Date   

127

morriso2002@...
 

I have picked up a 127 preamp power supply that is used to power a
couple of 1- or letter plugins for use as instrument amplifiers. It's
quite a boatanchor and seems to work OK but I want to replace the
selenium rectifiers in it with silicon for safety reasons.

There are 5 rectifiers in there. To save me a bit of measurement work,
does anybody have any info on function/ratings of the rectifiers or
whether Tek issued a bulletin on their replacement?

Morris


Re: Manual Sources

Stan or Patricia Griffiths <w7ni@...>
 

Hi Doug,

Are you really sure Tek still offers older manuals on microfiche? Last time
I checked I thought they had discontinued that, too.

Stan
w7ni@easystreet.com

dhuster@pb.k12.mo.us wrote:

Hi, Doug,

Check out the "Q&A" column in the February 2001 issue of "Poptronics"
magazine (formerly "Popular Electronics" and "Electronics Now"
magazines) for a list of manual sources. Also check out my post at
http://www.nostalgiaair.org/nostalgiaair/messageboard/newforum/840.htm
for manual source listings. Tek doesn't offer any manuals in paper
for older instruments, only on microfiche, but it's cheaper anyway.
Used 'fiche readers are cheap or many libraries have reader/printers
available.

Dean Huster
Contributing Editor, "Q&A"
"Poptronics Magazine"
q&a@gernsback.con
http://www.poptronics.com/forums/index.html

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Re: 7904 power supply

Stan or Patricia Griffiths <w7ni@...>
 

Hi Paul,

I can't help you with this one. You might try Deane Kidd
<dektyr@teleport.com>

Stan
w7ni@easystreet.com

ke4dnk@yahoo.com wrote:

I need a transformer or a working power supply for my 7904 scope.The
serial # is above B260000.

The transformer is T1310, part # 120-0742-00.

The power supply assembly is # 620-0461-00

Paul Lewis
1317 Kingston Ridge Rd.
Cary, NC 27511

1-919-467-2818

Please reply to ke4dnk@bellsouth.net

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Re: Manual Sources

dhuster@...
 

Hi, Doug,

Check out the "Q&A" column in the February 2001 issue of "Poptronics"
magazine (formerly "Popular Electronics" and "Electronics Now"
magazines) for a list of manual sources. Also check out my post at
http://www.nostalgiaair.org/nostalgiaair/messageboard/newforum/840.htm
for manual source listings. Tek doesn't offer any manuals in paper
for older instruments, only on microfiche, but it's cheaper anyway.
Used 'fiche readers are cheap or many libraries have reader/printers
available.

Dean Huster
Contributing Editor, "Q&A"
"Poptronics Magazine"
q&a@gernsback.con
http://www.poptronics.com/forums/index.html


7904 power supply

ke4dnk@...
 

I need a transformer or a working power supply for my 7904 scope.The
serial # is above B260000.

The transformer is T1310, part # 120-0742-00.

The power supply assembly is # 620-0461-00

Paul Lewis
1317 Kingston Ridge Rd.
Cary, NC 27511

1-919-467-2818

Please reply to ke4dnk@bellsouth.net


Re: Manual Sources

Doug <carroll@...>
 

Thanks to everyone who replied,
I've contact several and am looking for the best price

Doug

--- In TekScopes@y..., "Doug" <carroll@u...> wrote:
Hi,
my name is Doug and I am looking for a User Manual and Service
manual
for a Tek 454 Scope. I had seen a source on the web but can't seem
to find it now. Does anyone know were I might find these manuals?
I understand tek is very expensive for printed versions of the
manual

Thanks
DOug


Re: 454 with no vert. deflection

mtmpsmp@...
 

--- In TekScopes@y..., Stan or Patricia Griffiths <w7ni@e...> wrote:
Hi Mike,

Good news! It is always great to hear of a success like yours.

More comments below . . .

mtmpsmp@y... wrote:

Stan,
Now I have this 2213 that the trace only
covers half of screen........
Half the screen horizontaly or vertically? I might have some ideas
on this,
too, if you are stuck . . .

thanks. Mike Smith
OK, Mike. My pleasure.

Stan
w7ni@e...
......................................................................
The trace starts on center of screen and runs to right side, Vertical
seems to be ok. The output transistors voltages are comparable but
signal on + plate is very weak. I don't have manual for this one but
layout looks very close to my 2235 .
although parts are numbered different.
Mike


Re: 454 with no vert. deflection

Stan or Patricia Griffiths <w7ni@...>
 

Hi Mike,

Good news! It is always great to hear of a success like yours.

More comments below . . .

mtmpsmp@yahoo.com wrote:

Stan,
Well I have located a manual, I bid on the one you had on Ebay but
it got out of hand in short order! ( I know you were happy!)
Anyway I have located my problems. (plural) turns out someone had
lifted the end of D388 to check it at some time and the choke on the
back side of the board had come off. Also Q388 was bad I replaced the
transistor and resoldered the choke and things got interesting! The
position controls were working but gain was still way off. I started
checking for gain in each stage from the delay line and
got as far as Q 464,364 at this point gain fell drastically! :( Well
I Pulled those and low and behold they were npn not the expected pnp,
I replaced with two 151-0193 and I have a new scope!!!!
(This scope came from IBM so I really don't Know what to think about
this?)
Well, there are marginal technicians in every company . . .

So in closing I want to thank you for all your help It was very nice
of you to take the time. Now I have this 2213 that the trace only
covers half of screen........
Half the screen horizontaly or vertically? I might have some ideas on this,
too, if you are stuck . . .

thanks. Mike Smith
OK, Mike. My pleasure.

Stan
w7ni@easystreet.com


Re: 454 with no vert. deflection

mtmpsmp@...
 

--- In TekScopes@y..., Stan or Patricia Griffiths <w7ni@e...> wrote:
Do you think maybe a bad output transistor? thanks for your
help.
Mike
Maybe, Mike. Looking at my 454 manual, I see that the collector
voltage on
both Q394 and Q494 should be about 41-42 volts measured with a
voltmeter.
Also, I don't think the voltmeter should "load" the circuit such
that the
voltage changes very much because of attaching the voltmeter.
There are TWO
sets of vertical deflection plate pins. Are you sure all FOUR
pins
are
connected?

A good troubleshooting method for balanced circuits like
vertical
amplifiers
is to short together like points such as the upper and lower CRT
deflection
plates in order to force them to be at the same voltage. This
should force
the trace to be centered vertcially and should not damage the
circuitry. If
the trace is centered with the CRT vertical deflection plates
shorted
together (this is also the same as shorting the collectors of
the
vertical
output stage transistors together), it is a very good indication
that the CRT
itself is good.

Next, you can remove the short and move it to the emitters of
Q394
and Q494.
If the trace is once again centered vertically, most likely Q394
and Q494 are
good. Next, move the short to the base of Q374 and the base of
Q474. If the
trace is once again centered, most likely Q374 and Q474 are
good.
You can
work your way a stage at a time through the vertical amplifier
this
way until
you do not get a centered trace. Now you are very close to the
problem and
it is time to check for shorted or open transistors in this
immediate area.
Be careful not to brush ground with the loose end of the short
wire
while the
instrument is powered up and the other end is connected because
you
will have
a LOT of destroyed transistors if you do that . . . Also, be
sure
BOTH ends
of the short wire are disconnected before connecting one end to
another part
of the circuit . . .

Let me know how this works for you.

Stan
w7ni@e................................................................

....................................................................
..
Stan,
I got no farther than Q374 and Q474,
I replaced both transistors and the output transistors collector
voltage dropped to 40.5 and 35.2 volts. The trace is now in the
upper
half of screen and I have a small deflection of a square wave
signal
so gain is poor. Should Q374and Q474 be a matched duo?
This thing about having to touch the collectors to start the
transistors to conduct is really odd, you don't have to leave the
probe on just make a momentary contact with deflection pin or
collector.
I don't have a manual for this thing so I'm working mostly in the
dark. I would like to thank you very much for all the help you
have
given me. mike
Hi Mike,

You really need a 454 manual. The one I was using to remind me of
the Q
numbers was the one I now have up for sale on eBay right now. You
should
look at auction #1226363944 and think about bidding on it.

You probably have found at least one bad transistor, or maybe two.
You can
test those for most defects with an ohmmeter right on the bench.

The next thing I would do is short the emitters of Q394 and Q494
and see if
this forces the trace to the center of the screen. If it does,
then I would
say Q394 and Q494 are good and you need to progress with the
shorting process
to the previous stage, etc.

You really need the manual . . .

Stan
w7ni@e...
......................................................................
Stan,
Well I have located a manual, I bid on the one you had on Ebay but
it got out of hand in short order! ( I know you were happy!)
Anyway I have located my problems. (plural) turns out someone had
lifted the end of D388 to check it at some time and the choke on the
back side of the board had come off. Also Q388 was bad I replaced the
transistor and resoldered the choke and things got interesting! The
position controls were working but gain was still way off. I started
checking for gain in each stage from the delay line and
got as far as Q 464,364 at this point gain fell drastically! :( Well
I Pulled those and low and behold they were npn not the expected pnp,
I replaced with two 151-0193 and I have a new scope!!!!
(This scope came from IBM so I really don't Know what to think about
this?)
So in closing I want to thank you for all your help It was very nice
of you to take the time. Now I have this 2213 that the trace only
covers half of screen........
thanks. Mike Smith


Re: tek 475 vertical position pots - end of story!

pe1fbo@...
 

Thanks Emanuele for your extensive coverage for cleaning the pots of
an 475. I'm sure more people appreciate this nice stor, because it is
one of the most common failure's in 465, and 475 scopes, probably the
best scope line ever build by Tektronix.

Fred de Vries, Holland


Re: Hi all

morriso2002@...
 

--- In TekScopes@y..., Michael Dunn <mdunn@c...> wrote:

547 (my workhorse bench scope), 549, the enormous 555 scoposaurus,
575

Do you know how the 555 differs from that other monster, the
556?

I would love to have a 556. They are both massive double beam machines
but there are quite a few differences. The 556 is in one piece while
the 555 is quite a bit larger and has a separate power supply. The 555
has 4 plugins, 2 vertical and 2 special timebases while the 556 has
built in timebases. The 555 has twin distributed amplifiers and lumped
delay lines while I'm pretty sure the 556 has 549 type vertical amps
with a coaxial line and a pair of 8608s. They're different enough to
make them both desirable but unfortunately not many 556s made it down
here.


and many plugins including a homebrew spectrum analyzer built into
an
old plugin caracass
Please tell us something about your spectrum analyzer!
It's based on the unit described in QST in 1999 by Wes Hayward and
another fellow whose name escapes me. Wes (W7ZOI) has a website with
pictures of various versions including an early shot of mine before I
found an attenuator for it. You can probably find it by doing a
search. It goes up to 80 MHz and has 5 KHz resolution at its best. I
had to design an interface to the Tek plugin specification which works
quite well even if I say so myself.

Morris


Re: Introduction and 465 Help Request

Bill Wollam
 

--- In TekScopes@y..., dhuster@p... wrote:
Bill,

Don't play with the gain. Both channels are affected the same way,
and that pretty much says that the problem is in the vertical
output amplifier. First thing to check is the collector load
resistors
that
go from the board up to the terminal post. If they're the beige,
rectangular, silicone-covered resistors, they may be your problem.
They're double-counterwound, inductance-cancelling resistors and a
common problem is that one of the two internal parallel windings
opens up, increasing the resistor value by a factor of two. Those
were Tek-made parts and Tek quit making them (they were very
troubleshome) and started using outsourced parts. If one or both
of
those resistors have an open winding, they'll be inductive, the
gain
will be 'way low and the pulse response will be a HUGE ringing.

Dean
Dean, thanks for your quick response. I m not sure which collector
load resistors you are speaking of but you mention them going from
the video output amp board to the terminal assy. so I assume you mean
the two 18 ohm resistors which couple the next to last output stages
(Q4478 & Q4468) to the final output stage drivers. These appear to be
OEM and measure 18 ohms as they should.

If you are referring to the collector resistors of the final stage,
they are 430 ohm wire wounds at 7 watts. The final coupling resistors
to the vertical plates are indeed TEK home grown which consist of a
200 ohm resister paralleled with a .3uh choke winding. These have
almost no DC resistance for obvious reasons. BTW, there are two
different versions of the TEK video output amplifier and I have the
discreet component version as you can probably tell by now.

As you suggested, I am looking at component values but haven't found
anything suspicious yet. Your help is appreciated.

Bill


Re: Introduction and 465 Help Request

dhuster@...
 

Bill,

Don't play with the gain. Both channels are affected the same way,
and that pretty much says that the problem is in the vertical output
amplifier. First thing to check is the collector load resistors that
go from the board up to the terminal post. If they're the beige,
rectangular, silicone-covered resistors, they may be your problem.
They're double-counterwound, inductance-cancelling resistors and a
common problem is that one of the two internal parallel windings
opens up, increasing the resistor value by a factor of two. Those
were Tek-made parts and Tek quit making them (they were very
troubleshome) and started using outsourced parts. If one or both of
those resistors have an open winding, they'll be inductive, the gain
will be 'way low and the pulse response will be a HUGE ringing.

Dean


Introduction and 465 Help Request

Bill Wollam
 

Hello, I just discovered this group and look forward to
participating.
Right now I can use some technical help, though.

I am wrestling with a TEK 465 in the 32xxx serial # range that seems
to work fine in all areas except vertical position display. Both
channels have the same symptom, that is they have what seems to be an
accurate display when the vertical position is centered, but when the
position control for either channel is moved to either the top or
bottom of the screen, the trace only goes as far as the next to last
graticule and the signal gets compressed in amplitude until it
disappears altogether. I have been spending most of my troubeshooting
time in the vertical amplifier module because it appears that at
least one stage may be driving into cutoff or just the oposite (too
low gain) because the voltages on the vertical deflection plates do
not show the movement that the manual indicates. I have not yet tried
adjusting the gain pot because I need to find a signal source
compatible with the manual procedure on this. The manual gives you
the process but not much theory to allow for deviation.

If anyone has seen this before or has any suggestions, I would
appreciate hearing it. BTW, I am using a 453 to troubleshoot which
has an intermittent high voltage supply. That will be the next
project. Thanks in advance, good to have found this group.

Bill Wollam


Hi, I'm new!

George <mjman@...>
 

Hello,
I just found out about this group and decided to join. I've got an
interesting collection of Tek scopes and other stuff, consisting of
three RM561As, a 551, a 181A time mark generator, a 106 square wave
generator, about 12 plugins, HP 523DR (tube frequency counter!), two
HP122ARs (HP tube scope), North Atlantic Phase Angle Voltmeter, Fluke
Differential Voltmeter, Kepco Power Supply, Waveforms
Oscillator/voltmeter, 4 radios, 2 TVs (tube, one color, one B/W), an
organ (Estey, 1961), Sherwood AM/FM tuner, Dynaco PAS-2, home made
tube amp. I have a few other pieces of test equipment that are
solid-state. Not looking so much to increase the size of my
collection, more interested in keeping it all working and sharing
ideas and stories with others.

George


Re: Hi all

Michael Dunn <mdunn@...>
 

At 7:00 AM +0000 2001/4/10, morriso2002@yahoo.com.au wrote:
547 (my workhorse bench scope), 549, the enormous 555 scoposaurus, 575
Do you know how the 555 differs from that other monster, the 556?


and many plugins including a homebrew spectrum analyzer built into an
old plugin caracass and a Japanese commercial transistor testing
Please tell us something about your spectrum analyzer!


by it at the age of about 10. A few years later I saw my first Tek - a
549 with a 1A4 plugin - and it was a really mind blowing experience
At least 2 of us here have 549/1A4 combos! Yes, a nice piece of equipment...

Michael Dunn, listboss :-)


Freon TF availability

james89es@...
 

When I recently joined this group, I read alot of the old posts. I
saw in one the mention that Freon-TF, used to clean fans, wasn't
available anymore.

Where I work, they use something called "Freon TF" to clean sensors
on check-sorting equipment. The product says that "Freon is a
trademark of DuPont ... Contents: Trichlorotrifluoroethane".

Is this the same stuff you're talking about or is it a substitute.

If anyone is interested, I can give specifics on where to get it.

-Jim


Re: Hi all

europachris@...
 

Welcome aboard, Morris. I'm just a novice collector, and only have one scope (a late 535A, Scopemobile, and a few plugins). But, it's in almost mint condition and I have all the probes, cords, and manuals, even the little mini-manual under the popup hood on the top of the scope. The scope is a joy to use and works perfectly. Truly a tribute to good engineering and design. I like it because it's older than I am and is also the type of stuff that put America in space in the 60's. Think about it. We went to the moon over 30 years ago. Pocket calculators were just a dream. Amazing.

I digress...Enjoy the group and keep warm with your tubes!

Chris Beck
West Bend, Wisconsin.

TekScopes@yahoogroups.com wrote:

I'm very pleased to have found this group as I am a great lover and
collector of vacuum tube Tek scopes here in Melbourne Australia. My
collection includes examples of the 310A, 502, 524AD, 529, 533A, 535A,
547 (my workhorse bench scope), 549, the enormous 555 scoposaurus, 575
and many plugins including a homebrew spectrum analyzer built into an
old plugin caracass and a Japanese commercial transistor testing
plugin built into a Tek blank. I also have a number of other
manufacturers' scopes as well, and sundry other pieces of Tek
equipment and manuals.

My interests include restoration and using these wonderful machines. I
can remember the first time I saw an oscilloscope and being fascinated
by it at the age of about 10. A few years later I saw my first Tek - a
549 with a 1A4 plugin �- and it was a really mind blowing experience
compared to the sorts of scopes experimenters had access to in the
1960s. Now I'm very happy to be able to own some of these
instruments and fully understand their workings.

I hope I will be able to contribute to the discussions here, both in
the way of helping others and learning along the way.

Cheers,

Morris Odell

__________________________________________________________________
Get your own FREE, personal Netscape Webmail account today at http://webmail.netscape.com/


Hi all

morriso2002@...
 

I'm very pleased to have found this group as I am a great lover and
collector of vacuum tube Tek scopes here in Melbourne Australia. My
collection includes examples of the 310A, 502, 524AD, 529, 533A, 535A,
547 (my workhorse bench scope), 549, the enormous 555 scoposaurus, 575
and many plugins including a homebrew spectrum analyzer built into an
old plugin caracass and a Japanese commercial transistor testing
plugin built into a Tek blank. I also have a number of other
manufacturers' scopes as well, and sundry other pieces of Tek
equipment and manuals.

My interests include restoration and using these wonderful machines. I
can remember the first time I saw an oscilloscope and being fascinated
by it at the age of about 10. A few years later I saw my first Tek - a
549 with a 1A4 plugin - and it was a really mind blowing experience
compared to the sorts of scopes experimenters had access to in the
1960s. Now I'm very happy to be able to own some of these
instruments and fully understand their workings.

I hope I will be able to contribute to the discussions here, both in
the way of helping others and learning along the way.

Cheers,

Morris Odell


Re: Manual Sources

Michael Dunn <mdunn@...>
 

At 5:07 PM +0000 2001/4/08, Doug wrote:
Hi,
my name is Doug and I am looking for a User Manual and Service manual
for a Tek 454 Scope. I had seen a source on the web but can't seem
to find it now. Does anyone know were I might find these manuals?
I understand tek is very expensive for printed versions of the manual

Don't forget to monitor eBay!


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