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Re: 465 B sweep switch cam

 

I just successfully 3D Printed the little plastic part and am about to reassemble the "B" switch cam. It was an easy enough print, does not require extreme precision. I was able to get the dimensions by carefully measuring the fragments of the old part and the cam itself.. I will post how this went after I am done and can provide the STL file and printing instructions for anyone who cares to try this part.

--
Michael Lynch
Dardanelle, AR
Re: 2440 for sale

 

500Msamples/s


-----Mensaje original-----
De: [email protected] [mailto:[email protected]] En nombre de David Templeton
Enviado el: lunes, 21 de marzo de 2022 7:57
Para: [email protected]
Asunto: Re: [TekScopes] 2440 for sale

Just curious, what is the single shot bandwidth on that scope?

David

On 21 Mar 2022, at 06:31, Bob Albert via groups.io <bob91343@...> wrote:

?I changed my mind. I think I'll keep the scope.

Bob
Re: 7904 - NOS CRT ?

 

There have been multiple discussions here on the topic, with no definite conclusions. But perhaps the best discussion was a couple of years ago. Search for ¡°mechanism of double peaking¡± AND¡¯ed with ¡°updated¡±.

Cheers
Tom

Sent from my iThing; please forgive the typos and brevity

On Mar 21, 2022, at 11:19, David Templeton <vexorg.calibra@...> wrote:

?So what physically inside the tube cause it to dim then go brighter again

David

On 21 Mar 2022, at 17:55, n4buq <n4buq@...> wrote:

?Mark,

Okay - that makes better sense in that the brightness peaks twice.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Mark Vincent" <orangeglowaudio@...>
To: "tekscopes" <[email protected]>
Sent: Monday, March 21, 2022 11:58:27 AM
Subject: Re: [TekScopes] 7904 - NOS CRT ?
Barry,

What you seeing is a good tube. At high brightness, the phosphour is being
struck with a large amount of electrons exciting the phosphour around the ones
being struck causing them to glow. Double-peaking is when the tube is weak and
the brightness will be fair, low then fair again as the intensity is from low
to max. The focus is usually out not matter the position of the focus control.
The tube will also be slow to show a trace when turned on.

Mark
Re: 7904 - NOS CRT ?

 

Mark,

Okay - that makes better sense in that the brightness peaks twice.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Mark Vincent" <orangeglowaudio@...>
To: "tekscopes" <[email protected]>
Sent: Monday, March 21, 2022 11:58:27 AM
Subject: Re: [TekScopes] 7904 - NOS CRT ?
Barry,

What you seeing is a good tube. At high brightness, the phosphour is being
struck with a large amount of electrons exciting the phosphour around the ones
being struck causing them to glow. Double-peaking is when the tube is weak and
the brightness will be fair, low then fair again as the intensity is from low
to max. The focus is usually out not matter the position of the focus control.
The tube will also be slow to show a trace when turned on.

Mark
Re: Tektronix 7603/7L13 Calibrator accuracy...? /Ailtech 460

 

I'm aware that the 7L13 50Mhz calibrator signal is stated as -30dBm into 50 ohms, but how accurate is that spec...?
It should be as accurate as the 7L13 instrument itself. Note however that given their age, each 7L13 today most likely requires full calibration to achieve the factory specs. I had to calibrate mine, including the calibrator level. Fortunately the procedure is not very difficult although it takes time and effort.

HTH,
Best regards,
Nenad F.
Re: Type 130 L-C Meter

 

If not yet mentioned: the tek_type_130_factory_cal_proc.pdf also has the instructions for tuning T1. T1 is done before the S-30 comes into play. Albert
Re: 7904 - NOS CRT ?

 

Nope, it's not.

Double peaking, as I've heard it, is increasing the intensity, then while still advancing the control, the intensity diminishes, then starts to increase again.

As I've heard, the thickening of a trace with intensity beyond a certain point is normal, and I've seen it on all sorts of scope tubes.? The 7904 (and just heard about the 7704A) have dome mesh CRTS, which have their own effect on beam intensity and focus. The halo seems to be an artifact of the dome mesh, at least, early ones.

Note that electrons have the same charge, and tend to repel each other.? More electrons in the same space lets them repel each other better, hence a fatter beam.

Harvey

On 3/21/2022 12:36 PM, n4buq wrote:
Regarding this, I've seen the term "double-peaking" used but am not finding examples of it.

If I increase the intensity too much in my 7704A, I start seeing a thickening of area around the trace (halo?) whereas lower intensity traces are sharp and without that effect. Is the fatter trace double-peaking?

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "K7XYM" <public2@...>
To: "tekscopes" <[email protected]>
Sent: Monday, March 21, 2022 12:30:12 AM
Subject: [TekScopes] 7904 - NOS CRT ?
So I know its a ludicrous question, but, I want to ask anyway. Are there any NOS
CRTs that ever come up for the 7904 ?

I am asking because I am in the middle of a _major_ restore to new, complete
with tons of mods to go beyond original performance, on my 7904 and I am now
aware that these CRT age and have issues with beam spot size not related to
electronics. I have 3 7904's and I have swapped electronics, as a whole,
between the chassis only one tube ends with with a super sharp spot size. The
other 2 are larger spot size and one has kinda odd behavior with brightness
adjustments. Again that is with swapping ALL the electronics. Its a tube thing.

So no hope of getting a NOS CRT for these right ?

I am going to refurb and mod 2 and I might have to just buy 7904's looking for a
good tube.

Anyone have any full parted 7904 chassis with just the tube ?
Re: Type 106 Saga (Again)

 

On Mon, Mar 21, 2022 at 04:32 PM, Stephen wrote:
Actually I was able the get back to it a bit this weekend, and odds now I read
-161V at pin 3. And it is not significantly changing when turning the high
amplitude down.
Stephen, some time ago there was a problem with S242B. The switch seemed to be closed all the time. I assume your reading now is still in High Ampl mode. Then it looks like the opposite failure of S242B: open all the time. That results in pin 3 sitting at the most extreme negative voltage. The wiper of R246 is disconnected and Amplitude has no effect at all. Perhaps you can check the behavior of the switch with a resistance meter.

Albert
Tektronix 7603/7L13 Calibrator accuracy...? /Ailtech 460

 

Hi group...

I'm in the process of working on one of two Ailtech/Eaton AIL-460 Signal Generators that I have, and I need an RF level "standard" for both that purpose, and to calibrate an HP-411A RF millivolt meter.

I'm aware that the 7L13 50Mhz calibrator signal is stated as -30dBm into 50 ohms, but how accurate is that spec...?

Also, does anyone have a fair amount of experience with the AIL 460 SG, or that has one for some comparisons and queries...?

Thanks for reading this...73...Jordan VE6ZT
Re: 7904 - NOS CRT ?

 

Barry,

What you seeing is a good tube. At high brightness, the phosphour is being struck with a large amount of electrons exciting the phosphour around the ones being struck causing them to glow. Double-peaking is when the tube is weak and the brightness will be fair, low then fair again as the intensity is from low to max. The focus is usually out not matter the position of the focus control. The tube will also be slow to show a trace when turned on.

Mark
Re: 7904 - NOS CRT ?

 

Regarding this, I've seen the term "double-peaking" used but am not finding examples of it.

If I increase the intensity too much in my 7704A, I start seeing a thickening of area around the trace (halo?) whereas lower intensity traces are sharp and without that effect. Is the fatter trace double-peaking?

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "K7XYM" <public2@...>
To: "tekscopes" <[email protected]>
Sent: Monday, March 21, 2022 12:30:12 AM
Subject: [TekScopes] 7904 - NOS CRT ?
So I know its a ludicrous question, but, I want to ask anyway. Are there any NOS
CRTs that ever come up for the 7904 ?

I am asking because I am in the middle of a _major_ restore to new, complete
with tons of mods to go beyond original performance, on my 7904 and I am now
aware that these CRT age and have issues with beam spot size not related to
electronics. I have 3 7904's and I have swapped electronics, as a whole,
between the chassis only one tube ends with with a super sharp spot size. The
other 2 are larger spot size and one has kinda odd behavior with brightness
adjustments. Again that is with swapping ALL the electronics. Its a tube thing.

So no hope of getting a NOS CRT for these right ?

I am going to refurb and mod 2 and I might have to just buy 7904's looking for a
good tube.

Anyone have any full parted 7904 chassis with just the tube ?
Re: Stanford Research SR760 spectrum analyzer PAL code needed

 

On Mon, Mar 21, 2022 at 09:30 AM, Jon Harrison-Hughes wrote:


Jay,

Did you ever get the PAL code and do you still need it ?
Hi Jon,
Never did, but that analyzer is long gone (12 years!)
Thanks, though.
Jay
Re: 2440 for sale

Bob Albert
 

My 2440 seems to fall short of specs.? I measure about 290 MHz bandwidth, down 3 dB.
Bob

On Monday, March 21, 2022, 09:14:49 AM PDT, David Templeton <vexorg.calibra@...> wrote:

Yeah, I tend to forget how old they are. I¡¯m just so used to GHz scopes in single shot that I only see the analog bandwidth and assume it¡¯s single shot.

David

On 21 Mar 2022, at 16:06, Roger Evans via groups.io <very_fuzzy_logic@...> wrote:

?It was very common in the early years of DSOs for the analog signal to be severely under-sampled.? I have a late model 2211 which is hybrid analog/digital, has 100MHz analog bandwidth and only 20Msamples/s digitising bandwidth.? With my rule of thumb (at least two samples during the pulse rise time) that is no better than 7MHz single shot digital bandwidth, Tek claimed 10MHz.? When you first switch the 2211 into digital mode at a fast sweep speed it takes several seconds for the random equivalent time sampling to 'fill in the gaps'.? By the standards of the time the 2440 had a very respectable single shot digitising rate.

Roger
Re: 7904 - NOS CRT ?

 

If you find one that is known good, that should help. I do have known good ones, P31 type, that should be give a sharp enough trace for you. The odd behavior you describe may be the double-peaking.

Morris, the shipping to where you are is usually the expensive part due to the size instead of weight, in this type of case.

Mark
Re: 7904 - NOS CRT ?

 

LOL, dBdollars!? I'll have to remember that one!Jim Ford?Sent from my T-Mobile 4G LTE Device

-------- Original message --------From: Tom Lee <tomlee@...> Date: 3/21/22 2:29 AM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] 7904 - NOS CRT ? As you might have guessed, it is rare to find one that is truly NOS, and even rarer to find such a beast at a cost that doesn't have to be expressed in dBdollars to avoid sticker shock.To increase your odds slightly, you might consider also looking for a crt from a 7704A. It's the same jug as that in the 7904.Good luck!-- Cheers,Tom-- Prof. Thomas H. LeeAllen Ctr., Rm. 205350 Jane Stanford WayStanford UniversityStanford, CA 94305-4070 3/20/2022 22:30, K7XYM wrote:> So I know its a ludicrous question, but, I want to ask anyway. Are there any NOS CRTs that ever come up for the 7904 ?>> I am asking because I am in the middle of a _major_ restore to new, complete with tons of mods to go beyond original performance, on my 7904 and I am now aware that these CRT age and have issues with beam spot size not related to electronics. I have 3 7904's and I have swapped electronics, as a whole, between the chassis only one tube ends with with a super sharp spot size. The other 2 are larger spot size and one has kinda odd behavior with brightness adjustments. Again that is with swapping ALL the electronics. Its a tube thing.>> So no hope of getting a NOS CRT for these right ?>> I am going to refurb and mod 2 and I might have to just buy 7904's looking for a good tube.>> Anyone have any full parted 7904 chassis with just the tube ?>>> >>
Re: 2440 for sale

 

It was very common in the early years of DSOs for the analog signal to be severely under-sampled. I have a late model 2211 which is hybrid analog/digital, has 100MHz analog bandwidth and only 20Msamples/s digitising bandwidth. With my rule of thumb (at least two samples during the pulse rise time) that is no better than 7MHz single shot digital bandwidth, Tek claimed 10MHz. When you first switch the 2211 into digital mode at a fast sweep speed it takes several seconds for the random equivalent time sampling to 'fill in the gaps'. By the standards of the time the 2440 had a very respectable single shot digitising rate.

Roger
Re: Tek 2712 Adjustment

 

Hi Sergey,

Thanks. It's my first time fixing a spectrum analyser.

Regards,

Alfredo
Re: Tek 2715 Adjustments Procedure

 

Hi WB6CHK,

I will do that. Thanks for the helping hand.

Best regards,

Alfredo
Re: Tek 2715 Adjustments Procedure

 

Hi Gerald,

First thanks for the info. It seems I might have the same problem. Since I had noticed that the db values where always off from what I expected.

I will disassemble and check the transistor.

Again, thank you very much for sharing this information, I would have not gotten to this conclusion by myself!

Best regards,

Alfredo
Re: Type 106 Saga (Again)

 

On Thu, Mar 17, 2022 at 12:00 PM, Albert Otten wrote:

Hi Albert, Interleaved.


Stephen,

The current situation is that "A" reads -5.5 VDC and that this voltage doesn't
go more negative when you increase Amplitude. Right?
Actually I was able the get back to it a bit this weekend, and odds now I read -161V at pin 3. And it is not significantly changing when turning the high amplitude down.
I am of course setting the unit as mentioned in the manual, and followed the extra instructions: High Amplitude to full clockwise, and High Rise terminated into 50R, as mentioned at the bottom right of the schematic.

The differential voltages "A+150V", "A-150V" and "A-20V" versus "A" are OK
and also +/-10V are OK. Right?
Yep. All almost perfectly dead on. Certainly within tolerance.

Now with the voltage at pin 3 higher, or more negative, I don¡¯t know¡­

Albert
For the record, I had a brand new Q247 (RCA 2N3585). I switched it but absolutely nothing changed. The one that was in there was good.
I also replaced the 2x2.2uF (C247 & C248) with one single 1uF 900V polypropylene cap, which I have a small stock of.
Also, C224 was only 70nF instead of 100nF. The parts list calls for +50% -10% tolerance. I put a Mallory .1uF 630V in its place. That shouldn¡¯t be a problem, right?
That¡¯s all I was able to do so far.
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