Date   

Re: Tek 7603 Followed Me Home

tom jobe <tomjobe@...>
 

Hi Chuck,
I think he means it appears to have a dead short (or close to it) and this is why I say that:
I have been following this 7603 thread, and had printed the power supply schematic out on large size paper to study as I followed this interesting thread.
Yesterday I thought my interest in this 7603 thread might also be a good excuse to try to fix a 7603 I have that has a large note on it about blowing the fuse instantly when it gets powered on.
There did not appear to be any short on the primary side of the main transformer, so soon this 7603's power supply was out and apart so I could check the large filter capacitors for ESR and resistance in the circuit. C808 appeared to be a full short in circuit to an ESR meter and to an ordinary Fluke DMM.
A study of the circuitry around C808 shows several other paths a short circuit could come from with everything still in the circuit, and that is where I left my search yesterday.
I figured I would study the power supply schematic and see what else I could figure out before removing any of the possible problem components.
This morning I was quite surprised to see Robert's report of finding a shorted C808 in his 7603!
Then when I saw Chuck's question this morning... I realized that my thinking there could even be a dead short in an aluminum electrolytic cap might need to be re-thought.
Other details:
This capacitor is part of the filtering of the 50 VDC supply immediately after the full wave rectifier. This transformer winding is center tapped to ground and two capacitors are used on the plus and minus outputs of the rectifier to ground. This C808 is on the negative side to ground, and a C909 on the positive side to ground. These two capacitors are identical (1800 uF/75 v) and C909 does not appear to be shorted when tested in circuit (several thousand ohms) which left me 'scratching my head' at the end of yesterday's investigation.
tom jobe...

On 9/11/2018 5:15 AM, Chuck Harris wrote:
I am not sure what you are saying when you say that
C808 tests at 0.0 ohms. Do you perhaps mean 0.0 uf?

Typically, when ripple gets to be that excessive, the
capacitor's internal connection has been etched away
and is open circuit, or the capacitor's electrolyte
has dried up. The capacitance goes to near zero uf.

As a temporary fix, you can get back in business by
paralleling just about anything across the original
capacitor at its terminals. Even as little as 1/10th
the correct value will sometimes be close for the circuitry
to limp along and work. Tektronix was very generous
with its margins.

-Chuck Harris

Robert Hay wrote:
Chuck,

C808 on the -50 v unregulated is the only cap that tests at 0.0 Ohms and is the only
one that doesn't charge up to some value using the cap test position on my Tek DMM916.

I ordered some replacement caps although I am not sure whether to ultimately replace
all the cans in the back section. I may use two 1000ufd 100v caps to replace the
1800 ufd 75 volt C808 on the -50 unreg. In this case the can is connected to the -50
unregulated rather than ground so I need to tie all those loose ends together.

I'll hit up the local electronic surplus tomorrow to see if I can find a replacement
cap for testing while waiting for the ones I ordered.

Bob.

On 9/9/2018 9:57 AM, Chuck Harris wrote:
My guess would be the -50V unregulated supply's
filter capacitor is no longer any good.


Re: Tek 7603 Followed Me Home

Kevin Wood G7BCS
 

If it helps, I had a 7603 fault due to one of those reservoir caps failing
and, when I got round to checking them, most of the caps on that rectifier
board were on their way out, so I changed them all.

That doesn't mean yours will be, of course, and I'm not generally an
advocate of "re-capping" devices en-masse, but my recollection is that it
was not that easy to get to the board and change the caps either, so it
might be a false economy to change just one or two.

Beware that several of those caps have multiple can connections to the
board and, on some, I think they are used as "jumpers" to connect traces
across the board. If replacing with caps of a different form factor, which
will probably be almost inevitable, you might need to insert jumpers
across some of the can connections. Apologies if I'm delivering lessons in
"egg-sucking"!

Kevin
G7BCS

Chuck,

C808 on the -50 v unregulated is the only cap that tests at 0.0 Ohms and
is the only one that doesn't charge up to some value using the cap test
position on my Tek DMM916.

I ordered some replacement caps although I am not sure whether to
ultimately replace all the cans in the back section.  I may use two
1000ufd 100v caps to replace the 1800 ufd 75 volt C808 on the -50
unreg.  In this case the can is connected to the -50 unregulated rather
than ground so I need to tie all those loose ends together.

I'll hit up the local electronic surplus tomorrow to see if I can find a
replacement cap for testing while waiting for the ones I ordered.

Bob.


Re: Tek 466 analog storage

EB4APL
 

Toby,

There are three 466 manuals. If yours is the one named Tektronix 466 Service Manual (PDF, OCR) <http://w140.com/tekwiki/images/c/cc/070-1753-01.pdf>, I can improve it somewhat if you don't mind. I can number the pages to reflect the original numbering and also I can add markers to point to the pages listed in the Table of Contents. I always do that in my own equipment manuals to easy the finding of schematics and alignment instructions. It'll take quite time but I'll do it if anybody is interested.

Regards,

Ignacio, EB4APL

El 03/09/2018 a las 18:32, toby@... escribió:
On 2018-09-03 11:16 AM, Roger Evans via Groups.Io wrote:
There is a very decent PDF manual at w140.com/tekwiki/wiki/466.
That would be the one I scanned. I took a lot of care to make sure it's
clear -- if you find any problems, let me know, I still have the
original files and paper manual.

--Toby



For serious fault finding I print off a few pages, sometimes as two
sheets stuck together, and make a note on these where to find other
schematics and layout pages. It looks like all the lower voltages get
their reference from the +65V that you will find just below the +140V
supply on schematic <11> Power Supply and Distribution. If all of your
lower voltages are off by the same fraction eg all low by 20% it could
just be that the +65V is off spec and everything else is OK. If you
want I can talk you through some of the stages but I am far from being
an expert and you will have to wait until after our holiday!
Roger





Re: Tek 7603 Followed Me Home

Chuck Harris <cfharris@...>
 

I am not sure what you are saying when you say that
C808 tests at 0.0 ohms. Do you perhaps mean 0.0 uf?

Typically, when ripple gets to be that excessive, the
capacitor's internal connection has been etched away
and is open circuit, or the capacitor's electrolyte
has dried up. The capacitance goes to near zero uf.

As a temporary fix, you can get back in business by
paralleling just about anything across the original
capacitor at its terminals. Even as little as 1/10th
the correct value will sometimes be close for the circuitry
to limp along and work. Tektronix was very generous
with its margins.

-Chuck Harris

Robert Hay wrote:

Chuck,

C808 on the -50 v unregulated is the only cap that tests at 0.0 Ohms and is the only
one that doesn't charge up to some value using the cap test position on my Tek DMM916.

I ordered some replacement caps although I am not sure whether to ultimately replace
all the cans in the back section. I may use two 1000ufd 100v caps to replace the
1800 ufd 75 volt C808 on the -50 unreg. In this case the can is connected to the -50
unregulated rather than ground so I need to tie all those loose ends together.

I'll hit up the local electronic surplus tomorrow to see if I can find a replacement
cap for testing while waiting for the ones I ordered.

Bob.

On 9/9/2018 9:57 AM, Chuck Harris wrote:
My guess would be the -50V unregulated supply's
filter capacitor is no longer any good.


Re: telequipment s54a trace too low on y

james.simpson54@frontier.com
 

I took a quick look at that portion of the schem. and noticed that. One thing I don't understand is on all of the schematics it has what looks like test points and they are labeled with a number within a circle. They start with #1 on the first schem. and then 2,3 and so on. The schem notes "numbers within the circle denotes tag no. on p.c. 70" I was hoping these were test points and somewhere there would be a list with what the voltages were. Or I was hoping on the schem. it would show voltages at certain points "along the way" (I think the d54 schem. has voltages shown at certain areas)) None the less, I need to get it opened up and get a look at it. Wed. Night I go see Travis Tritt and Charlie Daniels band so I have to get mentally prepared for it.


Re: 310A scope : serial number oddity ? Ideas ?

David DiGiacomo
 

I am still a bit perplex : how can such a late 310A, have a serial number as low as #1239 ?! Baffles me...
There's no mystery. The serial numbers were not coordinated between
the manufacturing sites. Your scope was the 1239th 310A made on
Guernsey, but there could have been a million units made in Beaverton
before that.


Re: Bringing up a Tek 555 dual-beam scope

John Miles
 

True, the "bumble bee" caps in the signal path will likely be bad and need
replaced, but there is no danger in turning on the scope with these in the scope
if they are bad, and troubleshooting to find them is usually fairly easy.
I don't know about the 5xx scopes, but if you've worked on vintage radios you've probably seen cases where a leaky interstage coupling capacitor dumps a lot of positive bias onto a grid from the previous stage's plate circuit. The end result is excessive current through the plate (possibly lighting it up cherry-red) and the audio or IF transformer it drives.

Opinions will vary but I think it's better to get all of those paper caps out of the device before you even hit the power switch, certainly before you let it run for more than a few minutes. I agree with the "wait and see" approach with electrolytics, though, since there's no guarantee that NOS electros will be any better than the old ones.

I do remove the covers before I power up to scope the first time to check for
smoke. If you see smoke, resist the urge to immediately turn off the power.
The larger carbon comp resistors need several seconds of giving off smoke
before they burn or even discolor. But the value may change considerably when
they over heat. I had this happen a couple of times, and found it very difficult
to find the specific resistor to troubleshoot because I did not let it burn long
enough.
An IR camera is nice for this. You can watch an entire chassis or PCB on initial powerup and spot problems before the smoke starts, possibly months or years before. And overheating components will stay that way long enough to be identified.

These cameras used to be ridiculously expensive, but you can get smartphone IR camera adapters from companies like Seek or FLIR for a couple hundred bucks now. Not the sort of tool you use every day, but also not the sort of tool you will want to give up.

I always turn the focus knob to the stop and intensity down before initial power
up. I have had a few scopes with problems in the CRT grid circuit that resulted
in high beam current even with the intensity turned down, and if the CRT was
focused, the phosphor would likely be burned.
That's a good idea.... and IMHO, carbon resistors in focus dividers are another good part to replace "just because."

-- john, KE5FX


Re: Tek 7603 Followed Me Home

bobh@joba.com
 

Chuck,

C808 on the -50 v unregulated is the only cap that tests at 0.0 Ohms and is the only one that doesn't charge up to some value using the cap test position on my Tek DMM916.

I ordered some replacement caps although I am not sure whether to ultimately replace all the cans in the back section.  I may use two 1000ufd 100v caps to replace the 1800 ufd 75 volt C808 on the -50 unreg.  In this case the can is connected to the -50 unregulated rather than ground so I need to tie all those loose ends together.

I'll hit up the local electronic surplus tomorrow to see if I can find a replacement cap for testing while waiting for the ones I ordered.

Bob.

On 9/9/2018 9:57 AM, Chuck Harris wrote:
My guess would be the -50V unregulated supply's
filter capacitor is no longer any good.

His VAC readings are certainly Vrms as read by his
DVM, so they are 2 x 1.4Vp-p, or in other words, he
has: 13Vrms x 2.8Vp-p/Vrms, or 36Vp-p ripple on a 50V
unregulated supply. No way that can work!

-Chuck Harris

John Griessen wrote:
On 9/9/18 10:11 AM, Robert Hay wrote:
I'll re-check the voltages
50 and -50 being actual 44 and -44 is the big clue.

Chuck was saying you probably have a very much changed component contributing
the the +44 and -44 regulated voltages, so some individual component volt level
measurements are next to do.

Them both being the same 44V suggests some protection feature of the circuit is
kicking in because some
filter caps are too leaky, but not shorted or open yet.
Look for bad caps there after the regulator.

The -52 for unregulated 50 is not likely enough headroom to regulate to 50V, so that
is suspect also.
Look for bad caps there before the regulator.




Re: 310A scope : serial number oddity ? Ideas ?

John Griessen
 

On 9/10/18 6:45 PM, Vincent Trouilliez wrote:
However the big downside is that there is a thin layer of some very fine "powder", must be some oxide, yellow-ish/green-ish in colour, covering just about every single screw, head, thread, electrolytic can backing plate, every pot and trimmer (some have their shaft seized !), as well as all the little "lugs" on the tube sockets, where the anti-vibration copper "clip"/retainer attaches to, whatever it's called.
I would not dissolve the cadmium yellow, just find something to pint it with to bind it in place. Like acrylic clear paint applied with a brush in a thin mix. Dissolving it will not yield results since there is a thick layer of shiny white metal underneath it ready to turn into cadmium yellow as soon as exposed to the air.
--
John Griessen


Re: 310A scope : serial number oddity ? Ideas ?

Jim Ford
 

Yeah, we're supposed to wear gloves when handling the green plated military connectors at work because they contain cadmium, but nobody does.   We do wash our hands afterward, though.
Jim


Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Vincent Trouilliez <vincent.trouilliez@...> Date: 9/10/18 7:10 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] 310A scope : serial number oddity ? Ideas ?
On Mon, Sep 10, 2018 at 06:49 PM, J Mcvein wrote:
Cadmium! So common to electroplated hardware of the time.Toxic, don't eat,
inhale, etc.  Wash hands.  Plants that used to plate it here (US), were shut down by the 1970's

JimMc

Thanks Jim !

Now that I know what it is... I can go ask the chemists out there what chemicals I might use to "neutralize"/dissolve it... well if there is one that is, crossing fingers ! :-/


Vincent Trouilliez


Re: 310A scope : serial number oddity ? Ideas ?

Vince
 

On Mon, Sep 10, 2018 at 06:49 PM, J Mcvein wrote:
Cadmium! So common to electroplated hardware of the time.Toxic, don't eat,
inhale, etc.  Wash hands.  Plants that used to plate it here (US), were shut down by the 1970's

JimMc

Thanks Jim !

Now that I know what it is... I can go ask the chemists out there what chemicals I might use to "neutralize"/dissolve it... well if there is one that is, crossing fingers ! :-/


Vincent Trouilliez


Re: 310A scope : serial number oddity ? Ideas ?

J Mcvein
 

However the big downside is that there is a thin layer of some very fine >"powder", must be some oxide, yellow-ish/green-ish in colour, covering >just about every single screw, head/...
Cadmium! So common to electroplated hardware of the time.Toxic, don't eat, inhale, etc.  Wash hands.  Plants thatused to plate it here (US), were shut down by the 1970's

JimMc

On Monday, September 10, 2018, 4:45:49 PM PDT, Vincent Trouilliez <vincent.trouilliez@...> wrote:

On Sun, Sep  9, 2018 at 05:51 PM, ditter2 wrote:
[..] As for the BNC versus UHF connectors on your unit, they may have been upgraded.
[..] Tek offered a mod kit for several of the tub instruments to convert to BNC connectors.
[..] You can probably get a good idea of the manufacturing date  by looking at the date codes of the large electrolytic caps.
[..] Many tubes also have date codes.

- Steve
Hi Steve,

I didn't want to open up the scope, as I have already a couple scopes I am working on at the moment, spread all over the bench... I wanted to keep the surprise of the 310A for later, when I actually have time to work on it. But.... it would be rude not to reply to you, and it gives me a good excuse to open it up sooner than I planned, so thank you ! LOL ^^

I think the BNC was fitted at the factory... as my scope is a late model it appears, actually so late it might as well be early solid state ! LOL

I had no luck with the tubes... pulled a dozen of them, at random places, from various manufacturers (Brima, Toshiba, Mullard, General Electric), none of them had date codes ! Bummer. Looked at the "cans"... luckily all very easy to access. 5 of them. 4 had date codes on them, all consistent : one was marked "1366", and the others read, in clear, "March 1966". So, end of March 1966 it is !

I am still a bit perplex : how can such a late 310A, have a serial number as low as #1239 ?! Baffles me...

This first peek inside the scope gave me preview of what I can expect when I get round to restoring this puppy... mixed feelings ! :-/
Basically looks brand new inside, even found a couple rubber grommets whose rubber still looks and feels as good as new, still a deep shiny blakc, still supple, and I am not even kidding. How can rubber survive 50+ years this well, no idea. Zero dust, all ceramic strips, components and solder joints, all look sparkling new.

However the big downside is that there is a thin layer of some very fine "powder", must be some oxide, yellow-ish/green-ish in colour, covering just about every single screw, head, thread, electrolytic can backing plate, every pot and trimmer (some have their shaft seized !), as well as all the little "lugs" on the tube sockets, where the anti-vibration copper "clip"/retainer attaches to, whatever it's called.
Boy I will have some fun sorting all this out ! Hopefully there exists some chemical/product that can dissolve all that oxide efficiently/easily... then I will have to remove all the pots to dismantle/open them, to free the shafts and make sure the wipers in them are OK.

Lots of fun ahead ! .....

Kudos to the engineers who managed to cram so much stuff in so little space, it is EXTREMELY tight in there !  :-O
Kudos as well to all the little hands at the factory who were tasked with assembling these things ! They deserve a medal...




Vincent Trouilliez


Re: telequipment s54a trace too low on y

Jim Tibbits
 

well that was a bodge assuming the s54 and d54 had anything in common ...s54 appears to have 105v and 12.5v supplies on the vertical .

"Vertical Amplifier" section on page 8 has check and aligning proceedure

Jim


Re: 310A scope : serial number oddity ? Ideas ?

Vince
 

On Sun, Sep 9, 2018 at 05:51 PM, ditter2 wrote:
[..] As for the BNC versus UHF connectors on your unit, they may have been upgraded.
[..] Tek offered a mod kit for several of the tub instruments to convert to BNC connectors.
[..] You can probably get a good idea of the manufacturing date by looking at the date codes of the large electrolytic caps.
[..] Many tubes also have date codes.

- Steve
Hi Steve,

I didn't want to open up the scope, as I have already a couple scopes I am working on at the moment, spread all over the bench... I wanted to keep the surprise of the 310A for later, when I actually have time to work on it. But.... it would be rude not to reply to you, and it gives me a good excuse to open it up sooner than I planned, so thank you ! LOL ^^

I think the BNC was fitted at the factory... as my scope is a late model it appears, actually so late it might as well be early solid state ! LOL

I had no luck with the tubes... pulled a dozen of them, at random places, from various manufacturers (Brima, Toshiba, Mullard, General Electric), none of them had date codes ! Bummer. Looked at the "cans"... luckily all very easy to access. 5 of them. 4 had date codes on them, all consistent : one was marked "1366", and the others read, in clear, "March 1966". So, end of March 1966 it is !

I am still a bit perplex : how can such a late 310A, have a serial number as low as #1239 ?! Baffles me...

This first peek inside the scope gave me preview of what I can expect when I get round to restoring this puppy... mixed feelings ! :-/
Basically looks brand new inside, even found a couple rubber grommets whose rubber still looks and feels as good as new, still a deep shiny blakc, still supple, and I am not even kidding. How can rubber survive 50+ years this well, no idea. Zero dust, all ceramic strips, components and solder joints, all look sparkling new.

However the big downside is that there is a thin layer of some very fine "powder", must be some oxide, yellow-ish/green-ish in colour, covering just about every single screw, head, thread, electrolytic can backing plate, every pot and trimmer (some have their shaft seized !), as well as all the little "lugs" on the tube sockets, where the anti-vibration copper "clip"/retainer attaches to, whatever it's called.
Boy I will have some fun sorting all this out ! Hopefully there exists some chemical/product that can dissolve all that oxide efficiently/easily... then I will have to remove all the pots to dismantle/open them, to free the shafts and make sure the wipers in them are OK.

Lots of fun ahead ! .....

Kudos to the engineers who managed to cram so much stuff in so little space, it is EXTREMELY tight in there ! :-O
Kudos as well to all the little hands at the factory who were tasked with assembling these things ! They deserve a medal...




Vincent Trouilliez


Re: 7K series - Conceptual question - What's the 3rd most useful plugin

fiftythreebuick <ae5i@...>
 

Scott, I would disagree on the 7M13...

If you need to add a bit of documentation to a scope photo for inclusion in a report or for archival purposes, the 7M13 is absolutely great! I have a couple of them and have used them a lot.

Tom


Re: Bringing up a Tek 555 dual-beam scope

Dave Wise
 

I agree except to emphasize that plastic-enclosed oiled paper (e.g. "Black Beauty" aka "bumblebee") are always bad and should be replaced. There are several in the Holdoff circuit which slow or prevent sweep, and several in the power supplies which cause sub-normal voltage. Also some in the HV section, one of which will prevent the oscillator from starting.

Another thing to watch for is silver migration on the ceramic terminal strips. Adjacent terminals with a lot of potential difference will migrate and eventually flash over which can ruin the strip. Keep 'em clean.

Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of ditter2 via Groups.Io <ditter2@...>
Sent: Sunday, September 09, 2018 8:20 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Bringing up a Tek 555 dual-beam scope

I have restored over two dozen 500 series tube scopes, both plug-in and monolithic, including one 555.
My technique differs from Rajesh's quite a bit. I have a variac, but usually do not use it, rather, I just plug it

<big snip>


Re: telequipment s54a trace too low on y

james.simpson54@frontier.com
 

Thanks. Exactly the type of instruction I need to get started. Unfortunately,when changing tires on my car yesterday I discovered a broken sway bar link. I was going to take it in but I'm unemployed so I figured I'll do it myself. So I have to get that taken care of and then break that scope out again. Thanks again.


Re: telequipment s54a trace too low on y

jim <ab7vf@...>
 

I've got a D54 played with it loooong ago ..But First track down and measure the power supply voltages ..There are no special (or any at all) voltage regulator circuits , Just R's and C's Y amp has 75v supply and 16v supply ...If you don't want to clutter up the list, ab7vf at yahoo (dawt) com will work

Jim

On Sunday, September 9, 2018, 7:48:26 PM PDT, james.simpson54@... <james.simpson54@...> wrote:

It's a solid state scope. I just uploaded the manual to the files section. It is titled s54aoscilloscope that has the schematics for the unit. I was hoping someone may have already done a repir on this or a similar unit


Re: 7K series - Conceptual question - what is the _least_ useful 7000 plugin?

 

Hi Gary,

I replied about this plugin you are referring to the other day. Here again are my relevant comments:

-----Original Message-----
From: Dennis Tillman W7PF
Sent: Friday, September 07, 2018 8:22 PM
Subject: Re: [TekScopes] 7K series - Conceptual question - What's the 3rd most useful plugin

<snip>

The 7A21N would be a close tie for the 7A17. It was in the catalogs from
1972 until 1979. It was used with the 500MHz 7904 when the 7904 was the fastest 7000 scope. It boosted the bandwidth to over 1GHz by going direct to the 8cm x 10 cm CRT's deflection plates. The combined sensitivity was 4V/Div or 2V/Div differential. It was the only way to get to 1GHz until 1979 other than the 519. It sure was a lot better than a 519 (10V/cm) with a tiny 2cm x 6cm screen. I did use the 7A21N for several weeks more as an experiment than anything else. When the 7104 was introduced in 1979 it made the 7A21 obsolete.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Gary
Robert Bosworth
Sent: Sunday, September 09, 2018 7:31 PM
To: TekScopes@groups io <TekScopes@groups.io>
Subject: Re: [TekScopes] 7K series - Conceptual question - what is the
_least_ useful 7000 plugin?

There was a plug-in for the 7104 1GHz scope. I can't remember the model
number right now, but I own one. It was single channel and drove the
vertical plates directly to give the fastest possible response. It was
not widely publicized that you had to make several very complex
modifications inside the oscilloscope for the plug-in to function at all.
Needless to say, it was a waste of my money.

--
Gary Robert Bosworth
grbosworth@...
Tel: 310-317-2247



--
Dennis Tillman W7PF
TekScopes Moderator


Re: 7K series - Conceptual question - What's the 3rd most useful plugin

 

Hi Scott,

I have to disagree about the 7M13. It is nowhere near the bottom of my list.
I use the 7M13 frequently. It is very useful, particularly in a 4 slot
scope, for documenting odd test conditions for future reference when I take
scope pictures (which I do very often).

I am aware that I am probably an exception when it comes to the kinds of
things I measure and document. With my extensive collection of plugins some
of my "fun" comes from taking advantage of every instrument and plugin Tek
has given us.

The 7M11 is one I use very little but I have used it on occasion. In my
opinion its biggest drawback is the 175pS risetime. I wish there was an
equivalent with risetime faster than the S-6 (<= 30pS) and S-4 (<=25pS)
sampling heads. Then it would be handy for delaying signals so the 7T11
could trigger on them in sequential mode.

The 7A17 is still at the bottom of my list since I haven't found any use for
it so far in spite of it offering a very easy way to connect a signal to a
7K mainframe. I bought a 7A17 in 1977 when I bought my 7704A / 7A26 / 7B80 /
7B85 so I could use it as an inexpensive 3rd channel and fill what would
otherwise be an empty slot.

Over the years some possible ideas I toyed with for the 7A17 were as:

* A 2 channel multiplier. I later discovered that the 7A26 is a better
candidate as a 2 channel multiplier since both channels are already in the
plugin with all the attenuators and support circuitry. It might be as simple
as connecting the two output channels through an analog multiplier IC just
before they reach toe back connector.

* A logarithmic amplifier. When I started working with spectrum analyzers I
learned they already display spectral energy on a log scale and I lost
interest in that idea.

* A constant amplitude amplifier. The constant amplitude idea came out of
the annoyance of constantly adjusting the volts/div knob to keep a trace on
the screen in some measurement situations. It would work like an automatic
volume control does to hold the amplitude constant. You could choose an
incoming signal to occupy 1, 2, 3...7 or 8 divisions with a simple 8
position rotary switch. As the signal amplitude changed the amplitude on the
screen would remain constant but the readout would update to show how many
volts/div each division represented (within a few percent). I think this
idea is quite possible. Steve Ditter pointed out a combination DVM and
on-screen readout IC that Tek makes that should be able to display volts/Div
on the screen with an accuracy of a few percent. Thanks to Steve I was able
to buy a couple of these off Ebay at bargain prices a few years ago.

Dennis Tillman W7PF

-----Original Message-----
From: Scott McGrath
Sent: Saturday, September 08, 2018 6:38 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7K series - Conceptual question - What's the 3rd
most useful plugin

I think the vote for least useful plug in needs to be for the 7M13, which
allowed you to place text on the screen.

The 7M11 - may be a close second as its a dual 75 ns delay line which uses
the scope only for power

Content by Scott
Typos by Siri



--
Dennis Tillman W7PF
TekScopes Moderator

45541 - 45560 of 196532