Date   

Re: How to troubleshoot a faulty 7B50 timebase

Thierry Delaitre
 

thank you.

I can find a sweep at the base of the Q784 (output driver) and nothing after.

I have correct voltages for the line voltages -15V and 50V

Other voltages are as follows (with a time dev of 1ms):
- Collector of Q774: 5.6V instead of 6.41V
- Collector of Q764: 6.6V instead of 6.42V
- Emitter of Q794: 11.5 instead of 7.22V
- Emitter of Q784: 6V instead of 7.33V
- 13.1V across C799

I've also tried to disconnect C799 just in case if it was leaky but it is still the same

I've also checked the resistors (in-circuit) around Q774 and Q784/Q794 and none have exceeded their values.

Does it mean that one of the output driver Q784 and/or Q794 is leaky?

Should I replace them with a 2N4122 or are there any other equivalents that are easier to source?

Thanks

Thierry


Re: Thanks for the 3L5 mod info, now, about testing 561/564 frames...

 

On Thu, Jan 8, 2015 at 06:36 PM, ditter2 wrote:

Some of the pins of the plug-in interface give access to both the plate and
cathode of the series regulator tubes. No really large current capable tubes
such as 6080 are used. The assumption was that the plug-in itself would
contain power resistors used to shunt some ofthe current around the regulator
tube to keep the plate current down.
True, except that my 561A's and 564 do use a 6AS7G (which is identical to a 6080) for the +300v regulated supply and the +125 reg. The plates of the 6080 are +420 unregulated and +210 respectively, and made available to the plug-ins through 4k center-tapped power resistors.

I know this firsthand because I shorted one of the +420 through 2K leads while building an extender cable for the 561A, and spectacularly fried half of one of those resistors...

The 561B, using all transistors, does not have a pass tube, and those unregulated HV connections, to pins 6, 20 and 22, are omitted at the plug-in connectors (since presumably the redesigned power supply can provide the needed current on the +300 and +125 buses). (Late s/n do have a "+157" connection to plug-in pin 22. So maybe Tek backpedaled a little) ;)

Another not-so-great move was to put the 117 VAC line on pins 7 & 8. Right next to +420 pin 6... except, again, on the 561B where the manual shows that line power was omitted.


Re: TDS544A with strange display #photo-notice

Stephen
 

I can’t help you, but the Dropbox link works fine.


Re: TDS544A with strange display #photo-notice

durechenew@...
 

Again my English, supposed to be "...warmed up"


Re: TDS544A with strange display #photo-notice

durechenew@...
 

Here we go; first, I believe that it was my poor English and I wasn't properly understood when I tried to explain what I see and I apologize for that.
Second, Siggi, you may be right about an issue with blue trace; I still hold my position, but you may wish to look at the picture 4019-1 (this time with the scope well wormed up). Some vectors show in red (don't know what that means), but we've seen that on green too - it's only on fast changing portion of signal (rise, fall time), never on triangle.
Third, I wanted to take the shutter out of the picture: I made a short clip of the screen with stripes on blue, then...
I opened the scope and disconnected the shutter from the shutter driver board. Made a second clip, essentially in black and white or, if you wish, what CRT is displaying. I believe this completely takes out the shutter as reason for discussion if it has a role in this or not. Also clarifies (I hope) what I meant when saying the stripes wave like a flag.
As I cannot upload the clips here (not supported), the two files were uploaded to my Dropbox, link below:
https://www.dropbox.com/sh/8oo1j0060in4l8v/AAB-FuSaEN7gnGhagvCjWwjta?dl=0
I verified the link before posting, works for me; it would be nice if you could confirm it works for you too.
TT


Re: Restoring CRT emission?

Roger M
 

Hi Roy,
This is an arguable subject, and by its nature, chock full
of ill defined variables.

I can only speak, with first hand experience, to the efficacy of
"rejuvenation" in Tek CRT's (mostly television waveform monitors).
Results? Either it fails to improve emission, or can give upwards of
1000 hours of usable life to the treated jug.

For those of us who are curious, could you tell us what thesis you're
referring to and where you found it?
-Roger


Re: Alert for 519 owners

Sean Turner
 

I need the N50/T125 ones to finish my set of 519 accessories. Anyone want to split these with me if I buy them? I do not need two more T50/T125s.

Sean


Re: Restoring CRT emission?

Tom Lee
 

It wasn't recognized until the vacuum tube era had ended that cathodes are actually semiconductors, whose electrical properties are exquisitely sensitive to morphology and trace impurities, as your story shows.

Cheers
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 3/8/2021 12:00, Stephen Hanselman wrote:
As a tidbit of trivia and only a little bit off topic.

Eimac tried to build, I think it 8877's, at their plant in Salt Lake City with not much success. They determined that the "air in SLC was different than in San Carlos, CA and the cathodes were getting poisoned.

There seems to be a fair bit of magic in making tubes work properly

Steve

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Roy Thistle
Sent: Monday, March 8, 2021 11:40 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Restoring CRT emission?

Hi Charles:
I read through a two decades old PHd thesis on CRT cathodes. ( as anyone can too! There are any number of people posting here who will first humiliate one.. but, explain things one might not understand.) I also read through the "B&K 467 Cathode Ray Tube Restorer Analyser" manual. (There's even a nifty picture of Karl Corn inside the front cover... yes, those were the days!) In my opinion, people working with CRTs in the field (TV repairmen, video game repairmen) contributed to forming a model that was sufficient to explain a methodology... so that engineers (at B&K, Sencore and others) could design and build things like the 467. But to my knowledge the "model" that was used, by those designers, was never sufficiently explained scientifically. And the thesis referred to above offers several competing models: about what happens as CRT cathodes/filaments age, degrade, or become poisoned.
Just the same, I've seen several topics and posts ..,here on TekScopes ... about, "welding filaments", rejuvenating/brightening/rebuilding, old oscilloscope CRTs.
As far as I cant tell, a lot of what is reported on the Internet, about "rejuvenating" CRTs ... regarding "how rejuvenation works" and "whether it works" is foolishness.
Yes! TV repairmen did "rejuvenate/brighten" TV CRTs (using self devised methods, or gear like the 467); but, the old-timers that I knew ... they related that it was a temporary strategy. It allowed them to "rejuvenate" the CRT, on site, while they ordered in a new (or rebuilt) CRT. Rejuvenation didn't last very long!
There might be something different about the CRTs Tektronix used (and made) that might allow "rejuvenation."
But bear in mind that as far as I can tell, no CRT was designed to reliably withstand the peak pulse power (or the relatively large average current/voltages) that rejuvenation gear (or home-brew hacks) apply between the cathode and grid (or to the filament).
Best regards.



--
Roy Thistle










Re: Restoring CRT emission?

Stephen Hanselman
 

As a tidbit of trivia and only a little bit off topic.

Eimac tried to build, I think it 8877's, at their plant in Salt Lake City with not much success. They determined that the "air in SLC was different than in San Carlos, CA and the cathodes were getting poisoned.

There seems to be a fair bit of magic in making tubes work properly

Steve

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Roy Thistle
Sent: Monday, March 8, 2021 11:40 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Restoring CRT emission?

Hi Charles:
I read through a two decades old PHd thesis on CRT cathodes. ( as anyone can too! There are any number of people posting here who will first humiliate one.. but, explain things one might not understand.) I also read through the "B&K 467 Cathode Ray Tube Restorer Analyser" manual. (There's even a nifty picture of Karl Corn inside the front cover... yes, those were the days!) In my opinion, people working with CRTs in the field (TV repairmen, video game repairmen) contributed to forming a model that was sufficient to explain a methodology... so that engineers (at B&K, Sencore and others) could design and build things like the 467. But to my knowledge the "model" that was used, by those designers, was never sufficiently explained scientifically. And the thesis referred to above offers several competing models: about what happens as CRT cathodes/filaments age, degrade, or become poisoned.
Just the same, I've seen several topics and posts ..,here on TekScopes ... about, "welding filaments", rejuvenating/brightening/rebuilding, old oscilloscope CRTs.
As far as I cant tell, a lot of what is reported on the Internet, about "rejuvenating" CRTs ... regarding "how rejuvenation works" and "whether it works" is foolishness.
Yes! TV repairmen did "rejuvenate/brighten" TV CRTs (using self devised methods, or gear like the 467); but, the old-timers that I knew ... they related that it was a temporary strategy. It allowed them to "rejuvenate" the CRT, on site, while they ordered in a new (or rebuilt) CRT. Rejuvenation didn't last very long!
There might be something different about the CRTs Tektronix used (and made) that might allow "rejuvenation."
But bear in mind that as far as I can tell, no CRT was designed to reliably withstand the peak pulse power (or the relatively large average current/voltages) that rejuvenation gear (or home-brew hacks) apply between the cathode and grid (or to the filament).
Best regards.




--
Roy Thistle


Re: 3T77 tunnel diodes (again)

Albert Otten
 

So I would need, as you suggest, to connect the anode to +5V through the
trimpot., and pull down with the TTL output. Probably add a pullup resistor to
help with the other edge.
I'd say the anode straightforward to +5V and pull down the cathode via a trimpot. I assume an isolated power supply for the TD circuit part its +5V connected to scope GND. Usually the switch of the TD to it's high state is used as the leading edge which is a negative going edge now.
A pull-up resistor is not really needed because you already have a resistor path to +5V (the 3S2 input to scope GND).

Albert


Re: 547 HV Transformer: Bill Schell rewind failed

Chuck Harris <cfharris@...>
 

Hi Bernd,

As I said, anything that fits on the usual ferrite core,
and uses the usual cardboard former for the winding can
be wound with my machine. So, it's all the same to me.

I will make up the recipe's for the 547/545B, 647, and 576
first, and as demand happens, the recipe's for whatever...

The biggest issue is testing. I build a mock up of the
547/545B HV section so I could easily test the transformers
I built before. It will be difficult to do that if I am
winding the whole spectrum of HV transformers that Tek
once wound.

I will probably have to take some of my Kepco BOP supplies,
and use them to drive the primary, and some sort of generic
load for the secondary...

-Chuck Harris

widgethunter via groups.io wrote:

I do hope you are able to add 561/4B, 549 and 556, at some point...B



-----Original Message-----
From: Chuck Harris <cfharris@erols.com>
To: TekScopes@groups.io
Sent: Fri, Mar 5, 2021 11:18 am
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Hi Bernd,

Since the winding pattern is entirely under computer
control, I can wind anything that goes on the cardboard
former that tektronix used.

The only other issues with models other than the 547/545B,
is termination.  Small wires are easy, lugs or pins are
harder.

My highest priorities are 545B/547, 647A/B, and 576.

Anything that uses the same mounting as the 545B/547/647A/B
transformers should come essentially for free.

-Chuck Harris

widgethunter via groups.io wrote:
Chuck;Am pleased to see that your ambitious undertaking is coming to fruition.I know that many Tek owners, who weren't so fortunate as to be able to keep their scopes working, are eagerly awaiting the day.We talked about this in terms of a side business, initially.If you are able to rewind other models, as well, you may be busy enough to get there, after all these years.Bernd



-----Original Message-----
From: Chuck Harris <cfharris@erols.com>
To: TekScopes@groups.io
Sent: Thu, Mar 4, 2021 4:45 pm
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Hi Bernd,

All indications are that my new machine is going to
do an even better job than the best I could do with
the old manual machine.

As an example, I was able to get 2/3 of the way to a
full wind without using the rosin/alcohol mixture that
I developed to enhance the wire's friction...

Using the rosin/alcohol, I am there already.

And, I will be using beeswax.

I'm glad to hear the prototype is still soldiering
on.  Soon, I may be able to get you the winds I promised
oh so long ago...

-Chuck Harris

widgethunter via groups.io wrote:
My memory certainly hasn't improved with age.Not much else seems to have, either...But, the beeswax thing I'd be willing to put money on - fwiw.
Incidentally, I still have not installed the 2nd wax xfrmr you made for me, but the 1st prototype continues to perform flawlessly.Bernd



-----Original Message-----
From: Chuck Harris <cfharris@erols.com>
To: TekScopes@groups.io
Sent: Thu, Mar 4, 2021 4:05 pm
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Hi Bernd,

I guess the biggest indicator of a scatter wind would be
the presence of a spool.  The universal wind doesn't require
any additional support.

In addition to talking to you, I talked to Deane Kidd, and
Deane talked about Bill using beeswax, like tektronix did in
the earlier transformers.

But, like you, it has been a looong time, and I don't think
our memories are getting any better.

-Chuck Harris

widgethunter via groups.io wrote:
Hi Chuck;Assumed scatter because of the larger size of Schell rewinds.It has been a looong time, but I think I'd remember if he'd said anything about epoxy...B



-----Original Message-----
From: Chuck Harris <cfharris@erols.com>
To: TekScopes@groups.io
Sent: Wed, Mar 3, 2021 9:57 am
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Hi Bernd,

There have been several discussions about Bill's transformers of
late, and there is a picture on the group, that looks very much
like epoxy varnish, or some other non wax compound.

However, it is most definitely not scatter wound.  It is a nice
looking, self supporting, universal wind.

Bill didn't use an outer tape covering on this transformer.  The
naked winding is right there for you to see.

-Chuck Harris




























Re: Restoring CRT emission?

Roy Thistle
 

Hi Charles:
I read through a two decades old PHd thesis on CRT cathodes. ( as anyone can too! There are any number of people posting here who will first humiliate one.. but, explain things one might not understand.)
I also read through the "B&K 467 Cathode Ray Tube Restorer Analyser" manual. (There's even a nifty picture of Karl Corn inside the front cover... yes, those were the days!)
In my opinion, people working with CRTs in the field (TV repairmen, video game repairmen) contributed to forming a model that was sufficient to explain a methodology... so that engineers (at B&K, Sencore and others) could design and build things like the 467. But to my knowledge the "model" that was used, by those designers, was never sufficiently explained scientifically. And the thesis referred to above offers several competing models: about what happens as CRT cathodes/filaments age, degrade, or become poisoned.
Just the same, I've seen several topics and posts ..,here on TekScopes ... about, "welding filaments", rejuvenating/brightening/rebuilding, old oscilloscope CRTs.
As far as I cant tell, a lot of what is reported on the Internet, about "rejuvenating" CRTs ... regarding "how rejuvenation works" and "whether it works" is foolishness.
Yes! TV repairmen did "rejuvenate/brighten" TV CRTs (using self devised methods, or gear like the 467); but, the old-timers that I knew ... they related that it was a temporary strategy. It allowed them to "rejuvenate" the CRT, on site, while they ordered in a new (or rebuilt) CRT. Rejuvenation didn't last very long!
There might be something different about the CRTs Tektronix used (and made) that might allow "rejuvenation."
But bear in mind that as far as I can tell, no CRT was designed to reliably withstand the peak pulse power (or the relatively large average current/voltages) that rejuvenation gear (or home-brew hacks) apply between the cathode and grid (or to the filament).
Best regards.




--
Roy Thistle


Re: Q122/222 Jfet J300 subs for 2215A scope ?

SCMenasian
 

I have bought from them before and have had no problems except when they were out of stock and cancelled my order of some stuff. I don't think you will have any problems with the quality of the parts. The only question I have is whether these are "A", "B", "C" or "D" parts or unsorted. The datasheet says that transconductance increases going from A to D.

As a bonus, they have an active coupon which expires at the end of the day, today.
35% off - Coupon code is "SUNDAY"

I have no business relationship with them except as a customer.


Re: 547 HV Transformer: Bill Schell rewind failed

widgethunter <tubesnthings@...>
 

I do hope you are able to add 561/4B, 549 and 556, at some point...B

-----Original Message-----
From: Chuck Harris <cfharris@erols.com>
To: TekScopes@groups.io
Sent: Fri, Mar 5, 2021 11:18 am
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Hi Bernd,

Since the winding pattern is entirely under computer
control, I can wind anything that goes on the cardboard
former that tektronix used.

The only other issues with models other than the 547/545B,
is termination.  Small wires are easy, lugs or pins are
harder.

My highest priorities are 545B/547, 647A/B, and 576.

Anything that uses the same mounting as the 545B/547/647A/B
transformers should come essentially for free.

-Chuck Harris

widgethunter via groups.io wrote:
Chuck;Am pleased to see that your ambitious undertaking is coming to fruition.I know that many Tek owners, who weren't so fortunate as to be able to keep their scopes working, are eagerly awaiting the day.We talked about this in terms of a side business, initially.If you are able to rewind other models, as well, you may be busy enough to get there, after all these years.Bernd



-----Original Message-----
From: Chuck Harris <cfharris@erols.com>
To: TekScopes@groups.io
Sent: Thu, Mar 4, 2021 4:45 pm
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Hi Bernd,

All indications are that my new machine is going to
do an even better job than the best I could do with
the old manual machine.

As an example, I was able to get 2/3 of the way to a
full wind without using the rosin/alcohol mixture that
I developed to enhance the wire's friction...

Using the rosin/alcohol, I am there already.

And, I will be using beeswax.

I'm glad to hear the prototype is still soldiering
on.  Soon, I may be able to get you the winds I promised
oh so long ago...

-Chuck Harris

widgethunter via groups.io wrote:
My memory certainly hasn't improved with age.Not much else seems to have, either...But, the beeswax thing I'd be willing to put money on - fwiw.
Incidentally, I still have not installed the 2nd wax xfrmr you made for me, but the 1st prototype continues to perform flawlessly.Bernd



-----Original Message-----
From: Chuck Harris <cfharris@erols.com>
To: TekScopes@groups.io
Sent: Thu, Mar 4, 2021 4:05 pm
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Hi Bernd,

I guess the biggest indicator of a scatter wind would be
the presence of a spool.  The universal wind doesn't require
any additional support.

In addition to talking to you, I talked to Deane Kidd, and
Deane talked about Bill using beeswax, like tektronix did in
the earlier transformers.

But, like you, it has been a looong time, and I don't think
our memories are getting any better.

-Chuck Harris

widgethunter via groups.io wrote:
Hi Chuck;Assumed scatter because of the larger size of Schell rewinds.It has been a looong time, but I think I'd remember if he'd said anything about epoxy...B



-----Original Message-----
From: Chuck Harris <cfharris@erols.com>
To: TekScopes@groups.io
Sent: Wed, Mar 3, 2021 9:57 am
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Hi Bernd,

There have been several discussions about Bill's transformers of
late, and there is a picture on the group, that looks very much
like epoxy varnish, or some other non wax compound.

However, it is most definitely not scatter wound.  It is a nice
looking, self supporting, universal wind.

Bill didn't use an outer tape covering on this transformer.  The
naked winding is right there for you to see.

-Chuck Harris



















Re: Alert for 519 owners

Dave Seiter
 

Gold plated GR874 connectors are almost guaranteed to be 125 ohm, and applicable only to the 519.  I used to search hamfests and swap meets for them, and you can spot them a long way off.  The converse is not true- one of my 519s has non-Au plated connectors, and I have at least one adapter that is also missing the gold.  Sellers on ebay love to over price them because of the gold; most don't know what they are used for, and that they have a very limited user base.
-Dave

On Monday, March 8, 2021, 10:23:05 AM PST, Charles <charlesmorris800@centurytel.net> wrote:

While searching Ebay for a GR874 splitter tee, I came across this listing:
https://www.ebay.com/itm/Lot-of-4-Tektronix-017-054-017-052-With-General-Radio-GR-874-Connectors/362763553704

I think these are 50 ohm (silver) to 125 ohm (gold) GR adapters (which AFAIK are only used on the 519).


Re: 7603 horizontal performance

 

On Mon, Mar 8, 2021 at 05:50 PM, Jouko Koskinen wrote:


But I have also 7B87 and using high sweep speeds (<5ns/div) horizontal
linearity is poor.
The faster rates of the 7B87 are too fast for the 7603, by far: Fastest calibrated hor. sweep is 5ns/div. 7B87 goes down to 1 ns/div (with 10x multiplier).

Raymond


Re: Sampling head extender missing coax connectors

 

Shipping rates from Canada really suck.
So does the wait time from China...


Re: Q122/222 Jfet J300 subs for 2215A scope ?

charlesterrebonne@...
 

Would be nice to get a few NOS J300s...but...I dont know about that vendor but at 0.62$ each....no picture...does not say these are NOS?....Ive gotten so many fake semiconductos in the last few years, I am very carefull now...would like to hear from someone who bought these from there and tested them in a circuit where they must behave like a true J300...not just tested with a pic component ider/tester or a multimeter...


Re: Sampling head extender missing coax connectors

snapdiode
 


Re: TEK370A >> 370B ?

 

No, and not sure why you would want to, the topology and function are virtually identical. The 370 would be a different story.
I work on these models regularly, these are the differences that I know of:
The B CPU board and floppy controller are completely different. Likely due to part obsolescence. The B boots much faster than the A. The A will run without the floppy controller, the B won't.
The step amp board looks a bit different.
The B models I have seen were assembled in Beaverton, all others built in Japan.
No schematics for the B, so difficult to know all the changes, but other than the CPU and floppy, I don't think many.
Tek has almost no parts left for these including the CRT.

6541 - 6560 of 186311