Date   

Re: 454 screen brightness issues?

John
 

I assume your -1960V is checked ok. Ditto all three LV supplies. Have a look at the chain of 10M resistors R1442-6 : ohms law suggests you should have a much larger grid swing from the bias pot?

John


Re: Logic families

tek_547
 

Thanx for that, great value!!
René


Re: Tektronix 2245a Flickering Trace

battyhugh
 

Telonics 2003

I was hoping that the seller (of the manual) would link me with the buyer - no luck. So does some kind person had the manual for the earlier model - (or does anyone still have a 2003 manual loitering in a cupboard?? (or the old 3 pin plug?).

I'd hate to scrap it.

Cheers

hugh


Re: Trying to bring back a AA501

 

Is CR1412 good? I.e. not shorted?

On 1/5/2020 11:15 PM, Eric wrote:
This one did fail the truth table check when it was in the device. VCC is about 15V which means a HIGH is 15V. Output 3 has a 5V output and does not move from there. When it should be high it is at 5V when it should be low it is at 5V. In the 501 the truth table is frequency dependent on the input. As you roll through the frequency the outputs should do their thing. 1 2 and 4 seem to function as expected.

On 1/5/2020 3:30 PM, KB6NAX wrote:
Watch out! The CD and 74 pinouts are different.  You don't what to hack up your circuit board.

Also, be advised, when troubleshooting IC's in general having the schematic of the device gives understanding of how inputs and outputs work.  For example a tri-state output could be "off" and not "open."   A CMOS input is high impedance so you don't know if the input stage is blown unless a clamp diode is shorted.  The ultimate is to try the truth table, a lot of work on complex parts.  Parts substitution can't be beat for getting results.  I always buy two or more when in that situation.

eBay to the rescue - Item #372418190226

Arden

-----Original Message----- From: Eric
Sent: Sunday, January 05, 2020 6:51 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Trying to bring back a AA501

I did find out that the AA501 does need the VCC of 15V so the HC series
logic is out for sure. I am going to order some of the direct
replacement parts as there is a supply house that has then mouser and
digikey were out. Texas Instrument cross reference says a CD40175BE is a
comparable part as well. I have also confirmed the fault as with this IC
out of circuit the 501 says 100+% distortion on all frequencies also one
of the outputs is open when i check it with my small curve tracer. On
this one pin 14 is dead.


On 1/5/2020 1:08 AM, KeepIt SimpleStupid via Groups.Io wrote:
  My GOTO place has it: http://www.utsource.net/sch/MM74C175N
     On Saturday, January 4, 2020, 10:31:47 PM EST, Mlynch001 <@mlynch001> wrote:
  OK, learned something.  LSTTL and TTL are different animals? SN74HC175N Will drive 10 outputs of LSTTL.    Just trying to learn how logic works, I will likely encounter a similar issue in the future.

Thanks!








Re: Trying to bring back a AA501

Chuck Harris
 

I am having trouble imagining how a 15V CMOS device could spontaneously
generate 5V on one of its outputs.... I can see ~0V, or ~15V, or even 7.5V,
but 5V is an odd value for a device that has no resistors in it.

Are you sure that it isn't being bullied around by whatever it is driving?
old style CMOS has very little drive capability.

-Chuck Harris

Eric wrote:

This one did fail the truth table check when it was in the device. VCC is about 15V
which means a HIGH is 15V. Output 3 has a 5V output and does not move from there.
When it should be high it is at 5V when it should be low it is at 5V. In the 501 the
truth table is frequency dependent on the input. As you roll through the frequency
the outputs should do their thing. 1 2 and 4 seem to function as expected.

On 1/5/2020 3:30 PM, KB6NAX wrote:
Watch out! The CD and 74 pinouts are different. You don't what to hack up your
circuit board.

Also, be advised, when troubleshooting IC's in general having the schematic of the
device gives understanding of how inputs and outputs work. For example a tri-state
output could be "off" and not "open." A CMOS input is high impedance so you don't
know if the input stage is blown unless a clamp diode is shorted. The ultimate is
to try the truth table, a lot of work on complex parts. Parts substitution can't
be beat for getting results. I always buy two or more when in that situation.

eBay to the rescue - Item #372418190226

Arden

-----Original Message----- From: Eric
Sent: Sunday, January 05, 2020 6:51 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Trying to bring back a AA501

I did find out that the AA501 does need the VCC of 15V so the HC series
logic is out for sure. I am going to order some of the direct
replacement parts as there is a supply house that has then mouser and
digikey were out. Texas Instrument cross reference says a CD40175BE is a
comparable part as well. I have also confirmed the fault as with this IC
out of circuit the 501 says 100+% distortion on all frequencies also one
of the outputs is open when i check it with my small curve tracer. On
this one pin 14 is dead.


On 1/5/2020 1:08 AM, KeepIt SimpleStupid via Groups.Io wrote:
My GOTO place has it: http://www.utsource.net/sch/MM74C175N
On Saturday, January 4, 2020, 10:31:47 PM EST, Mlynch001
<@mlynch001> wrote:
OK, learned something. LSTTL and TTL are different animals? SN74HC175N Will
drive 10 outputs of LSTTL. Just trying to learn how logic works, I will likely
encounter a similar issue in the future.

Thanks!










Re: Tektronix 2245a Flickering Trace

William Schuler
 

Thanks Harvey, going through some family things right now, but hopefully I
can get to looking at the scope this weekend.

On Sun, Jan 5, 2020 at 9:35 PM Harvey White <madyn@...> wrote:

There are some tests you can do with a partially working scope, but you
are going to be very limited.

1) assuming horizontal sweep problems, you use an external ramp or the
"other" sweep if you have a dual sweep model.

2) if you have a horizontal amplifier problem, using the scope in XY
mode, even with the calibrator, can give you some idea of whether or not
it's the sweep or the amplifier.

3) if you have a dual channel scope, you can use a working channel to
debug the separate part of the vertical amplifier

These generally end up being go/no-go tests and are somewhat crude.

Function generators can make a very crude horizontal sweep. If they're
gated, then a gated ramp might work as a sweep.

Very crude, but better than nothing.

Generally, unless you have a scope specifically designed for self
diagnosis, you're better off with another, completely working, scope.

Even then, a scope designed for self diagnosis makes certain assumptions
about what's working, especially once you get past the "is the CPU
working...."

Harvey


On 1/4/2020 4:29 PM, Panos wrote:
I have read enough service manuals for the oscilloscopes, and till today
I didn't find any of them to mention, that someone can use the same faulty
scope (partially or totally) to repair his self.
But as always we can hope for something like that. After all, don't
they say that hope dies always last? :-)

In my opinion if you have time to play then do it by that way. But if
you want really to repair it, then proceed it with another oscilloscope.






Re: Tektronix 2245a Flickering Trace

William Schuler
 

Thanks Siggy, I appreciate the pointers. Nice “outer limits“ clip as well!

BTW, the fan runs fine.

On Sat, Jan 4, 2020 at 6:45 PM Siggi <siggi@...> wrote:

On Sat, Jan 4, 2020 at 8:13 PM William Schuler <guitardad1967@...>
wrote:

I am in no hurry, so I will give it a try just for fun. It would be
interesting to compare results with my buddy’s functional scope.

Hmmm, you already see the output of the horizontal amplifier - that's what
your CRT shows.
The only thing is that your horizontal output (
https://youtu.be/8dzxGlcErUo?t=10) is differential. By comparing both
sides, you'd be able to see whether this is due to one side pulling or both
- it's a data point at least. I'd bet that you'll find your problem
elsewhere than in the horizontal amp, though. I'm betting on power
supplies, as that's where ~90% of all trouble happens. Is the fan working
OK?
In any case, while I often^Wsometimes miss the most direct way to figure
out what's up, I find the detours are more than worth their while for the
learnin'.


Now to
figure out exactly where that horizontal amplifier is....
You have the service manual (

http://www.ko4bb.com/manuals/download.php?file=Tektronix/Tektronix_-_2245A/Tektronix_2245A_Oscilloscope_Service_Manual.pdf
)?

Have fun!
Siggi




Re: Tektronix 2245a Flickering Trace

Harvey White
 

There are some tests you can do with a partially working scope, but you are going to be very limited.

1) assuming horizontal sweep problems, you use an external ramp or the "other" sweep if you have a dual sweep model.

2) if you have a horizontal amplifier problem, using the scope in XY mode, even with the calibrator, can give you some idea of whether or not it's the sweep or the amplifier.

3) if you have a dual channel scope, you can use a working channel to debug the separate part of the vertical amplifier

These generally end up being go/no-go tests and are somewhat crude.

Function generators can make a very crude horizontal sweep.  If they're gated, then a gated ramp might work as a sweep.

Very crude, but better than nothing.

Generally, unless you have a scope specifically designed for self diagnosis, you're better off with another, completely working, scope.

Even then, a scope designed for self diagnosis makes certain assumptions about what's working, especially once you get past the "is the CPU working...."

Harvey

On 1/4/2020 4:29 PM, Panos wrote:
I have read enough service manuals for the oscilloscopes, and till today I didn't find any of them to mention, that someone can use the same faulty scope (partially or totally) to repair his self.
But as always we can hope for something like that. After all, don't they say that hope dies always last? :-)

In my opinion if you have time to play then do it by that way. But if you want really to repair it, then proceed it with another oscilloscope.



Re: Trying to bring back a AA501

Eric
 

This one did fail the truth table check when it was in the device. VCC is about 15V which means a HIGH is 15V. Output 3 has a 5V output and does not move from there. When it should be high it is at 5V when it should be low it is at 5V. In the 501 the truth table is frequency dependent on the input. As you roll through the frequency the outputs should do their thing. 1 2 and 4 seem to function as expected.

On 1/5/2020 3:30 PM, KB6NAX wrote:
Watch out! The CD and 74 pinouts are different.  You don't what to hack up your circuit board.

Also, be advised, when troubleshooting IC's in general having the schematic of the device gives understanding of how inputs and outputs work.  For example a tri-state output could be "off" and not "open."   A CMOS input is high impedance so you don't know if the input stage is blown unless a clamp diode is shorted.  The ultimate is to try the truth table, a lot of work on complex parts.  Parts substitution can't be beat for getting results.  I always buy two or more when in that situation.

eBay to the rescue - Item #372418190226

Arden

-----Original Message----- From: Eric
Sent: Sunday, January 05, 2020 6:51 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Trying to bring back a AA501

I did find out that the AA501 does need the VCC of 15V so the HC series
logic is out for sure. I am going to order some of the direct
replacement parts as there is a supply house that has then mouser and
digikey were out. Texas Instrument cross reference says a CD40175BE is a
comparable part as well. I have also confirmed the fault as with this IC
out of circuit the 501 says 100+% distortion on all frequencies also one
of the outputs is open when i check it with my small curve tracer. On
this one pin 14 is dead.


On 1/5/2020 1:08 AM, KeepIt SimpleStupid via Groups.Io wrote:
  My GOTO place has it: http://www.utsource.net/sch/MM74C175N
     On Saturday, January 4, 2020, 10:31:47 PM EST, Mlynch001 <@mlynch001> wrote:
  OK, learned something.  LSTTL and TTL are different animals? SN74HC175N Will drive 10 outputs of LSTTL.    Just trying to learn how logic works, I will likely encounter a similar issue in the future.

Thanks!






Re: Tektronix 2465 for sale ...

Alexandre Souza
 

Just out of curiosity, mosaicmerc...Where are you?

---8<---Corte aqui---8<---
http://www.tabajara-labs.blogspot.com
http://www.tabalabs.com.br
---8<---Corte aqui---8<---


Em dom., 5 de jan. de 2020 às 20:26, mosaicmerc via Groups.Io <mosaicmerc=
yahoo.com@groups.io> escreveu:

I have a couple working 2465s i don't use, but I am not in Continental
USA...so I could maybe scrap out a m'board from 1






454 screen brightness issues?

Jack Ohme
 

I received a verified-working Tek 454 scope from eBay, and it seems to now,
after shipping, have an issue where the CRT is incredibly bright, like
we're talking burn-a-hole-in-your-vision bright. Naturally I immediately
powered it off, fearing damage to the CRT, and upon turning it back on to
test it, dialing the trace way off the screen, there is still a sizeable,
though not dangerous, glow from electron splash. The grid appears to be at
-150 to -190 volts depending on the brightness setting, and the grid bias
trimmer does essentially nothing, moving the grid bias by around 8 volts
only (not sure if this is a fault or just the design). I checked for a G-K
short, but its about 25 megaohm between (in-circuit), so looks good. I'm
wondering if maybe the grid assembly was knocked loose during shipping
maybe? I'm not intimately familiar with the CRT construction, so maybe
someone more well-acquainted with Tek's CRTs could give me some idea of
what may be going on...


Re: Tektronix 570 Vacuum Tube Curve Tracer on eBay

Roy Thistle
 

On Sun, Jan 5, 2020 at 11:25 AM, Greg Muir wrote:


the vacuum tube equipment still possessed by the military for use when EMP
from a nuclear blast renders a portion of the solid-state hardware useless.
Hi Greg:
Although obviously I am privy to very little information about what the "military" has, or does not have... I am doubtful, if the military keeps any vacuum tube type equipment because of "transistorized" = solid state equipment failing due to NEMP. The reason I say this is that... at least the high EMF generated by the Type 1 pulse of a NEMP event requires relatively long conductors to couple energy. Small conducting paths; small inductor values, fully metallically shielded, and enclosed cases... besides other common EMP hardening measures... significantly null out NEMP effects.
That said... militaries are working on... and due claim to have... EMP weapons that act to produce extremely large local EMP pulse that can disable/destroy EMP hardened gear very locally... or so they say.
Cheers. Best regards and wishes.
Roy


Re: Tektronix 2465 for sale ...

rskrishnan@...
 

@mosacimerc - scrapping a working 2465 seems like a waste :( Why break a fine scope for a speculative fix?
I'll wait around a for a week or so - so people have a chance to come back from holidays etc. - if I still don't have any takers then off it goes to a school/church etc so kids can poke around and perhaps have some fun.


Re: Tektronix 2465 for sale ...

Tony Fleming
 

Despite having less and less room, if I was near you, you would have a
customer!
If you can't sell it, donate it to a club or school, church or other places
and have a great feeling about helping others!
Wish you good luck and happy 2020!

On Sun, Jan 5, 2020 at 5:26 PM mosaicmerc via Groups.Io <mosaicmerc=
yahoo.com@groups.io> wrote:

I have a couple working 2465s i don't use, but I am not in Continental
USA...so I could maybe scrap out a m'board from 1






Re: Tektronix 2465 for sale ...

mosaicmerc
 

I have a couple working 2465s i don't use, but I am not in Continental USA...so I could maybe scrap out a m'board from 1


Re: Tektronix 570 Vacuum Tube Curve Tracer on eBay

Richard Solomon <dickw1ksz@...>
 

Whoa Nelly, where did I say that ..."vacuum
tubes are history"... ??

Not in this shack where I have in the AM
station an Elmac AF-67 and Halli SX-117
in daily use. When I feel "continental", I
fire up the Geloso Twins.

What I did ask was what use a 570 had
in todays real world.

I have doubts that any of the tube sellers
on e-Bay use a 570 to characterize any
of the "Matched Pairs" they sell. More
likely they use a Tube Tester and if the
meter reads close they are matched.

The AudioPhool market is an aberration
that I have nothing to do with. $500 for
a Line Cord ??? Give me a break.

Going back now to work on restoring
a TMC GPR-90 that some hack really
messed up.

Tnx es 73, Dick, W1KSZ

On Sun, Jan 5, 2020 at 3:05 PM peter bunge <bunge.pjp@...> wrote:

I had a University EE Summer Student who did not know how a tube worked so
I broke a 6SN7 and showed him the parts. He then said tubes were no longer
used so I asked him what he thought was in our 100kW RF amp that drove the
Superconducting Cyclotron, and how he would replace it with Solid State. I
then told him his theories MIGHT work but how would Solid State handle the
huge reflected power often sent back to the amplifier, and survive?
I'm not sure how I would test a 4CW200,000 (if I remember the 200kW water
cooled tube number correctly). The HV power supply was bigger than our
kitchen.

On Sun, Jan 5, 2020 at 4:01 PM Dennis Tillman W7PF <@Dennis_Tillman_W7pF>
wrote:

Hi Richard,

It may seem that vacuum tubes are history but nothing could be further
from the truth. To my amazement I have sold almost 200 of my little VTCT
Adapter boards. That really surprised me. That gives people a way to
avoid
paying $5,000 for a 570 Tube Tester. It still costs at least a few
hundred
dollars with my adapter because you still need some kind of transistor
curve tracer and a tube tester.

There are many applications that use tubes these days. Vacuum tube
manufacturing never went away and now the Russians are producing a lot of
them. But there are many other companies also doing it. A top of the line
vacuum tube audio amplifier will set you back $100,000 and eventually the
push-pull output tubes will need balancing or replacing. Likewise, rock
guitarists all use tube amplifiers, not solid state. The sound of tube
guitar amplifiers is sweeter and the guitarist can create far more
classic
rock sound effects with tube amps than with solid state amplifiers. Like
with the home audio amplifiers, a lot depends on the push-pull output
tubes
being balanced. Having balanced output tubes is essential to getting the
most from your guitar amplifier.

Testing transmitter tubes is another application for a tube curve tracer.

Dennis Tillman W7PF

-----Original Message-----
From: Richard Solomon
Sent: Sunday, January 05, 2020 9:22 AM
Subject: Re: [TekScopes] Tektronix 570 Vacuum Tube Curve Tracer on eBay

Pardon me if this sounds like
Heresy, but what real world use
would have for one of these ?

I can see the "cool/nostalgia"
factor, but other than that, what
would one do with it ??

Thanks, Dick, W1KSZ

On Sun, Jan 5, 2020 at 8:32 AM Dave Daniel <kc0wjn@...> wrote:

I have been looking at sales of Tektronix 570s, mostly but not all on
ebay, for a long time now. All of then have had an asking price of
around $4k.

DaveD

Sent from a small flat thingy

On Jan 5, 2020, at 09:45, Eric <ericsp@...> wrote:

I would love to have a 570 in the lab but not for that that is nuts.


On 1/5/2020 9:36 AM, Mlynch001 wrote:
On Sat, Jan 4, 2020 at 10:48 PM, Dan Cordova wrote:

For less than $200, I put together a Dennis Tillman VTCT board,
and
modified
my Hickok Tube Tester to use with my Tektronix 575 curve tracer.
I
also made
the Daniel Schoo designed triode and pentode adapters for the
Tektronix 576
Curve Tracer at work.
I'm also not sure all my tubes and stereo gear are worth ~$4000
all
together.
;)
I KNOW my stereo gear is not worth that much! I have the stuff to
build Dennis Tillman's VTCT and I have a 576 as well. So even after I
buy a suitable tube tester, I am sure that all told I would have less
than
$1000 in the whole thing. It might not do what the 570 will do, but
likely 95% as much and still test solid state devices as well. You
would need to have a serious desire or even more serious need for this
thing in order to justify paying that price. From the description, it
sounds as though this thing is not quite ready to go as it is. The
elephant in the room is getting it shipped to ones location without it
being destroyed in the process. The seller does have a "Make an
Offer" option as well. This will be interesting to watch.









--
Dennis Tillman W7PF
TekScopes Moderator






Re: Tektronix 570 Vacuum Tube Curve Tracer on eBay

peter bunge
 

I had a University EE Summer Student who did not know how a tube worked so
I broke a 6SN7 and showed him the parts. He then said tubes were no longer
used so I asked him what he thought was in our 100kW RF amp that drove the
Superconducting Cyclotron, and how he would replace it with Solid State. I
then told him his theories MIGHT work but how would Solid State handle the
huge reflected power often sent back to the amplifier, and survive?
I'm not sure how I would test a 4CW200,000 (if I remember the 200kW water
cooled tube number correctly). The HV power supply was bigger than our
kitchen.

On Sun, Jan 5, 2020 at 4:01 PM Dennis Tillman W7PF <@Dennis_Tillman_W7pF>
wrote:

Hi Richard,

It may seem that vacuum tubes are history but nothing could be further
from the truth. To my amazement I have sold almost 200 of my little VTCT
Adapter boards. That really surprised me. That gives people a way to avoid
paying $5,000 for a 570 Tube Tester. It still costs at least a few hundred
dollars with my adapter because you still need some kind of transistor
curve tracer and a tube tester.

There are many applications that use tubes these days. Vacuum tube
manufacturing never went away and now the Russians are producing a lot of
them. But there are many other companies also doing it. A top of the line
vacuum tube audio amplifier will set you back $100,000 and eventually the
push-pull output tubes will need balancing or replacing. Likewise, rock
guitarists all use tube amplifiers, not solid state. The sound of tube
guitar amplifiers is sweeter and the guitarist can create far more classic
rock sound effects with tube amps than with solid state amplifiers. Like
with the home audio amplifiers, a lot depends on the push-pull output tubes
being balanced. Having balanced output tubes is essential to getting the
most from your guitar amplifier.

Testing transmitter tubes is another application for a tube curve tracer.

Dennis Tillman W7PF

-----Original Message-----
From: Richard Solomon
Sent: Sunday, January 05, 2020 9:22 AM
Subject: Re: [TekScopes] Tektronix 570 Vacuum Tube Curve Tracer on eBay

Pardon me if this sounds like
Heresy, but what real world use
would have for one of these ?

I can see the "cool/nostalgia"
factor, but other than that, what
would one do with it ??

Thanks, Dick, W1KSZ

On Sun, Jan 5, 2020 at 8:32 AM Dave Daniel <kc0wjn@...> wrote:

I have been looking at sales of Tektronix 570s, mostly but not all on
ebay, for a long time now. All of then have had an asking price of
around $4k.

DaveD

Sent from a small flat thingy

On Jan 5, 2020, at 09:45, Eric <ericsp@...> wrote:

I would love to have a 570 in the lab but not for that that is nuts.


On 1/5/2020 9:36 AM, Mlynch001 wrote:
On Sat, Jan 4, 2020 at 10:48 PM, Dan Cordova wrote:

For less than $200, I put together a Dennis Tillman VTCT board,
and
modified
my Hickok Tube Tester to use with my Tektronix 575 curve tracer.
I
also made
the Daniel Schoo designed triode and pentode adapters for the
Tektronix 576
Curve Tracer at work.
I'm also not sure all my tubes and stereo gear are worth ~$4000
all
together.
;)
I KNOW my stereo gear is not worth that much! I have the stuff to
build Dennis Tillman's VTCT and I have a 576 as well. So even after I
buy a suitable tube tester, I am sure that all told I would have less
than
$1000 in the whole thing. It might not do what the 570 will do, but
likely 95% as much and still test solid state devices as well. You
would need to have a serious desire or even more serious need for this
thing in order to justify paying that price. From the description, it
sounds as though this thing is not quite ready to go as it is. The
elephant in the room is getting it shipped to ones location without it
being destroyed in the process. The seller does have a "Make an
Offer" option as well. This will be interesting to watch.









--
Dennis Tillman W7PF
TekScopes Moderator




Re: Trying to bring back a AA501

David DiGiacomo
 

On Sun, Jan 5, 2020 at 1:31 PM KB6NAX <gumbear@...> wrote:

Watch out! The CD and 74 pinouts are different. You don't what to hack up
your circuit board.
That is not correct. CD40175 and 74C175 have the same pinout.


Re: Tektronix 570 Vacuum Tube Curve Tracer on eBay

 

Hi Greg,

That is less likely than you think. Almost since the beginning Tek has designed its circuitry using what is known as a "Long-Tailed Pair". One of the features of this circuit design is its high immunity to the parameter changes a tube undergoes as it ages. The circuit is stable until the tube is worn out. So you have no guarantee that a tube you pull out of a Tek scope will work. In addition there are so many people selling used tubes that there isn't much profit in it unless, like the eBay seller that was mentioned, he uses a 570 to match a pair of tubes and certifies that they meet the basic manufacturers specs for transconductance (gm), voltage gain (mu), and plate resistance (rp). That is a time consuming process requiring a very expensive tube tester. So this isn't a lucrative pastime.

Dennis Tillman W7PF

Here is an excerpt from Wikipedia describing the history and benefits of the "Long Tailed Pair":
The long-tailed pair was developed from earlier knowledge of push-pull circuit techniques and measurement bridges. An early circuit which closely resembles a long-tailed pair was published by British neurologist Bryan Matthews in 1934, and it seems likely that this was intended to be a true long-tailed pair but was published with a drawing error. The earliest definite long-tailed pair circuit appears in a patent submitted by Alan Blumlein in 1936. By the end of the 1930s the topology was well established and had been described by various authors including Frank Offner (1937), Otto Schmitt (1937) and Jan Friedrich Toennies (1938) and it was particularly used for detection and measurement of physiological impulses.

The long-tailed pair was very successfully used in early British computing, most notably the Pilot ACE model and descendants, Maurice Wilkes’ EDSAC, and probably others designed by people who worked with Blumlein or his peers. The long-tailed pair has many favorable attributes if used as a switch: largely immune to tube (transistor) variations (of great importance when machines contained 1,000 tubes or more), high gain, gain stability, high input impedance, medium/low output impedance, good clipper (with a not-too-long tail), non-inverting (EDSAC contained no inverters!) and large output voltage swings. One disadvantage is that the output voltage swing (typically ±10–20 V) was imposed upon a high DC voltage (200 V or so), requiring care in signal coupling, usually some form of wide-band DC coupling. Many computers of this time tried to avoid this problem by using only AC-coupled pulse logic, which made them very large and overly complex (ENIAC: 18,000 tubes for a 20 digit calculator) or unreliable. DC-coupled circuitry became the norm after the first generation of vacuum tube computers.

-----Original Message-----
From: Greg Muir
Sent: Sunday, January 05, 2020 9:44 AM
Subject: Re: [TekScopes] Tektronix 570 Vacuum Tube Curve Tracer on eBay

I'm sure that he probably has numerous Tek scopes and plugins in his back room missing all of their tubes. They will most likely be the next thing to show up on ePay.

Greg




--
Dennis Tillman W7PF
TekScopes Moderator


Re: Tektronix 570 Vacuum Tube Curve Tracer on eBay

 

Hi Richard,

It may seem that vacuum tubes are history but nothing could be further from the truth. To my amazement I have sold almost 200 of my little VTCT Adapter boards. That really surprised me. That gives people a way to avoid paying $5,000 for a 570 Tube Tester. It still costs at least a few hundred dollars with my adapter because you still need some kind of transistor curve tracer and a tube tester.

There are many applications that use tubes these days. Vacuum tube manufacturing never went away and now the Russians are producing a lot of them. But there are many other companies also doing it. A top of the line vacuum tube audio amplifier will set you back $100,000 and eventually the push-pull output tubes will need balancing or replacing. Likewise, rock guitarists all use tube amplifiers, not solid state. The sound of tube guitar amplifiers is sweeter and the guitarist can create far more classic rock sound effects with tube amps than with solid state amplifiers. Like with the home audio amplifiers, a lot depends on the push-pull output tubes being balanced. Having balanced output tubes is essential to getting the most from your guitar amplifier.

Testing transmitter tubes is another application for a tube curve tracer.

Dennis Tillman W7PF

-----Original Message-----
From: Richard Solomon
Sent: Sunday, January 05, 2020 9:22 AM
Subject: Re: [TekScopes] Tektronix 570 Vacuum Tube Curve Tracer on eBay

Pardon me if this sounds like
Heresy, but what real world use
would have for one of these ?

I can see the "cool/nostalgia"
factor, but other than that, what
would one do with it ??

Thanks, Dick, W1KSZ

On Sun, Jan 5, 2020 at 8:32 AM Dave Daniel <kc0wjn@...> wrote:

I have been looking at sales of Tektronix 570s, mostly but not all on
ebay, for a long time now. All of then have had an asking price of
around $4k.

DaveD

Sent from a small flat thingy

On Jan 5, 2020, at 09:45, Eric <ericsp@...> wrote:

I would love to have a 570 in the lab but not for that that is nuts.


On 1/5/2020 9:36 AM, Mlynch001 wrote:
On Sat, Jan 4, 2020 at 10:48 PM, Dan Cordova wrote:

For less than $200, I put together a Dennis Tillman VTCT board,
and
modified
my Hickok Tube Tester to use with my Tektronix 575 curve tracer.
I
also made
the Daniel Schoo designed triode and pentode adapters for the
Tektronix 576
Curve Tracer at work.
I'm also not sure all my tubes and stereo gear are worth ~$4000
all
together.
;)
I KNOW my stereo gear is not worth that much! I have the stuff to
build Dennis Tillman's VTCT and I have a 576 as well. So even after I
buy a suitable tube tester, I am sure that all told I would have less
than
$1000 in the whole thing. It might not do what the 570 will do, but
likely 95% as much and still test solid state devices as well. You
would need to have a serious desire or even more serious need for this
thing in order to justify paying that price. From the description, it
sounds as though this thing is not quite ready to go as it is. The
elephant in the room is getting it shipped to ones location without it
being destroyed in the process. The seller does have a "Make an
Offer" option as well. This will be interesting to watch.









--
Dennis Tillman W7PF
TekScopes Moderator