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Re: Can capacitors

Richard Coberly
 

I have been repairing tubed guitar/bass amps since the 1970's and mostly I use modern replacement caps. But now that some of these amps have become collector items, some believe that they must have OEM replacement parts. Thankfully, these folks seldom play/use these amps so the reliability is not much of a problem. And they don't seem to mind spending their money. Trickle down economics. If the client actually uses the amp, especially to play gigs for money, they get modern parts.
All my test equipment gets modern caps. I delineate between repair, refurbishment, and restoration with my clients.
Rick


Greetings From a New Member

Gordon Smith
 

Hi All,
Just wanted to introduce myself. I'm Gordon Smith, a technology enthusiast down here in San Diego, CA. Was recently given a Tek 502 Dual Beam Oscope and in researching it found your group. A Tek 547 with cart and three plug ins was also adopted (yes, it's got the dreaded HV transformer issue). Other than being dragged willingly into the vintage Tek Oscope cult, I enjoy Vintage technology like ham radio stuff (want to the learn Morse code. Have way too many radios), Test equipment (I have some wonderful Non-Linear systems edge lit voltmeters) and have wayyyyy too much....errr...."Stuff" in the garage. I'm a mechanical engineer by trade doing mainly R&D over many fields and was forced by circumstance to learn a lot of electrical and some electronics. Currently employed by General Atomics. Thank you for allowing the introduction and stay safe out there. Gordon


575 Curve Tracer - $550

John Dickens
 

Another Craigslist curve tracer in Wisconsin (I have no affiliation with the seller)

This vintage curve tracer has been in storage for many years. We are trying to find a good home for it. After cleaning it out inside and out, the unit powered up nicely. We haven't run many tests on it other than the basic display and power supply, but it seems perfectly functional. It is listed as fair right now, but that could change if we get more opportunity to test it. We really don't want to ship this heavy beast, so hopefully we can find a buyer in Wisconsin!
If you are unfamiliar with the 575, it is an awesome example of vacuum-tube based equipment. A picture of the vacuum tube deck is provided. It is capable of testing transistors or similar devices with up to 200 Volts and, at lower voltages, up to 20 Amps. See the attached pictures. Let us know if there is a specific test you would like to see verified.

https://madison.craigslist.org/bfs/d/verona-tektronix-type-575-curve-tracer/7233377161.html


576 Curve Tracer

John Dickens
 

This is near Madison Wisconsin. I have no connection to the seller or curve tracer.

Tektronix Type 576 Curve Tracer - $800 (Verona)

This vintage curve tracer has been in storage for many years. We are trying to find a good home for it. After cleaning it out inside and out, the unit powered up nicely. We haven't run many tests on it other than the basic display and power supply, but it seems perfectly functional. It is listed as fair right now, but that could change if we get more opportunity to test it. We really don't want to ship this heavy beast, so hopefully we can find a buyer in Wisconsin!
If you are unfamiliar with the 576, it is capable of testing transistors or similar devices with up to 1500 Volts and, at lower voltages, up to 10 Amps continuous. See the attached pictures. Let us know if there is a specific test you would like to see verified.

https://madison.craigslist.org/bfs/d/verona-tektronix-type-576-curve-tracer/7233373156.html


Re: (OT) Where to go for 70s IBM hardware? I'm looking for a terminal.

wagnerlip
 

I worked 19 years for IBM as a mainframe engineer until 1993, and added
teleprocessing in the curriculum.
3270 terminals were everywhere, they were tough, strong and dependable.

I even design and produced one portable device to test the controller and
terminals remotely (3271/3274/3275/3276/3278/3705/3725/2703 etc), without
the need of a mainframe, that became an IBM patent.
The 3270 protocol is something fascinating, you can find online the 3270
programming language, it means, the attributes to send to the terminal
memory in order to show text, position the cursor, create input fields,
start field, protected fields, highlight, etc. It was a great jump for IBM
and it was used for decades.
The best way to dive into this, is using a serial terminal, like the
3275/3276, just plug your computer with a cross cable (no modems necessary)
and talk to the unit at 2400/4800 bps.
The only problem for you, will be the new idiom, conversation language to
the unit, it doesn't use ASCII char set, they uses EBCDIC, and the
communication is not RS232-C async (start/stop) like your PC does.

The communication protocol is synchronous and the protocol is Bisync "BSC"
(Binary Synchronous Communication) or SNA SDLC (Synchronous Data Link
Control). BSC is much simpler (even so is complicated), SNA SDLC is
somehow similar to Ethernet, it is bit orientated instead of bytes, and
uses packages, frames, counters, etc. SNA SDLC is much more efficient for a
multitude of devices and addresses in a large environment and not very
productive for small network (communication flow bit count vs useful data
really transferred).
If you really want to play with it, look for a 3275 (very old) or 3276 (new
style terminal), both incorporate the communication controller inside, and
you can talk using a simple RS232C (full interface, 25 pins, the DBE 8 pins
connector doesn't carry all the interface wires necessary, including Tx/RX
clock, it is synchronous).

By the other side, it is very difficult to talk to 3278/3277 terminals via
the coax cable, the communication and speed is very very tricky, even so,
some external competitors made some hardware boards to insert into the
ISA/PCI slots of the PC and emulate such terminals, connected to
3271/3272/3274/3174 controllers. I don't remember seem something driven
directly a terminal via the coax cable, even that, it might exist.

BSC uses flow control as SOH, STX, ETX, EOT and CRC32 at the end to certify
at the reception end the frame is not corrupted.
Each frame sent requires an answer from the receiver ACKnowloging or
NotACKnowloging the block received, etc. The protocol is a bit complex and
has several other situations and actions.
By far, the SNA SDLC/HDLC is much more complex.

Wagner Lipnharski


On Tue, Nov 24, 2020 at 2:03 PM cheater cheater <cheater00social@gmail.com>
wrote:

Thanks everyone. Not really bothered about the dependency on a control
unit for two reasons. First of all, finding /anything/ of this era will be
difficult, whether it's the rarer RS232 kind, or less rare control unit
based type. Second of all, emulating the bus will likely be part of an
interesting challenge and a good way of figuring out the inner workings of
the display and input device, which is what I want to do, so rather than a
problem it's a positive thing for me. A $10 computer nowadays will be able
to do the job. My current biggest problem is locating those older terminals
in the first place. My assumption is they're mostly in defunct computer
graveyards, warehouses, university store rooms, or bank or utilities store
rooms, dusting and decaying away.






Re: Tek blue (and gray) paint

Dave Casey
 

On a pallet in the back of an 18-wheeler either belonging to the
distribution company itself or a contracted freight carrier.

Dave Casey

On Tue, Dec 8, 2020 at 11:26 AM Colin Herbert via groups.io <colingherbert=
blueyonder.co.uk@groups.io> wrote:

One wonders how any of this stuff gets to retail outlets, presumably by
the manufacturing company itself?
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Jean-Paul
Sent: 08 December 2020 16:36
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek blue (and gray) paint

Hi there Nothing to do with the Virus, the regs are worse ever year as
prices rise on shipping anything.

All common carriers Post/Fed/UP have tightened restrictions in recent
years, eg Li batts, Haz mat, chemicals, and Aerosol.

Blame the liability lawyers.


Suggest to take the numbers on the can, check with a Pan-tone book, and
get a custom (NON aerosol) mix at a good paint store.

Of course, it must be an oil based lacquer, so many jurisdictions (EG all
of Claif) will prohibit due to VOC.

Will they ever just let us be to do our work?

Jon












Re: Tek blue (and gray) paint

Colin Herbert
 

One wonders how any of this stuff gets to retail outlets, presumably by the manufacturing company itself?
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jean-Paul
Sent: 08 December 2020 16:36
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek blue (and gray) paint

Hi there Nothing to do with the Virus, the regs are worse ever year as prices rise on shipping anything.

All common carriers Post/Fed/UP have tightened restrictions in recent years, eg Li batts, Haz mat, chemicals, and Aerosol.

Blame the liability lawyers.


Suggest to take the numbers on the can, check with a Pan-tone book, and get a custom (NON aerosol) mix at a good paint store.

Of course, it must be an oil based lacquer, so many jurisdictions (EG all of Claif) will prohibit due to VOC.

Will they ever just let us be to do our work?

Jon


Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!

 

On Tue, Dec 8, 2020 at 05:41 PM, Jeff Dutky wrote:


I'm still a little mystified by exactly what concrete tasks I might need a
volts or watts per frequency measurement for, but I'm happy to wait for
enlightenment while I play with a new toy. I'm a very hands-on learner, even
when I'm rigorously going through theory need to have concrete examples to
test myself against and to illustrate academically presented topics.

I see that there were two SAs in the 400 series, one much more "analog" (and
of much older manufacture) than the other, and at least two more in the 2700
series (they look like siblings to the 2200 and 2400 series scopes). They seem
pretty rare on eBay, and are asking much higher prices than the comparable era
scopes. At some point I will need to read through the manuals for the 491,
just to see how the spectrum analysis was done in the days before
microprocessors.
You may consider downloading the docs on this page:

https://www.hpmemoryproject.org/news/an150/an150_page_00.htm

It's not Tek but they haven't been dominating the SA-field like they have the 'scope field for a number of years.
HP have lots of docs in the field that I found much more enlightening than others'.

Raymond


Re: Calibrating a PG506 w/o Sampling System

Chuck Harris <cfharris@...>
 

I use SD24's... primarily because they have a TDR source built into
them.... and TDR is way cool! But the cheaper SD26's would also be fine.

Don't forget your SMA attenuators! The SD's have a limited safe range
of input voltages.... +/-3V is it. Their maximum input voltage for
measurement is +/-1V.

Static electricity will finish off an SD so quick you won't even know
it happened. Use a wrist strap.

The "C" model is the pinnacle of the species. I wouldn't waste my time
on the plain, "A", or "B"... though you might because the prices are much
cheaper.. as are the CSA models... though with them you lose half the
plugin slots, as they are reserved for level shifters, and fiber optic
receivers..

-Chuck Harris

Rick wrote:

Chuck, the Tek 11801C is intriguing. What sampling head do you use or should be used for the PG506?

Rick






Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!

 

Tom,

Well, my neural net seems to be quite open to calibration, but my eyes are another story

I have actually been running tests (quantitatively unsuccessful, but qualitatively enlightening) on the visual bandwidth of my scopes (feeding in a Z-axis signal and seeing how many discernible dots I can fit across the screen), and this has really driven home what the actual precision of the scope display is (it's not more than about 9 bits in either direction). I recall my father saying something similar about the 4014 terminals that he used: the resolution of the drawing commands was 4k x 4k, but the actual screen resolution was much lower (I don't recall the exact numbers, but i now expect that they couldn't resolve more than 512 dots across the small [12 inch?] screens, and probably not more than 1k across the large [20 inch?] CAD displays we saw once at a Goddard open house). By my calculation the 400 and 2200 series scopes aren't actually displaying more than 640x400 pixels, and only 320x200 resolvable, distinct lines. This severely limits the precision of any measurements you make by eye on screen despite the apparent smoothness of the waveforms.

I'm still a little mystified by exactly what concrete tasks I might need a volts or watts per frequency measurement for, but I'm happy to wait for enlightenment while I play with a new toy. I'm a very hands-on learner, even when I'm rigorously going through theory need to have concrete examples to test myself against and to illustrate academically presented topics.

I see that there were two SAs in the 400 series, one much more "analog" (and of much older manufacture) than the other, and at least two more in the 2700 series (they look like siblings to the 2200 and 2400 series scopes). They seem pretty rare on eBay, and are asking much higher prices than the comparable era scopes. At some point I will need to read through the manuals for the 491, just to see how the spectrum analysis was done in the days before microprocessors.

Everything I have learned since taking up this hobby has fed a keen awareness that, even when they are in perfect working order, your instruments are lying to you (if only by omission).

-- Jeff Dutky


Re: Tek blue (and gray) paint

Jean-Paul
 

Hi there Nothing to do with the Virus, the regs are worse ever year as prices rise on shipping anything.

All common carriers Post/Fed/UP have tightened restrictions in recent years, eg Li batts, Haz mat, chemicals, and Aerosol.

Blame the liability lawyers.


Suggest to take the numbers on the can, check with a Pan-tone book, and get a custom (NON aerosol) mix at a good paint store.

Of course, it must be an oil based lacquer, so many jurisdictions (EG all of Claif) will prohibit due to VOC.

Will they ever just let us be to do our work?

Jon


Re: Calibrating a PG506 w/o Sampling System

Rick
 

Chuck, the Tek 11801C is intriguing. What sampling head do you use or should be used for the PG506?

Rick


Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!

Tom Lee
 

Jeff,

If you ever wish to examine the spectral content of a signal, you need an SA. Using a scope's presentation of a sinusoid, you'd be hard-pressed to resolve distortions below a percent, and you'd only do that well for certain types of distortion, and if your eyeballs and neural net are pretty damn well calibrated. A properly designed spectrum analyzer can resolve distortion levels in the ppm range (and still better ones exist). Better still, you see the nature of the distortion -- e.g., is the distortion dominated by a certain harmonic or group of harmonics? Is it not distortion at all, but interference or power supply noise creeping into the system? Etc.

So, depending on context, either a scope (for volts vs. time) or a spectrum analyzer (for volts vs. frequency) may be the right tool. If you have both, you've got both domains covered.

I should mention that some digital scopes have an FFT capability, giving you something that looks like what a spectrum analyzer would present. But there are many tradeoffs in trying to make a scope also act as a decent spectrum analyzer, so most scopes are not decent SAs. But if the software comes for free, one cannot complain too much, as long as one is aware that the instrument may present a screenful of lies.

-- 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 12/7/2020 23:54, Jeff Dutky wrote:
Tom,

I've had a look at the TinySA home page (www.tinysa.org/wiki), watched several of the recommended videos, and I'm sold.

I've just got one question: aside from using it as a signal generator, what would I DO with a spectrum analyzer?

-- Jeff Dutky




Re: Can capacitors

 

See also the earlier discussion on Multi section electrolytic capacitors:

https://groups.io/g/TekScopes/topic/multi_section_electrolytic/78408639

Regards,
John


Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!

 

Tom,

I've had a look at the TinySA home page (www.tinysa.org/wiki), watched several of the recommended videos, and I'm sold.

I've just got one question: aside from using it as a signal generator, what would I DO with a spectrum analyzer?

-- Jeff Dutky


Re: Tek blue (and gray) paint

 

Dave Casey wrote:

I would think UPS Ground would take it, just as they do Lithium batteries.
I would have thought that too, and the seller seemed to expect that as well, but his impression was that they were refusing to ship aerosol cans during the pandemic. Whatever the case I will find out this week, as I plan to call both UPS and FedEx to verify what their current policies are.

-- Jeff Dutky


Re: Tek blue (and gray) paint

Dave Casey
 

I would think UPS Ground would take it, just as they do Lithium batteries.

Dave Casey

On Tue, Dec 8, 2020 at 12:28 AM Jeff Dutky <jeff.dutky@gmail.com> wrote:

I ordered some of the spray paint from the eBay seller, but he had to
cancel my order today because he can't find a shipper who will handle
aerosol spray paint. I was a little worried about this when I made the
order. I know that USPS won't handle such things, and I was worried that
UPS and FedEx might balk (which, apparently they have).

I am going to investigate UPS ground and FedEx this week, to see if there
is any way to ship these items, but the seller didn't sound optimistic.

-- Jeff Dutky






Re: Tek blue (and gray) paint

 

I ordered some of the spray paint from the eBay seller, but he had to cancel my order today because he can't find a shipper who will handle aerosol spray paint. I was a little worried about this when I made the order. I know that USPS won't handle such things, and I was worried that UPS and FedEx might balk (which, apparently they have).

I am going to investigate UPS ground and FedEx this week, to see if there is any way to ship these items, but the seller didn't sound optimistic.

-- Jeff Dutky


Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!

 

Tom, Raymond, Harvey, and John,

This is an absolutely amazing wealth of information. I've already copied it into a notebook page, and will be going through it carefully over the next week (and trying to cross reference it to the 475A calibration process). This sort of information needs to be collected in one place and presented as a coherent alternative to the Tek-specified process (and, yes, I'm volunteering to do that).

Thanks for all this wonderful commentary and information. It almost sounds like I rolling my own calibration fixtures isn't nearly as challenging as I had feared it would be (probably much less challenging than buying the vintage equipment and restoring it to correct working order).

I've got a significantly-more-than-ten-dollar pulse generator (http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=124&products_id=295&zenid=2cd5390de5b54cabb48f8ed903b80480) but I'm kind of excited to build the rest of the kit (I really need to get my feet wet with transistors, and I just finished reading about ECL for exactly this kind of project).

-- Jeff Dutky


Re: Anyone need 561 parts?

Bruce Atwood
 

I'm rewinding the HV XFMR in my 561 but would not mind a backup plan. How is the T600 in yours? As an aside, does yours have a 4.3 Ohm resister in series with the 1 turn secondary for the filament of the HV rectifier? Every schematic I see has one but there is no trace of it in my 561.

Fully OT: My 561 is almost all that is left of ITI Electronics (I also have their GR impedance bridge, a real marvel). ITI did TVs for bars and hotels in the late '40 and '50. My dad, Horace, W2SXW, was founder and president. One of the few small firms founded in the 40s that made it to the 80s. Dad told me of the IRE show where Tektronix showed of their first calibrated sweep, triggered sweep, calibrated gain scope where the assembled engineers all agreed it was a marvel but wondered who the hell would pay $ks for a 'scope. He was designing 'scopes for Allen B DuMont the time, later doing TVs for him.

cheers

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