Date   
Falcon on the launchpad.

Andrew Jonathan Fine <eternalsquire@...>
 

I did a few "idiot tests" on my setup, the most important one being to
check that all tubes were glowing in the L20, the 585, and the 81.
I was assured by the vendors of both the L20 and the 585 that they
were recently in good working order.

The only unknown quantity was the 81 Adapter, that was bought in
unknown condition. but those are much less expensive to replace.

I disconnected my boxes and found the switch on the back of the L20.
There is a selection of 100 V Sawtooth vs 150 V Sawtooth. I also found
a sweep input on the front of the L20. I assume that's where the sawtooth
goes. But where do I get the sawtooth from the 585?

Oh, my kingdom for some manuals!

The Eternal Squire.

----- Original Message -----
From: Richard Solomon, W1KSZ <w1ksz@...>
To: eternalesquire <eternalsquire@...>
Sent: Friday, July 11, 2003 6:01 AM
Subject: RE: [TekScopes] getting my millennium falcon to fly.


If I remember correctly, now this was back in the Mesozoic era,
you needed to connect a sweep signal to the L20 input. There was
a pin jack on the L20 that connected to the external sweep BNC on
the scope. On the back of the L20 was a slide switch that set the
sweep voltage. Since all that stuff is long gone, this is all from
a fuzzy memory.
Hope this helps,

73, Dick, W1KSZ

-----Original Message-----
From: eternalesquire [mailto:eternalsquire@...]
Sent: Friday, July 11, 2003 4:56 AM
To: TekScopes@...
Subject: [TekScopes] getting my millennium falcon to fly.


Hi everyone!

I'd like to ask some advance on debugging a scope configuration.
I've put together a Tek 585, 81 Adapter, and L20, all tubes.
I'm getting a wierd readout on my CRT, and I would like to know
if anyone understands immediately what I am doing wrong based
on what I am describing:

There is a vertical fuzzy bar in the middle of the CRT.
On the upper and lower right hand side of the CRT I
am seeing "fluffy angels wings". The horizonal position
moves the fuzzy bar from left to right. I get this on
channel A only, I get no readout from channel B.

Injecting a signal into the main L20 input makes no difference.
The bar is still fuzzy even through I brought it into focus
as much as I could.

Does anyone have any advice as to how I might need to operate
different, or what area I should begin debugging?

Thanks in advance,

The Eternal Squire.





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Re: Ebay item

Andreas Troschka - IK2WQI <signupbox@...>
 

Thanks for the hint, Craig!
It is exactly what I'm looking for.

It is really interesting to have the signals on the rear connectors.

This is a series that leaves some free space for experimenting.

--

Cheers.

Andreas Troschka - IK2WQI - JN45OL

--

Re: 575

Stan & Patricia Griffiths <w7ni@...>
 

Hi Morris,

There was a kit made by Tek to modify a standard 575 to a 122C. I
personally installed this kit a few times. It took a couple of days . . . !
Anyway, I have the kit instructions for this which include updated pages for
the standard manual. Would copies of the manual update do? If so, it will
take me some time to get them made and I will quote you a price. Let me
know.

Stan
w7ni@...

----- Original Message -----
From: "Morris Odell" <morriso@...>
To: "Tekscopes (E-mail)" <TekScopes@...>
Sent: Sunday, July 06, 2003 4:47 PM
Subject: [TekScopes] 575


Hi all,

A friend of mine is restoring a 575 curve tracer mod 122C. It's a bit
different from the non-mod 122C manual we have. Is anyone able to help me
with a copy of the schematics (or the whole manual)? Usual costs
reimbursed
etc..

Thanks,

Morris




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Re: 3RP1 for a 310A

Stan & Patricia Griffiths <w7ni@...>
 

I have never actually tried a 3RP1 in a 310 or 310A but it is not the one
Tek recommends. Tek wants you to use a 3WP2 or one with a Tek Part Number.
You can check that out on the following web page:

www.reprise.com/host/tektronix/reference/default.asp

I think I have a spare 3WP2. If you need one, I can quote you a price.

Stan
w7ni@...

----- Original Message -----
From: "Robert Morein" <morepub@...>
To: <TekScopes@...>
Sent: Thursday, July 03, 2003 7:59 PM
Subject: [TekScopes] Re:3RP1 for a 310A


3RP1 for a 310A

Will this CRT fit this scope?








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Re: 475/A not really ideal for audio, and some noise thoughts.

Robert Morein <morepub@...>
 

For audio, why not a 434?
It has 1 mv sensitivity.
With a sweep oscillator and the storage tube, you can get a nice graph of frequency response.
The scopes are cheap. Although speced at 25 mHz, they measure out to about 38 mHz.
They weigh 24 lbs, and were stated by Tek to be designed for rugged environments.

I think one has to really think twice about the "one scope fits all" idea.

Although this is a Tek scope group, I'd like to point out that there are other worthy scopes out there. I purchased a Leader LBO-518 at a Verizon auction for $55. It looked like a trashcan, but cleaned up nicely. Surprisingly, it was perfectly functional.
It's a 100 mHz scope with FOUR channels, dual time based, delayed sweep, and 1mv sensitivity.
Surprisingly, the scope does not appear to have a switching power supply, which is probably why it still works perfectly. Weight is under 20 lbs, and the knobs and feel are very familiar.

Sorry, Tek lovers. I couldn't help but mention it.

----- Original Message ---

Re: 7904 Mainframe production dates

Miroslav Pokorni
 

Hello Fred,

What you are saying is kind of nit picking, 10000 pieces here and there.
That can not amount to more than 50K difference. The piece from Stan, which
Craig dug out, explains how those large numbers were arrived at without
producing corresponding number of units. Now that I read it, I realized that
I have seen it when Stan posted it originally. The sad thing is that I did
not even remember that there was such a post. I did remember the story about
'Gold Plated 7A26', but rolling last four digits of serial number into the
number of modified unit, practically adding multiple 10K units at each
modification, just slipped my mind.

Regards

Miroslav Pokorni

----- Original Message -----
From: "Fred Olsen" <fwolsen@...>
To: "Miroslav Pokorni" <mpokorni2000@...>; "washesmelon"
<vwthingy@...>
Cc: <TekScopes@...>
Sent: Thursday, July 10, 2003 10:41 PM
Subject: Re: [TekScopes] 7904 Mainframe production dates


I had said:
>>Jeff, the only one I can address at the moment is the early 7904. It
>>would be reasonable to assume that early production exceeded the 250k
>>point, hence the restart at 260k rather than 250.
>>That said, I still would find it difficult to
>>comprehend that Tek built over a quarter-million 7904s!

to which
Miroslav Pokorni wrote:
> When you expressed doubt that Tektronix built over a quarter million
> 7904, I did agree, but did not think it was worth commenting.

I didn't mean to imply that Tek had built anywhere near a
quarter-million 7904s in the first series. I can't believe that.
First, in the later years many (all?) units' S/Ns started with B010100
rather than the traditional 00101 of the old days. Second, I suspect
that many of the runs were discontinuous. Earlier on Tek seemed to put
a clean break at a major rev, a redesign, such as "1A1 >S/N 20000" -
which was when the FET front end started IIRC. Later on the "greater
than"s seem to more often be in succession with lesser revisions which
were handled with a numeric break. So do I think that there were 19999
Nuvistor 1A1s? No, but close to it.

As a hypothetical I grabbed a late-production 7A26 manual from the file.
First Printing was Oct '72 at model start, with a Revised Feb '87. A
good example in later gear (all right, I know that the "new Tektronix"
doesn't consider a 7k-anything to be "later") - a good example is board
revisions. The amp board P/N went through a bunch of revs: -00 through
-08, -10, -13, -15, -17, and -21. All of those are listed with
consecutive S/N breaks. Bear with me, it's easier to see in a little
chart.

-00 B010100 ~ B049999
-01 B050000 ~ B069999
-02 B070000 ~ B083789
-03 B083790 ~ B089999
...
-17 B245520 ~ B251089
-21 B251090

I would suggest that it's reasonable to assume that revisions such as
the -02 to -03 were running changes and were indeed made at that S/N
break. But the ones at an even ten thousand, such as -00 to -01 or -01
to -02, would seem to simply be available blocks of assigned numbers.
There is no reason to think that all of those blocks were filled. There
might have been as few as a hundred or less used out of any 10000. It
all depended on sales demand, and what was at the time their traditional
engineering-driven continuous implementation of design improvements.

The only way to know for certain would be either to have a large pile of
all of the change sheets, which perhaps only Tucker might have been able
to put together outside of Tek; or to gain access to Tek's production
numbers, which isn't likely to happen even if they still have them.

So, do I think that they built a quarter-million 7A26s? No way. Or
that many 7904s? Even less likely. When I told Jeff that the
early-series 7904 production exceeded the 250k point, it was meant only
as a number break and not as an actual quantity. Granted that this
doesn't take into account the non-U.S. production using different S/N
series, but in most cases those numbers were small compared to
Beaverton's.

If pressed for a SWAG of the number of 'early' 7904s, the ones below
260k, I wouldn't think it could exceed four figures. Much of this is of
course my opinion, and I'll readily concede that I'm no expert. So,
grain of salt, YMMV. Anyone with actual knowledge of this please weigh
in.

Best to all,
Fred
--
<><
--
Outgoing checked by Norton AV

475/A not really ideal for audio, and some noise thoughts.

 

In the recent thread about using a single scope to do "everything", I
think it's worthwhile to make a few audio related points:

1. all 475's are noiser than any 465, so they are really NOT a good
choice for audio work, especially if low level signals are being
observed. They also respond to many spurious ambient signals when
connected to a high impedance node, so it can be quite irritating to
determine what's really there. YES, you can reduce the bandwidth to
reduce this effect, but then why have a 475?

2. both CRTs and internal parts are much scarcer for the 475's, so a
repair to the scope is not trivial or cheap.

3. I agree with the comments about the 7K frames and using a 7A22 for
real audio work, it is a powerful weapon. A 7603 with a 7A26 and 7A22
and a 7B53A is almost ideal for audio: huge screen, great performance,
no noisy fan, and it's STILL portable.

An important point about used 475's and 465's: many (>75%) are
missing the internal case ground fingers (removed for some unknown
reason by an earlier lazy technician), this makes them even NOISIER
than normal. There should be case ground fingers at both the vertical
amp side and horizontal sweep side. if you have a thick trace, check
this out!

all the best,
walter
http://www.sphere.bc.ca

Re: P6138a probe compatibility with 2400 series scopes

Stan & Patricia Griffiths <w7ni@...>
 

I don't know the answer to your question without doing some research, but
here is a place to go to find out how to get the answer yourself.

http://www.reprise.com/host/tektronix/reference/default.asp

There is a page there that will tell you how to compare the scope and probe
specifications so you can tell if they are compatible or not.

Stan
w7ni@...

----- Original Message -----
From: "tbfowler100" <tfowler@...>
To: <TekScopes@...>
Sent: Tuesday, July 01, 2003 12:37 PM
Subject: [TekScopes] P6138a probe compatibility with 2400 series scopes


Does anyone know if this probe is compatible with the 2400 series
scopes? Tek's website says that it is for the newer TDS400 scopes,
but it looks like it would work with the older scopes as well.





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Nuvistors on sale

Dr. Charles E. Morris <charlesmorris@...>
 

FYI, Antique Electronic Supply (tubesandmore.com) has new-in-box 7586
Nuvistors on sale for $11.20 each, through July 15.

I just bought two for a plugin repair and to have a spare. They are
Sylvania, date coded 1978. This is much cheaper than the $25-$30 most other
places (including AES, normally $30.25). There is allegedly a supply of
Russian-made ones for $3.50 each from a guy in Lithuania but who knows.
Stock up now!

-Charles
(no connection to the company).

Re: 475 and 475A serial number vs production dates

eboytoronto
 

Hi,
I would like to raise the question:

Why is the date of manufacture so important ?

I would generally consider condition to be more important than when it was made.

May be there were some *significant* improvements made to the design. Perhaps some of the (Ex) TEK people can fill us in on the modification history.

Some time cost reductions and manufacturability improvements will lower reliability and /or performance.

Regards,


John

---------- Original Message ----------------------------------
From: "tss_steve_990" <stevehogan@...>
Date: Fri, 11 Jul 2003 12:20:26 -0000

Thanks to all who have helped with 7000 series configurations for my
Audio R&D. I will likely build up my second scope using some
combination of what has been suggested, but for now I need a portable
that will do "everything". It seems that a late model 475 or perhaps
a 475A might still be the best choice since I can't fit a scope cart
with a 7904 frame in the back of my Saturn station wagon and take it
to the recording studio to find the oscillations in the console.

I must say that the Tektronics S/N system, although it does make
sense (to the Tek folks) is tough to discern when you don't have the
magic decoder ring. The term "Part Number Rationalization effort" was
used a couple of times (disparagingly) in recent posts. What was that
effor and when did it happen? (And why didn't it get applied to the
scopes made in Holland?) :)

Does the same S/N scheme apply to to the later 475 and 475A scopes as
has been explained for the 7000 series?

So far I know for sure the following about both 475 and 475A scopes:
If the S/N begins with B it was made in Beaverton
If the S/N begins with 7 it was made in Holland
Bigger serial numbers have later production dates
One 1977 475 service manual states that it is for Serial Numbers
B250000 or higher.

Based on the discussions put forth so far re: 7000 series scopes, I
have concluded the following:
A 475 scope with a S/N lower than B250000 was built between 1973 and
1976
A 475 scope with a S/N higher than B250000 was the beginning of a
major revision in 1977.
A 475 scope with the S/N B267390 is later than that and has a minor
revision step over the B25xxxx.
A 475 scope with the S/N B274639 is later yet and has another minor
revision step over the B26xxxx

A 475A scope with the S/N B012776 is near the beginning of the 1977
production run if S/B B010100 is the first scope produced.
A 475A scope with the S/N B025132 is later than 1977 and has a minor
revision.

This leaves the question of how to figure out the 475A scopes made in
Holland. I'm guessing that
S/N 711982 is near the beginning of the Holland production run,
especially since it has only a 6 digit S/N instead of 7.

So does anybody know how to figure out the 7711043 serial number.
What does the extra 7 mean?

I guess one way to figure this out is to visit the local surplus
house and look at date codes on the internal parts and relate that to
the serial numbers of the scopes.

If anyone can confirm my initial decoded production date vs s/n data,
or if you can further clarify this jumble please chime in!

Thanks to you all!

Steve






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475 and 475A serial number vs production dates

tss_steve_990
 

Thanks to all who have helped with 7000 series configurations for my
Audio R&D. I will likely build up my second scope using some
combination of what has been suggested, but for now I need a portable
that will do "everything". It seems that a late model 475 or perhaps
a 475A might still be the best choice since I can't fit a scope cart
with a 7904 frame in the back of my Saturn station wagon and take it
to the recording studio to find the oscillations in the console.

I must say that the Tektronics S/N system, although it does make
sense (to the Tek folks) is tough to discern when you don't have the
magic decoder ring. The term "Part Number Rationalization effort" was
used a couple of times (disparagingly) in recent posts. What was that
effor and when did it happen? (And why didn't it get applied to the
scopes made in Holland?) :)

Does the same S/N scheme apply to to the later 475 and 475A scopes as
has been explained for the 7000 series?

So far I know for sure the following about both 475 and 475A scopes:
If the S/N begins with B it was made in Beaverton
If the S/N begins with 7 it was made in Holland
Bigger serial numbers have later production dates
One 1977 475 service manual states that it is for Serial Numbers
B250000 or higher.

Based on the discussions put forth so far re: 7000 series scopes, I
have concluded the following:
A 475 scope with a S/N lower than B250000 was built between 1973 and
1976
A 475 scope with a S/N higher than B250000 was the beginning of a
major revision in 1977.
A 475 scope with the S/N B267390 is later than that and has a minor
revision step over the B25xxxx.
A 475 scope with the S/N B274639 is later yet and has another minor
revision step over the B26xxxx

A 475A scope with the S/N B012776 is near the beginning of the 1977
production run if S/B B010100 is the first scope produced.
A 475A scope with the S/N B025132 is later than 1977 and has a minor
revision.

This leaves the question of how to figure out the 475A scopes made in
Holland. I'm guessing that
S/N 711982 is near the beginning of the Holland production run,
especially since it has only a 6 digit S/N instead of 7.

So does anybody know how to figure out the 7711043 serial number.
What does the extra 7 mean?

I guess one way to figure this out is to visit the local surplus
house and look at date codes on the internal parts and relate that to
the serial numbers of the scopes.

If anyone can confirm my initial decoded production date vs s/n data,
or if you can further clarify this jumble please chime in!

Thanks to you all!

Steve

Ebay item

Craig Sawyers <c.sawyers@...>
 

During my daily trawl of eBay, I came across this 2544857008. It is a
TM503, but unusually has Option 2 with a 50-way D-Type connector and three
BNC's on the rear panel. They guy has it on a buy it now for $44.95.

No personal interest in this - just thought that it might be of interest to
the list

Craig

Re: 7904 Mainframe production dates

Craig Sawyers <c.sawyers@...>
 

So, do I think that they built a quarter-million 7A26s?
And here's another Stan archive quote:

"Here is a little more info about the 7A26 which was the instrument Tek
built
the
most of, ever. I personally know the design team leader for that product
and I
have seen the "Gold-Plated 7A26" they gave him when they passed the
"100,000 sold" mark! I told him I want if for my collection . . . he will
probably
outlive me since he is younger than me and rides a bike a lot so it will
probably
never make it into my collection . . . oh, well . . .

The 7A26 first appeared in the Tek 1974 catalog and last appeared in the
1991 catalog so that would mean it was in production for at least 18 years.
This has to be some sort of longevity record for a product of this type. In
1985,
they were up to serial number B255000+. That is the latest record I have of
7A26 serial numbers but it was in the catalog for 6 years after that so they
probably sold another 25 or 30 thousand of them after that. On a product
where the serial numbers ran so high, it is really hard to tell just how
many
were made. They also built this product in Guernsey with an entirely
different
run of serial numbers. The design team leader is still a personal friend of
mine so I
can ask him next time I see him which will probably be at the Longview, WA
hamfest and flea market tomorrow . . . his name is Tom Rouseau, K7PJT . . .
an engineering genious and all-round great guy."

Craig

Re: 7904 Mainframe production dates

Craig Sawyers <c.sawyers@...>
 

So, do I think that they built a quarter-million 7A26s?
Here's a quote from Stan, found by searching the archive:

"You are right about the numbers being too high on the scope numbers for
those models. I have asked Tektronix for quantity produced info before but
they never want to share that information with anyone. I guess they regard
it as "company confidential" or something. Even so, I have a pretty good
way to estimate the numbers right here. As you probably know, Tek starts
numbering at 101. For the very early instruments, it really was number 101,
and that is the actual number of the first production instrument. Later,
they added leading zeros and the first production instrument carried the
number "000101". Still later, for instruments built in Beaverton, the first
production instrument would carry the number "B010101" with the "B" meaning
Beaverton ("G" was for Guernsey, "H" was for Herenveen, and I think "070"
was for Tokyo.) In any case, they would increment the last four numbers.
In the "B01" series, if they made a major change in the instrument, they
would increment to "B02" but the last 4 digits remained in sync with "B01"
numbers. This would work fine until you got to 9999 instruments, which was
not often. (The CA got to over 70,000 instruments but they were not using
the "B01" type of serial numbers on the CA.) (The 7A26 went over 100,000
instruments and they had to start the last 4 digits over several times, but
by the time they needed to do that, they had already gone past B01 into B03
or B04 and it was not a problem with duplicating any serial numbers.

Well, you probably also know that Tek kept very good records on each and
every change that was made to the circuitry in each instrument as they
evolved. This was all documented in the "Modification Summary" of each
product, including the serial number of the exact time of the circuit
change. Since I have almost all of the Modification Summaries, I can look
and see what the serial number of the last documented change was for each
product type. This will be very close to the serial number of the last
instrument produced and should provide a very close estimate of the total
produced. So for the 7500 Series, got the following results:

7503 approximately 1100 produced
7504 approximately 1100 produced
7514 approximately 1100 produced
7704 approximately 2000 produced"

So the answer is more than 100,000 7A26's

Craig

Re: 7A22/7A13, was RE: 475 instead of 475A?

fjh001 <javier2945@...>
 

--- In TekScopes@..., "Craig Sawyers" <c.sawyers@t...>
wrote:

I'd also add the 7A13 diffential comparator. This has a poorer
CMRR than
the 7A22 of around 2x10^4 and only goes to 1mV/div. But you can
offset the
effective dc threshold of the measurement with a comparison voltage
up to
(effectively) hundreds or thousands of volts with digital readout
(depending
on range selected) - so slow waveforms riding on DC (like power
supply
ripple) can be looked at without the amplitude and phase distortion
introduced by ac coupling (of course you can ac couple instead if
you wish).

Sometimes it is not possible to ac couple. Some years ago I was
tracing a small noise on some ozone analyzers, that finally
demostrated to come from a voltage regulator. The problem to measure
the noise was that the noise was only a few millivolts on one of the
power supplies, and at a very low frequency, so ac coupling were not
useful. On that time, my oscilloscope was a 466 and I had to build a
differential amplifier to sustract the dc component using a low noise
adjustable dc source, and be able to trace the noise on all the
circuits. I wish I had then a 7A13... now I have one :-)

Regards,

Javier

Re: VSWR tester

Dave Brown <tractorb@...>
 

Denis-

What you have is basically a return loss bridge with a built in reference
arm termination of 50 ohms plus an rf detector on the output port. So you
get a dc signal out of the thing that is proportional to the mismatch (wrpt
the reference termination) seen at the test port. Unfortunately, the
detector has a conversion characteristic that needs to be accounted for, as
they are definitely non-linear other than maybe over a narrow level range.
For a given (and constant) drive level at the swept rf source port, you
will get two extremes of DC output as the load on the test port is varied,
zero with a good 50 ohm load, and maximum DC with a complete mismatch. ie
open or short cct. These extremes correspond to very high return loss (the
well-matched condition) and zero return loss (very bad mismatch).

The easiest way to caibrate the thing for all the ' in-between' values of
return loss (or VSWR-it's an easy conversion, right?) is to establish
reference calibrations on the scope screen with 'known return loss'
terminations.

This may sound difficult but all you need is an adjustable attenuator (must
be good to excellent over the frequency range of interest) plus an open or a
short cct termination. Connect the measuring port on the autotester to the
input of the attenuator, ideally directly, and the open or short to the
attenuator output. Then just set the attenuator for the required return
loss.

But bear in mind that the attenuator introduces TWICE the indicated value of
return loss. With say 6 dB in the attenuator, you have 12 dB return loss,
etc .Why TWICE-- well think of it as 6dB on the way out and another 6 on the
way back.
So you can set up whatever you want for maximum deflection desired on
screen to correspond to worst case expected return loss and (usually) a few
other in-between levels as well.

And if you really want to use just a fixed frequency source and a milliovolt
meter, rather than a scope and sweeper, the same principle applies for
calibration at whatever spot frequencies you care to use.

If you tend to have particular worst case VSWR values that you want on
screen (or on meter) just make up known return loss or VSWR terminations to
calibrate maximum deflection against. eg use a 100 ohm load (or at low freqs
a pair of 50 ohm loads and a coax tee-to make 25 ohms- same VSWR) to cal the
screen for 2:1 VSWR max., (or approx 10dB return loss) etc. Lower (better
return loss) values can be filled in with use of the attenuator, as above,
to make a screen overlay in the first instance.

The directivity spec is another matter- just consider it to be a limit to
the upper return loss that you can measure. Return loss readings over say,
30 dB, will not be as accurate as lower values.

Regards,
Dave Brown
Christchurch, NZ

----- Original Message -----
From: "Denis Cobley" <denis.cobley@...>
To: <TekScopes@...>
Sent: Friday, July 11, 2003 12:38 PM
Subject: [TekScopes] VSWR tester


Hi all
Slightly off subject but there seems to be a good knowledge base on the
group.
We have a Wiltron 97A50 VSWR Autotester to measure VSWR.
Only problem is we have no idea how to interpret the detected output back
to VSWR.
Anyone have a manual or can give me info on how to convert the millivolt
output to VSWR
At 100Mhz into an open circuit we get -22mVDC out, with a 50 ohm term we
get 0VDC.
We need to know what this means in terms of VSWR (1.3:1 , 2:1 ??)
The cal report that we have with it gives us readings in Directivity >36dB
but this is meaningless in terms of VSWR to us.

Regards
Denis Cobley








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getting my millennium falcon to fly.

eternalesquire <eternalsquire@...>
 

Hi everyone!

I'd like to ask some advance on debugging a scope configuration.
I've put together a Tek 585, 81 Adapter, and L20, all tubes.
I'm getting a wierd readout on my CRT, and I would like to know
if anyone understands immediately what I am doing wrong based
on what I am describing:

There is a vertical fuzzy bar in the middle of the CRT.
On the upper and lower right hand side of the CRT I
am seeing "fluffy angels wings". The horizonal position
moves the fuzzy bar from left to right. I get this on
channel A only, I get no readout from channel B.

Injecting a signal into the main L20 input makes no difference.
The bar is still fuzzy even through I brought it into focus
as much as I could.

Does anyone have any advice as to how I might need to operate
different, or what area I should begin debugging?

Thanks in advance,

The Eternal Squire.

7A22/7A13, was RE: 475 instead of 475A?

Craig Sawyers <c.sawyers@...>
 

The 7A22 has a sensitivity of 10uV /div and has built in high and
low pass filters. The maximum bandwidth is limited to 1MHz. The
differential input will allow you to look at ballanced as well as
unbalanced signals. It is well suited for audio work.
I'll second that John! Used in differential mode, it will also give a CMRR
of 10^5 at 10uV/div to 10mV/div with matched probes (P6055). This falls to
10^3 for 20mV/div - 10V/div. There is a variation with frequency and ac/dc
coupling, but the above a typical figures in the audio range. There is a
basic dc offset control to measure signals on DC, with a range depending on
sensitivity.

I'd also add the 7A13 diffential comparator. This has a poorer CMRR than
the 7A22 of around 2x10^4 and only goes to 1mV/div. But you can offset the
effective dc threshold of the measurement with a comparison voltage up to
(effectively) hundreds or thousands of volts with digital readout (depending
on range selected) - so slow waveforms riding on DC (like power supply
ripple) can be looked at without the amplitude and phase distortion
introduced by ac coupling (of course you can ac couple instead if you wish).
It has the advantage of going to >100MHz in the right mainframe.

Oh, and with a mainframe, you can also get a 7L5 audio frequency spectrum
analyzer. These are still quite expensive, going for around $500-800
typical; however, option 25 that adds a tracking generator so that you can
do swept frequency responses. If you are *really* lucky you might find the
version that comes with log sweep too. The 7L5 has digital memory, so you
don't need a storage scope to view the trace on slow high resolution sweeps.

All in all a mainframe wins every time for flexibility and upgradeability.
The only disadvantage it is relatively heavier and larger than a 475 and if
portablility is an issue that might be a significant consideration.

Craig

Re: 7904 Mainframe production dates

Denis Cobley <denis.cobley@...>
 

Hi all
B010100 is always the first saleable unit serial number.
All below that were non saleable demo units (they were often upgraded for
sale at a later date and sold with full warranty as ex demo units).
Major serial number breaks were used to denote significant changes in
hardware.
Tek often had a number of ongoing mods as late field / customer identified
problems were fixed or redesign took place,.
These were incorporated into new board layouts and circuits (this is why you
have 2465B service manuals for below B050000 - discrete components and
B050000 and above - same scope but now with several boards surface mount
parts only).
As has already been noted, Tek recycle the same serial numbers on most
products and use the first letter/number to designate the plant / country of
manufacture.
A couple that were not mentioned are "N" which denotes manufacture by
Hinditron - this was Tek India and "C" which you will find on more products
as China. All The current TDS1000/2000 range is only made in China (as were
the later TDS200 series).
Regards
Denis

----- Original Message -----
From: "Fred Olsen" <fwolsen@...>
To: "Miroslav Pokorni" <mpokorni2000@...>; "washesmelon"
<vwthingy@...>
Cc: <TekScopes@...>
Sent: Friday, July 11, 2003 3:41 PM
Subject: Re: [TekScopes] 7904 Mainframe production dates


I had said:
>>Jeff, the only one I can address at the moment is the early 7904. It
>>would be reasonable to assume that early production exceeded the 250k
>>point, hence the restart at 260k rather than 250.
>>That said, I still would find it difficult to
>>comprehend that Tek built over a quarter-million 7904s!

to which
Miroslav Pokorni wrote:
> When you expressed doubt that Tektronix built over a quarter million
> 7904, I did agree, but did not think it was worth commenting.

I didn't mean to imply that Tek had built anywhere near a
quarter-million 7904s in the first series. I can't believe that.
First, in the later years many (all?) units' S/Ns started with B010100
rather than the traditional 00101 of the old days. Second, I suspect
that many of the runs were discontinuous. Earlier on Tek seemed to put
a clean break at a major rev, a redesign, such as "1A1 >S/N 20000" -
which was when the FET front end started IIRC. Later on the "greater
than"s seem to more often be in succession with lesser revisions which
were handled with a numeric break. So do I think that there were 19999
Nuvistor 1A1s? No, but close to it.

As a hypothetical I grabbed a late-production 7A26 manual from the file.
First Printing was Oct '72 at model start, with a Revised Feb '87. A
good example in later gear (all right, I know that the "new Tektronix"
doesn't consider a 7k-anything to be "later") - a good example is board
revisions. The amp board P/N went through a bunch of revs: -00 through
-08, -10, -13, -15, -17, and -21. All of those are listed with
consecutive S/N breaks. Bear with me, it's easier to see in a little
chart.

-00 B010100 ~ B049999
-01 B050000 ~ B069999
-02 B070000 ~ B083789
-03 B083790 ~ B089999
...
-17 B245520 ~ B251089
-21 B251090

I would suggest that it's reasonable to assume that revisions such as
the -02 to -03 were running changes and were indeed made at that S/N
break. But the ones at an even ten thousand, such as -00 to -01 or -01
to -02, would seem to simply be available blocks of assigned numbers.
There is no reason to think that all of those blocks were filled. There
might have been as few as a hundred or less used out of any 10000. It
all depended on sales demand, and what was at the time their traditional
engineering-driven continuous implementation of design improvements.

The only way to know for certain would be either to have a large pile of
all of the change sheets, which perhaps only Tucker might have been able
to put together outside of Tek; or to gain access to Tek's production
numbers, which isn't likely to happen even if they still have them.

So, do I think that they built a quarter-million 7A26s? No way. Or
that many 7904s? Even less likely. When I told Jeff that the
early-series 7904 production exceeded the 250k point, it was meant only
as a number break and not as an actual quantity. Granted that this
doesn't take into account the non-U.S. production using different S/N
series, but in most cases those numbers were small compared to
Beaverton's.

If pressed for a SWAG of the number of 'early' 7904s, the ones below
260k, I wouldn't think it could exceed four figures. Much of this is of
course my opinion, and I'll readily concede that I'm no expert. So,
grain of salt, YMMV. Anyone with actual knowledge of this please weigh
in.

Best to all,
Fred
--
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--
Outgoing checked by Norton AV







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Re: 7A21N question

Morris Odell <morriso@...>
 

Miroslav wrote:

Well, GenRad was not exactly averse to non-50 Ohm lines and connectors, so
it is hard to say whose tail was twisted to arrive at 125 Ohm connectors
used in 519.
Without going into the details of its design, I suspect the 125 ohm
environment was used in the 519 because of its unique CRT. The distributed
deflection system is a single ended arrangement with 125 ohm GR connections
for the input and the termination. A similar but much more advances system
is used in the 7000 series high speed scopes.

The 519 CRT contains several in-line vertical deflection plates connected to
a pre-aligned delay line. Y shift is acheived by controlling the voltage to
the other plate which is at AC ground potential. Inside the scope there's no
vertical amp, only a delay line consisting of a coil of rigid coaxial line
between the input connector and the CRT.

The 125 ohm GR connectors look like the 50 ohm ones from the outside, but
the centre connector is different - it's a sort of "fork" arrangement with a
smaller diameter to match the higher characteristic impedance. It looks more
fragile than the 50 ohm GR system.

Morris