Date   

Re: How Many Scopes?

John Ferguson
 

What Craig,  no 24**'s ??

On 12/6/18 5:23 PM, Craig Sawyers wrote:
Thinking that no rational person needs so many scopes I offered it to the local university science
dept
who had mentioned to me that they needed a good analog scope - Voila they would get the 2465.
OK - 7904, 7904A, 7834 ,7844, 7104, 7313, 7623B, 7633, 7603, 7704A, 7854, 7403N, 7912HB, 7934
545A, 545B, 564 , 575, 576, 577D2, 575 mod 122C, 585A, 475/DM44, 453

That is kind of the tip of the iceberg. Pass the tablets and a glass of water.

Craig


Re: How Many Scopes?

Craig Sawyers <c.sawyers@...>
 

Thinking that no rational person needs so many scopes I offered it to the local university science
dept
who had mentioned to me that they needed a good analog scope - Voila they would get the 2465.
OK - 7904, 7904A, 7834 ,7844, 7104, 7313, 7623B, 7633, 7603, 7704A, 7854, 7403N, 7912HB, 7934
545A, 545B, 564 , 575, 576, 577D2, 575 mod 122C, 585A, 475/DM44, 453

That is kind of the tip of the iceberg. Pass the tablets and a glass of water.

Craig


Re: How Many Scopes?

Tom Gardner
 

On 06/12/18 21:19, John Ferguson via Groups.Io wrote:
So I'm back to where I was at the end of last week with too many scopes.

Most of the problem seems to be with "parts" scopes.  If I got one that actually didn't work it would be what I'd expected, but the damn things keep showing up with nothing serious wrong with them. And I cannot bring myself to scrap a working scope.  I doubt if any of you can either.

What am I missing?
A1: N+1 scopes, the next one being better for some purposes

A2: a support group. Try:
http://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/
but note that after the first 10,000 responses it degenerates :)


Re: How Many Scopes?

tom jobe <tomjobe@...>
 

You're not 'missing' anything!
Life is good and people are great!

On 12/6/2018 1:19 PM, John Ferguson via Groups.Io wrote:
Without actually knowing anything, I now have two 2445B's, one 2465, and just now a 2445 plus the cute little SC501 that fits in a TM case.  The first 2445b was bought to use, then the second because it worked well on all but channel one whose attenuator hadn't been adequate for oomph of whatever Bozo plugged it into. I had one of our colleagues re-cap the power supply, change the NVRAM for a FRAM, and replace the leaking SMD caps and fix the damage they'd done. This scope is now VERY nice.

Now I had a really good 2445B and the second one which also now has FRAM and better caps on A5, but whatever PS caps were in it. It works ok manually but the Parametric functions don't work. It was a lab scope so footless, no handle,  and missing those nice rubber things on the rear.

So fool that I was I thought I'd buy just those things ..... hah, hah, hah - cheaper to buy a parts scope which is where the 2465 came from. Someone had let it down a bit ungently on the time knob, destroyed the knob and broke the VAR pot shaft.  I was able to find a complete right-side panel on ebay and when it replaced the bad one all was well and the scope worked nicely although the trace could lose a bit of weight.

I also discovered that the shaft on the trace-intensity knob had also been there for the great fall, so it was replaced and now the thing is perfect, more or less.

Thinking that no rational person needs so many scopes I offered it to the local university science dept who had mentioned to me that they needed a good analog scope - Voila they would get the 2465.

But then when I was cleaning it up, I decided to keep it.

There was a 2445 cheap on Ebay which allegedly needed repair. It didn't and it is really nice - so FAU gets that one. And its trace is really fine.

So I'm back to where I was at the end of last week with too many scopes.

Most of the problem seems to be with "parts" scopes.  If I got one that actually didn't work it would be what I'd expected, but the damn things keep showing up with nothing serious wrong with them. And I cannot bring myself to scrap a working scope.  I doubt if any of you can either.

What am I missing?





Re: 7S12 versus 7T11(A)/7S11 for general purpose sampling

Jim Ford
 

Thanks, Albert.
I will indeed put a 7T11 or 7T11A on my wishlist.  Yes, it can be a pain to get a signal to trigger on for the S-51 or S-53.  I am fortunate enough to have both.
I figured the 7S12 had the TDR capability while the 7S11 + 7T11 did not, so I opted for the 7S12.  Then I  needed a 2nd channel, so I bought a 7S11 and another S-4.  Working well so far.
Thanks again. 
Jim F


Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Albert Otten <aodiversen@concepts.nl> Date: 12/6/18 1:17 PM (GMT-08:00) To: TekScopes@groups.io Subject: [TekScopes] 7S12 versus 7T11(A)/7S11 for general purpose sampling
Hi Jim,

Since your question is not related to the problems in the "7T11 horizontal memory" thread I opened this new topic for my answer.
With the 7S12 you would also need an S-53 and an S-51 head for the same triggering capabilities as the 7T11.
The most annoying aspects of the 7S12 for general purpose use are the heavy crank-handle drive (versus a multiturn TIME POSITION pot in the 7T11) and lack of internal triggering capability. The trigger output of sampling heads (not all heads have this) is simply terminated in 50R in the 7S12 and not used at all.
Sometimes you need the slower sweep ranges of the 7T11.
The 7S12 goes to 20 ps/div, the 7T11 to 10 ps/div.
The 7T11 can do random sampling, the 7S12 can't. I know that the quality of random sampling is not overwhelming, but this capability is perhaps a strong argument to convince the committee.

Albert

On Thu, Dec  6, 2018 at 07:25 PM, Jim Ford wrote:


Say, since I have the 7S12 and 7S11, is there any reason to obtain a 7T11 or
7T11A?  Aside from the fact that it's another cool piece of Tek gear to own,
I mean.  IOW, do I have a justification before the finance committee (my wife
;) )?
TIA.
Jim F


Re: How Many Scopes?

John Ferguson
 

Sent from Mail for Windows 10

From: Harvey White
Sent: Thursday, December 6, 2018 4:29 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] How Many Scopes?

On Thu, 6 Dec 2018 16:19:16 -0500, you wrote:

You're missing space for more scopes.

Depending on what you think of as the service life of the scope,
coupled with how long you will be using it, and throw in the little
bit that these scope parts are in limited supply.....

I'd like to have a good working scope, one working spare, and enough
parts units to be able to replace almost everything once.

Having said that, you may want to look into calibration equipment for
your scopes, if you want to start doing that yourself.

Those plugins will fit in a TM506 right next to the SC501.

Hi Harvey,

I’m actually up to my ears with other projects and one of our members here in the US does terrific repairs and calibrations.
This is probably not very smart but I compared the measurement I get on the other scopes to the calibrated one and find them pretty close, certainly close enough for what I do.

Best regards, john


Re: How Many Scopes?

Harvey White
 

On Thu, 6 Dec 2018 16:19:16 -0500, you wrote:

You're missing space for more scopes.

Depending on what you think of as the service life of the scope,
coupled with how long you will be using it, and throw in the little
bit that these scope parts are in limited supply.....

I'd like to have a good working scope, one working spare, and enough
parts units to be able to replace almost everything once.

Having said that, you may want to look into calibration equipment for
your scopes, if you want to start doing that yourself.

Those plugins will fit in a TM506 right next to the SC501.



Harvey


Without actually knowing anything, I now have two 2445B's, one 2465, and
just now a 2445 plus the cute little SC501 that fits in a TM case.  The
first 2445b was bought to use, then the second because it worked well on
all but channel one whose attenuator hadn't been adequate for oomph of
whatever Bozo plugged it into. I had one of our colleagues re-cap the
power supply, change the NVRAM for a FRAM, and replace the leaking SMD
caps and fix the damage they'd done. This scope is now VERY nice.

Now I had a really good 2445B and the second one which also now has FRAM
and better caps on A5, but whatever PS caps were in it. It works ok
manually but the Parametric functions don't work. It was a lab scope so
footless, no handle,  and missing those nice rubber things on the rear.

So fool that I was I thought I'd buy just those things ..... hah, hah,
hah - cheaper to buy a parts scope which is where the 2465 came from.
Someone had let it down a bit ungently on the time knob, destroyed the
knob and broke the VAR pot shaft.  I was able to find a complete
right-side panel on ebay and when it replaced the bad one all was well
and the scope worked nicely although the trace could lose a bit of weight.

I also discovered that the shaft on the trace-intensity knob had also
been there for the great fall, so it was replaced and now the thing is
perfect, more or less.

Thinking that no rational person needs so many scopes I offered it to
the local university science dept who had mentioned to me that they
needed a good analog scope - Voila they would get the 2465.

But then when I was cleaning it up, I decided to keep it.

There was a 2445 cheap on Ebay which allegedly needed repair. It didn't
and it is really nice - so FAU gets that one. And its trace is really fine.

So I'm back to where I was at the end of last week with too many scopes.

Most of the problem seems to be with "parts" scopes.  If I got one that
actually didn't work it would be what I'd expected, but the damn things
keep showing up with nothing serious wrong with them. And I cannot bring
myself to scrap a working scope.  I doubt if any of you can either.

What am I missing?






Re: How Many Scopes?

John Ferguson
 

Without actually knowing anything, I now have two 2445B's, one 2465, and just now a 2445 plus the cute little SC501 that fits in a TM case.  The first 2445b was bought to use, then the second because it worked well on all but channel one whose attenuator hadn't been adequate for oomph of whatever Bozo plugged it into. I had one of our colleagues re-cap the power supply, change the NVRAM for a FRAM, and replace the leaking SMD caps and fix the damage they'd done. This scope is now VERY nice.

Now I had a really good 2445B and the second one which also now has FRAM and better caps on A5, but whatever PS caps were in it. It works ok manually but the Parametric functions don't work. It was a lab scope so footless, no handle,  and missing those nice rubber things on the rear.

So fool that I was I thought I'd buy just those things ..... hah, hah, hah - cheaper to buy a parts scope which is where the 2465 came from. Someone had let it down a bit ungently on the time knob, destroyed the knob and broke the VAR pot shaft.  I was able to find a complete right-side panel on ebay and when it replaced the bad one all was well and the scope worked nicely although the trace could lose a bit of weight.

I also discovered that the shaft on the trace-intensity knob had also been there for the great fall, so it was replaced and now the thing is perfect, more or less.

Thinking that no rational person needs so many scopes I offered it to the local university science dept who had mentioned to me that they needed a good analog scope - Voila they would get the 2465.

But then when I was cleaning it up, I decided to keep it.

There was a 2445 cheap on Ebay which allegedly needed repair. It didn't and it is really nice - so FAU gets that one. And its trace is really fine.

So I'm back to where I was at the end of last week with too many scopes.

Most of the problem seems to be with "parts" scopes.  If I got one that actually didn't work it would be what I'd expected, but the damn things keep showing up with nothing serious wrong with them. And I cannot bring myself to scrap a working scope.  I doubt if any of you can either.

What am I missing?


7S12 versus 7T11(A)/7S11 for general purpose sampling

Albert Otten
 

Hi Jim,

Since your question is not related to the problems in the "7T11 horizontal memory" thread I opened this new topic for my answer.
With the 7S12 you would also need an S-53 and an S-51 head for the same triggering capabilities as the 7T11.
The most annoying aspects of the 7S12 for general purpose use are the heavy crank-handle drive (versus a multiturn TIME POSITION pot in the 7T11) and lack of internal triggering capability. The trigger output of sampling heads (not all heads have this) is simply terminated in 50R in the 7S12 and not used at all.
Sometimes you need the slower sweep ranges of the 7T11.
The 7S12 goes to 20 ps/div, the 7T11 to 10 ps/div.
The 7T11 can do random sampling, the 7S12 can't. I know that the quality of random sampling is not overwhelming, but this capability is perhaps a strong argument to convince the committee.

Albert

On Thu, Dec 6, 2018 at 07:25 PM, Jim Ford wrote:


Say, since I have the 7S12 and 7S11, is there any reason to obtain a 7T11 or
7T11A? Aside from the fact that it's another cool piece of Tek gear to own,
I mean. IOW, do I have a justification before the finance committee (my wife
;) )?
TIA.
Jim F


Re: 7T11 horizontal memory

Jim Ford
 

Say, since I have the 7S12 and 7S11, is there any reason to obtain a 7T11 or 7T11A?  Aside from the fact that it's another cool piece of Tek gear to own, I mean.  IOW, do I have a justification before the finance committee (my wife ;) )?
TIA.
Jim F


Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Albert Otten <aodiversen@concepts.nl> Date: 12/6/18 2:56 AM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] 7T11 horizontal memory
On Wed, Dec  5, 2018 at 10:19 PM, cmjones01 wrote:


- in real time mode, it's hard to get a trace that makes sense. presumably the
50kHz-ish clock from the real time multivibrator limits the display to about
one sample every 20us, so some of the faster sweep speeds don't show a lot.
Even on the slower sweeps, the edges of my test squarewave exhibit terrible
risetime (about half a division) which is puzzling, and very different to the
behaviour in equivalent time. Maybe it's something to do with the recovery
time of the sampling head, or there's something amiss with the 7S11. I tried
adjusting the 'dot response' control and making sure smoothing was switched
off, but it didn't improve much.
Just to be sure that the fault is in the 7S11, you might check that the terrible rise time is also present when you use the 7S11 in combination with an ordinary timebase unit in stead of the 7T11.
You probably did not verify that you could adjust the dot response for loop gain one, it only "improved not much". I would check this first of all. The sampling head has an internal GAIN adjustment that could be too far off to correct with the 7S11 dot response adjustment.

You can probably tell that I'm new to the
7000-series sampling world. I regularly use my CSA803A/SD24 sampling setup,
but that makes it all so easy...
I followed the normal(?) route. I started with sampling units for the 564, then for the 7000 series and now I also have a CSA803A  with SD-20 and SD-26. Still waiting for a good opportunity to buy an SD-24.

Albert


Re: TDS3032 does not boot. LCD backl-ight and fan working.

David Kuhn
 

" @Dave, when you have had the bad NVRAM installed, how did the no-boot
situation look? I.e., was it also a white screen, no beeps and no relay
clicks, or did it at least show the DPO splash screen? "

Gosh, I'm afraid I am of no help then. I looked through old message
threads I had on here from the last month and found my message concerning
the fake NVRAM from China:

""After re-assembly, it will not boot past the "Digital Phoshor
Oscilloscope" splash screen. During bootup, you do hear the hear the
relays click, the splash screen flickers a bit and the floppy drive seeks.
The splash screen never goes away. ""

My TDS3032 did get to the splash screen and locked up with the fake Chinese
i.c..

Sorry. The NVRAM is probably about the only thing you can fix on that main
board. It cost about $38.00. You have to decide if it's worth a shot. I
wonder if you removed it (lot of careful de-soldering - use a powered
de-soldering pump (i.e. Hakko 808). Maybe if you removed it it would boot
to the splash screen, then you know. If it is still totally dead, I doubt
there is much you can fix. Look for a XTAL near the microprocessor and
make sure it is good and not broken (if scope was dropped).

I will be getting mine back with calibration seals, so I will not be able
to open it to help do comparisons with you.

Dave

On Thu, Dec 6, 2018 at 5:42 AM benj3867 via Groups.Io <benj3867=
yahoo.com@groups.io> wrote:

@Dave, when you have had the bad NVRAM installed, how did the no-boot
situation look? I.e., was it also a white screen, no beeps and no relay
clicks, or did it at least show the DPO splash screen?

Thanks,
Benjamin




Re: 7T11 horizontal memory

Albert Otten
 

On Wed, Dec 5, 2018 at 10:19 PM, cmjones01 wrote:


- in real time mode, it's hard to get a trace that makes sense. presumably the
50kHz-ish clock from the real time multivibrator limits the display to about
one sample every 20us, so some of the faster sweep speeds don't show a lot.
Even on the slower sweeps, the edges of my test squarewave exhibit terrible
risetime (about half a division) which is puzzling, and very different to the
behaviour in equivalent time. Maybe it's something to do with the recovery
time of the sampling head, or there's something amiss with the 7S11. I tried
adjusting the 'dot response' control and making sure smoothing was switched
off, but it didn't improve much.
Just to be sure that the fault is in the 7S11, you might check that the terrible rise time is also present when you use the 7S11 in combination with an ordinary timebase unit in stead of the 7T11.
You probably did not verify that you could adjust the dot response for loop gain one, it only "improved not much". I would check this first of all. The sampling head has an internal GAIN adjustment that could be too far off to correct with the 7S11 dot response adjustment.

You can probably tell that I'm new to the
7000-series sampling world. I regularly use my CSA803A/SD24 sampling setup,
but that makes it all so easy...
I followed the normal(?) route. I started with sampling units for the 564, then for the 7000 series and now I also have a CSA803A with SD-20 and SD-26. Still waiting for a good opportunity to buy an SD-24.

Albert


Re: TDS3032 does not boot. LCD backl-ight and fan working.

benj3867
 

@Dave, when you have had the bad NVRAM installed, how did the no-boot situation look? I.e., was it also a white screen, no beeps and no relay clicks, or did it at least show the DPO splash screen?

Thanks,
Benjamin


Re: Tube test adaptor for Tektroinx 575 was: Re: [TekScopes] FS: miscellaneous Tektronix manuals

 

Another thing to consider (if you are feeding tube filaments via AC
power) and want to minimize hum is to use twisted pair wiring to
distribute AC power to the tube filament socket connections (rather than
individual single conductor wires which are haphazardly separated from
each other). Twisted pair tends to minimize inductive (magnetic)
radiation within the equipment/chassis that could otherwise occur with
separated wires supplying AC to the tube socket filament pins; the
magnetic field (at 60 hz) can lead to audio hum. Of course, it's also
OK to use single conductor wires which are twisted together in "paired"
wiring for the filament power distriubtion.

Mike Dinolfo N4MWP

On 12/5/18 10:06 PM, Jim Ford wrote:
Yep, a colleague several decades ago told me if you ever work with audio tubes, try D.C. for the heater instead of A.C., you'll like it.  I never forgot that, although I have not worked with tubes much.
Jim F


Sent from my Verizon, Samsung Galaxy smartphone
-------- Original message --------From: Harvey White <madyn@dragonworks.info> Date: 12/5/18 5:23 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: Tube test adaptor for Tektroinx 575 was: Re: [TekScopes] FS: miscellaneous Tektronix manuals
On Wed, 5 Dec 2018 22:11:12 +0000 (UTC), you wrote:

Brad,
Thank you!
My main interest is audio tubes. I have >1000 different tubes, mostly audio output and small signal/preamp tubes. I also own a Hickok 580A tube tester and a Tektronix 575 Curve Tracer. Thus my interest in using a Tek 575 to match tubes for use in DIY preamps and amps I am planning to make.
I was a electronics tech in the military a long time ago, in the time when tubes were going away and being replaced with solid state, but before the internet and PCs. I don't write code, although I did take a course in Fortran back in the early 1980s.
This group has been a tremendous resource. I truly appreciate the responses that I have humbly received from you and others in the group. I say humbly received because I'm just a audio hobbyist and ME who is humbled because I realize that I know so little about audio electronics who is trying to learn.
For example, I didn't know until recently that tubes usually use AC voltage for the heater. I'm also learning the different terms, such as the anode is usually called the plate. It's humbling that this old technology was invented well before I was born and is still useful today.
Again, thanks to all who responded with the lessons and great information.
Dan
Here's another one, and you may want to think of this in a high end
application.

The original heaters (called filaments) were the same as light bulbs,
simply tungsten wires that were heated to boil off electrons.

These were the first heaters, and needed 'A' batteries to run them.
(the "B" batteries provided plate voltages, and the "C" batteries
provided bias voltages, which were difficult to do without a negative
supply since the filament was both the cathode and the electron
supply.  You simply couldn't have the cathodes at any different
potential since they were supplied by the same battery)

Now another problem was that because the heaters had relatively small
thermal inertia (they heated up and cooled down quickly), the use of
AC for the heaters induced hum on the signal ... think of it, your
electron supply was increasing and decreasing with the AC supply
voltage.

So the solution was to put the heater inside a tube, but electrically
isolated from it.  So the heater could run off AC, and the thermal
inertia of the tube (called the cathode), kept the electron flow more
even.

You could even self bias the tubes by elevating the cathode above
ground.

Lead to a lot of nice designs.

Now, there's still a bit of hum induced by the heater in the cathode
sleve.  (cathode sleve has materials on it that release electrons when
heated). In your amplifier/preamp/whatever, you *may* get a reduction
in hum by running the heater from DC.

Just a thought, you may want to look it up.

Harvey





    On Wednesday, December 5, 2018, 1:28:41 PM PST, Brad Thompson <brad.thompson@valley.net> wrote:

On 12/4/2018 4:52 PM, Dan Cordova via Groups.Io wrote:
  Hi Brad,
Do you have or know anyone selling an adapter/fixture to match tubes on a Tektronix 575?
Or, do you know if there is a schematic I can buy?
Glydeck has a blog about this, but there is no schematic or info to contact him.
Hello, Dan and the group--

Thank you for your inquiry. Here's a column I wrote for Test &
Measurement World
magazine (subsequently absorbed by EDN) which describes my version of
a tube-test adaptor for the Tek 575:

https://www.edn.com/design/test-and-measurement/4389419/Old-dog-newer-trick

You can view a schematic and photos here...

https://www.flickr.com/photos/aa1ip_pix/

I used an external tube socket, small PC board and some two-piece
surplus connectors to build an adaptor, which suffices for small tubes
that don't need plate voltages in excess of what the 575 can deliver.
Heater or filament and screen voltages get supplied by "wall warts" or
other power supplies

In the schematic, J1 and J2 form a "crossover network" to match a
particular tube's pinout. This approach requires wiring or rewiring
the J1-J2 adaptor to test each tube type and thus is best suited to
testing a batch of identically-pinned tubes at once.

Newcomers to tube technology may be surprised to learn that many tubes
with different part numbers can share a common pinout. For example,
JEDEC base code 8BD
defines an octal (8-pin) base which applies to the 6SN7-GT, the 6SL7-GT
and their
heater-voltage cognates along with 25 or so other tube-part numbers.
Providing 12 pins
accommodates "modern" Compactron tubes.

While I noted no spurious oscillations while testing a batch of 6SN7s, you
may need to slip ferrite beads onto plate and grid leads if needed for
parasitic-oscillation suppression.

One point: use care in selecting the grid/base voltage you apply to the
tube under test. If the tube manual states "maximum positive grid
voltage = 0 volts", believe it! Running the grid voltage positive causes
large amounts of grid current to flow can melt the grid.

Questions welcomed-- I don't have any spare adaptor boards left over
but would investigate making more if there's interest.

73--

Brad  aA1IP










Re: Tube test adaptor for Tektroinx 575 was: Re: [TekScopes] FS: miscellaneous Tektronix manuals

Jim Ford
 

Yep, a colleague several decades ago told me if you ever work with audio tubes, try D.C. for the heater instead of A.C., you'll like it.  I never forgot that, although I have not worked with tubes much.
Jim F


Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Harvey White <madyn@dragonworks.info> Date: 12/5/18 5:23 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: Tube test adaptor for Tektroinx 575 was: Re: [TekScopes] FS: miscellaneous Tektronix manuals
On Wed, 5 Dec 2018 22:11:12 +0000 (UTC), you wrote:

Brad,
Thank you!
My main interest is audio tubes. I have >1000 different tubes, mostly audio output and small signal/preamp tubes. I also own a Hickok 580A tube tester and a Tektronix 575 Curve Tracer. Thus my interest in using a Tek 575 to match tubes for use in DIY preamps and amps I am planning to make. 
I was a electronics tech in the military a long time ago, in the time when tubes were going away and being replaced with solid state, but before the internet and PCs. I don't write code, although I did take a course in Fortran back in the early 1980s. 
This group has been a tremendous resource. I truly appreciate the responses that I have humbly received from you and others in the group. I say humbly received because I'm just a audio hobbyist and ME who is humbled because I realize that I know so little about audio electronics who is trying to learn.
For example, I didn't know until recently that tubes usually use AC voltage for the heater. I'm also learning the different terms, such as the anode is usually called the plate. It's humbling that this old technology was invented well before I was born and is still useful today. 
Again, thanks to all who responded with the lessons and great information.
Dan 
Here's another one, and you may want to think of this in a high end
application.

The original heaters (called filaments) were the same as light bulbs,
simply tungsten wires that were heated to boil off electrons.

These were the first heaters, and needed 'A' batteries to run them.
(the "B" batteries provided plate voltages, and the "C" batteries
provided bias voltages, which were difficult to do without a negative
supply since the filament was both the cathode and the electron
supply.  You simply couldn't have the cathodes at any different
potential since they were supplied by the same battery)

Now another problem was that because the heaters had relatively small
thermal inertia (they heated up and cooled down quickly), the use of
AC for the heaters induced hum on the signal ... think of it, your
electron supply was increasing and decreasing with the AC supply
voltage.

So the solution was to put the heater inside a tube, but electrically
isolated from it.  So the heater could run off AC, and the thermal
inertia of the tube (called the cathode), kept the electron flow more
even.

You could even self bias the tubes by elevating the cathode above
ground.

Lead to a lot of nice designs.

Now, there's still a bit of hum induced by the heater in the cathode
sleve.  (cathode sleve has materials on it that release electrons when
heated). In your amplifier/preamp/whatever, you *may* get a reduction
in hum by running the heater from DC.

Just a thought, you may want to look it up.

Harvey





    On Wednesday, December 5, 2018, 1:28:41 PM PST, Brad Thompson <brad.thompson@valley.net> wrote:

On 12/4/2018 4:52 PM, Dan Cordova via Groups.Io wrote:
  Hi Brad,
Do you have or know anyone selling an adapter/fixture to match tubes on a Tektronix 575?
Or, do you know if there is a schematic I can buy?
Glydeck has a blog about this, but there is no schematic or info to contact him.
Hello, Dan and the group--

Thank you for your inquiry. Here's a column I wrote for Test &
Measurement World
magazine (subsequently absorbed by EDN) which describes my version of
a tube-test adaptor for the Tek 575:

https://www.edn.com/design/test-and-measurement/4389419/Old-dog-newer-trick

You can view a schematic and photos here...

https://www.flickr.com/photos/aa1ip_pix/

I used an external tube socket, small PC board and some two-piece
surplus connectors to build an adaptor, which suffices for small tubes
that don't need plate voltages in excess of what the 575 can deliver.
Heater or filament and screen voltages get supplied by "wall warts" or
other power supplies

In the schematic, J1 and J2 form a "crossover network" to match a
particular tube's pinout. This approach requires wiring or rewiring
the J1-J2 adaptor to test each tube type and thus is best suited to
testing a batch of identically-pinned tubes at once.

Newcomers to tube technology may be surprised to learn that many tubes
with different part numbers can share a common pinout. For example,
JEDEC base code 8BD
defines an octal (8-pin) base which applies to the 6SN7-GT, the 6SL7-GT
and their
heater-voltage cognates along with 25 or so other tube-part numbers.
Providing 12 pins
accommodates "modern" Compactron tubes.

While I noted no spurious oscillations while testing a batch of 6SN7s, you
may need to slip ferrite beads onto plate and grid leads if needed for
parasitic-oscillation suppression.

One point: use care in selecting the grid/base voltage you apply to the
tube under test. If the tube manual states "maximum positive grid
voltage = 0 volts", believe it! Running the grid voltage positive causes
large amounts of grid current to flow can melt the grid.

Questions welcomed-- I don't have any spare adaptor boards left over
but would investigate making more if there's interest.

73--

Brad  aA1IP






Re: Tube test adaptor for Tektroinx 575 was: Re: [TekScopes] FS: miscellaneous Tektronix manuals

Harvey White
 

On Wed, 5 Dec 2018 22:11:12 +0000 (UTC), you wrote:

Brad,
Thank you!
My main interest is audio tubes. I have >1000 different tubes, mostly audio output and small signal/preamp tubes. I also own a Hickok 580A tube tester and a Tektronix 575 Curve Tracer. Thus my interest in using a Tek 575 to match tubes for use in DIY preamps and amps I am planning to make. 
I was a electronics tech in the military a long time ago, in the time when tubes were going away and being replaced with solid state, but before the internet and PCs. I don't write code, although I did take a course in Fortran back in the early 1980s. 
This group has been a tremendous resource. I truly appreciate the responses that I have humbly received from you and others in the group. I say humbly received because I'm just a audio hobbyist and ME who is humbled because I realize that I know so little about audio electronics who is trying to learn.
For example, I didn't know until recently that tubes usually use AC voltage for the heater. I'm also learning the different terms, such as the anode is usually called the plate. It's humbling that this old technology was invented well before I was born and is still useful today. 
Again, thanks to all who responded with the lessons and great information.
Dan 
Here's another one, and you may want to think of this in a high end
application.

The original heaters (called filaments) were the same as light bulbs,
simply tungsten wires that were heated to boil off electrons.

These were the first heaters, and needed 'A' batteries to run them.
(the "B" batteries provided plate voltages, and the "C" batteries
provided bias voltages, which were difficult to do without a negative
supply since the filament was both the cathode and the electron
supply. You simply couldn't have the cathodes at any different
potential since they were supplied by the same battery)

Now another problem was that because the heaters had relatively small
thermal inertia (they heated up and cooled down quickly), the use of
AC for the heaters induced hum on the signal ... think of it, your
electron supply was increasing and decreasing with the AC supply
voltage.

So the solution was to put the heater inside a tube, but electrically
isolated from it. So the heater could run off AC, and the thermal
inertia of the tube (called the cathode), kept the electron flow more
even.

You could even self bias the tubes by elevating the cathode above
ground.

Lead to a lot of nice designs.

Now, there's still a bit of hum induced by the heater in the cathode
sleve. (cathode sleve has materials on it that release electrons when
heated). In your amplifier/preamp/whatever, you *may* get a reduction
in hum by running the heater from DC.

Just a thought, you may want to look it up.

Harvey





On Wednesday, December 5, 2018, 1:28:41 PM PST, Brad Thompson <brad.thompson@valley.net> wrote:

On 12/4/2018 4:52 PM, Dan Cordova via Groups.Io wrote:
  Hi Brad,
Do you have or know anyone selling an adapter/fixture to match tubes on a Tektronix 575?
Or, do you know if there is a schematic I can buy?
Glydeck has a blog about this, but there is no schematic or info to contact him.
Hello, Dan and the group--

Thank you for your inquiry. Here's a column I wrote for Test &
Measurement World
magazine (subsequently absorbed by EDN) which describes my version of
a tube-test adaptor for the Tek 575:

https://www.edn.com/design/test-and-measurement/4389419/Old-dog-newer-trick

You can view a schematic and photos here...

https://www.flickr.com/photos/aa1ip_pix/

I used an external tube socket, small PC board and some two-piece
surplus connectors to build an adaptor, which suffices for small tubes
that don't need plate voltages in excess of what the 575 can deliver.
Heater or filament and screen voltages get supplied by "wall warts" or
other power supplies

In the schematic, J1 and J2 form a "crossover network" to match a
particular tube's pinout. This approach requires wiring or rewiring
the J1-J2 adaptor to test each tube type and thus is best suited to
testing a batch of identically-pinned tubes at once.

Newcomers to tube technology may be surprised to learn that many tubes
with different part numbers can share a common pinout. For example,
JEDEC base code 8BD
defines an octal (8-pin) base which applies to the 6SN7-GT, the 6SL7-GT
and their
heater-voltage cognates along with 25 or so other tube-part numbers.
Providing 12 pins
accommodates "modern" Compactron tubes.

While I noted no spurious oscillations while testing a batch of 6SN7s, you
may need to slip ferrite beads onto plate and grid leads if needed for
parasitic-oscillation suppression.

One point: use care in selecting the grid/base voltage you apply to the
tube under test. If the tube manual states "maximum positive grid
voltage = 0 volts", believe it! Running the grid voltage positive causes
large amounts of grid current to flow can melt the grid.

Questions welcomed-- I don't have any spare adaptor boards left over
but would investigate making more if there's interest.

73--

Brad  aA1IP






WTB Dead TM500 plugins

Paul Amaranth
 

Does anyone have any dead TM500 plugins they want to sell (cheaply)?

I'm looking for a couple of carcasses to build some custom
modules with.

thanks

Paul
--
Paul Amaranth, GCIH | Rochester MI, USA
Aurora Group, Inc. | Security, Systems & Software
paul@AuroraGrp.Com | Unix & Windows


Re: 7T11 horizontal memory

Jim Ford
 

Chris, I'm envious that you have a CSA803 and SD24!  I had that setup about 25 years ago at my employer the time.  Nice!
Have to make do with 7904, 7S12, 7S11, and two S-4's in my garage lab for now.  I use an S-53 or S-51 for triggering.  Works for what I need it to do.  Someday I'll have a CSA803 again.  And an S-6 for TDR, etc., etc.
Jim F


Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: cmjones01 <chris@stumpie.com> Date: 12/5/18 1:19 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] 7T11 horizontal memory
On Wed, Dec  5, 2018 at 08:17 AM, Albert Otten wrote:

I might have good news for you.
The real time multivibrator doesn't work when you don't have a 7S11 adjacent
to (or otherwise connected to) the 7T11. So then the memory gate is always
blocked and you have no sweep output at the front panel.
Aha! Your news is indeed good :-) I put the 7T11 in to a slot next to my 7S11 and I now have a horizontal sweep in the rea ltime ranges.

You mean U512 I suppose.
It was U512 when I killed it, but I swapped it with U572 to check that it was actually faulty. My 741 kludge seems to work but I'm not convinced it's perfect. The Tek chip seems specified quite fast (80MHz gain-bandwidth product!) and I think the rather pedestrian 741 may be running out of speed (or slew rate) in the faster real-time ranges.

In real time ranges the horizontal amplifier now has
one continuous ramp as input during the whole sweep of the 7T11. It depends on
the time/div setting which outputs of U512 are really used in the amplifier
chain. Not used outputs can be overdriven within short time without any
consequence, and stay at some very high maximum level during the rest of the
sweep .  It's what I see happening.
Yes, I've observed that in the U512A/B/C/D chain too. The ramp only really makes sense properly after the last stage.

The good news is that, coupled with my 7S11, I now have something resembling a working sampling system. I have three rather tired-looking sampling heads in unknown condition (an S-1 and two S-2s, one labelled 50ps risetime and the other labelled 75ps). I have only tried the S-1 but it does actually work. Observations so far:
- equivalent time mode works a lot better than real time mode. At least, the waveform I see on the screen in equivalent-time mode looks like what I'd expect. I haven't tried a really fast edge in to the sampling head yet to see how the performance is at the really short time'div settings.
- in real time mode, it's hard to get a trace that makes sense. presumably the 50kHz-ish clock from the real time multivibrator limits the display to about one sample every 20us, so some of the faster sweep speeds don't show a lot. Even on the slower sweeps, the edges of my test squarewave exhibit terrible risetime (about half a division) which is puzzling, and very different to the behaviour in equivalent time. Maybe it's something to do with the recovery time of the sampling head, or there's something amiss with the 7S11. I tried adjusting the 'dot response' control and making sure smoothing was switched off, but it didn't improve much.

Thank you for your help so far. You can probably tell that I'm new to the 7000-series sampling world. I regularly use my CSA803A/SD24 sampling setup, but that makes it all so easy...

Chris


3L10 similarity to 1L10

Kurt Rosenfeld
 

How electrically similar is the 3L10 to the 1L10? Components are numbered similarly. But clearly the circuits are different, at least at the output, since 560-series plug-ins must directly drive the CRT deflection plates (20 V/div).


Re: Tube test adaptor for Tektroinx 575 was: Re: [TekScopes] FS: miscellaneous Tektronix manuals

Dan Cordova <danny_cordov@...>
 

Brad,
Thank you!
My main interest is audio tubes. I have >1000 different tubes, mostly audio output and small signal/preamp tubes. I also own a Hickok 580A tube tester and a Tektronix 575 Curve Tracer. Thus my interest in using a Tek 575 to match tubes for use in DIY preamps and amps I am planning to make. 
I was a electronics tech in the military a long time ago, in the time when tubes were going away and being replaced with solid state, but before the internet and PCs. I don't write code, although I did take a course in Fortran back in the early 1980s. 
This group has been a tremendous resource. I truly appreciate the responses that I have humbly received from you and others in the group. I say humbly received because I'm just a audio hobbyist and ME who is humbled because I realize that I know so little about audio electronics who is trying to learn.
For example, I didn't know until recently that tubes usually use AC voltage for the heater. I'm also learning the different terms, such as the anode is usually called the plate. It's humbling that this old technology was invented well before I was born and is still useful today. 
Again, thanks to all who responded with the lessons and great information.
Dan

On Wednesday, December 5, 2018, 1:28:41 PM PST, Brad Thompson <brad.thompson@valley.net> wrote:

On 12/4/2018 4:52 PM, Dan Cordova via Groups.Io wrote:
  Hi Brad,
Do you have or know anyone selling an adapter/fixture to match tubes on a Tektronix 575?
Or, do you know if there is a schematic I can buy?
Glydeck has a blog about this, but there is no schematic or info to contact him.
Hello, Dan and the group--

Thank you for your inquiry. Here's a column I wrote for Test &
Measurement World
magazine (subsequently absorbed by EDN) which describes my version of
a tube-test adaptor for the Tek 575:

https://www.edn.com/design/test-and-measurement/4389419/Old-dog-newer-trick

You can view a schematic and photos here...

https://www.flickr.com/photos/aa1ip_pix/

I used an external tube socket, small PC board and some two-piece
surplus connectors to build an adaptor, which suffices for small tubes
that don't need plate voltages in excess of what the 575 can deliver.
Heater or filament and screen voltages get supplied by "wall warts" or
other power supplies

In the schematic, J1 and J2 form a "crossover network" to match a
particular tube's pinout. This approach requires wiring or rewiring
the J1-J2 adaptor to test each tube type and thus is best suited to
testing a batch of identically-pinned tubes at once.

Newcomers to tube technology may be surprised to learn that many tubes
with different part numbers can share a common pinout. For example,
JEDEC base code 8BD
defines an octal (8-pin) base which applies to the 6SN7-GT, the 6SL7-GT
and their
heater-voltage cognates along with 25 or so other tube-part numbers.
Providing 12 pins
accommodates "modern" Compactron tubes.

While I noted no spurious oscillations while testing a batch of 6SN7s, you
may need to slip ferrite beads onto plate and grid leads if needed for
parasitic-oscillation suppression.

One point: use care in selecting the grid/base voltage you apply to the
tube under test. If the tube manual states "maximum positive grid
voltage = 0 volts", believe it! Running the grid voltage positive causes
large amounts of grid current to flow can melt the grid.

Questions welcomed-- I don't have any spare adaptor boards left over
but would investigate making more if there's interest.

73--

Brad  aA1IP

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