You can absolutely trigger on low frequency signals including slow
ramps.  Be sure to set TRIG MODE (below the time/div control on the
right side) to NORM instead of AUTO to prevent the sweep from free
running when the triggers occur slower than about 20 Hz.

You may need to use DC input coupling and DC trigger coupling.

On Fri, 01 Mar 2013 22:12:46 -0600, Cliff White
 wrote:

I have a case where I need to use my 466 to view a /very/ slow (less 
than one Hertz) 5 volt p-p square wave. Is it possible and/or easy to 
make it trigger on such a signal? By using the storage mode I can make 
it easily viewable, and stay on the screen until the next sweep, I just 
can't seem to make it reliably trigger. Ideas?

-Cliff

------------------------------------

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I should have said GR-874 to BNC female adapter. I suspect the
adapter will be better than using a questionable Chinese panel BNC.

On Fri, 01 Mar 2013 22:55:06 -0000, "iglesia_cristiana_arpas_eternas"
<iglesia_cristiana_arpas_eternas@...> wrote:

Thanks David, seems this GR connectors will cost more than I paid for the whole generator!!.
Gabriel.
--- In TekScopes@..., David <davidwhess@> wrote:

I have found Chinese BNC connectors to be dimensionally questionable.
So much so that I suspect you would be better off keeping the GR-874
connector and buying one BNC adapter.

I just recent made the jump into GR-874 connectors to support my S-1
and S-2 sampling head habit. Besides being hermaphroditic, I have
found them to be very rugged and reliable.

On Fri, 01 Mar 2013 19:45:38 -0000, "iglesia_cristiana_arpas_eternas"
<iglesia_cristiana_arpas_eternas@> wrote:

Well Craig, what you say is exactly what I think about.
Once the generator arrive , and measure the natural pulse length, then I
will decide add more or not more length inside, or put a bnc instead GR
and have the facility to change pulse width as needed.
What suggestion to test if Chinese bnc are useable?...you are talk about
dielectric losses..or else?
I cant imagine that Chinese not maintain the physical dimension to
maintain 50 Ohms..but who know?.
Mi first notice that GR are "hermaphrodite" ..we can be confident
about sex even in connector matter!! [:D]

What would be useful is add a repetition rate knob adj.
Thanks Craig, for your valuable input
Gabriel.
--- In TekScopes@..., "Craig Sawyers" <c.sawyers@> wrote:

Hi Albert..probably I put some meters of RG147 as fixed(solder)

internal

line

in order to obtain a 100nS pulse width.
What is the secret about this GR connectors ?, I have the temptation

to

replace by a BNC, any wrong with this change?.
Gabriel.

My version of this generator has a fixed solid line coiled up inside.

There

is also a front panel SMA to attach more line if needed.

Nothing special about GR connectors. Essential if you have a lot of

GR

gear; they were really GR's solution to a 5GHz connector, introduced

in

1943. Then later they introduced the GR900 series that went higher in
frequency. Both "hermaphrodite" in that there was not a male and

female

connector - everything was identical. There were lots of in-house
connectors designed - anyone remember the Rhode&Schwarz Dezifix? All
superceded by the N-type for this frequency range. But really, a high
quality, branded BNC would be fine (all BNC's are not created equal!)

Craig

------------------------------------

Yahoo! Groups Links

?

?

From: Cliff White
Subject: [TekScopes] 466 Trigger on <1Hz Square Wave?
To: TekScopes@...
Date: Friday, March 1, 2013, 8:12 PM

?

I have a case where I need to use my 466 to view a very slow (less than one Hertz) 5 volt p-p square wave. Is it possible and/or easy to make it trigger on such a signal? By using the storage mode I can make it easily viewable, and stay on the screen until the next sweep, I just can't seem to make it reliably trigger. Ideas?

-Cliff

?

Howdy back Nigel,

<<<“but I suspect the 7000 series fittings are different”>>>

Quite the contrary it appears that they are identical. The trick is not compression of the 115 and 116 but rather the taper and getting 118 to slide into/underneath ?the ?tabs on 115. I use a small nut I taped to prevent scratching in case I slip. I place it on the bench aligned on 115 (just so that it is well seated against 116 and the case. with the inside of the case facing up. ?I then use the snap ring pliers to get 118 sliding into position. The fit is quite tight so trying to get it to slid on with just a screwdriver (or other implement) is difficult at best. The pliers at the following link are the kind I use/have. I modified them by grinding (with a Dremmle and file) ?one of the pins (more or less flat) flat so that it holds on 118 better sliding it onto/under 115. With the pliers as wide open as they are at first there is a slight alignment issue.

Anyway it worked “ok” even without grinding the pliers pin on the first few. Once you do one or two it will be obvious as to the modification.

I, as you; have become convinced that Tektronic's had some kind of a “jig” for doing these. ?However my conclusion was that it was likely a set of pliers of some sort that held onto the tabs of 115 making/trivial it easy to slide 118 into place.

Finally it does make a difference on what part of 117 you are on. Basically you want to slide everything together as if 118 is in the locked position.

Again, hopefully helpful and that you are reading this well rested and spry for the new attempts.

Rob

From: TekScopes@... [mailto:TekScopes@...] On Behalf Of poldhu1901@...
Sent: Tuesday, February 26, 2013 7:03 PM
To: TekScopes@...
Subject: Re: [TekScopes] 2901 Time Mark Generator Case Fixings

?

Hi Bob

Many thanks for your reply, the pliers you describe are what we call circlip pliers in the UK but I suspect the 7000 series fittings are different as those pliers wouldn't work for what I'm trying to do.

I've created an album in the group photos area called "2901 Time mark Generator" and have uploaded a drawing?to that showing the 2901 covers and fittings.

On this version of the drawing, item 115 is the countersunk securing pin, item 116 is the dished serrated spring washer, item 117 is the plastic index plate, and item 118 is the locking plate that I need to latch into a groove?at the end of the pin.

My problem is the amount of force that's required to compress item 116, I've tried supporting the head of the pin and pressing?down on the locking plate with a nutdriver that fits over the inside end of the pin?but it just won't press down far enough to allow the locking plate to slide into its groove and I'm concerned that the amount of force I'm having to apply is going to damage the cover around the fitting, especially if I slip.

Next up I'm planning to try?a couple of nutdriver heads from a socket set, one pressing on the outside of the countersunk pin and the other over the inside of the pin pressing against the locking plate as before, but this time I'll try compressing them either in a vice or using a G-clamp, which hopefully will allow better control and reduce?the risk of applying pressure to the cover.

It's just getting really silly, I keep thinking I'm missing something but what I've got exactly matches the drawing and there must have been an assembly tool for this, there's no way these latches could have been assembled in a production environment without one.

Regards

Nigel

GM8PZR

In a message dated 26/02/2013 18:00:37 GMT Standard Time, rgwood@... writes:

?

I am on the road and cannot provide pictures until the weekend. The case rings/locks on 7000 series boxes sounds very similar to what you describe. ??

In that case, I modified a standard set of “snap ring” or “C-ring” pliers *at least that what I learned to call them *. They are pliers that in one setting the jaws compress the c-ring to place it internal to a shaft. The other position they expand to open the ring on the outside of a shaft.

In any event they work good to push the tab under the slot with very little if any downward force. I’ll send pictures this weekend if needed, Hopefully the description gets you started.

Hopefully helpful

Thanks as always for the bandwidth.

Rob ?

From: TekScopes@... [mailto:TekScopes@...] On Behalf Of poldhu1901@...
Sent: Tuesday, February 26, 2013 5:37 AM
To: TekScopes@...
Subject: [TekScopes] 2901 Time Mark Generator Case Fixings

?

I'm sure this is?could turn out to be a very silly question, BUT.......

Some time ago?I bought a 2901 that was?quite grubby and?removed the top and bottom cover "twist to lock" fixings in order to clean?beneath them.

So far so good, and all cleaned up nicely, but I've yet to find a way of getting them back again that isn't likely to cause damage to the covers!

The fitting method is simple enough in principle, the locking "lever" drops over a slotted shaped end to the locking "screw" and then slides into place to hold the whole thing together against the tension of?a dished serrated?compression washer?that sits under the countersunk "s crew head", but there's so little give in those compression washers that any attempts so far have risked putting sufficient?pressure on the quite thin aluminium covers to damage them.

This is a similar sort of arrangement to the cover fixings on the old 500 series scopes etc but I recall those as being bigger and never causing this sort of aggravation. I'm sure there must have been other small TEK cases with these fasteners, and there has?to be a quick and safe way of fitting them, but I'm wondering now if there was some kind of shaped tool that compressed the fitting from either side without putting pressure on the surrounding metalwork.

Any thoughts would be much appreciated.

As an aside, for anyone who might be interested, I found some nice internal photos of the 2901 here....

Regar ds

Nigel

GM8PZR

Hi David-

Thanks for responding, I just yesterday got a chance to look at it.

First checking power supplies, the +350 measured in excess of 470V, and the +500 measured over 580V, both with lots of ripple. I found C760 very leaky and replaced it. That took care of the ripple, but not the level. After some investigation, I replaced V754, now all rails are within spec.

No impact on the trace compression problem, however. I did find that the problem does not appear until after the unit has warmed up for 20 minutes or so.

Thinking maybe the over-voltage on those two rails may have damaged another tube in the horiz amp section, I did a one-by-one substitute of all of them- no change. That included V343, V364, V384, and V398.

Looking today with a test scope, here are a few photos:




You can see the sawtooth going into R343 at grid of V343A is misshaped slightly, but the correct level.

The sawtooth in front of that, at the cathodes of V173 has good shape but seems to be too high a level?

I couldn't find the legend in the manual for how to read the blue voltages given on the schematic- when one is printed on top of another. For instance, at the cathode of V173 the schematic has -3.7 over +60 in blue. How to interpret that?



So do I understand correctly from the above photo that the signal at V173 cathodes is about 35 volts too high?

BTW- the square wave shown on the photos is the input, but not referenced to the same ground point on the test scope as the other traces.

Suggestions on how to proceed?

Thanks,
Keith Ostertag


--- In TekScopes@..., David <davidwhess@> wrote:

I have seen this problem before in the vertical direction where a load
resistor in the CRT vertical amplifier was open.

Be sure to check power supply voltages and that the deflection plates
are actually connected. Sometimes the leads loosen and fall off.

Since the trace unrolls when the position control is used indicating
that the sweep signal is not the problem, I would look after that
point on schematic 10. There are lots of DC levels shown on the
schematic which can be checked to narrow down the possibilities.

Some of the voltages are high so be cautious.

Problem solved! Your best solution is a GR874 to BNC female adapter. With
this adapter you don't have to modify the plugin at all. These adapters are
readily available and reasonably priced. Once you put that adapter on
everything you use to connect to the instrument will be BNC. Since these
were specifically made by reliable companies long before the Chinese started
making connectors they are 50 ohm and have excellent dimensions and high
frequency response.

If you like I can send you a GR to BNC Female adapter for $25 + shipping.


Dennis

-----Original Message-----
From: Of iglesia_cristiana_arpas_eternas, Sent: Friday, March 01, 2013 2:55
PM

Thanks David, seems this GR connectors will cost more than I paid for the
whole generator!!.
Gabriel.

--- In TekScopes@..., David <davidwhess@> wrote:

I have found Chinese BNC connectors to be dimensionally questionable.
So much so that I suspect you would be better off keeping the GR-874
connector and buying one BNC adapter.

I just recent made the jump into GR-874 connectors to support my S-1
and S-2 sampling head habit. Besides being hermaphroditic, I have
found them to be very rugged and reliable.

On Fri, 01 Mar 2013 19:45:38 -0000, "iglesia_cristiana_arpas_eternas"
<iglesia_cristiana_arpas_eternas@> wrote:

Well Craig, what you say is exactly what I think about.
Once the generator arrive , and measure the natural pulse length,
then I will decide add more or not more length inside, or put a bnc
instead GR and have the facility to change pulse width as needed.
What suggestion to test if Chinese bnc are useable?...you are talk
about dielectric losses..or else?
I cant imagine that Chinese not maintain the physical dimension to
maintain 50 Ohms..but who know?.
Mi first notice that GR are "hermaphrodite" ..we can be confident
about sex even in connector matter!! [:D]

What would be useful is add a repetition rate knob adj.
Thanks Craig, for your valuable input Gabriel.
--- In TekScopes@..., "Craig Sawyers" <c.sawyers@> wrote:

Hi Albert..probably I put some meters of RG147 as fixed(solder)

internal

line

in order to obtain a 100nS pulse width.
What is the secret about this GR connectors ?, I have the
temptation

to

replace by a BNC, any wrong with this change?.
Gabriel.

My version of this generator has a fixed solid line coiled up inside.

There

is also a front panel SMA to attach more line if needed.

Nothing special about GR connectors. Essential if you have a lot
of

GR

gear; they were really GR's solution to a 5GHz connector,
introduced

in

1943. Then later they introduced the GR900 series that went higher
in frequency. Both "hermaphrodite" in that there was not a male
and

female

connector - everything was identical. There were lots of in-house
connectors designed - anyone remember the Rhode&Schwarz Dezifix?
All superceded by the N-type for this frequency range. But really,
a high quality, branded BNC would be fine (all BNC's are not
created equal!)

Craig

Don't worry about the connector - worry about the cable. If you add "regular" cable externally, it can increase the pulse width accordingly, but it will show a marked discontinuity and droop during its portion of the pulse, unless it is very low in loss. The best is to continue with the .141 semi-rigid type. Even the smaller .085 type will show a large difference, although it's pretty good stuff. If you use RG-58, you will be very disappointed.

There is a limit to the pulse duration - the line charging circuit has to replenish the charge (figure about ten time constants) to nearly the full supply voltage between shots. With excessive line length, you will have to reduce the repetition rate in order to get to full voltage. It doesn't seem like it would be that big of a deal, but if you do the math considering the joules per pulse and repetition rate, you will find that it takes quite a bit of power to run. The output power is in the 50-100 W range during those nanoseconds of pulsing, and it's less than 50 percent efficient in delivery - not even counting the charging phase. If you hook a 10X or 100X 10 megohm scope probe to the charge line, you can observe the process from the line's point of view, and get a better feel for what's going on in there.

The main thing for these pulsers is to get a fast front edge, then reach and hold a flat zone that's long enough to convey the amplitude information even for lower bandwidth scopes. Increasing the pulse width makes it easier to see and use, but eventually the rep-rate suffers - that is usually more important than pulse width.

Ed

--- In TekScopes@..., "iglesia_cristiana_arpas_eternas" <iglesia_cristiana_arpas_eternas@> wrote:

Well Craig, what you say is exactly what I think about.
Once the generator arrive , and measure the natural pulse length, then I
will decide add more or not more length inside, or put a bnc instead GR
and have the facility to change pulse width as needed.
What suggestion to test if Chinese bnc are useable?...you are talk about
dielectric losses..or else?
I cant imagine that Chinese not maintain the physical dimension to
maintain 50 Ohms..but who know?.
Mi first notice that GR are "hermaphrodite" ..we can be confident
about sex even in connector matter!! [:D]

What would be useful is add a repetition rate knob adj.
Thanks Craig, for your valuable input
Gabriel.
--- In TekScopes@..., "Craig Sawyers" <c.sawyers@> wrote:

Hi Albert..probably I put some meters of RG147 as fixed(solder)

internal

line

in order to obtain a 100nS pulse width.
What is the secret about this GR connectors ?, I have the temptation

to

replace by a BNC, any wrong with this change?.
Gabriel.

My version of this generator has a fixed solid line coiled up inside.

There

is also a front panel SMA to attach more line if needed.

Nothing special about GR connectors. Essential if you have a lot of

GR

gear; they were really GR's solution to a 5GHz connector, introduced

in

1943. Then later they introduced the GR900 series that went higher in
frequency. Both "hermaphrodite" in that there was not a male and

female

connector - everything was identical. There were lots of in-house
connectors designed - anyone remember the Rhode&Schwarz Dezifix? All
superceded by the N-type for this frequency range. But really, a high
quality, branded BNC would be fine (all BNC's are not created equal!)

Craig

Well Craig, what you say is exactly what I think about.
Once the generator arrive , and measure the natural pulse length, then I
will decide add more or not more length inside, or put a bnc instead GR
and have the facility to change pulse width as needed.
What suggestion to test if Chinese bnc are useable?...you are talk about
dielectric losses..or else?
I cant imagine that Chinese not maintain the physical dimension to
maintain 50 Ohms..but who know?.
Mi first notice that GR are "hermaphrodite" ..we can be confident
about sex even in connector matter!! [:D]

What would be useful is add a repetition rate knob adj.
Thanks Craig, for your valuable input
Gabriel.
--- In TekScopes@..., "Craig Sawyers" <c.sawyers@> wrote:

Hi Albert..probably I put some meters of RG147 as fixed(solder)

internal

line

in order to obtain a 100nS pulse width.
What is the secret about this GR connectors ?, I have the temptation

to

replace by a BNC, any wrong with this change?.
Gabriel.

My version of this generator has a fixed solid line coiled up inside.

There

is also a front panel SMA to attach more line if needed.

Nothing special about GR connectors. Essential if you have a lot of

GR

gear; they were really GR's solution to a 5GHz connector, introduced

in

1943. Then later they introduced the GR900 series that went higher in
frequency. Both "hermaphrodite" in that there was not a male and

female

connector - everything was identical. There were lots of in-house
connectors designed - anyone remember the Rhode&Schwarz Dezifix? All
superceded by the N-type for this frequency range. But really, a high
quality, branded BNC would be fine (all BNC's are not created equal!)

Craig

I have found Chinese BNC connectors to be dimensionally questionable.
So much so that I suspect you would be better off keeping the GR-874
connector and buying one BNC adapter.

I just recent made the jump into GR-874 connectors to support my S-1
and S-2 sampling head habit. Besides being hermaphroditic, I have
found them to be very rugged and reliable.

On Fri, 01 Mar 2013 19:45:38 -0000, "iglesia_cristiana_arpas_eternas"
<iglesia_cristiana_arpas_eternas@...> wrote:

Well Craig, what you say is exactly what I think about.
Once the generator arrive , and measure the natural pulse length,
then I will decide add more or not more length inside, or put a bnc
instead GR and have the facility to change pulse width as needed.
What suggestion to test if Chinese bnc are useable?...you are talk
about dielectric losses..or else?
I cant imagine that Chinese not maintain the physical dimension to
maintain 50 Ohms..but who know?.
Mi first notice that GR are "hermaphrodite" ..we can be confident
about sex even in connector matter!! [:D]

What would be useful is add a repetition rate knob adj.
Thanks Craig, for your valuable input Gabriel.
--- In TekScopes@..., "Craig Sawyers" <c.sawyers@> wrote:

Hi Albert..probably I put some meters of RG147 as fixed(solder)

internal

line

in order to obtain a 100nS pulse width.
What is the secret about this GR connectors ?, I have the
temptation

to

replace by a BNC, any wrong with this change?.
Gabriel.

My version of this generator has a fixed solid line coiled up inside.

There

is also a front panel SMA to attach more line if needed.

Nothing special about GR connectors. Essential if you have a lot
of

GR

gear; they were really GR's solution to a 5GHz connector,
introduced

in

1943. Then later they introduced the GR900 series that went higher
in frequency. Both "hermaphrodite" in that there was not a male
and

female

connector - everything was identical. There were lots of in-house
connectors designed - anyone remember the Rhode&Schwarz Dezifix?
All superceded by the N-type for this frequency range. But really,
a high quality, branded BNC would be fine (all BNC's are not
created equal!)

Craig