Date   

Re: Tek 335

Artekmedia <manuals@...>
 

Steve

(Reply off list)

He was asking about a 335 ...not a 535 :-)

Dave


On 6/20/2013 4:36 PM, Steve wrote:
 

--- In TekScopes@..., ka4dkj@... wrote:
>
> Hi Everyone
>
> I stumbled across a 335 for a very reasonable price.
> The problem is that it doesnt work on AC.
>
> My question is.....how hard is the AC PS to service??
> At this time i do not have the manuals but they are on the way.
>
> Ralph
>

The power supply is linear and very easy to troubleshoot. Manuals are available on line. The power supply of the 535 is identical to the 531, and quite possibly the 541 and 545 as well, although the latter may have additional tubes (in parallel) in some of the power supplies to handle the increased currents required for the distributed amplifier. Also, the shunt resistors (placed around the series regulating tubes) have different values, again for the differences in load between the 53x and 54x, as well as the added circuitry for the second time bases in the 5x5.

Two points of caution: the "low voltage" power supplies run up to 500 VDC and have large electrolytic caps which store a lot of energy. Shocks can be more than painful – possibly life threating. Use the "one hand in the pocket" rule when working around these. I have also found that insulating all but the very tip of your voltmeter probe with a section of plastic sleeving will help prevent damage from shorts if the probe slips off the lead and the point contacts the chassis (ground). Fluke makes probe leads which have this feature built in (1000 V rating), which are convenient.

Some of the regulators use a circuit topology where the feedback comparator tube pulls down on the grid of the series regulator tube to cut it off. A resistor pulls the grid up to the plate. In this topology, removing the comparator tube during troubleshooting will cause the series regulator tube to saturate, pulling the supply to the positive rail. This has the potential to damage many other components in the scope. Use care when troubleshooting, and really understand the circuit operation before removing any tube.

I find working on these old scope entertaining, as many in this group do. Have fun with your restoration and report back your results.

- Steve


-- 
Dave Henderson
Manuals@...
www.Artekmanuals.com
PO Box 175
Welch,MN 55089
651-269-4265


Re: Tek 335

ditter2
 

--- In TekScopes@yahoogroups.com, ka4dkj@... wrote:

Hi Everyone

I stumbled across a 335 for a very reasonable price.
The problem is that it doesnt work on AC.

My question is.....how hard is the AC PS to service??
At this time i do not have the manuals but they are on the way.

Ralph
The power supply is linear and very easy to troubleshoot. Manuals are available on line. The power supply of the 535 is identical to the 531, and quite possibly the 541 and 545 as well, although the latter may have additional tubes (in parallel) in some of the power supplies to handle the increased currents required for the distributed amplifier. Also, the shunt resistors (placed around the series regulating tubes) have different values, again for the differences in load between the 53x and 54x, as well as the added circuitry for the second time bases in the 5x5.

Two points of caution: the "low voltage" power supplies run up to 500 VDC and have large electrolytic caps which store a lot of energy. Shocks can be more than painful – possibly life threating. Use the "one hand in the pocket" rule when working around these. I have also found that insulating all but the very tip of your voltmeter probe with a section of plastic sleeving will help prevent damage from shorts if the probe slips off the lead and the point contacts the chassis (ground). Fluke makes probe leads which have this feature built in (1000 V rating), which are convenient.

Some of the regulators use a circuit topology where the feedback comparator tube pulls down on the grid of the series regulator tube to cut it off. A resistor pulls the grid up to the plate. In this topology, removing the comparator tube during troubleshooting will cause the series regulator tube to saturate, pulling the supply to the positive rail. This has the potential to damage many other components in the scope. Use care when troubleshooting, and really understand the circuit operation before removing any tube.

I find working on these old scope entertaining, as many in this group do. Have fun with your restoration and report back your results.

- Steve


Re: 453 CRT removed from screen: photos

John
 

--- In TekScopes@yahoogroups.com, "Ed Breya" <edbreya@...> wrote:

I'd say it has suffered some damage, and may not work properly any more. Ed
Ed:

Much as it grieves me, I have to concur. ;-(


Re: 453 CRT removed from screen: photos

John
 

"those corners are not intentionally glued"

Oh yes they were! Brown fine-pored foam, just in the four corners. It wasn't going to pop out with mere mortal efffort.

John

--- In TekScopes@yahoogroups.com, larrys@... wrote:

"Michael A. Terrell" <mike.terrell@...> wrote:

He definitely defaced it.
Groan! Seriously, .
They do stick pretty badly sometimes. The proper way to get the
tube out is to loosen the clamp around the neck (inside the shield)
and push like crazy on the center of the base with your thumbs.
Have a soft landing zone ready for when it pops out. No shocks and
no prying. That's bad mojo.
-ls-


Re: 453 CRT removed from screen: photos

teamlarryohio
 

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote:

He definitely defaced it.
Groan! Seriously, those corners are not intentionally glued.
They do stick pretty badly sometimes. The proper way to get the
tube out is to loosen the clamp around the neck (inside the shield)
and push like crazy on the center of the base with your thumbs.
Have a soft landing zone ready for when it pops out. No shocks and
no prying. That's bad mojo.
-ls-


Re: 453 CRT removed from screen: photos

Michael A. Terrell
 

Ed Breya wrote:

I'd say it has suffered some damage, and may not work properly any more. Ed

He definitely defaced it.


Re: 453 CRT removed from screen: photos

Ed Breya
 

I'd say it has suffered some damage, and may not work properly any more. Ed

--- In TekScopes@yahoogroups.com, "John S" <John@...> wrote:


Purely from curiosity, I removed this CRT from its Mumetal screen: not an easy task, as it was "glued" in at the front corners with what looked like foam.

To my surprise, the front face detached in the process, so I've taken some photos looking back down the tube. I was also surprised to see a "window" through which the electron beam fires: the last object prior to hitting the screen. You can just see where beam has "written" on this window.

The Y-plates are segmented, but all wired in parallel: I did wonder if this was a part common to the 454, and for this latter variant they added inductors to create the delay line?

Photos at

http://www.flickr.com/photos/jaybs/sets/72157630205984812/

John


Re: Waaayyyy OT for Portland folks

Ed Breya
 

Yes, the computer was prominently displayed along with racks of other equipment behind the DJ's station. I don't know who programmed it, but it seemed to work. The earthquake began at 8:00 PM, as I recall - signaling the end of happy hour with several kW of audio power available, in case you didn't notice the light show.

It was the Studio 54 of Beaverton, or perhaps the whole state. A lot of fun times.

Ed

--- In TekScopes@yahoogroups.com, larrys@... wrote:

"Ed Breya" <edbreya@...> wrote:
Ethel's was long gone even twenty five years ago - I think a car parts
store was in its place the last time I was there about fifteen years
ago.
The story back then was that programming for the fancy lighting
effects was done by one of Howard's sons. It supposedly ran on a PDP-8.
-ls-


Re: OT: Capacitors in general

vdonisa
 

Hello again, I went through all the suggested documents and I now feel better educated. Thank you all for providing the links.

I just wanted to add that in its March 2013 through-hole MLCC catalog, TDK has introduced a couple of C0G caps in larger capacitance values than available one year ago. So now you can get 0.1uF, 0.15uF and 0.22uF / 50V in stable C0G dielectric for your filter / oscillator or similar project.

As reported previously, I got a pair of the .22 ones, they look great on the LCR meter, and I have this strong feeling that they'll go inside my 2467B HVPS. :-)

Cheers,
Valentin


Re: 453 CRT removed from screen: photos

 

On the 7834 where I have separated the shield from the CRT a couple of
times, they are completely separate pieces. There it is possible to
install the CRT without the shield although all of the magnetic
interference from the rest of the oscilloscope renders the CRT useless
until the shield is installed; the display becomes a smear.

On Thu, 20 Jun 2013 16:01:06 -0000, "John S" <John@sykesj.co.uk>
wrote:

Purely from curiosity, I removed this CRT from its Mumetal screen: not an easy task, as it was "glued" in at the front corners with what looked like foam.

To my surprise, the front face detached in the process, so I've taken some photos looking back down the tube. I was also surprised to see a "window" through which the electron beam fires: the last object prior to hitting the screen. You can just see where beam has "written" on this window.

The Y-plates are segmented, but all wired in parallel: I did wonder if this was a part common to the 454, and for this latter variant they added inductors to create the delay line?

Photos at

http://www.flickr.com/photos/jaybs/sets/72157630205984812/

John


Re: Waaayyyy OT for Portland folks

 

On Thu, Jun 20, 2013 at 8:24 PM, <larrys@teamlarry.com> wrote:
Dave C <davec2468@yahoo.com> wrote:
The story back then was that programming for the fancy lighting
effects
What "fancy lighting effects" are those?
Been a long time. ISTR some really flexible chase lights, strobes,
screens rolling down from the ceiling (for earthquake loops),
synchronized with loud audio. Back around 1980, it was one of those
places where "If you have a trip to Beaverton you have to go there."
In today's world, it would probably be called quaint :-/
-ls-
Quaint is the new exciting, though.


Re: OT: Capacitors in general

keantoken
 

Look at this page for a bridge comparison of different capacitors, with some pictures of the residuals.

Also see his article on a capacitance bridge:

http://www.conradhoffman.com/cap_bridge.pdf


Re: Waaayyyy OT for Portland folks

teamlarryohio
 

Dave C <davec2468@yahoo.com> wrote:
The story back then was that programming for the fancy lighting
effects
What "fancy lighting effects" are those?
Been a long time. ISTR some really flexible chase lights, strobes,
screens rolling down from the ceiling (for earthquake loops),
synchronized with loud audio. Back around 1980, it was one of those
places where "If you have a trip to Beaverton you have to go there."
In today's world, it would probably be called quaint :-/
-ls-


Re: Waaayyyy OT for Portland folks

Dave C <davec2468@...>
 

The story back then was that programming for the fancy lighting
effects 

What "fancy lighting effects" are those?

Dave


Re: Waaayyyy OT for Portland folks

teamlarryohio
 

"Ed Breya" <edbreya@yahoo.com> wrote:
Ethel's was long gone even twenty five years ago - I think a car parts
store was in its place the last time I was there about fifteen years
ago.
The story back then was that programming for the fancy lighting
effects was done by one of Howard's sons. It supposedly ran on a PDP-8.
-ls-


Re: Did anyone see this 2465?

Michael A. Terrell
 

Michael A. Terrell wrote:

http://www.ebay.com/itm/350805825418

"Tektronix-2465-4-Channel-300-MHz-Portable-OscilloscopeDisplay-Flashes-Parts-"

BIN $174.99 & free shipping

It arrived today, and is in good condition, other than one push button. I plan on cleaning the case and recapping it before I see what else it may need. The seller packed it with rigid polyurethane foam, about 1.5" on all sides.


453 CRT removed from screen: photos

John
 

Purely from curiosity, I removed this CRT from its Mumetal screen: not an easy task, as it was "glued" in at the front corners with what looked like foam.

To my surprise, the front face detached in the process, so I've taken some photos looking back down the tube. I was also surprised to see a "window" through which the electron beam fires: the last object prior to hitting the screen. You can just see where beam has "written" on this window.

The Y-plates are segmented, but all wired in parallel: I did wonder if this was a part common to the 454, and for this latter variant they added inductors to create the delay line?

Photos at

http://www.flickr.com/photos/jaybs/sets/72157630205984812/

John


Re: CRT magnetic screens: Mumetal?

Ed Breya
 

It's not about degaussing, it's a problem with losing the grain orientation that was imparted during annealing.

Annealing it is very difficult since the temperature is quite high - like approaching its melting point, and the hydrogen atmosphere is very risky. It occured to me once to maybe try an oxy-hydrogen torch with an over-rich flame, but then the problem is what do you do about the opposite side, and the transition region from flame to not, and hot to cold. It really needs to be in a uniform environment.

If you buy raw sheet stock, it may be un-annealed, so won't work as well as that in a finished piece that definitely would have been. If the stock is labeled so or known to be annealed, then it's good stuff to keep around.

Ed

--- In TekScopes@yahoogroups.com, Peter Hildebrandt <petertech99h@...> wrote:

Hi Steve,

Can you save a dropped shield with a AC degauss coil?  How high a temperature
was needed to anneal the Mu metal?
A local guy over here is sitting on a little stock of Mu, maybe I'll get it for future
use! you never know!

see ya

Peter
 
 




________________________________
From: Steve <ditter2@...>
To: TekScopes@yahoogroups.com
Sent: Wednesday, June 19, 2013 5:05:53 PM
Subject: [TekScopes] Re: CRT magnetic screens: Mumetal?



 
--- In TekScopes@yahoogroups.com, "John S" <John@> wrote:


I've always assumed that the blue screen around the CRT on Tek scopes (400 series etc) was made of Mumetal. Is this actually true?

John
Yes.

Tek fabricated them from raw stock. After they were cut, bent and spot welded, they went into an oven to be annealed (mu metal loses its shielding properties if physically bent or modified (drilling holes etc.) after annealing. If you drop a shield on the floor and the corner bends - throw it away.) The ovens operated at high temperature in a pure hydrogen (reducing) atmosphere. Opening an oven door before it had cooled posed an explosion hazard. To minimize the danger, Tek used several small ovens, each could only contain about 4 or 6 shields.

- Steve


Re: CRT magnetic screens: Mumetal?

Ed Breya
 

That's a good question - I have only used tin snips, which necessarily bend the two sides of the cut. A saw or wheel would be better in that respect. I think a very fine carbide-tipped saw would give the cleanest cut. The material may be soft enough to gum up an abrasive wheel, but I don't know. If you try these methods, please let us know how they work.

I usually assume that any reworked piece will have less than half of its original effectiveness just from handling, and maybe one-tenth near any stressed zones. Even if you beat the hell out of it, it's still at least as good as the original un-annealed material, which I would think is at least as good as steel.

Ed

--- In TekScopes@yahoogroups.com, d.seiter@... wrote:

While I've never played with Mu-metal, I have kept all my shields too, knowing about the properties of the material. My question- I know bending and heating affect the metal, but I didn't know that cutting it had an effect. What is the best way to cut it? I'd assume no deflection, so a small cutting disc on well supported stock with coolant would seem to be the best approach?


-Dave

----- Original Message -----
From: "Ed Breya" <edbreya@...>
To: TekScopes@yahoogroups.com
Sent: Wednesday, June 19, 2013 4:36:41 PM
Subject: [TekScopes] Re: CRT magnetic screens: Mumetal?






I think in the earlier days, or in some manuals, there were warnings about avoiding stresses on the material. It's not practical to re-anneal to original performance if seriously banged up, but the overall shielding is still pretty good even so, and certainly better than nothing. For our purposes, I wouldn't worry too much about a few dings here and there - just don't put any magnets near the defects, which could become slightly magnetized and possibly cause distortion in the CRT.

I've saved the shields from every CRT item I've ever junked out, and have worked and re-used the material for a number of applications. It loses some of its effectiveness near any cuts or sharp bends, but large planar areas that aren't stressed too much tend to be OK.

Ed

--- In TekScopes@yahoogroups.com , "John S" <John@> wrote:


Thanks for the confirmation guys: must have been an expensive component. There's no "warning" lable on either the shield or the manual to tell you not to knock etc.

John


Tek 335

vdonisa
 

Hello gents, quick question - what would be the entertainment factor in trying to restore a Tek 335? Would this be some pleasurable exercise or a nightmare where you need 3-4 hands in order to dis(assemble) the thing, and some unobtainium parts too for adding spice?

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