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I don't think it's possible to have too many 'scopes!!!!

I'm at 4 and counting ;-)

Dave








!DSPAM:5c09a7c9180633695612851!

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?

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

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?

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

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

- 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.

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...

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@...> Date: 12/5/18 5:23 PM (GMT-08:00) To: [email protected] 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@...> 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:



You can view a schematic and photos here...



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

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@...> 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:



You can view a schematic and photos here...



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