开云体育

Yes, LEVER switches. Thanks Dave. I had a mental block.

Please include a screen shot of the schematic and of the capacitor,

Jon

Bert, any chance I can take you up on your 335 or tube?

Thanks,
-S

On that auction place. Price seems high but maybe not to someone who really needs one ;)

My 7854 recently started to act up and after investigation I found the +15v regulated supply was sagging to 14.2v and had some ~50kHz 20mV ripple. Probing deeper into the SMPS I further found the unreg +17v supplying the +15v regulator had the same 50kHz ripple but at 168mV! The problem turned out to be C142 on the A12 control rectifier board. This 330uF Sprague axial lead capacitor had dried up and was not doing it's job. I the process of replacing most of the capacitors in the SMPS I've come across an infamous Rifa safety cap across the mains input. After ordering a modern X2 rated replacement for it I realized the Rifa is not a safety cap, but a snubber. It has a built-in 22 ohm resistor in series with the .1uF capacitor. Looking at the schematic, I see Tek built a snubber out of discrete parts, but at some later point replaced the parts with the Rifa.

The question... how important is the resistor? Will the new X2 safety cap by itself be okay, or should I endeavor to add the series resistance?

They definitely did use them early on. I have a Type B plug in that has several of the buggers. Kinda like selenium rectifiers (the B has one of those too...) you can assume they are no good.

Sean

Lever switches.

From: [email protected] [mailto:[email protected]] On Behalf Of Joel B Walker via groups.io
Sent: Saturday, April 10, 2021 5:58 PM
To: [email protected]
Subject: Re: [TekScopes] tek scopes spotted?

Sorry, rocker switches is what came to mind. I can't think off hand the proper name for the type of switches on the 547. They are on both time bases. The 549 has them as well as the 544.

Sorry, rocker switches is what came to mind. I can't think off hand the proper name for the type of switches on the 547. They are on both time bases. The 549 has them as well as the 544.

THANKS TO ALL WHO INQUIRED. THIS HAS BEEN SPOKEN FOR!
--
William, k6whp
"A friend told me to cheer up, things could be worse.
So I cheered up and, sure enough, things got worse!"

That’s called deflection blanking. The 321 uses that system.

Dave Wise

From: [email protected] [mailto:[email protected]] On Behalf Of Bert Haskins via groups.io
Sent: Saturday, April 10, 2021 12:52 PM
To: [email protected]
Subject: Re: [TekScopes] Looking for a 335 CRT


On 4/10/2021 11:58 AM, Stefan wrote:

Pulled the tube last night and found a rice grain sized piece of glass and a smaller bit of metal rattling around inside. I assume ANY loose bits in a tube is a bad sign? Also, it looks like the tube was stabilized with wax, which has certainly deteriorated in the past 40 or so years - yuck!

I seem to remember that blanking doesn't work the same way on the 335 as
on other Teks.

There is a deflection? plate that just repels the beam off to one side
for blanking and in dim light with the intensity turned way up you may
see a glow when looking at the face of the tube when blanked.

XY mode forces unblanking.

I hope that someone will correct me if I am wrong on this.

Bert

Swapped from Tek 485 scope as working when it was. Has socketed NPNs, etc.

Free to good home; just reimburse me for shipping from SoCal - 92708.
--
William, k6whp
"A friend told me to cheer up, things could be worse.
So I cheered up and, sure enough, things got worse!"

Hi Harvey,

I don't have a [5]CT1N - yet - just a low priority slot on the wish-list.

If you have boards left after distributing to everyone with more concrete use for them, please email me your address. Via my profile here.

I've had a few experiences like this, here are just a few that come to mind:

1. I picked up a P6045 active FET probe in non working but otherwise as-new condition. It even had an "Instrument Checked" tag from the local Tek distributor. The reason it didn't work was that the tiny 100 ohm resistor in series with the probe tip had never been installed! I installed a small SMD part and it hasn't missed a beat.

2. On one of my non-working 7000 series plugins one of the screws that held a PCB down was missing. It happened to be the one that acted as the chassis return for the PCB so once it was replaced all was well.

3. Recently I've been helping a friend restore a late model 549 and we have found several mistakes and differences between the manual and reality. One interesting one was a couple of resistors that had been added in series with the relay contacts, probably to prevent them welding when the power supply caps charged up. The manual schematic showed them as an addition. These had the effect of increasing the ESR of a filter cap to the point where the power supply ripple was excessive and that in turn affected triggering.

Morris

On Fri, Apr 9, 2021 at 11:34 PM, Dave Peterson wrote:

/g/TekScopes/album?id=262825

This is about a 100MHz signal. I also have to say I happen to live about
2000ft. away from Sutro Tower in San Francisco

When I bought my 465B, I had it shipped to me at work, and, of course, I checked it out there and found it to be perfect. When I brought it home, I discovered noise on the most sensitive setting that hadn't been there at work. I tried different outlets around the house, but that made little difference. This was puzzling, until I noticed a correlation with the station my radio happened to be playing. Turning the radio off didn't help. Took the scope back to work and there it was fine.

Conclusion: There's a fundamental difference between a wood frame house and a steel building.

I find myself seeing TEK equipment in some of the strangest places on TV. Now I need to make notes!
--
Michael Lynch
Dardanelle, AR

On Fri, Apr 9, 2021 at 05:25 PM, stevenhorii wrote:

The small image on upper right clearly shows a Tek scope on a cart. It looks
to be a 500-series, but the image resolution is too poor to make out much
more. The image in the lower center shows a very early (likely prototype)
articulated arm scanner. My question is what is that scope? It clearly uses
plug-ins and the CRT is rectangular (or has a rectangular mask).

The scope in the 3rd photo on that page is a Tek 564B/MOD121N (auto erase.) The fact that there are 5 knobs in the upper right corner give away the auto erase feature. However, this an unusual 564B: There's no calibrator, which would normally have been right above the right hand plugin. TekWiki shows 3 different variations of the 564 but no variations of the 564B. All versions shown have calibrators.

My 564B/121N, sitting just to my right as I type this, is the same as this one:



except the 121N has 6 horizontal pushbuttons (instead of 4) and 5 knobs in the UR corner (instead of 4.)

Wasn't that Nikola Tesla's idea of broadcasting power, rather than sending
it through cables ?
Saw a TV prog on Wardenclyffe, Shoreham NY. I bet if that thing had worked
it would have zapped a few front-ends !!

Tim



On Sat, 10 Apr 2021 at 18:37, J Hunt via groups.io <jmailhunt=
[email protected]> wrote:

Dave,
I visited Smith-Kettlewell Eye Research Institute in SF around 1974 for
some collaborative work. Google maps shows them about 2.5 miles from the
Sutro Tower that is your RF ground noise nemesis. One of the EEs there
showed me a small hand-wired board he built that consisted of maybe ten
4000 series CMOS logic ICs. He was puzzled that it ran (though eratically)
without the battery connected. It turns out that the input protection
diodes on the gates along with the short and tidy wiring were acting as
crystal sets and providing enough Vcc and current to run the circuit
(depending on the level of modulation from the nearby radio stations).
Mounting the board in an aluminum project box solved the problem, but he
did need to install a battery.

John HuntPortland, OR

There are horizontal glass rods that support the vertical deflection plates; one of these rods is cracked and the plate is slightly shifted. If there is a blanking plate, it must be connected at the neck. Only 4 wires lead to the mid-section.

-S

On Fri, Apr 9, 2021 at 02:11 PM, Dave Peterson wrote:

Oh, yep, there you go. Disregard my last message. That's what I'm talking
about. I think this is one of the features of a pre SN B250K. I'm only
guessing based on the now two examples. I don't know where these details might
be documented.

Dave

I’m not sure they are.
Also, mine is a European made model. With my limited experience, I noticed that, given the same model, European made ones are, usually, closer to later US made ones. Probably because European factories were setup later than US ones, and modifications/upgrades had already been made. But I would assume they used older parts they had, even on more recent/upgraded units, just to not waste them. That would make sense. All companies do that. But who knows really....?

I’m wondering if the regular philips screws that hold the front bezel are original. I’ve never seen that.

PS: That power supply is not very friendly with me at the moment.
I think I have been having a thing with power supplies lately. They just don’t like me, I guess. ?

On Fri, Apr 9, 2021 at 02:07 PM, Dave Peterson wrote:

Stephen,

Compare your scopes TIME/DIV B-sweep knob and HORIZ DISPLAY A button to the
picture of my pre SN B250K. There is no "LOCK KNOBS" text on them. I'm
presuming this is a pre SN B250K feature. I don't know that that is the case,
I'm just presuming so.

Maybe... who knows...

Could it be that someone has swapped these components on yours or mine?

I highly doubt that.

My scope's condition is pretty good. A bit dirty in the usual places, but doesn't
seem to have been dismantled before.

Mine as well. Everything is stock as can be. The only person sho has bee in there was only to take a few compositions out; maybe in a attempt to repair it. Other than that, it was extremely dirty. A thick layer of soot was nearly everywhere inside. I cleaned it up pretty nicely.
The exterior was pretty much in the same condition. That thing was absolutely filthy inside and out.