Date   
Re: HV Probe?

Chuck Harris
 

I keep 3 pieces of Sencore gear in my shop:

1) LC-102 Capacitor/inductor tester.
2) CR-70 CRT rejuvinator.
3) VR-62A Universal Video analyzer tester.

The VA62 happened when I was testing a lot of TV's, and
needed an easy way, and it was. Over time, its reference
xtal drifted out of range of adjustment, and really should
have been replaced, but I just added more capacitance... or
did I remove capacitance? I can't remember. I only still
have it because I didn't get rid of it at a good time.
I just can't bring myself to sell it for $35.

The capacitor tester is the most useful of anything of theirs
I have owned. It still owns some bench space.

-Chuck Harris

Bert Haskins bhaskins@... [TekScopes] wrote:



On 10/8/2017 1:12 PM, Barry n4buq@... [TekScopes] wrote:

Of course, and you can also string together a few dozen
1 or 2M 2W resistors....and so I have.

I think in general, it would be smarter to buy the right
probe for the meter you have.

Stuff that was made for TV repair is usually the absolute
minimum that will work for the job. TV's weren't exactly
demanding patients.

-Chuck Harris
I bought an HP 459A a few years ago intending to use it with my HP
410B/C; however, the resistor in it is broken.

Surprised at the comments regarding Sencore. I've not owned any of
their equipment, but thought it was better built than what I'm hearing.

Yeah, I've seen the built-in style meter/probes and definitely didn't
think those were very good for what I'd like to have.

Guess I'll keep looking for probe that matches with one or more of my
meters.

Thanks again,
Barry - N4BUQ
Well, I have owned/used several of the Sencore FE series Fet VOMs and on
occasion was able to have them cal checked by departments that were
doing calibration work fo NASA.
They were always within the published specs and were quite well made.
I still own two of these and have the high voltage probe for them.
I have several Tek meters also and cross check between them quite often.
I cannot vouch for all of their other stuff but my meters are good
pieces of gear.
Bert

Re: HV Probe?

Ed Breya
 

There is no need to worry about "matching" a HVDC probe to any particular meter. As long as you know what the top resistor value is, and the input R of the meter, you can figure out simple resistor scaling at the bottom end to get the right numerical readout. You don't even have to do that much if you just do a little math to scale it. Anyone who can tear into a scope can rig up the right fix for any situation.

You can usually know the top resistor value from the probe specs if available, or by unscrewing the probe tip assembly from the base, exposing the big R, which will typically be marked. Some probes have a clear tip, and you can see the resistor and label directly.

It's also not good to rely on having a particular meter always available to go with a given probe. Keep your options open, especially on things that only have occasional use.

BTW I have a couple of old Sencore instruments, and yes, they are "inferior" to the Teks and HPs and Flukes we are used to. So are the other lesser brands like B&K and Hikock, et al. They were aimed at different markets and prices, so shouldn't be expected to compare well with the old high grade pre-owned stuff that we typically acquire nowadays for pennies on the dollar - this spoils our perception.

Ed

Re: HV Probe?

Bert Haskins
 

On 10/8/2017 1:12 PM, Barry n4buq@... [TekScopes] wrote:

Of course, and you can also string together a few dozen
1 or 2M 2W resistors....and so I have.

I think in general, it would be smarter to buy the right
probe for the meter you have.

Stuff that was made for TV repair is usually the absolute
minimum that will work for the job. TV's weren't exactly
demanding patients.

-Chuck Harris
I bought an HP 459A a few years ago intending to use it with my HP
410B/C; however, the resistor in it is broken.

Surprised at the comments regarding Sencore. I've not owned any of
their equipment, but thought it was better built than what I'm hearing.

Yeah, I've seen the built-in style meter/probes and definitely didn't
think those were very good for what I'd like to have.

Guess I'll keep looking for probe that matches with one or more of my
meters.

Thanks again,
Barry - N4BUQ
Well, I have owned/used several of the Sencore FE series Fet VOMs and on
occasion was able to have them cal checked by departments that were
doing calibration work fo NASA.
They were always within the published specs and were quite well made.
I still own two of these and have the high voltage probe for them.
I have several Tek meters also and cross check between them quite often.
I cannot vouch for all of their other stuff but my meters are good
pieces of gear.
Bert










Re: NVRAM rework of later (RoHS) Tek scopes

Chuck Harris
 

The Dallas NVRAM won't read or write if the internal cell
is too low in voltage. Because of a leakage path between
the 5V and the internal cell, it is possible to charge the
lithium cell slightly, and very slowly when power is applied
to the part.

-Chuck Harris

erkka.sointula@... [TekScopes] wrote:


My experience of Dallas NVRAM or other through-pin part removal from later Tek models (my -05 TDS7404B) using lead-less solder.

I tried multiple suction tools without success.
The final working solution was to use air compressor and sand blasting handle (overkill? but had them)
The sand input was connected to my Weller suction tool.
Operating steps:
- remove first with the suction tool as much as possible solder from the pins/holes.
- add with soldering iron leaded solder to the pins/holes to soften the solder joint.
- keep std soldering iron and the sand blaster handle in the other hand and the suction iron in the other.
- heat the pins/holes well with the soldering iron
- immediately suck solder out with the suction tool by moving the nozzle around the pins for 3...5 sec.
- push now the sand blaster nozzle against a rubber sheet closing the nozzle and reverting the airflow to go out from the suction nozzle. The remaining solder will now blow out to the other side (and under the circuit).

The PCB around the removed part needs to shielded on both sides of the PCB to avoid solder flakes making shorts.
The removed part and PCB under it will have solder shorts > good cleaning is absolutely necessary.
In my case the ground and Vcc pin holes did not clear up, I heated them up one by one with iron and dragged the part out, but lost Vcc pin. I then used my Dremel tool to dig out the contact point on the Dallas part and soldered new pin.

When I first read the content on the NVRAM I got random data, few ours later with some errors,
Kept Vcc on and the next day NO ERRORS. Why? Maybe the battery voltage or something else changed due to the heat or Vcc charged the battery a bit?

Re: Successful restoration of 564B and 3L5, now looking for 7L5

David Holland
 

Hey,

(Been traveling the last few weeks and not had time to read much mail.
Fortunately, it appears some other folks appear to have been able to chime
in..)

Sounds like there should be a 4th manual version out there somewhere, go
figure...

<snippage>

Did you, by any chance, measure the shape factors of RBW settings of your
3L5?
No, but honestly, I don't claim to entirely know entirely what I'm doing...
:-}

I've very little "use" for my equipment. I mostly fix radios/TVs, and
SpecAn's generally aren't needed.....

Re: HV Probe?

Joe Laffey
 

Not sure how high voltage of a probe you need, but Fluke makes some great ones you can get reasonably priced on eBay sometimes. I got their 5KV model for around $28 delivered last year. Safe, reliable, accurate.


--
Joe Laffey
K0OKS

On Oct 8, 2017, at 12:12 PM, Barry n4buq@... [TekScopes] <TekScopes@...> wrote:

Of course, and you can also string together a few dozen
1 or 2M 2W resistors....and so I have.

I think in general, it would be smarter to buy the right
probe for the meter you have.

Stuff that was made for TV repair is usually the absolute
minimum that will work for the job. TV's weren't exactly
demanding patients.

-Chuck Harris
I bought an HP 459A a few years ago intending to use it with my HP 410B/C; however, the resistor in it is broken.

Surprised at the comments regarding Sencore. I've not owned any of their equipment, but thought it was better built than what I'm hearing.

Yeah, I've seen the built-in style meter/probes and definitely didn't think those were very good for what I'd like to have.

Guess I'll keep looking for probe that matches with one or more of my meters.

Thanks again,
Barry - N4BUQ

[Non-text portions of this message have been removed]

Re: HV Probe?

n4buq
 

Good Day,
my 2€- cent ' s worth advice: Go for a Simpson HV Probe. Reliable and known
for quality for decades. Look for a NOS or rarely used one on epay etc.
Cheers,
Magnus
Is there a particular model you'd recommend?

Thanks,
Barry - N4BUQ

Re: HV Probe?

n4buq
 

Of course, and you can also string together a few dozen
1 or 2M 2W resistors....and so I have.

I think in general, it would be smarter to buy the right
probe for the meter you have.

Stuff that was made for TV repair is usually the absolute
minimum that will work for the job. TV's weren't exactly
demanding patients.

-Chuck Harris
I bought an HP 459A a few years ago intending to use it with my HP 410B/C; however, the resistor in it is broken.

Surprised at the comments regarding Sencore. I've not owned any of their equipment, but thought it was better built than what I'm hearing.

Yeah, I've seen the built-in style meter/probes and definitely didn't think those were very good for what I'd like to have.

Guess I'll keep looking for probe that matches with one or more of my meters.

Thanks again,
Barry - N4BUQ

Re: Thank you, and question about a very unusual CRT

 

Hi Håkan,
Interesting theory. I know who invented the method used to do the enhanced accuracy of the 11K. He got a patent for it. I will ask him about the CRT.
Dennis Tillman W7PF

-----Original Message-----
Sent: Sunday, October 08, 2017 3:27 AM
Subject: RE: [TekScopes] Re: Thank you, and question about a very unusual CRT

This doesn't make sense to me since the construction of the CRT gun is so weird.
Dennis,


Both the 11301, 11301A manuals and the micro fiche says it's right.

When the analog 11k's do EA (Enhanced Accuracy) one part is adjusting the gains to match the graticule.
They way they do that vertically is to generate two short horizontal traces, about one div in length,
and separated vertically by a small gap then moving the pair slowly up and down across the first and
then the last graticule lines. The scope detects when the pair crosses the lines and adjusts the gain
after that info. Same thing is done horizontally but with vertical traces and on graticule lines 2 and 10.
Maybe/probably that sensing feature requires some odd stuff in the CRT.

/Håkan
------------------------------------
Posted by: hahi@...
------------------------------------

Re: Thank you, and question about a very unusual CRT

 

Hi Dave,
No, I don't think that is correct. According to the catalog the 400MHz 11301 is an ordinary CRT. You are probably thinking of the 500MHz 11302 which is a MCP CRT.

We thought the tube we had might be a MCP at first but it quickly became clear it wasn't. There was no provision for the necessary bias voltages on the front of the CRT that the MCP needed.

Dennis Tillman W7PF

-----Original Message-----
Sent: Sunday, October 08, 2017 3:31 AM
Subject: Re: [TekScopes] Re: Thank you, and question about a very unusual CRT

On 8 Oct 2017, at 11:26, hahi@... [TekScopes] <TekScopes@...> wrote:

This doesn't make sense to me since the construction of the CRT gun is so weird.
Dennis,

Both the 11301, 11301A manuals and the micro fiche says it's right.
It’s a Micro-Channel Plate (MCP) CRT, so that adds some interesting structures to the gun.
------------------------------------
Posted by: Dave Voorhis <voorhis@...>
------------------------------------

Re: NVRAM rework of later (RoHS) Tek scopes

stefan_trethan
 

There are venturi style vacuum generators (using compressed air) that
work on the same principle as your sand blaster. SMC makes them and
others. They create a surprisingly good vacuum (approx. -0.8 bar, 80%
of atmosphere). The advantage over mechanical pumps is that the vacuum
is applied instantly (very important to suck the solder before the
airstream cools it). They are also quieter (once exhaust mufflers are
fitted) than many mechanical pumps and have nothing to go wrong
inside.

It would stand to reason that compressed air has the capability of
blowing out more solder than vacuum does, because you are not limited
to one atmosphere. But in 99% of cases the regular desoldering
stations work fine for me if one follows the steps you described with
fresh solder etc.

ST

On Sun, Oct 8, 2017 at 4:39 PM, erkka.sointula@... [TekScopes]
<TekScopes@...> wrote:

My experience of Dallas NVRAM or other through-pin part removal from later Tek models (my -05 TDS7404B) using lead-less solder.

I tried multiple suction tools without success.
The final working solution was to use air compressor and sand blasting handle (overkill? but had them)
The sand input was connected to my Weller suction tool.
Operating steps:
- remove first with the suction tool as much as possible solder from the pins/holes.
- add with soldering iron leaded solder to the pins/holes to soften the solder joint.
- keep std soldering iron and the sand blaster handle in the other hand and the suction iron in the other.
- heat the pins/holes well with the soldering iron
- immediately suck solder out with the suction tool by moving the nozzle around the pins for 3...5 sec.
- push now the sand blaster nozzle against a rubber sheet closing the nozzle and reverting the airflow to go out from the suction nozzle. The remaining solder will now blow out to the other side (and under the circuit).

The PCB around the removed part needs to shielded on both sides of the PCB to avoid solder flakes making shorts.
The removed part and PCB under it will have solder shorts > good cleaning is absolutely necessary.
In my case the ground and Vcc pin holes did not clear up, I heated them up one by one with iron and dragged the part out, but lost Vcc pin. I then used my Dremel tool to dig out the contact point on the Dallas part and soldered new pin.

When I first read the content on the NVRAM I got random data, few ours later with some errors,
Kept Vcc on and the next day NO ERRORS. Why? Maybe the battery voltage or something else changed due to the heat or Vcc charged the battery a bit?





------------------------------------
Posted by: erkka.sointula@...
------------------------------------


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

Yahoo Groups Links


Re: Thank you, and question about a very unusual CRT

Dave Voorhis
 

Yup, sure enough. Apologies for wrongness.

On 8 Oct 2017, at 12:24, hahi@... [TekScopes] <TekScopes@...> wrote:

It’s a Micro-Channel Plate (MCP) CRT
11302 / 11320A are MCP, 11301 / 11301A are not.

/Håkan


[Non-text portions of this message have been removed]

NVRAM rework of later (RoHS) Tek scopes

Erkka Sointula
 

My experience of Dallas NVRAM or other through-pin part removal from later Tek models (my -05 TDS7404B) using lead-less solder.

I tried multiple suction tools without success.
The final working solution was to use air compressor and sand blasting handle (overkill? but had them)
The sand input was connected to my Weller suction tool.
Operating steps:
- remove first with the suction tool as much as possible solder from the pins/holes.
- add with soldering iron leaded solder to the pins/holes to soften the solder joint.
- keep std soldering iron and the sand blaster handle in the other hand and the suction iron in the other.
- heat the pins/holes well with the soldering iron
- immediately suck solder out with the suction tool by moving the nozzle around the pins for 3...5 sec.
- push now the sand blaster nozzle against a rubber sheet closing the nozzle and reverting the airflow to go out from the suction nozzle. The remaining solder will now blow out to the other side (and under the circuit).

The PCB around the removed part needs to shielded on both sides of the PCB to avoid solder flakes making shorts.
The removed part and PCB under it will have solder shorts > good cleaning is absolutely necessary.
In my case the ground and Vcc pin holes did not clear up, I heated them up one by one with iron and dragged the part out, but lost Vcc pin. I then used my Dremel tool to dig out the contact point on the Dallas part and soldered new pin.

When I first read the content on the NVRAM I got random data, few ours later with some errors,
Kept Vcc on and the next day NO ERRORS. Why? Maybe the battery voltage or something else changed due to the heat or Vcc charged the battery a bit?

Re: Need Advice on a good used shop scope

Harvey White
 

On Sun, 8 Oct 2017 06:59:10 +0200, you wrote:

I agree completely.

Just to clarify, what I meant with "real work" was the opposite of "playing".
When I am in the midst of working on some problem, no matter if day
job or personal, I do not want to deal with the distraction of an
analog scope.
I personally don't find them distracting, but then again, that's me.

Using the digital scope is just so much easier and quicker for me.
Analog is fine when the problem is simple, and I have time to "play",
although I still prefer the 7D20 even then.
I need to fix my 7D20.


Even basic things like storing a trace for reference, that is one
press of a button on a digital scope and I get a nice trace that I can
move around, maybe even zoom in and stuff, in a different color to
tell them apart. On the analog storage scope it needs some fussing
around, and significantly more prior planning.
The other day I was working on a LED lamp and quickly threw a math
trace on the screen that shows power, just two examples where a
digital scope makes your life really easy.
Mine is (sadly) monochrome. Anyone know how to make a TDS540A output
color? External VGA would be fine.




When I am concentrating on a problem and having trouble to even
provoke the event I want to look at the tool should be as efficient
and simple to use as possible, while offering as much capability as
possible.

Of course it depends on what you are used to also. I only got analog
scopes because that was all I could afford at the time, not because it
was all I wanted. If the cheap but somewhat functional scopes like
Rigol etc. would have been around back then I might never have gotten
into Tek stuff, and might not have learned so much, and might not even
know you all.
I got into analog scopes because there were no digital scopes. Got
into digital scopes with a 2430A, then the TDS540A, with a side trip
to the 7D20 which is not fully functional, and a pair of 468's.




There are people, like Arthur Seibt of Tek fame, that go around
claiming analog scopes are superior and you can not even do switchmode
power supply work with a digital scope. Well, frankly, that's
nonsense. Virtually everyone has learned to cope with the few
disadvantages of digital in order to benefit from the vast advantages.
The market reflects this, I think there are only a couple Chinese
firms left that even manufacture analog scopes.
Digital scopes are ultimately cheaper to make. Once you solve the
front end/digitizing part of it, the rest is a computer and software.
Compare that to the internal complexity and design of a 7904 or a
7104.

Perhaps the pros and cons of analog and digital may be expressed as
follows:

analog pros: inexpensive, parts may be available, continuous and not
sampling, any transient may be seen (emphasis may), HF rolloff not
sharply limited. A number of these on the used market. 7000 series
is incredibly versatile.

analog cons: lack of math functions, 4 channels at the most, mostly
monochrome, may or may not have readouts, large (7000 series), missing
many of the convenience functions found on digital scopes. Using
digital logic pushes the user into getting a logic analyzer. some
custom parts are difficult to find.

Digital pros: convenience functions, math functions, storage,
effectively higher bandwidth in some cases. Size, potentially color,
newer technology.

Digital cons: sampling mode. (no idea of what happens between
samples), likely no chips are available for replacement. Dependence
on an operating system internally (custom or windows likely), possibly
cost especially for newer oscilloscopes.

Skill sets vary somewhat between types in terms of what you need to
know to run them. My favorite analog setup is a 7904 with 7a26/24,
7D12 with voltage sampling, 7d15 counter, and 7D92A timebase. The
TDS540A will do this, but is equally fussy about some setups. For
portable, I'd go with the 468.


Perhaps the best advise is any scope is a whole lot better than no scope.
Go and pick up whatever you can find and strikes your fancy. Because I
don't think we are _meant_ to avoid the collection of mostly useless
scopes that mostly sit around idle, it's all part of the process.
Well, the storage scope and the 7104 sit around. The 7104 due to CRT
life and specialized use. I pull out the stuff I need when I need it.
That's my story, sticking to it.....

Harvey


ST


On Sun, Oct 8, 2017 at 12:25 AM, Harvey White madyn@...
[TekScopes] <TekScopes@...> wrote:
On Sat, 7 Oct 2017 20:23:32 +0200, you wrote:

Given that this old stuff is now dirt cheap, you can just go with the
best, and that is a 7000 series in my opinion.
If you have the bench space and don't need portability it's really
hard to beat, and even takes a 7D20 plugin for some basic digital
scope functionality.
7D20's are not cheap, not that I've found. Correct about the
capability, though.


That said, personally I could not imagine using an analog scope for
real work every day.
Actually, I could. It depends *very* much what you define as real
work (as opposed to unreal?).

If you're not dealing with much that's digital, then you really don't
need a digital scope. The sharply tuned input filters that are needed
to avoid anti-aliasing limit the bandwidth, while analog scopes just
roll off gracefully.

You need not worry about sampling rates, either. You get everything,
and not just what's happening at the sample points.

On the other hand, if you want to look at steady representations of
low rep rate stuff, digital is your friend, otherwise you need a
storage scope.

Even with an extremely limited budget there are now cheap crappy
Chinese scopes and they often beat an analog scope in terms of
useability.
If you're dealing with an analog scope trying to decode a digital data
stream, then yes.

it all depends on what you mean by useable, and for what purpose.

Sure there are always points where the analog scope is superior
(bandwidth, noise, repairability, etc..) but my analog scopes see
practically zero use these days.
and I typically spend time with both digital scopes (TDS540A), analog
(7000 series), and the HP Logic analyzer (16702B). Then again, it
very much depends on what I need to see and why.


Since you work with vacuum tube gear I expect you have significant
experience with analog scopes and might find them more practical than
I do.
I'd agree with this. If he finds something that an analog scope won't
do (typically, for me, related to storage and not necessarily related
to data decoding), then a digital scope can be recommended. the 468
is both, within some limitations. The digital section is pretty much
independent of the analog section.

(Except that you need the digital section to control the analog
section in certain aspects, I think.)

Harvey




ST

On Sat, Oct 7, 2017 at 7:27 PM, pdulaff@... [TekScopes]
<TekScopes@...> wrote:
Hello


I am Paul, WB2NMI. I am looking for recommendations on good affordable used scopes for my home shop. I work on vacuum tube and solid state amateur gear. Something like the 465/475 scopes make sense but there are these combo digital/analog scopes that maybe add additional versatility, but I don't have experience with digital scopes. I would like to buy used and keep the scope affordable and am willing to repair the scope provided parts and documentation are available.


Let me know your thoughts.


Paul - WB2NMI








------------------------------------
Posted by: pdulaff@...
------------------------------------


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

Yahoo Groups Links




------------------------------------
Posted by: Harvey White <madyn@...>
------------------------------------


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

Yahoo Groups Links


Re: HV Probe?

Chuck Harris
 

Of course, and you can also string together a few dozen
1 or 2M 2W resistors....and so I have.

I think in general, it would be smarter to buy the right
probe for the meter you have.

Stuff that was made for TV repair is usually the absolute
minimum that will work for the job. TV's weren't exactly
demanding patients.

-Chuck Harris

'Michael A. Terrell' mike.terrell@... [TekScopes] wrote:

You can modify a TV HV probe to negative by reversing the leads on the meter movement, or by adding a small full wave bridge at the meter movement. Then it will display either polarity without a switch.

-----Original Message-----
From: "Bob Albert bob91343@... [TekScopes]" <TekScopes@...>
Sent: Oct 8, 2017 12:28 AM
To: "TekScopes@..." <TekScopes@...>
Subject: Re: [TekScopes] HV Probe?

My opinion of Sencore is with Chuck's. I do have a transistor tester of theirs. Not user friendly and screams CHEAP at you. I have always found their advertising objectionable.
Bob


On Saturday, October 7, 2017 9:24 PM, "Chuck Harris cfharris@... [TekScopes]" <TekScopes@...> wrote:


Sencore was their own standard. They built things their
way, and convinced the TV repair world they were better than
all the rest. If you ever get inside of one of their instruments,
you will not be impressed... more like MFJ inside.

I would not buy their probe unless you already... had their meter.

Get a fluke, or Keithley. Be mindful of the intended output
impedance, it will be probably be 10M or 20M.

Don't let your meter be in autorange, and connect the ground clip
before the HV. Autoranging into a 200M impedance 2V scale won't
be amusing.

Under no circumstances buy one of the probes that has a little
mechanical movement meter built in. They are positive voltage
only... and are meant for TV's.

-Chuck Harris

Re: HV Probe?

Harvey White
 

On Sun, 8 Oct 2017 04:35:49 +0000 (UTC), you wrote:

They were big enough to have an art department?
Same guy who did the wiring?

Harvey



On Saturday, October 7, 2017 9:33 PM, "Vince Vielhaber vev@... [TekScopes]" <TekScopes@...> wrote:


� Their advertising is priceless. I once got an ad in the mail for their
freq counter. The ad went on and on about how good it is in high rf
environments. The reading on the display was in the 220 ham band, the
supposed source of that reading was a 2 meter hand held. Huh? So I
called them to ask WTF. They told me they were in a high rf environment
and couldn't get a stable reading so the art dept put the freq in for
the ad!

Vince.

On 10/08/2017 12:28 AM, Bob Albert bob91343@... [TekScopes] wrote:


My opinion of Sencore is with Chuck's. I do have a transistor tester of
theirs. Not user friendly and screams CHEAP at you. I have always
found their advertising objectionable.
Bob


On Saturday, October 7, 2017 9:24 PM, "Chuck Harris cfharris@...
[TekScopes]" <TekScopes@...> wrote:


Sencore was their own standard. They built things their
way, and convinced the TV repair world they were better than
all the rest. If you ever get inside of one of their instruments,
you will not be impressed... more like MFJ inside.

I would not buy their probe unless you already... had their meter.

Get a fluke, or Keithley. Be mindful of the intended output
impedance, it will be probably be 10M or 20M.

Don't let your meter be in autorange, and connect the ground clip
before the HV. Autoranging into a 200M impedance 2V scale won't
be amusing.

Under no circumstances buy one of the probes that has a little
mechanical movement meter built in. They are positive voltage
only... and are meant for TV's.

-Chuck Harris

Barry n4buq@... [TekScopes] wrote:
Given my recent/ongoing trials with HV issues in my 465M, I'm
considering getting a good HV probe.

Is anyone familiar with the Sencore 39A19 as shown in the following
eBay ad? I've looked for info on it and haven't found much. I don't
quite understand how it is connected, etc., nor do I know whether it's
decent quality probe. I think Sencore makes/made pretty high quality
gear so am assuming this would be a good probe.

Anyone know about it?

http://www.ebay.com/itm//202071277710

Thanks,
Barry - N4BUQ
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Re: Thank you, and question about a very unusual CRT

 

11302 / 11320A are
Typo, 11320A should off course be 11302A

/Håkan

Re: Thank you, and question about a very unusual CRT

 

It’s a Micro-Channel Plate (MCP) CRT
11302 / 11320A are MCP, 11301 / 11301A are not.

/Håkan

Re: Thank you, and question about a very unusual CRT

Dave Voorhis
 

On 8 Oct 2017, at 11:26, hahi@... [TekScopes] <TekScopes@...> wrote:


This doesn't make sense to me since the construction of the CRT gun is so weird.
Dennis,

Both the 11301, 11301A manuals and the micro fiche says it's right.
It’s a Micro-Channel Plate (MCP) CRT, so that adds some interesting structures to the gun.



[Non-text portions of this message have been removed]

Re: Thank you, and question about a very unusual CRT

 

This doesn't make sense to me since the construction of the CRT gun is so weird.
Dennis,

Both the 11301, 11301A manuals and the micro fiche says it's right.

When the analog 11k's do EA (Enhanced Accuracy) one part is adjusting the gains to match the graticule.
They way they do that vertically is to generate two short horizontal traces, about one div in length,
and separated vertically by a small gap then moving the pair slowly up and down across the first and
then the last graticule lines. The scope detects when the pair crosses the lines and adjusts the gain
after that info. Same thing is done horizontally but with vertical traces and on graticule lines 2 and 10.
Maybe/probably that sensing feature requires some odd stuff in the CRT.

/Håkan