Date   
Re: 7904 excessive shadow/flare

Chuck Harris
 

The dome mesh is an anode, though it is called a "Slot Lens", on
the schematic. It is at pin 4 on the CRT.

I don't know if "Slot Lens" is the more formal name, or if perhaps
it isn't a dome?

The traditional dome mesh lens, as I have seen them is a super fine
stainless steel window screen with a pronounced bow in the screen
direction. Maybe the 7904 is using a special lens that only magnifies
the Y direction, and not the X direction, using slots instead of holes,
like the mesh lens?

I haven't broken a 7904 CRT as yet, so I haven't seen the lens.

They use two quad pole lenses to focus the beam before and after
the vertical plates.

I looked at my 7904 and 7854 more closely, and the 7904 is adjusted
to have a much hotter beam, just about always, than the 7854. The
way I can tell, is the beam spot, although P31 phosphor, is always
a lot bluer than the 7854, which is simply a boring green spot on a
green trace.

The 7854 is also 100MHz lower bandwidth than the screaming 500MHz
7904. It is different, even though it uses the same CRT.

And, (there is always an and with me...) the 7854 is 10 years newer
than the 7904. Surely there were some CRT improvements in that time?

-Chuck Harris

unclebanjoman wrote:

On Thu, May 23, 2019 at 02:42 PM, Chuck Harris wrote:


I know that, but my 7904's beat my 7854 in the flare department
by easily double. They also have much brighter maximum intensity
than does the 7854.

I haven't explored the differences, but the 7904's all have a worse
time than *any* other scope I have ever seen.
O.K. indeed the artifact is two times more pronounced with my 7904 with respect to my 7854 (grossly speaking).
The question that arise is: why?
Both the two models share the same tube type.
The post acceleration voltage is the same (21 kV).
Catode voltage is the same.(I presume).

If this is due to the dome mesh, where is it located on the diagram?
is there a regulation that affects it?
On the 7904 scheme I also see an adjustment for the preset shield volt (I adjusted as per manual): what's the use?

Max



465B Attenuator servicing

NigelP
 

I've just acquired a 465B in quite reasonable condition but there is a problem with CH2 attenuator. Essentially signals are not transferring from the BNC through to the input of the amplifier. Setting the attenuator to max sensitivity, where there SHOULD be a low resistance path of 75 ohms, shows as open circuit. With the attenuator still in situ I can see that the signal gets through to the first attenuator input switch but no further. It appears to be a lack of connection in the switch fingers although I can't actually see any visual problem with them.

So next is to remove the complete attenuator and have a good look at it; any suggestions/issues re getting just the one attenuator out as opposed to the "book" method of removing the complete CH1/2 input blocks plus mode switches? I'm hoping I can just undo the screws fixing the attenuator board to the cam block, and of course the two nuts fixing the whole to the front-panel.

I should say that at one point I had the channel working normally but after another good blast of IPA it went pear-shaped!!! I'm suspecting something somehow lodged in the switch-fingers but cannot see anything right now without a very close look.

Re: Photo Storage Space Solution, was IMPORTANT: Photos are eating up our storage

TomC
 

I'm pretty sure that the Arc files were transferred to the groups.io photo library.

Tom

On 5/23/2019 2:13 AM, Dave Daniel wrote:
I believe it is TekScopesArc, still on Yahoo.
DaveD
Sent from a small flat thingy

On May 23, 2019, at 02:28, Dennis Tillman W7PF <@Dennis_Tillman_W7PF> wrote:

Hi Harvey,
Not that I know of. You may be thinking of TekScopes2 and there was another one devoted to Tek Archives but the name escapes me. It may have been TekScopesArc or something like that.
Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Harvey White
Sent: Wednesday, May 22, 2019 4:24 PM
Subject: Re: [TekScopes] Photo Storage Space Solution, was IMPORTANT: Photos are eating up our storage

Didn't tekscopes have some other groups that were created solely for image storage back on Yahoo?
Harvey


On 5/22/2019 7:02 PM, nonIonizing EMF wrote:
I was wondering if moving the images and details related like including the link to the groups.io or other post to Tekwiki might be a solution. I'm not sure about the server limitations and expense there however.



--
Dennis Tillman W7PF
TekScopes Moderator


Re: 465B Attenuator servicing

Colin Herbert
 

What do you mean by a "good blast" of IPA? I don't know of any pressurized cans of IPA, only switch-cleaner such as Servisol or De-oxit. You should use nothing but IPA on the attenuator contacts, as anything else can damage or destroy the substrate. Cleaning the finger-contacts with IPA is done after pulling each of the attenuator modules out and carefully cleaning the gold-plated finger-contacts that are then visible by trapping IPA-wetted paper between the fingers and the substrate contacts and _gently_ pulling the paper out without bending the fingers. The method has been mentioned several times on this Forum. I do hope you haven't trashed a good 465B!
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of NigelP
Sent: 23 May 2019 17:25
To: TekScopes@groups.io
Subject: [TekScopes] 465B Attenuator servicing

I've just acquired a 465B in quite reasonable condition but there is a problem with CH2 attenuator. Essentially signals are not transferring from the BNC through to the input of the amplifier. Setting the attenuator to max sensitivity, where there SHOULD be a low resistance path of 75 ohms, shows as open circuit. With the attenuator still in situ I can see that the signal gets through to the first attenuator input switch but no further. It appears to be a lack of connection in the switch fingers although I can't actually see any visual problem with them.

So next is to remove the complete attenuator and have a good look at it; any suggestions/issues re getting just the one attenuator out as opposed to the "book" method of removing the complete CH1/2 input blocks plus mode switches? I'm hoping I can just undo the screws fixing the attenuator board to the cam block, and of course the two nuts fixing the whole to the front-panel.

I should say that at one point I had the channel working normally but after another good blast of IPA it went pear-shaped!!! I'm suspecting something somehow lodged in the switch-fingers but cannot see anything right now without a very close look.

Re: Procedure to measure rf watts

fiftythreebuick
 

Hi Randy-

Would it be alright to contact you off list about this?

Very 73

Tom AE5I

WTB 7L12 + S-6 + S-52

Kyle Rhodes
 

Watching the CuriousMarc YouTube channel has me wanted to setup a TDR rig
in a bad way...

I'm interested in purchasing a 7L12 along with a pulse generator and
sampling head, such as the S-6 and S-52.

I see a complete setup on eBay, but it's being sold as-is / untested. I
don't really want to risk that -- I'm going to presume it was tested, and
is bad...

Any help in finding a setup is appreciated!


Thanks,
Kyle

Re: Procedure to measure rf watts

Larry McDavid
 

Well, yes, but the whole point of interchangeable Bird slugs is to select one that measures your power near the top of the meter scale. That's one reason so many different slugs are available. You would never select a 10 Watt slug to measure a 1 Watt power. It is difficult to beat the ruggedness and reliability of the Bird watt meter.

When transporting the Bird watt meter, the meter movement should be damped by shorting its meter coil. That can be accomplished by removing the slug and inserting the solid aluminum slug provided. But, it is far easier to just rotate any slug 90° but leave it in-place. That simple solution is not always known...

Larry

On 5/23/2019 6:06 AM, Chuck Harris wrote:
The venerable bird wattmeter is really quite awful in terms of
accuracy. At its rated best, it is +/- 5% of full scale.
So, if you are using a 10W slug, its accuracy band is +/- 0.5W.
Ok, if you are measuring 10 W, but it gives you a 50% uncertainty
if you are measuring 1W.... 20% if you are measuring 5W.
Your scope can do much better than that.
-Chuck Harris

Dennis Tillman W7PF wrote:
Hi Randy,
How about a Bird Wattmeter. They are the first thing a ham thinks of ...
--
Best wishes,

Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)

Re: WTB 7L12 + S-6 + S-52

Jim Ford
 

Hi, Kyle. I think you want a 7S12, not a 7L12.  7S12 is the TDR/sampler.  The 7L12, while a desirable spectrum analyzer plug-in in its own right, won't get you TDR functionality. Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Kyle Rhodes <ksrhodes@...> Date: 5/23/19 9:48 AM (GMT-08:00) To: TekScopes@groups.io Subject: [TekScopes] WTB 7L12 + S-6 + S-52 Watching the CuriousMarc YouTube channel has me wanted to setup a TDR rigin a bad way...I'm interested in purchasing a 7L12 along with a pulse generator andsampling head, such as the S-6 and S-52.I see a complete setup on eBay, but it's being sold as-is / untested.  Idon't really want to risk that -- I'm going to presume it was tested, andis bad...Any help in finding a setup is appreciated!Thanks,Kyle

Re: WTB 7L12 + S-6 + S-52

Kyle Rhodes
 

Yes, sorry, that was a typo — I also already have a 7L12, which is a lot of fun! :)

On May 23, 2019, at 1:11 PM, Jim Ford <james.ford@...> wrote:

Hi, Kyle. I think you want a 7S12, not a 7L12. 7S12 is the TDR/sampler. The 7L12, while a desirable spectrum analyzer plug-in in its own right, won't get you TDR functionality. Jim Ford Sent from my Verizon, Samsung Galaxy smartphone
-------- Original message --------From: Kyle Rhodes <ksrhodes@...> Date: 5/23/19 9:48 AM (GMT-08:00) To: TekScopes@groups.io Subject: [TekScopes] WTB 7L12 + S-6 + S-52 Watching the CuriousMarc YouTube channel has me wanted to setup a TDR rigin a bad way...I'm interested in purchasing a 7L12 along with a pulse generator andsampling head, such as the S-6 and S-52.I see a complete setup on eBay, but it's being sold as-is / untested. Idon't really want to risk that -- I'm going to presume it was tested, andis bad...Any help in finding a setup is appreciated!Thanks,Kyle

Re: OT: App that keeps track of "Or Best Offer" auctions on eBay to tell you what a seller will accept.

Dave Seiter
 

While you can no longer get this info, you can usually get a ball park value by sorting the completed search list by $$$.  Sometimes there aren't enough results to get a reasonable value, but expanding the search parameters may get you within a few dollars.
-Dave

On Wednesday, May 22, 2019, 11:24:51 AM PDT, radioconnection@... <radioconnection@...> wrote:

At one time eBay posted the sale price for an accepted best offer.  I think they changed that, at least in the US listings.

I am not sure how a program can predict what a seller will accept since that info is no longer shown?

Re: Photo Storage Space Solution, was IMPORTANT: Photos are eating up our storage

Dave Daniel
 

Which groups.io group?

Sent from a small flat thingy

On May 23, 2019, at 12:24, TomC <tomc@...> wrote:

I'm pretty sure that the Arc files were transferred to the groups.io photo library.

Tom



On 5/23/2019 2:13 AM, Dave Daniel wrote:
I believe it is TekScopesArc, still on Yahoo.
DaveD
Sent from a small flat thingy
On May 23, 2019, at 02:28, Dennis Tillman W7PF <@Dennis_Tillman_W7PF> wrote:

Hi Harvey,
Not that I know of. You may be thinking of TekScopes2 and there was another one devoted to Tek Archives but the name escapes me. It may have been TekScopesArc or something like that.
Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Harvey White
Sent: Wednesday, May 22, 2019 4:24 PM
Subject: Re: [TekScopes] Photo Storage Space Solution, was IMPORTANT: Photos are eating up our storage

Didn't tekscopes have some other groups that were created solely for image storage back on Yahoo?
Harvey


On 5/22/2019 7:02 PM, nonIonizing EMF wrote:
I was wondering if moving the images and details related like including the link to the groups.io or other post to Tekwiki might be a solution. I'm not sure about the server limitations and expense there however.



--
Dennis Tillman W7PF
TekScopes Moderator



Re: WTB 7L12 + S-6 + S-52

Jim Ford
 

I bet!  Not quite as much fun as my HP 8566, but I have to hope the 8566 doesn't crap out someday.  Might be nice to have a 7L12 or 7L18 as a backup.Still, I hesitate to use a Tek spec an 25 years after being forced to use one (a real PITA).  HPAK spec ans rule, IMO.  If it weren't for the space and weight I would have several 8566's.JimSent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Kyle Rhodes <ksrhodes@...> Date: 5/23/19 10:25 AM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] WTB 7L12 + S-6 + S-52 Yes, sorry, that was a typo — I also already have a 7L12, which is a lot of fun! :)> On May 23, 2019, at 1:11 PM, Jim Ford <james.ford@...> wrote:> > Hi, Kyle. I think you want a 7S12, not a 7L12.  7S12 is the TDR/sampler.  The 7L12, while a desirable spectrum analyzer plug-in in its own right, won't get you TDR functionality. Jim Ford Sent from my Verizon, Samsung Galaxy smartphone> -------- Original message --------From: Kyle Rhodes <ksrhodes@...> Date: 5/23/19  9:48 AM  (GMT-08:00) To: TekScopes@groups.io Subject: [TekScopes] WTB 7L12 + S-6 + S-52 Watching the CuriousMarc YouTube channel has me wanted to setup a TDR rigin a bad way...I'm interested in purchasing a 7L12 along with a pulse generator andsampling head, such as the S-6 and S-52.I see a complete setup on eBay, but it's being sold as-is / untested.  Idon't really want to risk that -- I'm going to presume it was tested, andis bad...Any help in finding a setup is appreciated!Thanks,Kyle> >

Re: WTB 7L12 + S-6 + S-52

Kyle Rhodes
 

As luck would have it — I just plugged in my 7L12 and got the dreaded click of death...pulled the unit and it let the smoke out somewhere inside. Ugh!!

On May 23, 2019, at 1:42 PM, Jim Ford <james.ford@...> wrote:

I bet! Not quite as much fun as my HP 8566, but I have to hope the 8566 doesn't crap out someday. Might be nice to have a 7L12 or 7L18 as a backup.Still, I hesitate to use a Tek spec an 25 years after being forced to use one (a real PITA). HPAK spec ans rule, IMO. If it weren't for the space and weight I would have several 8566's.JimSent from my Verizon, Samsung Galaxy smartphone
-------- Original message --------From: Kyle Rhodes <ksrhodes@...> Date: 5/23/19 10:25 AM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] WTB 7L12 + S-6 + S-52 Yes, sorry, that was a typo — I also already have a 7L12, which is a lot of fun! :)> On May 23, 2019, at 1:11 PM, Jim Ford <james.ford@...> wrote:> > Hi, Kyle. I think you want a 7S12, not a 7L12. 7S12 is the TDR/sampler. The 7L12, while a desirable spectrum analyzer plug-in in its own right, won't get you TDR functionality. Jim Ford Sent from my Verizon, Samsung Galaxy smartphone> -------- Original message --------From: Kyle Rhodes <ksrhodes@...> Date: 5/23/19 9:48 AM (GMT-08:00) To: TekScopes@groups.io Subject: [TekScopes] WTB 7L12 + S-6 + S-52 Watching the CuriousMarc YouTube channel has me wanted to setup a TDR rigin a bad way...I'm interested in purchasing a 7L12 along with a pulse generator andsampling head, such as the S-6 and S-52.I see a complete setup on eBay, but it's being sold as-is / untested. Idon't really want to risk that -- I'm going to presume it was tested, andis bad...Any help in finding a setup is appreciated!Thanks,Kyle> >

Re: WTB 7L12 + S-6 + S-52

Bill (Doc) Courtright
 

Kyle,I am in a similar quandary. Awhile back when setting up a new bench space I powered up the 7623A that my 7L12 resided in and the MF supply went into tic mode. Pulled the SA and the MF came up fine with normal H/V PI's in. Found that the negative bipolar line was shorted somewhere deep inside the 7L12. Well it still sits on the shelf. I am betting on the typical shorted tantalum but to dismantle far enough to get to the module where it resides and re-assemble it properly close to calibration looks nearly impossible. I will take a chance some day.Bill

-----Original Message-----
From: Kyle Rhodes <ksrhodes@...>
To: TekScopes <TekScopes@groups.io>
Sent: Thu, May 23, 2019 1:53 pm
Subject: Re: [TekScopes] WTB 7L12 + S-6 + S-52

As luck would have it — I just plugged in my 7L12 and got the dreaded click of death...pulled the unit and it let the smoke out somewhere inside. Ugh!!



On May 23, 2019, at 1:42 PM, Jim Ford <james.ford@...> wrote:

I bet!  Not quite as much fun as my HP 8566, but I have to hope the 8566 doesn't crap out someday.  Might be nice to have a 7L12 or 7L18 as a backup.Still, I hesitate to use a Tek spec an 25 years after being forced to use one (a real PITA).  HPAK spec ans rule, IMO.  If it weren't for the space and weight I would have several 8566's.JimSent from my Verizon, Samsung Galaxy smartphone
-------- Original message --------From: Kyle Rhodes <ksrhodes@...> Date: 5/23/19  10:25 AM  (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] WTB 7L12 + S-6 + S-52 Yes, sorry, that was a typo — I also already have a 7L12, which is a lot of fun! :)> On May 23, 2019, at 1:11 PM, Jim Ford <james.ford@...> wrote:> > Hi, Kyle. I think you want a 7S12, not a 7L12.  7S12 is the TDR/sampler.  The 7L12, while a desirable spectrum analyzer plug-in in its own right, won't get you TDR functionality. Jim Ford Sent from my Verizon, Samsung Galaxy smartphone> -------- Original message --------From: Kyle Rhodes <ksrhodes@...> Date: 5/23/19  9:48 AM  (GMT-08:00) To: TekScopes@groups.io Subject: [TekScopes] WTB 7L12 + S-6 + S-52 Watching the CuriousMarc YouTube channel has me wanted to setup a TDR rigin a bad way...I'm interested in purchasing a 7L12 along with a pulse generator andsampling head, such as the S-6 and S-52.I see a complete setup on eBay, but it's being sold as-is / untested.  Idon't really want to risk that -- I'm going to presume it was tested, andis bad...Any help in finding a setup is appreciated!Thanks,Kyle> >

Re: Photo Storage Space Solution, was IMPORTANT: Photos are eating up our storage

Polaraligned
 

Can you post pictures on groups.io via 3rd party hosting (like imgur) and have them show without having to click on a link for them?

Scott

Re: Old Tektronix Books

treasurer@...
 

Someone in my copy of Typical Scope Circuitry ( Third printing October 1966 revision - forth printing 1968 ) has neatly indicated the scope models on the schematics. Figure 12-20 is marked 531 CRT circuit which agrees with the manual. Figure 12-16 is 531A & 545A. 11-3 is marked 531A. Figure 11-8 is 531A & 545A. 11-12 is 531A & 545A. I didn't verify the A scope versions. The spine of the book has the squared CRT in the logo whilst the front page has the round CRT in logo. When did they begin using the new logo?
Bruce

Craigslist- Northern Virginia Tek 545B for sale

 

Craigslist Northern Virginia (specifically- Lorton VA) advertising a Tektronix 545B with a plugin unit for $100. Possibly in working condition; not clear (to me) if the price includes the scope cart (shown in the Craigslist ad) or the probe(s) (also shown in the ad), but someone here might be interested. I would consider it myself except that I have no room left in my basement, and my back would suffer dearly from moving such a beast. I have no affiliation with the seller: <https://washingtondc.craigslist.org/nva/ele/d/oscilloscope/6893855462.html>

Mike Dinolfo N4MWP

Re: Craigslist- Northern Virginia Tek 545B for sale

Brenda
 

I would love to have that scope as well, but too far away and looks like the CRT has seen better days with the 2 rather nasty burn ins. Hopefully the HV transformer is decent and not lossy as I have read in other posts.

Isolation???

Mike Harmon
 

I'm working on an old Motorola power supply. One of the adjustment steps says to connect a scope between the positive DC output terminal and a +41V test point inside the power supply, and look at the waveform. I have a 7904A with 7A26 vertical plugins. The problem is that whichever point I connect the common probe lead to is going to be taken to chassis (earth) ground! I'm not comfortable with lifting the scope chassis above ground by disconnecting the ground wire at the AC input.

I think I have an old A6902 Isolator unit somewhere in the dungeon that someone stole the probes from. As I recall, the only thing in the side bage is the pigtails coming out of the isolator to connect the probes to. Would it make sense to just connect a standard scope probe to the pigtail(s) and feed the isolator to the scope's vertical input?. I guess I'd have to install a BNC female connector on the end of the pigtails. Getting the correct probes for the isolator would cost more than the isolator is worth. I've had it for years and this is the first time I've thought of trying to use it!

Is this a crazy idea? Does anyone have a better (safer) way to measure the differential waveform?

Thanks for the help!!
Mike Harmon, WB0LDJ
mharmon at att dot net

Tektronix 564 WW resistor for -100V supply

Brenda
 

HI everyone! I thought I would take my 564 out and see what I possibly do to get the storage section of the CRT working again. I fired up the scope and only to find that absolutely nothing worked. I measured all the low voltage supplies and they are all severely off. The -100V was reading -77, and with that, decided to check everything in the -100V circuit. All of the resistors were still in tolerance except for R617 which is an 80K WW 1W resistor and it was completely open. The brand of the resistor is Reon. I am wondering if any 80K resistor would work in it's place as long as the wattage is greater than 1W and is within the 1% tolerance spec? Or does it have to be a WW resistor?

Brenda