Date   

Re: 576 HV transformer problems - something to ponder

greenboxmaven
 

It was not a pure brilliant red, sort of a translucent reddish brown. I will guess different manufacturers or batches of the condensers could vary considerably in color, especially if they are translucent. I never thought to douse the lights and see if the flashover was visible.

Bruce, KA2IVY

On 9/4/19 11:59 PM, Glenn Little wrote:
Was the cap red?
I had a 453 MOD703H with no HV.
Found the red doorknob 500 pF HV filter cap had arced internally (saw the blackened area through the translucent red epoxy).
Replaced the cap with a ceramic 500 pF doorknob cap and the scope has worked fine since.
This was about 20 years ago.

Glenn

On 9/4/2019 3:35 PM, greenboxmaven via Groups.Io wrote:
I was doing some cleaning up in my shop and came across something?? from a Tektronix 454 scope that resonates with this transformer discussion. I think "contaminated" epoxy?? may have caused another problem in a scope high voltage power supply. The 454 had several problems that were easy to find and remedy. It still would not give anything more than a very pale glow on the screen. The second anode voltage was only about 2,000 volts. Disconnecting the transformer from the tripler circuit gave a husky corona arc to a screwdriver, so I began testing the diodes and condensers in the multiplier circuit. As I reconnected each stage, the voltage incresed. Finally I reconnected the 500 PFD "doorknob" condenser,and the voltage plummited. Having worked on television receivers decades ago, I had several replacement condensers on hand, and installing one brought the scope to life with a dazzling trace. One of the NuVistors in the preamp was barely alive, so that channel could not be brought onto the screen. A replacement got the scope working very well. I took the condenser over to a friend who has a Hipot tester, and it was fine until the voltage reached about 2,000 volts. The condenser is rated at 20KV, and the voltage on it in the scope is 12KV. The bad condenser is epoxy molded, the 60 year old replacement is tan high voltage bakelite. I wonder if Tektronix specified or accepted an epoxy formula that goes bad?

?????????? Bruce Gentry, KA2IVY


On 9/3/19 9:23 AM, Chuck Harris wrote:
The epoxy changes and makes an already lossy situation even
worse.


-Chuck Harris








Harmonica connectors repair

EB4APL
 

Hi,

I have observed in my limited number of series 7000 scopes (only three)
that the plastic contact holders of these harmonica connectors
disintegrates easily when its color is blue. Maybe it is caused by a
degradation of the plastic due to the blue pigment.

I found an easy and also dirty cheap replacement for these: I use Dupont
.1" pitch connector housings. When I began my tests I supposed that I
would need to use some glue for retaining the contacts, but it is not
needed, the pins, which are mechanically different form the Dupont pins,
are retained by the retention mechanism.

Maybe this is widely known, but I never had read anything about it.

Regards,

Ignacio EB4APL



---
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https://www.avast.com/antivirus


Re: 576 HV transformer problems - something to ponder

Glenn Little
 

Was the cap red?
I had a 453 MOD703H with no HV.
Found the red doorknob 500 pF HV filter cap had arced internally (saw the blackened area through the translucent red epoxy).
Replaced the cap with a ceramic 500 pF doorknob cap and the scope has worked fine since.
This was about 20 years ago.

Glenn

On 9/4/2019 3:35 PM, greenboxmaven via Groups.Io wrote:
I was doing some cleaning up in my shop and came across something?? from a Tektronix 454 scope that resonates with this transformer discussion. I think "contaminated" epoxy?? may have caused another problem in a scope high voltage power supply. The 454 had several problems that were easy to find and remedy. It still would not give anything more than a very pale glow on the screen. The second anode voltage was only about 2,000 volts. Disconnecting the transformer from the tripler circuit gave a husky corona arc to a screwdriver, so I began testing the diodes and condensers in the multiplier circuit. As I reconnected each stage, the voltage incresed. Finally I reconnected the 500 PFD "doorknob" condenser,and the voltage plummited. Having worked on television receivers decades ago, I had several replacement condensers on hand, and installing one brought the scope to life with a dazzling trace. One of the NuVistors in the preamp was barely alive, so that channel could not be brought onto the screen. A replacement got the scope working very well. I took the condenser over to a friend who has a Hipot tester, and it was fine until the voltage reached about 2,000 volts. The condenser is rated at 20KV, and the voltage on it in the scope is 12KV. The bad condenser is epoxy molded, the 60 year old replacement is tan high voltage bakelite. I wonder if Tektronix specified or accepted an epoxy formula that goes bad?

?????????? Bruce Gentry, KA2IVY


On 9/3/19 9:23 AM, Chuck Harris wrote:
The epoxy changes and makes an already lossy situation even
worse.


-Chuck Harris






--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@arrl.net AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"


Re: 2440 cal errors

Bob Albert
 

So replacing the battery might solve most of the problems...

On Tuesday, August 20, 2019, 08:19:55 AM PDT, Robert Simpson via Groups.Io <go_boating_fast=yahoo.com@groups.io> wrote:

OK,
Thanks, Bob


Re: production volumes

Jim Ford
 

TekWiki (www.w140.com/tekwiki/) says over 120,000 7A26's were produced.Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Sparky99 <jnolan@iprova.com> Date: 9/4/19 3:22 PM (GMT-08:00) To: TekScopes@groups.io Subject: [TekScopes] production volumes I was wondering if there is any information on the production numbers for products made by Tektronix.  Based on eBay a sales I get the feeling that things like the 7A26 were produced in very high numbers (in fact this is one of the few items I have seen a number for - I think 200,000 going from memory), whereas I can imagine earlier/less popular products, such as the 500 scopes, were a lot less.  Anyone have any info on production numbers?All the best,Julian


production volumes

Sparky99
 

I was wondering if there is any information on the production numbers for products made by Tektronix. Based on eBay a sales I get the feeling that things like the 7A26 were produced in very high numbers (in fact this is one of the few items I have seen a number for - I think 200,000 going from memory), whereas I can imagine earlier/less popular products, such as the 500 scopes, were a lot less. Anyone have any info on production numbers?

All the best,

Julian


Re: 555 restoration

Sparky99
 

Hi everyone, thanks for the replies - I investigated further tonight and indeed the red glow from both upper beam HV rectifiers disappears when the trace fades. I will investigate more tomorrow and post my findings!

Julian


Re: 576 HV transformer problems - something to ponder

John Ferguson
 

at 76, I grew up with condensers - that's what Dad, an EE, called them.

On 9/4/19 4:34 PM, greenboxmaven via Groups.Io wrote:
I am strange in many ways, I think condenser is easier to say than capacitor, and is the term used by older broadcast engineering and industrial electronics and control texts.  I also like to say kilo or mega cycles, it describes something that is happening. I do prefer the European name for those devices that glow and control current, valve is much more descriptive than tube. And, I often refer to a CRT as a jug. At 67 years old, things get imprinted and if they work as well or better, why not?

         Bruce Gentry, KA2IVY


On 9/4/19 3:41 PM, John Ferguson via Groups.Io wrote:
Bruce, what a delight to see a reference to condensers.

Cheers,

John Ferguson, AI4TO

On 9/4/19 3:35 PM, greenboxmaven via Groups.Io wrote:
 ....As I reconnected each stage, the voltage incresed. Finally I reconnected the 500 PFD "doorknob" condenser,and the voltage plummited. Having worked on television receivers decades ago, I had several replacement condensers on hand, and installing one brought the scope to life with a dazzling trace. ....

      Bruce Gentry, KA2IVY


Re: 576 HV transformer problems - something to ponder

greenboxmaven
 

I am strange in many ways, I think condenser is easier to say than capacitor, and is the term used by older broadcast engineering and industrial electronics and control texts. I also like to say kilo or mega cycles, it describes something that is happening. I do prefer the European name for those devices that glow and control current, valve is much more descriptive than tube. And, I often refer to a CRT as a jug. At 67 years old, things get imprinted and if they work as well or better, why not?

Bruce Gentry, KA2IVY

On 9/4/19 3:41 PM, John Ferguson via Groups.Io wrote:
Bruce, what a delight to see a reference to condensers.

Cheers,

John Ferguson, AI4TO

On 9/4/19 3:35 PM, greenboxmaven via Groups.Io wrote:
....As I reconnected each stage, the voltage incresed. Finally I reconnected the 500 PFD "doorknob" condenser,and the voltage plummited. Having worked on television receivers decades ago, I had several replacement condensers on hand, and installing one brought the scope to life with a dazzling trace. ....

Bruce Gentry, KA2IVY






Re: 576 HV transformer problems - something to ponder

Dave Wise
 

Fascinating diagnosis, Bruce. You give us another hard-to-spot failure mode to be alert to. It brings home the most basic test of any component, "Does it work in the circuit?".

Dave Wise

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of John Ferguson via Groups.Io
Sent: Wednesday, September 04, 2019 12:41 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 576 HV transformer problems - something to ponder

Bruce, what a delight to see a reference to condensers.

Cheers,

John Ferguson, AI4TO

On 9/4/19 3:35 PM, greenboxmaven via Groups.Io wrote:
 ....As I reconnected each stage, the voltage incresed. Finally I
reconnected the 500 PFD "doorknob" condenser,and the voltage
plummited. Having worked on television receivers decades ago, I had
several replacement condensers on hand, and installing one brought the
scope to life with a dazzling trace. ....

      Bruce Gentry, KA2IVY




Re: 576 HV transformer problems - something to ponder

John Ferguson
 

Bruce, what a delight to see a reference to condensers.

Cheers,

John Ferguson, AI4TO

On 9/4/19 3:35 PM, greenboxmaven via Groups.Io wrote:
 ....As I reconnected each stage, the voltage incresed. Finally I reconnected the 500 PFD "doorknob" condenser,and the voltage plummited. Having worked on television receivers decades ago, I had several replacement condensers on hand, and installing one brought the scope to life with a dazzling trace. ....

      Bruce Gentry, KA2IVY



Re: 576 HV transformer problems - something to ponder

greenboxmaven
 

I was doing some cleaning up in my shop and came across something from a Tektronix 454 scope that resonates with this transformer discussion. I think "contaminated" epoxy may have caused another problem in a scope high voltage power supply. The 454 had several problems that were easy to find and remedy. It still would not give anything more than a very pale glow on the screen. The second anode voltage was only about 2,000 volts. Disconnecting the transformer from the tripler circuit gave a husky corona arc to a screwdriver, so I began testing the diodes and condensers in the multiplier circuit. As I reconnected each stage, the voltage incresed. Finally I reconnected the 500 PFD "doorknob" condenser,and the voltage plummited. Having worked on television receivers decades ago, I had several replacement condensers on hand, and installing one brought the scope to life with a dazzling trace. One of the NuVistors in the preamp was barely alive, so that channel could not be brought onto the screen. A replacement got the scope working very well. I took the condenser over to a friend who has a Hipot tester, and it was fine until the voltage reached about 2,000 volts. The condenser is rated at 20KV, and the voltage on it in the scope is 12KV. The bad condenser is epoxy molded, the 60 year old replacement is tan high voltage bakelite. I wonder if Tektronix specified or accepted an epoxy formula that goes bad?

Bruce Gentry, KA2IVY

On 9/3/19 9:23 AM, Chuck Harris wrote:
The epoxy changes and makes an already lossy situation even
worse.


-Chuck Harris




Re: Microfiche Prioritization

Brian Bloom
 

I may be mistaken here, but from what I understand, the problem with getting them scanned and in pdf format isn’t necessarily the funds, it’s getting the manpower to get it done. Of course they could hire people to do it, but then they would have to deal with payroll and taxes etc and the added expense of an accountant’s time.

Then again, with the state of today’s young “work force”, who knows if they’ll even be able to find anyone to hire.


2465 Option 4Z

Don N3DEB
 

What is option 4Z? I have a 2465 that back plate indicates present.

Thank you,

Don


Portland Craigslist Tek scopes

Ken Eckert
 

Some various oldies for sale.....

https://portland.craigslist.org/search/sss?query=tektronix&;excats=137-8-1-39&sort=rel


Re: Microfiche Prioritization

ArtekManuals <manuals@...>
 

I DO NOT have a dog  in this fight but seems to me that those who "contributed" last year when the museum was soliciting donations for a Fiche scanner should have first dibs on setting prioritizes on what gets scanned/converted.  Just my opinion ...flame suit on....8^)

Dave
manuals@artekmanuals.com

On 9/4/2019 12:40 PM, bobkrassa wrote:
Following the discussion of the offer of the big microfiche library from England, and the indication that the Museum already has a similar collection and is willing to scan specific materials on request, leads me to suggest a discussion about what batch microfiche scanning should take priority.

I would suggest that mod summaries would be by far the most useful category to batch scan. Transformer winding info might be second.

As far as manuals, I will admit that I too have spent quite a bit of time searching for later manuals for some Tek equipment, but on those occasions when I have been successful have not found that the revised manual was all that different, except of course for parts lists and schematics which would be in the mod summaries.

If there is consensus on batch scanning then perhaps we could all donate some money to the Museum to have it done.

Also, some mod summaries were scanned and some of us have them. I am not at home but think I have several pdfs. Perhaps all of us should see what we have and send pdfs to the Museum and to Tekwiki.

73s Bob Krassa ACØJL


--
Dave
Manuals@ArtekManuals.com
www.ArtekManuals.com


Re: Need Help Troubleshooting Tektronix PS280

daven9ooq <daven9ooq@...>
 

Chuck, My apologies also, We got started off on the wrong foot, Can we Please forget all that and put it behind us!I do appreciate your help very much!
I have this Supply now and am commited to fixing it, I have a awefull lot going on at this time , Can we pick this up again next week.
This is a learning experience for me!  I wouldn't ask for help if I didn't need it.
Many thanks
 Dave


Microfiche Prioritization

bobkrassa
 

Following the discussion of the offer of the big microfiche library from England, and the indication that the Museum already has a similar collection and is willing to scan specific materials on request, leads me to suggest a discussion about what batch microfiche scanning should take priority.

I would suggest that mod summaries would be by far the most useful category to batch scan. Transformer winding info might be second.

As far as manuals, I will admit that I too have spent quite a bit of time searching for later manuals for some Tek equipment, but on those occasions when I have been successful have not found that the revised manual was all that different, except of course for parts lists and schematics which would be in the mod summaries.

If there is consensus on batch scanning then perhaps we could all donate some money to the Museum to have it done.

Also, some mod summaries were scanned and some of us have them. I am not at home but think I have several pdfs. Perhaps all of us should see what we have and send pdfs to the Museum and to Tekwiki.

73s Bob Krassa ACØJL


Re: Tek 468 $20 on CL in Austin

Abc Xyz
 

I would love to have it!

On Wed, Sep 4, 2019, 6:42 AM dnmeeks <dan-meeks@austin.rr.com> wrote:

I am getting this scope - will pick up later in the week or over the
weekend. I don't need it but would like to find it a good home. I would
ship from 78732 for actual shipping cost (plus the $20 purchase price).




Re: Tek 468 $20 on CL in Austin

vaclav_sal
 

great,the owner just told me I was not the first to inquire about it.

i was actually interested if the delay sweep switch is same as in 464.So if in you ar planning to take it apart keep me in mind.
But if your plan is to resurrect it, no problem.
Cheers

On Wednesday, September 4, 2019, 8:42:41 AM CDT, dnmeeks <dan-meeks@austin.rr.com> wrote:

I am getting this scope - will pick up later in the week or over the weekend. I don't need it but would like to find it a good home. I would ship from 78732 for actual shipping cost (plus the $20 purchase price).

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