It sounds very much like you have an excessive current load on the +110V line. If you look at the power distribution diagram, schematic <11>, then the horizontal amplifier would be a good starting point, there are two loads via the 100R resistor R1267 so try measuring the voltage drop across R1267 and also check C1267 and VR1267. Also check the value of R1267, it may have overheated.

Roger



Re: 11801 question

Albert Otten
 

Hi Reg,

In another thread you say:
"Watching the clock period vary by 100 femtoseconds over the course of 15-30 seconds with a 1 s gate time is rather interesting.".
I'm not sure whether I read this correctly. Does the 5 ns period vary 0.1 ps in 15-20 s (I hope not!)?
I measured the 200 MHz clock of a CSA803A using the DC510 as counter. Counter already warmed up.
Frequency dropped from 200,000.62 MHZ at startup of the CSA to 200,000.26 MHz after 30 minutes. In those last 10 minutes the drop was 0.02 MHz or 0.1 ppm. That means 0.5 fs increase in period.

I don't know how the time base delays are created. Long delays could be obtained as multiples of the 5 ns period. But somehow the dot steps as short as 0.1 fs (!) need a classical ramp and comparator circuit I guess.

You seem to forget that you are in the lucky circumstance of having internal triggering so far. The delay from trigger event to strobe event will likely be less jittery than from external trigger event to strobe event. In your applications you probably need external triggering with a pretrigger signal generated by the DUT. That introduces extra jitter and might even be the main source of jitter. (I am a layman w.r.t. to the intended use you mention.)
In my opinion the internal channel drift cannot be caused by the time base. The schematics suggest that one and the same time base event starts the strobe action for both heads.

Albert

On Thu, Mar 28, 2019 at 12:52 AM, Reginald Beardsley wrote:


I've got the unit running with a pair of SD-22s fed by a 2 port splitter from
the calibrator into ports 5 & 7. I was finally able to figure out how to
manually adjust the skew so the two traces overlaid. The cables are about 1/2
mm different lengths

I'm seeing the displacement between the two traces vary from 0 to about 10 ps
over the course of a few minutes. Is this normal or is there a fault? I've
read the user manual once, but it's not great. Certainly no match for a 465
or 485 manual.

Does anyone know why this is happening? I've got the internal clock output
connected to an HP 8356A and I can see the period varying. I don't have the
8356A connected to a GPSDO at the moment, but it has the OXCO option and is
very stable.

Is there any reason to think that replacing the 200 MHz master oscillator with
one of Leo Bodnar's GPSDOs would eliminate the interchannel drift?

I discovered this shortly after making an offer for four SD-26 heads. My
intended use is to measure actual FPGA word skew of a DSP stream, so this
would be a serious problem.

Thanks,
Reg

Re: I wonder if there is much interest in vacuum tube oscilloscopes such as the 500 series

Nenad Filipovic
 

My 536 serves as a lab power supply for occasional tube experiments.
Otherwise is in excellent condition, complete and functional, and will keep
it as such. On winter evenings I sometimes fire it up with covers off, when
some of my vintage-fan friends drop by for a visit. 536 is an X-Y
instrument, so with 2 CA plugins we once played stuff like
https://www.youtube.com/user/jerobeamfenderson1

A year ago I rescued a 555 about to be ripped apart by audiophools.
Restored it to a quite decent condition, but alas I do not have its power
supply, only the mainframe. Still looking for one.

Re: Tek 2710 focus issue

john@...
 

Hi Chuck,

Many thanks for your reply.

Checking the main power supply board but cannot relate PCB revision to component identities. For ex ample R107 t0 R xxx

For example, 1 Meg resisters are 330K resistors

Regars

Hohn

Re: I wonder if there is much interest in vacuum tube oscilloscopes such as the 500 series

Dave Wise
 

I have a small fleet of 500-series, all daily runners. Each needed sorting when I got it but since then has gone for years without missing a beat.
535
535A
545
547
B,C,CA,D,G,H,K,L,O,TU-7,Z,1A1,1A2,1A4,1A5,1A7,1S1
132

All restored by me except the O and 132 which are in the queue.

Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Leanna L Erickson <lle@...>
Sent: Wednesday, March 27, 2019 8:40 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] I wonder if there is much interest in vacuum tube oscilloscopes such as the 500 series

I have a bunch of 500 series working scopes.

Real room heaters.

Keith

Wayzata, mn.
On Mar 27, 2019, at 9:52 PM, John Williams <books4you@...> wrote:

It seems like most people here would actually use a scope. The other side would be those of us that don’t have scopes to use, but to restore and preserve. I only use a scope to fix a different scope, or some associated equipment. And for that I use the 475 or 2213. So I won’t try to guess which is the dark side. But there is a distinct difference. And never acquire anything you can’t fix. Probably that is.


Re: I wonder if there is much interest in vacuum tube oscilloscopes such as the 500 series

Brenda
 

Hello John!

I have noticed the same trend myself. But I have am very interested in these 500 series scopes, for me, they are a real pleasure to use and at the time, reminds me of how much thought and work was put into these scopes. I have picked up a Tektronix 535A with the Type 202-2 cart. The 535A came with a CA plug-in and a Type L plug-in. Spent 2 weeks cleaning all the cigarette smoke out of the scope and the CA plug-in. Unfortunately, I was not able to save all the lettering on some of the tubes due to the amount of smoke. It was so bad that the tubes would actually stick to your hands! But after cleaning the scope, powered it up, and I couldn't believe my eyes, the darn thing works perfectly, or I think so as I need to get a manual. I know that I could download a manual but I am old school and prefer the actual manual. At the same time, I also picked up a 533A with another CA plug-in, and I am sure that I will be asking questions about that soon enough along with the 535A and the 545A.


Brenda

Re: I wonder if there is much interest in vacuum tube oscilloscopes such as the 500 series

Kevin Wood G7BCS
 

I wonder if the lack of 500 series chat is down to them "just working" and
not needing much tweaking?

I have a 546 + 1A2 that came home from school in a wheelbarrow in my early
teenage years. It was donated to the school by a local firm (Marconi, if
memory serves) but was too complex for their purposes. A bit of
negotiation and it was mine! 30+ years later I've still got it and the
only thing I've had to do is swap in one of Chuck's rewound HV
transformers, although the trigger on one of the timebases has started to
play up, so I might be on the look out for a tunnel diode soon.

Kevin
G7BCS

013-0097-01 retractable hook probe tip- orphans available?

Renée
 

hi everyone-
Thought I would ask if anyone has an orphan that might be available as I acquired a P6202A and am in need of the retractable hook tip. I could make one from a regular 013-0107-07 prefer not to do so.....also looking for the 010-0384-00 100X attenuator and the 010-0360-00 Capacitor IFF they are languishing in a drawer......
let me know cost etc...plse contact me direct......k6fsb.1  at gmail
Thanks
Renée

Spotted in Seattle area: Tek 515, etc.

Bruce Lane
 

Those who are within range of the Seattle area (Bellevue, to be exact)
may want to drop in at Vetco Electronics and take a look in their
upstairs surplus room. As of yesterday (27-Mar-19), there was a pair of
fairly nice-looking Tek 500 series 'scopes (a 515, I think, and one
other), as well as a 475. All seemed to be priced pretty cheap as 'tech
specials.'

You're welcome. ;-)

--
---
Bruce Lane, ARS KC7GR
http://www.bluefeathertech.com
kyrrin (at) bluefeathertech dot com
"Quando Omni Flunkus Moritati" (Red Green)

Re: I wonder if there is much interest in vacuum tube oscilloscopes such as the 500 series

Dave Wise
 

Oh, I forgot, I also have a 1L5. I haven't used it aside from restoring it; I prefer my HP 141T/8556A.

Most recent repair: 1S1 unstable Memory Balance. Cause: Zener in the heater current regulator intermittently going open-circuit. There was also a manufacturing defect (?) that had a pass transistor pin touching the heat sink.

Most recent use: 535+B, viewing transistor breakdown. I was trying to distinguish between avalanche mode and punch-through. I got self-contradictory results. The 2N1304 required shunt capacitance to break down, which suggests it was avalanche, but reverse bias on the base didn't affect it much, which suggests punch-through. BC337 is the reverse, not needing a cap but being sensitive to bias.
I initially used the 1S1, to confirm that the rise time was less than 1ns, but it's no good for viewing the overall waveform because unless you include a lot of attenuation ahead of the bridge, there's risk of blowing it due to capacitive coupling of the fast edge. I guess I need one of those 500-ohm or 5000-ohm resistor probes.

Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Nenad Filipovic <ilmuerte@...>
Sent: Thursday, March 28, 2019 7:57 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] I wonder if there is much interest in vacuum tube oscilloscopes such as the 500 series

My 536 serves as a lab power supply for occasional tube experiments.
Otherwise is in excellent condition, complete and functional, and will keep
it as such. On winter evenings I sometimes fire it up with covers off, when
some of my vintage-fan friends drop by for a visit. 536 is an X-Y
instrument, so with 2 CA plugins we once played stuff like
https://www.youtube.com/user/jerobeamfenderson1

A year ago I rescued a 555 about to be ripped apart by audiophools.
Restored it to a quite decent condition, but alas I do not have its power
supply, only the mainframe. Still looking for one.