Date   
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

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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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: 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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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: 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

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: 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: 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: 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

--

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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Tek Serial Number Scheme

tss_steve_990
 

Deane Kidd has kindly supplied the following understanding of the
Beaverton Serial numbering scheme.

On Any Given Model of Scope:

The first Letter "B" stands for Manufactured at Beaverton Plant
The next two digits are the Bill of Materials for that scope model
The next 4 digits are the actual serial number of that scope

Thus an introductory model B010100 is serial number 100 built from
the first production BOM

B02xxxx is the first revision after BOM B01xxxx
B25xxxx uses bill of materials #25 etc.

No guesses as to the scopes made in Holland except that the first
number is 7.

This concludes my quest for understanding Tek Serial Numbers unless
someone has some insight into the Dutch numbering scheme.

Some of you have rightly questioned whether the S/N (i.e. date of
manufacture) is really that important relative to the present
condition of the scope. Obviously a perfect condition earlier unit is
better than a later unit that has much more "mileage" on it. I am
using the S/N as only one data point in selecting a used scope.
Given the Tektronix philosophy during the period when the scopes I am
considering were built, I am making the assumption (perhaps not
correct in all cases) that the later models had fixes and
improvements over earlier models. And a perfect condition 20 year
old scope might have more life left in it than a perfect condition 30
year old scope of the same model. I have just now becoming aware
(with the help of many of you who have responded to my inquiries) of
the wide variety of choices available in the Tek line, including the
9000 series, which I really didn't know much about. Remember my only
scope is a 535 with a CA plug-in, used mainly to heat the garage in
the winter.
Thanks to this group I have met many of you who know Tek equipment
far better than I do. I have learned about the DSESR meter to locate
failing caps in vintage gear. I have gotten a lot from you all.

Thanks,

Steve Hogan

Re: fast storage vs. slow storage?

Stan & Patricia Griffiths <w7ni@...>
 

The main difference between fast and slow storage tubes is contrast. Better
contrast in the slow ones.

Stan
w7ni@...

----- Original Message -----
From: "Robert Morein" <morepub@...>
To: <TekScopes@...>
Sent: Sunday, July 06, 2003 9:22 PM
Subject: [TekScopes] fast storage vs. slow storage?


The Tek 434 has much slower writing speed than the "fast" scopes.
I notice there was an almost free option to supply a faster writing CRT.
From this, I'm guessing there is some advantage to a CRT with slow
writing speed.
Durability, perhaps?
Resistance to burn?
Does anyone have any figures for number of storage hours for the various
tubes?







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Re: 7603

Stan & Patricia Griffiths <w7ni@...>
 

On the off hand chance that your beam finder is also broken or the trace is
SO FAR OFF screen that the beam finder won't find it, try shorting the CRT
vertical plates together right at the CRT and see if that gives you a trace
or not. It should (if your sweep is running and the horizontal amp works).
This should cause no damage to the instrument if you don't brush one lead of
the shorting wire against ground as you do this . . .

Stan
w7ni@...

----- Original Message -----
From: "ukcartman" <johnbloom@...>
To: <TekScopes@...>
Sent: Monday, July 07, 2003 3:05 PM
Subject: [TekScopes] 7603


Hi,
Can anyone help with the fault on this one? I have readout but no
trace on screen, this is the same on the beam find switch so it
appears that the trace is not there, not just off screen.
Thanks,
John.





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Re: 7904 Mainframe production dates

Stan & Patricia Griffiths <w7ni@...>
 

I guess I need to step in here and explain a little about Tek's serial
number system. It is covered pretty well in my book on page 39, but here is
some helpful info.

The earliest Tek instruments started with 3 digit numbers and Tek always
skipped the first 100. That means the first one off the line was s/n 101.
Numbers below 101 were used for protypes and only a few of them made it to
the surplus market, mostly through Tek employees taking them home (with
permission) after the design was complete. They stamped these numbers
directly on the panel. Later, the numbers were stamped on an aluminum
insert and leading zeros were added to make the number 6 digits. Sometimes
at the introduction of a newer model like when the 545A replaced the 545, a
bunch of numbers were skipped and the new instrument started serial numbers
at a higher convenient place like 0200001 for the first 545A. The 310/310A
transistion was like that also, going from stampling the number directly on
the front panel to an aluminum insert and skipping up to 0100001 for the
first 310A.

At some time later, a "B" was added in front of the serial numbers of
instruments built in Beaverton and an entirely new scheme of serial
numbering began. The first two digits following the "B" represented the
first major form of the instrument. So the first 465, for example, would be
B010101: "B" = Beaverton, "01" = the first major form of the instrument,
"0101" = the first unit off of the line. If a "major" change was introduced
into the instrument, the first 3 characters of the serial number were
incremented to "B02" and the following 4 digits continued on from where the
last "B01" serial number had stopped. (Don't ask me what a "major" change
was that triggered a new series of numbers . . . I don't know . . . ) This
scheme works fine until you get to B0?9999 and then you run out of numbers.
I think then, Tek just incremented the B0? to the next one and started again
at "0101" (or maybe "0000", I don;t know for sure . . . ) So, generally, if
you see a s/n starting with something like B26...., then it means either
that Tek built a LOT of them or they made a lot of major changes in the
design along the way . . . major enough to cause them to roll the "B" number
up to the next one.

Regarding how many of any particular model that Tek built, I have been asked
many times to provide that info. It is not readily available but some good
guesses can be made by studying the serial numbers found in the Modification
Summary for each instrument. The 570, for example, numbers about 1500
instruments, total. The 7A26 is the most common instrument Tek ever made
with something like 130,000 made. I would be surprised if Tek made more
than 10,000 or so 7904's and maybe only 5000 or so 7104's. The CA plugin
numbers about 75,000.

The point is that Tek skipped a LOT of serial numbers and it probably was
not to confuse the enemy. More likely it was so that by reading the serial
number, a service technician would have a good idea what to expect when he
took the covers off.

I hope this helps a little . . .

Stan
w7ni@...

----- Original Message -----
From: "Miroslav Pokorni" <mpokorni2000@...>
To: "washesmelon" <vwthingy@...>; "Fred Olsen" <fwolsen@...>
Cc: <TekScopes@...>
Sent: Thursday, July 10, 2003 11:25 AM
Subject: Re: [TekScopes] 7904 Mainframe production dates


Hello Fred,

When you expressed doubt that Tektronix built over a quarter million 7904,
I
did agree, but did not think it was worth commenting. Now that Craig asked
a
question about 7A21 (a direct access unit), I went and looked at my copy
of
plug-in. The serial number was in 40000. That is really hard to believe. A
direct access unit did not have so much applications that 40000 units
could
have been stamped out. I think that was time when reason departed
Beaverton
and scheming got into swing, 'to confuse competition' or to retain job of
the guy who was dreaming up schemes.

Regards

Miroslav Pokorni

----- Original Message -----
From: "Fred Olsen" <fwolsen@...>
To: "washesmelon" <vwthingy@...>
Cc: <TekScopes@...>
Sent: Wednesday, July 09, 2003 6:54 PM
Subject: Re: [TekScopes] 7904 Mainframe production dates


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. Mine is a "late
early", at B2464xx. That said, I still would find it difficult to
comprehend that Tek built over a quarter-million 7904s!

Fred
--
<><
--
Outgoing checked by Norton AV






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Falcon on the launchpad.

eternalesquire <eternalsquire@...>
 

Hi everyone!

Thanks for all the advice so far. I've located the sawtooth
source on the 585, but got no signal from there. I put back
the original 82 plugin to test the 585 as a scope, and have
discovered that timebase A is not working, but that timebase B
however is.

Does anyone have suggestions for how I should begin debugging
timebase A?

Thanks again,

The Eternal Squire

Re: Falcon on the launchpad.

Robert Morein <morepub@...>
 

The pulse shaping tubes in the timebase frequently fail to work without testing bad.
Any tube with less than 90% emission should be swapped.

----- Original Message -----
From: eternalesquire
To: TekScopes@...
Sent: Saturday, July 12, 2003 11:10 PM
Subject: [TekScopes] Falcon on the launchpad.


Hi everyone!

Thanks for all the advice so far. I've located the sawtooth
source on the 585, but got no signal from there. I put back
the original 82 plugin to test the 585 as a scope, and have
discovered that timebase A is not working, but that timebase B
however is.

Does anyone have suggestions for how I should begin debugging
timebase A?

Thanks again,

The Eternal Squire




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Re: Falcon on the launchpad.

Craig Sawyers <c.sawyers@...>
 

Does anyone have suggestions for how I should begin debugging
timebase A?
OK. First try free-running the timebase by setting the "Stability" control
fully clockwise. If there is still no trace when the "Horizontal Display"
switch is in the "A" position, then there is a fault in the A timebase
generator circuit. Here is what the manual says (you absolutely *must* get
a manual! It is the only way to ensure sanity with one of these units)

"No Horizontal Sweep
====================
If the Time-Base "A" generator is not producing a sawtooth sweep voltage
when the Stability Control is adjusted for a free running sweep, some defect
in the generator is holding the Miller Runup circuit. Depending on the the
on-off states of the Disconnect Diodes V152 (6AL5), the Miller Runup circuit
may be held at either the high end or the low end of the sawtooth. The
manner in which it is held may be determined by measuring the voltage at the
Sawtooth A binding post. If the Miller Runup circuit is held at the high
end of the sawtooth the front panel binding post may measure about +300V; if
held at the low end the voltage at this point will measure anywhere between
ground and -20V, depending on the cause. If it rests at -20V, the trouble
probably is non-conductance of V152A, and it should be replaced. It could
also mean that R151 (1k, between pins 7 and 8 of V152) is open.

If the Miller runup circuit is held at the high voltage end of the runup,
replace V152 as it can mean that both heaters can be open or its cathode can
have low emission and give the same effect. Usually if V161 (6CL5) is not
conducting, B167 wil be glowing brightly.

In the event the front panel Sawtooth A connector voltage rests at +350V,
there is probably a plate to grid short within V173 (6DJ8); replace it.
When this occurs B167 glows brightly at the electrode attached to pin 6 of
V161. If this reverse conduction condition is permitted to contine for
longer than about 15 minutes it may be necessary to replace B167 with a new
neon glow tube. The reason for this is that B167 may be unstable
thereafter.

If the heater of V173 is open, both neon glow tubes will be glowing brightly
and there will be no sweep.

If all the tubes have been checked, then check for open plate or cathode
resistors in the Sweep Gating Multivibrator circuit, the Hold-Off circuit or
the runup CF circuit. Also check that the Stability control can vary the
voltage at the grid of V135A"

Good luck!

Craig

Re: Falcon on the launchpad.

Stan & Patricia Griffiths <w7ni@...>
 

You definitely need a manual set for this system. Timebase A not working
will be a serious problem since there is no sawtooth output from timebase B
and you definitely need it to make the L20 work.

90% of all scope problems are in the power supply so you should start there
by checking to see if you have -150, +100, +225, +350, and +500 within 2%
and regulating properly. The procedure for doing this is in the manual . .
. Once you know the power supplies are working, then you can proceed to the
rest of the scope. By the way, a plugin MUST be installed in the scope to
put the proper load on the power supplies to make them regulate. There was
a "Test Load Plugin" made by Tek for this very purpose but you don't really
have to have one of those to make the scope work. It just helps to make
sure it is working 100% correctly.

Also, I faintly recall that some modifications may need to be installed in
the 585 to make the sawtooth compatible with the L20 but this will require
some research on my part to be sure. No point in doing this until you get a
set of manuals and get the A sweep working again.

Another useful trouble-shooting technique is to locate someone with a known
good scope to test the L20 in separately. If it doesn't work in that one,
you probably have an L20 problem, too, however, don't overlook that this
other scope may need sawtooth out mods, too, for the L20 to work in it.

Good luck on this and ask again when you have verified the 585 power
supplies and have A sweep working. By the way, if the power supplies are
working and A sweep is not, it is very probably a bad tube in A sweep
somewhere . . .

Stan
w7ni@...

----- Original Message -----
From: "eternalesquire" <eternalsquire@...>
To: <TekScopes@...>
Sent: Saturday, July 12, 2003 8:10 PM
Subject: [TekScopes] Falcon on the launchpad.


Hi everyone!

Thanks for all the advice so far. I've located the sawtooth
source on the 585, but got no signal from there. I put back
the original 82 plugin to test the 585 as a scope, and have
discovered that timebase A is not working, but that timebase B
however is.

Does anyone have suggestions for how I should begin debugging
timebase A?

Thanks again,

The Eternal Squire







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Re: 7603

Robert Morein <morepub@...>
 

The driving amplifier won't be bothered by a shorted load?

----- Original Message -----
From: Stan & Patricia Griffiths
To: ukcartman
Cc: TekScopes
Sent: Saturday, July 12, 2003 12:43 PM
Subject: Re: [TekScopes] 7603


On the off hand chance that your beam finder is also broken or the trace is
SO FAR OFF screen that the beam finder won't find it, try shorting the CRT
vertical plates together right at the CRT and see if that gives you a trace
or not. It should (if your sweep is running and the horizontal amp works).
This should cause no damage to the instrument if you don't brush one lead of
the shorting wire against ground as you do this . . .

Stan
w7ni@...

----- Original Message -----
From: "ukcartman" <johnbloom@...>
To: <TekScopes@...>
Sent: Monday, July 07, 2003 3:05 PM
Subject: [TekScopes] 7603


> Hi,
> Can anyone help with the fault on this one? I have readout but no
> trace on screen, this is the same on the beam find switch so it
> appears that the trace is not there, not just off screen.
> Thanks,
> John.
>
>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>


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