Date   
Re: 2N2207 replacement in 547.

Adrian
 

I was thinking about that recently when recalling how Parylene conformal coating saved my bacon on high power/ high voltage controller printed circuit boards used in aircraft. It is a vacuum vapour deposition process and it has amazing penetration into the tiniest of gaps. (That made it a nightmare to mask the connectors of course) but I would think it would be the ideal treatment after cooking the transformers?

Adrian

On 5/29/2019 6:04 PM, fiftythreebuick wrote:
I have a theory but have not tried it yet. I suspect that if the transformer is put in a vacuum chamber and held at a deep vacuum for a length of time that is sufficient to pull any moisture out of it and then sealed with something like beeswax, the transformer might be recovered. Planning to give that a try when I have time.

Re: 2N2207 replacement in 547.

Chuck Harris
 

Hi Tom,

Your "theory" has been tried to no avail. The epoxy has changed
into something that is lossy all by itself... more lossy with
moisture infiltrated into it... But, it can only get a tiny little
bit better by baking... Only a tiny little bit better by replacing
the vacuum tube diodes with fast silicon diodes... and only a tiny
little bit better by aggressively cooling it... But never, better.

Beeswax/paraffin mix is not any more resistant to moisture than the
epoxy. Its infiltration rate is almost identical. Its benefit over
epoxy is it is lower loss... by a factor of almost 10x... than the
epoxy even when the epoxy is new. Its other benefit is if moisture
makes it get hot, it melts, releasing the moisture.

Tektronix knew all of this, which is why they designed the HV box
to accept a heatsink under the core. They were married to the idea
of a high temperature scope (647), and a sealed, modular HV compartment,
which is why the stuck with epoxy, warts and all.

I have wound hundreds of these transformers... until I was cross eyed,
and numb, from the highly repetitive task. At my best, I had to wind
4 transformers to get 3 that worked... which is not that good.

To ease the extreme toll winding causes me, I designed a computerized
coil winder, and after I finished the hardware, but before I could write
the software, I got old... Suddenly, other tasks demand higher priority.

I can foresee a day when I will be winding again, but unless I break my
leg, it won't be anytime soon.

-Chuck Harris

fiftythreebuick wrote:

Glad to hear that you have jumped into the vintage Tektronix oscilloscope world! Honestly, once you get spoiled by a 500 series Tek oscilloscope, you're spoiled for good... :-)

The 547 is really a nice scope and I know you will enjoy them. I hate to tell you, but the very high probability is that your HV transformer is the source of the problem. A quick test, if you'd like to run it, is to run the scope until it fails and then hit the HV transformer with a burst of freeze spray that's sufficient to cool it significantly. If the trace returns and then fairly quickly goes away again, then it's the xfmr. The 547 is one of the known bearers of this problem.

There are a couple of folks who rewind the xfmrs, but I don't know who exactly is currently doing it. My buddy who reworked them years ago is out of it now.

I have a theory but have not tried it yet. I suspect that if the transformer is put in a vacuum chamber and held at a deep vacuum for a length of time that is sufficient to pull any moisture out of it and then sealed with something like beeswax, the transformer might be recovered. Planning to give that a try when I have time.

The worst problem with HV xfmr failure that I am aware of was with the 549 mainframe. I've worked on probably 20 or more of them and have never seen one with an original transformer that didn't have the defect. In the case of the 549s that I have, once the coil was removed and replaced with a rewound one, the problem disappeared and the scope worked as new.

Interestingly enough, the problem was extremely rare in the earlier, open frame xfmrs such as those in the Type 555 and 545A, etc.

If it turns out that you do need a xfmr, I bet someone here can point you in the right direction.

Tom



Re: 2N2207 replacement in 547.

Chuck Harris
 

Tektronix tried:

Beeswax/paraffin
Epoxy varnish (brown)
Epoxy potting (brown)
Epoxy potting (black)
Epoxy varnish (brown) potted in clear RTV silicone, in a metal can...

The black Epoxy was the only one of these variations that worked.
What the epoxy was, I haven't a clue.

There isn't more than a couple of hundred volts between any two wires,
so the epoxy/beeswax/??? isn't there improve the HV resilience. It is
more to keep the winding together.

The brown epoxy is about 10x more lossy than beeswax/paraffin... even
when new.

Even in the hayday of flyback transformers in TV sets, etc.. they still
failed due to potting failure.

-Chuck Harris

Adrian wrote:

I was thinking about that recently when recalling how Parylene conformal coating
saved my bacon on high power/ high voltage controller printed circuit boards used in
aircraft. It is a vacuum vapour deposition process and it has amazing penetration
into the tiniest of gaps. (That made it a nightmare to mask the connectors of course)
but I would think it would be the ideal treatment after cooking the transformers?

Adrian

On 5/29/2019 6:04 PM, fiftythreebuick wrote:
I have a theory but have not tried it yet. I suspect that if the transformer is
put in a vacuum chamber and held at a deep vacuum for a length of time that is
sufficient to pull any moisture out of it and then sealed with something like
beeswax, the transformer might be recovered. Planning to give that a try when I
have time.


Power Supply Overheating 2901 Time Mark Generator

 

Hi All,

I have been given a functioning 2901 time mark generator. The previous
owner has fixed an apparent overheating problem but I, and I believe neither
is he, am not convinced that it's gone away.



The 3.6V PSU shows signs of overheating. The PCB is badly singed and the
shell for P4 has decayed through heat. CR411 has been replaced with an
encapsulated bridge that is currently raised off the board. This is very
warm to the touch. R411 has been replaced and is also clear of the board
and also warm. C411 has been replaced with a 4700uF 63V electrolytic.
There is evidence that CR411 and R411 historically were very hot and I
assume failed along with the reservoir capacitor 411. Q424, the main
regulating transistor for the 3.6V supply is cool to the touch.



Both the 3.6 and -30 volts regulators appear to be regulating correctly and
within spec according to the manual.



So. Questions:

1) The obvious one, has anyone knowledge of an obvious "go here" for
this device? In my valve radio repairing guise the "that capacitor" that
usually fails;

2) What sort of current should the 3.6 and -30V supplies provide in
normal operations?

3) I'm assuming that these units should NOT overheat like this - yes?



I'd obviously love to make this problem go away and I'm sure the previous
owner would be as intrigued as me if we can find out what's wrong.



Thanks in advance and kind regards



Robin Birch


_____


<https://home.mcafee.com/utm_medium=email&utm_source=link&utm_campaign=sig-e
mail&utm_content=emailclient?utm_medium=email&utm_source=link&utm_campaign=s
ig-email&utm_content=emailclient> Scanned by McAfee
<https://home.mcafee.com/utm_medium=email&utm_source=link&utm_campaign=sig-e
mail&utm_content=emailclient?utm_medium=email&utm_source=link&utm_campaign=s
ig-email&utm_content=emailclient> and confirmed virus-free.

Chassis for free

Dave Seiter
 

I have at least 4 chassis from x3 mainframes that are taking up space, and I realized that I'm probably never going to need/use them. (Too many others!) I think two are 7603, and the other two are 7623, but I can't be sure. Basically the frames and exterior sheet metal and some of the crt shields/coil assemblies. Free for local pick up 94085 (San Jose, Ca area). I really don't want to ship them because larger boxes are harder to come by.

-Dave

Re: Chassis for free

 

On Wed, May 29, 2019 at 10:31 PM, Dave Seiter wrote:


I have at least 4 chassis from x3 mainframes that are taking up space
Here's a tip what you can do with empty 7k frames .... http://www.hakanh.com/dl/pi_storage.htm

/Håkan

Re: Chassis for free

Dave Seiter
 

That's a great idea, but I have boxes of plugins (and those are the ones I don't use!)
-Dave

On Wednesday, May 29, 2019, 1:59:52 PM PDT, zenith5106 <hahi@...> wrote:

On Wed, May 29, 2019 at 10:31 PM, Dave Seiter wrote:


I have at least 4 chassis from x3 mainframes that are taking up space
Here's a tip what you can do with empty 7k frames .... http://www.hakanh.com/dl/pi_storage.htm

/Håkan

Re: Chassis for free

Jim Ford
 

Hi, Dave.Any 7k, 5k, or TM500 series plug-ins you'd like to have a new home?  Shipping is a lot less of an ordeal for those.  I'm in So Cal, so shipping should be inexpensive - I will pay.Thanks.Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Dave Seiter <d.seiter@...> Date: 5/29/19 2:03 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Chassis for free That's a great idea, but I have boxes of plugins (and those are the ones I don't use!)-Dave    On Wednesday, May 29, 2019, 1:59:52 PM PDT, zenith5106 <hahi@...> wrote: On Wed, May 29, 2019 at 10:31 PM, Dave Seiter wrote:>> I have at least 4 chassis from x3 mainframes that are taking up space>Here's a tip what you can do with empty 7k frames .... http://www.hakanh.com/dl/pi_storage.htm/Håkan

Re: Chassis for free

Dave Seiter
 

Hi Jim- No, even though I have extras, I never know when I'll need them😉.

-Dave

On May 29, 2019, at 3:01 PM, Jim Ford <james.ford@...> wrote:

Hi, Dave.Any 7k, 5k, or TM500 series plug-ins you'd like to have a new home? Shipping is a lot less of an ordeal for those. I'm in So Cal, so shipping should be inexpensive - I will pay.Thanks.Jim Ford Sent from my Verizon, Samsung Galaxy smartphone
-------- Original message --------From: Dave Seiter <d.seiter@...> Date: 5/29/19 2:03 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Chassis for free That's a great idea, but I have boxes of plugins (and those are the ones I don't use!)-Dave On Wednesday, May 29, 2019, 1:59:52 PM PDT, zenith5106 <hahi@...> wrote: On Wed, May 29, 2019 at 10:31 PM, Dave Seiter wrote:>> I have at least 4 chassis from x3 mainframes that are taking up space>Here's a tip what you can do with empty 7k frames .... http://www.hakanh.com/dl/pi_storage.htm/Håkan

Re: Chassis for free

Harvey White
 

I'm in the market for the personality modules for a 7D02...

Harvey

On 5/29/2019 6:01 PM, Jim Ford wrote:
Hi, Dave.Any 7k, 5k, or TM500 series plug-ins you'd like to have a new home?  Shipping is a lot less of an ordeal for those.  I'm in So Cal, so shipping should be inexpensive - I will pay.Thanks.Jim Ford Sent from my Verizon, Samsung Galaxy smartphone
-------- Original message --------From: Dave Seiter <d.seiter@...> Date: 5/29/19 2:03 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Chassis for free That's a great idea, but I have boxes of plugins (and those are the ones I don't use!)-Dave    On Wednesday, May 29, 2019, 1:59:52 PM PDT, zenith5106 <hahi@...> wrote: On Wed, May 29, 2019 at 10:31 PM, Dave Seiter wrote:>> I have at least 4 chassis from x3 mainframes that are taking up space>Here's a tip what you can do with empty 7k frames .... http://www.hakanh.com/dl/pi_storage.htm/Håkan

Re: 2215 problem

Bob Albert
 

Leo, I found some IRF820s locally for a good price so I bought two.  But I tested the old one and it checks good with my little Chinese magic box tester.  So the problem apparently lies elsewhere.
The next thing I want to try is to run it from an external 40V source.  I have a supply that puts out 40V maximum; will that do, or must I get 43 V?  I could probably piggy back another supply if I had to.
Bob

On Wednesday, May 29, 2019, 12:06:08 AM PDT, Bob Albert via Groups.Io <bob91343=yahoo.com@groups.io> wrote:

Thanks Leo, I was beginning to despair of getting a response.  Tomorrow I plan on doing what you suggest, feeding 42V in place of the FET.  It will take some careful positioning of the various boards that now are hanging loose.  I hope I didn't confuse the + and - leads.  The manual says make notes, which I didn't, but also doesn't say how to figure out which goes where.
Bob
    On Tuesday, May 28, 2019, 11:55:43 PM PDT, satbeginner <@satbeginner> wrote:

Hi, I'm traveling right now, so I can not look for the details, but...

If I remember well, yes there are several (quite similar) power supplies for a 2215/2215A and others.

The power supply first stage makes a 42V , and the second part creates the other voltages from that 42V.

If you remove the IRFxxx you can feed a separate 42V into the scope and see if that works.

That way you know you have to concentrate on the first PS stage.

Look in this thread too:

https://groups.io/g/TekScopes/topic/2215a_lvps_repair/23804512?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,23804512

Success,

Leo

Re: TDS744 not 'A' has a problem , help needed

Brian
 

Hi again and thank you for your assistance , I have some good news -- its fixed. I did some probing around the L10412 chips and doing a bit of tracing on the pcb to see if there was a bad via , while doing that I noticed a 10uF ceramic cap on CH1 that had blown apart ??,I checked the ferrite in series with it and it was ok . I began to wonder if there was a similar problem on CH3 so I checked , a 10uF ceramic cap was shorted and the series ferrite was open . The coresponding parts on CH2 and CH4 checked out ok . At the moment I am running it with the failed caps missing and a wire link in place of the open ferrite -- it passes SPC and I have my 4 traces on screen now . I have ordered replacement parts - its going to be a long 2 weeks waiting for them .Once again thank you for your help

On Wednesday, 29 May 2019, 17:13:12 BST, Bob Koller via Groups.Io <testtech=yahoo.com@groups.io> wrote:

There may be one on eBay, searching for the p/n returns one possible hit, but the description is poor.
You might be able to probe around the chip.
Tekwiki has the service manual for the Tek 1740A series, this part is used there as well, and the schematic <9> shows the pinout.The DACULATOR outputs go to a track and hold.

Whenever I suspect one, I just replace it, pretty much always solves the problem, but you may have something else going on of course...

Re: Chassis for free

Jim Ford
 

Yep, I know the feeling!  My wife does not, however...Thanks anyway. JimSent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Dave Seiter <d.seiter@...> Date: 5/29/19 3:27 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Chassis for free Hi Jim- No, even though I have extras, I never know when I'll need them😉. -Dave> On May 29, 2019, at 3:01 PM, Jim Ford <james.ford@...> wrote:> > Hi, Dave.Any 7k, 5k, or TM500 series plug-ins you'd like to have a new home?  Shipping is a lot less of an ordeal for those.  I'm in So Cal, so shipping should be inexpensive - I will pay.Thanks.Jim Ford Sent from my Verizon, Samsung Galaxy smartphone> -------- Original message --------From: Dave Seiter <d.seiter@...> Date: 5/29/19  2:03 PM  (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Chassis for free  That's a great idea, but I have boxes of plugins (and those are the ones I don't use!)-Dave    On Wednesday, May 29, 2019, 1:59:52 PM PDT, zenith5106 <hahi@...> wrote:  On Wed, May 29, 2019 at 10:31 PM, Dave Seiter wrote:>> I have at least 4 chassis from x3 mainframes that are taking up space>Here's a tip what you can do with empty 7k frames .... http://www.hakanh.com/dl/pi_storage.htm/Håkan> >

Re: Clock error on TDS3034

 

I have successfully removed the empty lithium battery in my DALLAS DS1742W-150 and connected an external Lithium cell (CR2032).
The clock runs fine again and remembers time and date.

I'd like to reset the number of powerups (655) and more importantly, the total operating time, which is shown as -23598522 hours!
Any ideas?

Raymond

Re: Clock error on TDS3034

 

On Thu, May 30, 2019 at 05:31 AM, Raymond Domp Frank wrote:


I'd like to reset the number of powerups (655) and more importantly, the total
operating time, which is shown as -23598522 hours!
Any ideas?
I have a working GPIB connection and have successfully cleared the error log in the TDS3034. It had many entries from a failed plug-in interface module, sometime in the past. But a command to (re)set total operating time?
The 'scope is still nicely in calibration so I wouldn't want to go that way.

Raymond

Re: Clock error on TDS3034

Jim Ford
 

Sounds like the girl from the relativity limerick had owned it:There once was a girl named Miss BrightWho traveled much faster than lightShe departed one dayThe Einsteinian wayAnd returned on the previous night!Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Raymond Domp Frank <@Raymond> Date: 5/29/19 8:31 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Clock error on TDS3034 I have successfully removed the empty lithium battery in my DALLAS DS1742W-150 and connected an external Lithium cell (CR2032).The clock runs fine again and remembers time and date.I'd like to reset the number of powerups (655) and more importantly, the total operating time, which is shown as -23598522 hours!Any ideas?Raymond

Re: Clock error on TDS3034

 

I have a working GPIB connection and have successfully cleared the error log in the TDS3034. It had many entries from a failed plug-in interface module, sometime in the past.

Hi Raymond,

What command clears the logs?

Thanks.

Jay

Re: Clock error on TDS3034

 

A few months ago, Håkan responded as follows to my question re. clearing the error log of my THS720A:

If you connect a PC running a terminal program to the serial port of the THS
you can try sending first PASSWORD PITBULL and then ERRLOG CLEAR.
It doesn't clear any RS232 errors but it resets the numbers of power up and
most likely power on errors (mine has no errors so I can't say for sure).
It worked fine on my THS720A and on my TDS3034, it clears the error log but neither # of powerups nor power on hours.

Raymond

Re: Clock error on TDS3034

David Kuhn
 

" I recently bought a nice TDS3034.
Unfortunately, its clock has a problem: I may set date and time but it does
not keep it, not even without a restart. "

Hello Raymond. I found a Dallas DRAM from some place in Florida that
someone on here recommended (it may have been on the EEVBLOG forum. I know
that's not much help. But once replaced, the scope booted all weird and
wouldn't boot. I needed to hold in the "B TRIG" button while powering-up
to reset the scope.

With my nearly dead DRAM, not only did it loose time, it also could not
remember the GPIB address, it kept resetting to "0".

Do not buy the DALLAS DRAM on EBAY from China. They send you a fake chip
for ~$35.

Okay, I think I found it. I think I bought the DALLAS DRAM chip from:
NAC Group, Inc. dba NAC Semi <http://www.nacsemi.com/>http://www.nacsemi.com
I got lucky and go a chip with some battery life left in. When I replace
it, I solder lead carriers in to the board. They were short enough that
the chip could get installed and have room (with may 1/4" to spare) for the
I/O module cage when re-assembling. I paid $38.99 for the chip.
Dave

On Sun, May 26, 2019 at 1:42 PM Raymond Domp Frank <@Raymond>
wrote:

I recently bought a nice TDS3034.
Unfortunately, its clock has a problem: I may set date and time but it
does not keep it, not even without a restart.
Could this be just a bad backup battery and if so, could the calibration
state be affected, either already or when replacing the battery? Does this
model have a Dallas NVRAM?
I’m not at home so I haven’t had time to check amplitude calibration etc.
nor opened the case. Fast edge seems ok (have a Leo Bodnar pulser with me).
Thanks for any responses!
Raymond



Corona Electric FT-100A

Kurt Rosenfeld
 

The Corona Electric FT-100A is a 500-series plug-in for plotting Ft of transistors. Does anyone have photos of this unit that they can share?

thanks, -Kurt