Date   
Re: Tektronix 2465

Jose Alfredo
 

Hi Guys, the problem was the output impedance of the Function Generator. Now it's ok, and the 50 ohm resistor, in both channels are good.

After doing lots of tests, a new issue came out: if I input a 500 mVpp on Channel 1, and the vertical scale switch is set to 500 mV, the signal is shown within 1 graticule in the scrren. OK. If I input 1V and with the same 500 mV setup, the sign shows within 2 graticules, again, corectly. If, at this point, I change the vertical scale to 1V, expecting the signal to fit within 1 graticule in the screen, the signal increases in amplitude, using almost 7 graticules, as the input voltage where 7 Vpp.

Everything is just fine above the 1V vertical scale setting. The problem occurs when I change the switch from 500 mV to 1V.

So I thought it could be the problem Chuck described concerning the relays contacts. I was able to remove the channel 1 attenuator module and, very carefully, cleaned all the pad contacts in the module. Also cleaned the pins of the relays and  the relay contacts. Assembled it back and the problem presists.

Note: When changing the vertical scale, the correct value is shown in screen. That made me thought, maybe that's not a problem with the relays contacts!

Channel 2, in the other hand, is all well. Works just fine in any vertical scale.

Guys, do you think I'd better remove the attenuator module again and try a better cleanning, or does anyone of you have any idea on what could be causing this issue?

Thanks all of you ...

Jose Alfredo


Em 27/12/2019 13:46, Chuck Harris escreveu:

The 50 ohm load resistor in the 2465 is a metal film
resistor that is deposited on the ceramic substrate
of the attenuator module. It is covered with
a temperature sensor film thermistor, and when it
reports that it is too warm, the CPU cuts it out of the
circuit.

To blow it, you have to do something really egregious,
like connect it to a high current supply that can
get the resistor really hot, really quickly.

I would guess that it can protect itself from an insult
in the several watt range. I have never felt the urge
to test it, though.

The manual has this obscure phrase:

5V rms; 0.5W-seconds during any 1-s interval for instantaneous
voltage from 5V to 50V.

Note that 5V -> 0.5W, and 50V -> 50W.

So, I think they are saying it can take 5Vrms for 1 second,
and 50V for 1/100th of a second.

If you can stand a little change in performance, it would not
be impossible to attach a SMD 50 ohm resistor in its place.

As I said earlier, the relays are common problem areas.. both
their contact regions, and the socketed coil pins.

It is a little difficult to remove the attenuator, you have to
remove the bezel, CRT knobs, and front panel assembly, and
several screws reachable from the hole where the front panel
assembly goes, and below the attenuator's bezel extension, and
unsolder a lead from a trimmer cap, and the vertical hybrid...

But, once you have it out of the circuit, everything likely to
be bad can be checked with a DVM. Take it easy on the gold.

-Chuck Harris

satbeginner wrote:
Hi,

There is something wrong with either just the input 50 Ohm resistor, and/or the input attenuator box.

The change when you remove the external 50 Ohm is as expected, a rise in amplitude when you remove it.

However, the fact there is no change when you switch off the internal 50 Ohm terminator, indicates there is a problem there.

Such damage does happen when a too high voltage was inserted while set at internal terminator, that resistor usually is damaged, and, if the voltage was really high, the variable attenuator box behind that resistor is damaged too.

Can you check the same things on Ch2?

Un saludo,
Leo



Re: Ultimately recyclers have to scrap our treasures - an idea so maybe some can survive

Chuck Harris
 

That's a great idea! Who is that person that wants all of our
junk?

The kids don't want it... it doesn't play Best Fiends. The schools
don't want it, too much liability, and takes too much space... Besides,
they have tons of stuff they are dumping themselves...

Maker spaces want to tear it apart and make "art". You know, take the
nixies and make a clock, or build little resistor men, or use it as a
stand for a coffee table... stuff like that. They have no interest
in using it.

The steam punks want to pervert it... take a manual typewriter and use
it as I/O for their PC.

Putting together a list of people that want your stuff for free will
gather together a bunch of leeches that want to cherry pick the good
things so they can sell them, and leave you with the debris.

Ask the hams about the silent-key sales. You never see any of the
good stuff, it all goes to other members of the club. Only the trash
gets sold to help the X-XYL.

If you want your stuff to go somewhere nice after you die, you had
better get it there while you are still alive. Otherwise, it is all
going in the trash.

It is probably better just to not care what happens to it.

As an example, my uncle was a real audio enthusiast. He made a pair
of Klipch Horns from prints he got from Paul Klipch when they worked
together (1940's). He built all of his vacuum tube audio amplifiers
from parts he got from the Army, when he was in this, or that lab,
and he was using the best designs available at the time.

Did I mention he was a "real" audio enthusiast? Well, he was, and that
meant when better technologies arrived, he followed along... but he
couldn't just throw his old stuff away... to much of him was invested
in it.

When he died, his kids put all of his collection on the curb for the
garbage to collect. Because I "built things", they called me to see if
I wanted any of the plywood and lumber he had... so, I came over and
found thousands of dollars of tube audio equipment (by today's) prices
at the curb with a half ton of lumber scraps tossed on top.

Your heirs have no interest in anything but your money and your bling.

-Chuck Harris (I can feel Dennis's glaring eyes on the back of my neck)

bhome1959 wrote:

Why not donate the equipment to those who need or can use it while the person getting
the equipment covers costs of getting the equipment to them? It really hurts me when
I see otherwise good equipment trashed. This might be a more workable solution.

-Chris

Re: Stan Griffiths Craigslist Posting

n4buq
 

This link may be easier to use:

https://tinyurl.com/BeavertonSale

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Dennis Tillman W7PF" <@Dennis_Tillman_W7pF>
To: TekScopes@groups.io
Sent: Tuesday, January 14, 2020 1:07:10 PM
Subject: [TekScopes] Stan Griffiths Craigslist Posting

I saw this today in Craigslist:
https://seattle.craigslist.org/skc/ele/d/beaverton-estate-radio-repair-shop-
sale/7055039838.html

The photo looks like this is Stan Griffith's collection and he is selling
it.
I also heard a rumor to this effect last week from a friend.
If this is Stan's I can say from seeing it many times that it is an enormous
collection.
Full disclosure: I am not involved in any way.

Dennis Tillman W7PF



--
Dennis Tillman W7PF
TekScopes Moderator



Re: Stan Griffiths Craigslist Posting

Richard R. Pope
 

Vince,
That will work but if you copy the complete url right up to the .html and then paste it that works also. It has to be this: minus the quotes.

"https://seattle.craigslist.org/skc/ele/d/beaverton-estate-radio-repair-shop-

sale/7055039838.html"

GOD Bless and Thanks,
rich!

On 1/14/2020 1:45 PM, Vince Vielhaber wrote:

It's there. Go to: https://seattle.craigslist.org/ and search for "beaverton estate" and it'll come up.

I copied the url, but it was the same as what Dennis posted.

Vince.




On 01/14/2020 02:20 PM, Dan Cordova via Groups.Io wrote:
Your link says there is nothing there...
On Tuesday, January 14, 2020, 11:07:21 AM PST, Dennis Tillman W7PF <@Dennis_Tillman_W7pF> wrote:

I saw this today in Craigslist:
https://seattle.craigslist.org/skc/ele/d/beaverton-estate-radio-repair-shop-
sale/7055039838.html

The photo looks like this is Stan Griffith's collection and he is selling
it.
I also heard a rumor to this effect last week from a friend.
If this is Stan's I can say from seeing it many times that it is an enormous
collection.
Full disclosure: I am not involved in any way.

Dennis Tillman W7PF


Re: Stan Griffiths Craigslist Posting

Vince Vielhaber
 

It's there. Go to: https://seattle.craigslist.org/ and search for "beaverton estate" and it'll come up.

I copied the url, but it was the same as what Dennis posted.

Vince.

On 01/14/2020 02:20 PM, Dan Cordova via Groups.Io wrote:
Your link says there is nothing there...
On Tuesday, January 14, 2020, 11:07:21 AM PST, Dennis Tillman W7PF <@Dennis_Tillman_W7pF> wrote:

I saw this today in Craigslist:
https://seattle.craigslist.org/skc/ele/d/beaverton-estate-radio-repair-shop-
sale/7055039838.html

The photo looks like this is Stan Griffith's collection and he is selling
it.
I also heard a rumor to this effect last week from a friend.
If this is Stan's I can say from seeing it many times that it is an enormous
collection.
Full disclosure: I am not involved in any way.

Dennis Tillman W7PF


Re: Stan Griffiths Craigslist Posting

Richard R. Pope
 

To whom it concerns,
You need to do a copy and paste of this complete URL. Clicking on the link will not work.

https://seattle.craigslist.org/skc/ele/d/beaverton-estate-radio-repair-shop-

sale/7055039838.html

GOD Bless and Thanks,
rich!

On 1/14/2020 1:36 PM, greenboxmaven via Groups.Io wrote:
It does not work. Nothing there


On 1/14/20 2:26 PM, Mark Huffstutter wrote:
Wow, that is a Lot of equipment!
Could only be Stan's. Or the store room at Vintage Tek
Museum!

Mark
KB7WAL


I saw this today in Craigslist:
https://seattle.craigslist.org/skc/ele/d/beaverton-estate-radio-repair-shop-
sale/7055039838.html

The photo looks like this is Stan Griffith's collection and he is selling
it.
I also heard a rumor to this effect last week from a friend.
If this is Stan's I can say from seeing it many times that it is an
enormous
collection.
Full disclosure: I am not involved in any way.

Dennis Tillman W7PF



--
Dennis Tillman W7PF
TekScopes Moderator








Re: Stan Griffiths Craigslist Posting

greenboxmaven
 

It does not work. Nothing there

On 1/14/20 2:26 PM, Mark Huffstutter wrote:
Wow, that is a Lot of equipment!
Could only be Stan's. Or the store room at Vintage Tek
Museum!

Mark
KB7WAL


I saw this today in Craigslist:
https://seattle.craigslist.org/skc/ele/d/beaverton-estate-radio-repair-shop-
sale/7055039838.html

The photo looks like this is Stan Griffith's collection and he is selling
it.
I also heard a rumor to this effect last week from a friend.
If this is Stan's I can say from seeing it many times that it is an
enormous
collection.
Full disclosure: I am not involved in any way.

Dennis Tillman W7PF



--
Dennis Tillman W7PF
TekScopes Moderator





Re: Commercial Circuit Simulator that includes vacuum tube library is now free.

Vince Vielhaber
 

Actually the term "lusers" comes from the BOFH (you'll have to look up that acronym). It referred to the clueless users in the office or school and especially the ones that were always needing help. Side note, it was before linux even existed!

*end of history lesson*

Vince.

On 01/14/2020 01:58 PM, Jim Tibbits wrote:
And for all us (L)users...."linux users"...works fine with WINE on my mint
19.2

Jim

On Tue, Jan 14, 2020 at 10:38 AM Ancel <@Protofabtt> wrote:

https://hackaday.com/2020/01/08/commercial-circuit-simulator-goes-free/

Looks useful, a step up from LTspice, no micro-controllers though.
Ancel



Re: Stan Griffiths Craigslist Posting

Dan Cordova <danny_cordov@...>
 

Okay, got it.  
You have to copy and paste.

On Tuesday, January 14, 2020, 11:24:16 AM PST, Dale H. Cook <bridgewaterma@...> wrote:

On 1/14/2020 2:20 PM, Dan Cordova wrote:

  Your link says there is nothing there...
The line wrapped in Dennis' post
--
Dale H. Cook, Member, NEHGS, AGS, MA Soc. of Mayflower Descendants;
Plymouth Co. MA Coordinator for the USGenWeb Project
Administrator of https://plymouthcolony.net

Re: Stan Griffiths Craigslist Posting

Mark Huffstutter
 

Wow, that is a Lot of equipment!
Could only be Stan's. Or the store room at Vintage Tek
Museum!

Mark
KB7WAL

I saw this today in Craigslist:
https://seattle.craigslist.org/skc/ele/d/beaverton-estate-radio-repair-shop-
sale/7055039838.html

The photo looks like this is Stan Griffith's collection and he is selling
it.
I also heard a rumor to this effect last week from a friend.
If this is Stan's I can say from seeing it many times that it is an
enormous
collection.
Full disclosure: I am not involved in any way.

Dennis Tillman W7PF



--
Dennis Tillman W7PF
TekScopes Moderator



Re: Stan Griffiths Craigslist Posting

Dale H. Cook
 

On 1/14/2020 2:20 PM, Dan Cordova wrote:

Your link says there is nothing there...
The line wrapped in Dennis' post
--
Dale H. Cook, Member, NEHGS, AGS, MA Soc. of Mayflower Descendants;
Plymouth Co. MA Coordinator for the USGenWeb Project
Administrator of https://plymouthcolony.net

Re: Stan Griffiths Craigslist Posting

Dan Cordova <danny_cordov@...>
 

Your link says there is nothing there...

On Tuesday, January 14, 2020, 11:07:21 AM PST, Dennis Tillman W7PF <@Dennis_Tillman_W7pF> wrote:

I saw this today in Craigslist:
https://seattle.craigslist.org/skc/ele/d/beaverton-estate-radio-repair-shop-
sale/7055039838.html

The photo looks like this is Stan Griffith's collection and he is selling
it.
I also heard a rumor to this effect last week from a friend.
If this is Stan's I can say from seeing it many times that it is an enormous
collection.
Full disclosure: I am not involved in any way.

Dennis Tillman W7PF 



--
Dennis Tillman W7PF
TekScopes Moderator

Stan Griffiths Craigslist Posting

 

I saw this today in Craigslist:
https://seattle.craigslist.org/skc/ele/d/beaverton-estate-radio-repair-shop-
sale/7055039838.html

The photo looks like this is Stan Griffith's collection and he is selling
it.
I also heard a rumor to this effect last week from a friend.
If this is Stan's I can say from seeing it many times that it is an enormous
collection.
Full disclosure: I am not involved in any way.

Dennis Tillman W7PF



--
Dennis Tillman W7PF
TekScopes Moderator

Re: Commercial Circuit Simulator that includes vacuum tube library is now free.

Jim Tibbits
 

And for all us (L)users...."linux users"...works fine with WINE on my mint
19.2

Jim

On Tue, Jan 14, 2020 at 10:38 AM Ancel <@Protofabtt> wrote:

https://hackaday.com/2020/01/08/commercial-circuit-simulator-goes-free/

Looks useful, a step up from LTspice, no micro-controllers though.
Ancel



Re: Ultimately recyclers have to scrap our treasures - an idea so maybe some can survive

Dan Cordova <danny_cordov@...>
 

Easy.  Do an online search by typing in "Maker Space."  Almost every college and university has at least one maker space, even one near you.

On Tuesday, January 14, 2020, 10:55:16 AM PST, W1RS <deflatermaus@...> wrote:

Perhaps the "Maker Spaces" concept could work.  I have heard of them but am not familiar with the maker universe.  Maybe somebody else could enlighten me.

Re: Ultimately recyclers have to scrap our treasures - an idea so maybe some can survive

W1RS
 

Perhaps the "Maker Spaces" concept could work. I have heard of them but am not familiar with the maker universe. Maybe somebody else could enlighten me.

Commercial Circuit Simulator that includes vacuum tube library is now free.

 

https://hackaday.com/2020/01/08/commercial-circuit-simulator-goes-free/

Looks useful, a step up from LTspice, no micro-controllers though.
Ancel

Re: 454 HV regulation off

Albert Otten
 

Hi Jack,

(Not important for your problem.) To answer my own questionmark here
There was about 2 V 100 Hz sawtooth ripple at the fuse side 19 V. But that's
not due to the HV supply. Note that this is unregulated voltage from the
bridge rectifier. (Bad reservoir caps?)
I looked at the LV supply <13>. That magnitude of ripple is to be expected. The current via sense resistor R1142 is about 0.63 A (measured). Add about 0.27 A for the HV supply, Total about 0.90 A load for C1142, 2800 uF. In 10 ms the voltage drop would be 3.2 V. But the pure discharge time is more like 6 ms; the ripple is more triangular than sawtooth. That leaves 1.9 V pp. Nice!

You must also have noted that ripple in your HV waveform.

Albert

Re: 454 HV regulation off

Albert Otten
 

I still believe in my earlier explanation that this is due to the long RC time constant in the grid supply circuit.
Albert

On Tue, Jan 14, 2020 at 05:25 AM, Jack Ohme wrote:


Recovers for about 1-1.5 seconds then comes back. And its a drop down in
brightness, back down to a normal level. I'm not sure whether or not its
linear, I could try and do some tests, but feedback is a possibility, since
there is a feedback string that people have pointed to before as a possible
source of issues.

On Mon, Jan 13, 2020 at 8:10 PM Eric <ericsp@...> wrote:

When you say the brightness returns to a normal level then gets bad again I
have 2 questions that come to mind. How long is the brightness recovery
time. Also does the ramp up in brightness seem linier. If I put this in my
audio head I would blame some for of oscillation or feedback that is taking
time to build. When it gets disturbed adjusting the pot it takes a short
time to build back. Just a random thought.

Re: 454 HV regulation off

Albert Otten
 

On Tue, Jan 14, 2020 at 04:06 AM, Jack Ohme wrote:


Admittedly, however, the more I look at this machine, the less sure I am
that it must be the HV section. This trace shows the driving transistor
Q1430's collector voltage, not only incredibly shaky, but also driven quite
a bit beyond its stated voltage of +19v peak. I also note that when I tweak
the HV control pot, which, as I mentioned previously, fixes the brightness
issue momentarily, this trace returns to much closer to what it should be
according to my datasheet, as well as cleaning up the signal greatly to a
more pure sine wave. I should note as well that the trough of this signal
should be around +5v, where in actuality its very close to zero. So this
signal is being driven around 5-6 volts too far in both directions, for
some reason, to a point where it causes noticeable distortion. Tweaking the
HV pot produces no meaningful long-lasting results, turning the wiper all
the way, while changing the wave's amplitude, does not bring it within
acceptable value. Whether this is a symptom or the cause, I cannot say, but
it's certainly intriguing.
[image https://ibb.co/f2hdnBz ]

Hi Jack,
I feel quite sure that the waveform is perfectly normal.
- The ripple is simply due to excited much higher frequencies. The oscillator frequency is only one of several resonance frequencies. With higher load the distortion and hence the presence of such higher frequency components increase somewhat.
- You must be mistaken in observing a bottom value near zero. Most likely your zero reference is one division (5 V) wrong. The average voltage should be about +19 V. With your zero line it would be about +13 V. Also, when the emitter is about -0.2 V, the knee voltage of the transistor will prevent the collector voltage from dropping that far.
I could easily check these things in my 454.
- Same kind of ripple.
- Voltages between about 8.5 V and 32.5 V. Somewhat lower at (much too) high intensity. Average about 19 V, also measured at the fuse. Amplitude about 24 V, like yours. Frequency 27 kHz, like yours. Emitter at -0.2 V.
There was about 2 V 100 Hz sawtooth ripple at the fuse side 19 V. But that's not due to the HV supply. Note that this is unregulated voltage from the bridge rectifier. (Bad reservoir caps?)
Also measured fuse current. Up to just visible trace:270 mA, surprisingly stable within 1 mA during some minutes of warming up. At full intensity increasing to 345 mA.
Yep, I cleaned my contact points to a shiny polish to make sure, they were
pretty darn dirty. And yes, physically on top of each other, there's 3. And
none of those caps are measuring infinite, 10M or 20M in the case of that*
one. *I'm considering just redoing the entire grid bias section of the HV,
honestly. Would only be 20 bucks or so to get new caps, resistors,
diodes... I just want the damned thing to work, haha.
Did you ever try what your DMM measures when you parallel a 10M resistor with a good (15 nF, in this case) capacitor? Could it be that your DMM has a resistance measurement principle other than with constant DC at the pins? Easy to check with your 468.
I would never replace all those components...

Albert