Date   
Tek 555 K601 contacts chattering and sparking

Matt Russell
 

upon powering the unit on with interconnection cable tied between power supply and the indicator unit, I get bright sparks in unison with the K601 contactor? chattering. when I disconnect the the indicator unit from the power supply I still get the R601 contactor chatter, but no sparking. Now also note the chattering is when the thermal delay/45 second delay kicks in the H.V.
is there any direction that can be offered to me or is it just follow the schematics and test your way through. My hope is that there are many of you whom have forgotten more than I know about this device that may lead me in the right direction for a quick repair, as opposed to me slowly digging through the device. Thank you in advance for any help you all may be able to offer Thanks -Matt

Re: Tek 555 K601 contacts chattering and sparking

John Williams
 

Hmm. This sometimes happens when you power up a unit with no prior tests. The problem is that you can’t leave it on long enough to gather any information. I think I would leave the cable disconnected and take out the K601. Then take a look at what happens before the relay closes. You can maybe take some voltage measurements to see if the outputs of each rectifier bank shows what should be there. Once the relay closes all power is applied. A common problem with this power supply is leaky or shorted filter electrolytic capacitors. Once I find something suspicious I usually start lifting one end of each capacitor and see if that makes any difference.

Warning: you are working with potentials lethal voltages which are everywhere,including stored in capacitors, so be very careful.

Re: Tek 555 K601 contacts chattering and sparking

John Williams
 

Just got an idea (another first, right) from this eevblog.com. Never seen that before. Anyway I was trying to figure out how you could power the supply with reduced line voltage if you don’t have big honkin variac. I came across this:

https://www.eevblog.com/forum/projects/light-bulb-is-series-with-unit-under-test/

Might give you an idea.

Re: 7A26 attenuator compensation problem

Harvey White
 

On Wed, 6 Feb 2019 23:37:13 +0100, you wrote:

Hi Fabio,
I should have some 7A26 parts, you might want to contact me. No idea
of how good they are, though.

Harvey



I do own a 7A26 myself and 10 and 20mV ARE NOT the ranges where all the
high impedance attenuators are BYPASSED.
My mistake while writing my own post in haste, sorry, of course the 5mV and
10mV are the bypass ranges.

My 7A26 is serial B226210, which means it's a later model that has the 3rd
implementation (revision) of the JFET input buffer (can find it in the 1983
and 1986 instruction manuals). My issue is most certainly in the area of
attenuator blocks and the JFET buffer, as I can see the aberration if I
look at the buffer output using another scope. And everything is cleaned so
no lousy contacts, DC noise...etc.

Regarding your calibration procedure I agree, not sure though whether it is
really necessary to switch from 50ohm to 1M normalize every time. Either
way I indeed manage to calibrate everything properly, at least in the
frequency range that the adjustments have effect on. In more detail -
compensation can be best observed using square wave signals in the
1kHz-5kHz range. If I set it right at these frequencies, I get the
aberration seen on the photos I posted od 100kHz. I currently have it set
as a compromise between 1kHz, 10kHz and 100kHz, but I'm not happy with it.

The area of attenuator blocks and JFET buffer is *very* sensitive to stray
capacitance, e.g. if you touch the attenuator blocks with your fingers, the
response in the problematic range (10-100kHz) changes substantially. In
another words, just a few pF means a lot to the response, at one point I
managed to get the 500mV (the most problematic setting) perfect just by
holding my finger in the right place. This lead me to believe that there
may be a certain value of C130 and C134 at which everything "fits", so I
increased C130/C134 and re-calibrated everything again just to find out
that if I make the 500mV perfect by looking at the 100kHz square, then
10kHz is no longer good. Again the conventional calibration (trimmers in
the attenuator blocks) act on lower frequencies (best seen in ~1kHz-5kHz
range) than where the problem appears afterwards (~10kHz-100kHz range). A
home made normalizer can be used to set all the inputs to the same
capacitance, but cannot really tell you whether you are exactly at 22pF.
For this reason the C130 adjustment from the service manual is pointless,
as you can set it to any value and match it using normalizer adjustment.
But question remains how far you can safely deviate from 22pF and still be
able to compensate all attenuator blocks.

Just to add to the confusion, those nasty carbon composite resistors next
to attenuator blocks have all drifted +10% to +20% in value, but replacing
them did not make any change. I suppose these come into play on very high
frequencies (>100Mhz), as another group post has demonstrated:
https://groups.io/g/TekScopes/topic/19243444

Perhaps some other component has drifted in value, e.g. in the JFET buffer.
Unfortunately I do not have another 7A26 to swap parts, but in a few months
I may get another one that is sitting at a friend in US and waiting for
someone to carry it over the ocean.

Best Regards,
Nenad FIlipovic


Re: Tek 555 K601 contacts chattering and sparking

ROLYNN PRECHTL K7DFW
 

Just got an idea (another first, right) from this eevblog.com. Never seen that before. Anyway I was trying to figure out how you could power the supply with reduced line voltage if you don’t have big honkin variac. I came across this:

https://www.eevblog.com/forum/projects/light-bulb-is-series-with-unit-under-test/

======================================================================

With this type and era of Tektronix scope, with a time delay and relays involved, low line voltage will result in relay chatter. Be sure it is not low line V that is causing this reaction. You should have line voltage in the area of 90V to 95V or more for things to fall into place properly with the time delay.

Rolynn
Tek Bvtn and Sunset 1966-1971

Re: Tek 555 K601 contacts chattering and sparking

John Williams
 

Good point. The line voltage should be checked right at the power transformer with a true rms voltmeter if possible. An extension cord should be the heavy air conditioner type. Also ac is sent from the power supply to the indicator unit which means the fake cable should be heavy enough.

Re: Interested in comments on Chinese oscilloscopes

fiftythreebuick
 

John, everybody has their "likes" and "dislikes" and what they'll put up with and what they won't..... I got my first scope in 1965 and have used CRT based scopes ever since. Been using Tektronix scopes ever since 1976.

I've used digital/LCD scopes before where I once worked (inexpensive Chinese as well as a mid-line Tek unit) and I didn't like either one. I don't like the display that's composed of pixels and I don't like the "feel" of the instruments. I'll take an analog unit with a CRT every time.

Tom

Re: Rickreall OR Hamfest

 

Hi Harvey,

Walter and I have been good friends for the past 15 years. Although it is a
6 hour drive to Kelowna BC from Seattle and it can be problematic in the
winter because of the mountains I go up to Sphere to see Walter and Susan
every 2 years or so, spend the night, catch up on what we've been doing, and
how their son and daughter are doing, and have my fill of bacon in the
morning. Later I take a walk through his house picking out whatever catches
my eye from the staggering collection of electronic instrumentation and
parts he and Susan have collected over the years. Then the horse trading
starts.

Going back through Customs at the border can be the most exciting part of
the trip depending on what I am bringing back. Once my van was filled front
to back, left to right, top to bottom with over 100 Tek CRTs in their
original boxes. Customs didn't know what to do about that. Once I tried to
go through on my Irish passport since my US passport had expired and the new
one didn't arrive in time. I learned never to try that again. The customs
agent said he wouldn't let Irish riffraff into the US. He lectured me for 10
minutes before letting on that his last name was Murphy and this was how
Customs treated his ancestors during the turn of the century. In the end he
wanted me to understand that traveling on an Irish Passport was not a good
idea if my legal address was in Washington.

Dennis Tillman W7PF

-----Original Message-----
From: Harvey White
Sent: Wednesday, February 06, 2019 6:27 PM
Subject: Re: [TekScopes] Rickreall OR Hamfest

On Wed, 6 Feb 2019 18:02:40 -0800, you wrote:
The Rickreall Oregon hamfest is in 10 days on Feb 16.
I will be there and I will have a table with Tek stuff on it.
If you are going come and find me. The folks at the door can tell you
which table I'm at and where in the hall it is located. I'm usually
along a wall since I requested a table with power.
I think I'll pass on this one. You do realize how far Florida is from
Oregon?
Thanks for the invite, though.... <grin>

Go up to Sphere and get some goodies....
Harvey



--
Dennis Tillman W7PF
TekScopes Moderator

Re: Interested in comments on Chinese oscilloscopes

hardyhansendk
 

Hi
I am using Rigol ds1054z,very satisfied-it can be upgraded free to an ds1014z with all optionds enabled--bw about 140Mhz.Ofcourse its not the same as a tek - but price versus performance are super.
Hardy

-----Oprindelig meddelelse-----
Fra: TekScopes@groups.io [mailto:TekScopes@groups.io] På vegne af John Williams
Sendt: 6. februar 2019 23:53
Til: TekScopes@groups.io
Emne: Re: [TekScopes] Interested in comments on Chinese oscilloscopes

Many thanks to both you and Harvey for your information. I also have a 475A and find it very useful. I took a look at your website and found it very refreshing to look at after my messy shop.

I don’t know that I would actually use a “lunchbox “ scope or not. I would purchase one more to see what some of the new stuff is like. I have looked at some of the sellers feedback and was not impressed by some of what I read. For working on plugins which is what I do mostly now I use the 551 setup, lower to connect the plugin and upper to trace through it. For working on scopes I use the 475 or 2213.

Still these lunchbox scopes interest me and I might just pick one up for fun. They say you can’t have enough love, money, or scopes. So one out of three is not bad, right?



---
Denne mail er kontrolleret for vira af AVG.
http://www.avg.com

TEK: 475 Long stabilization times normal: or Failure dooming.

Redguuz
 

Hi,
I own a TEK 475 scope (Made in Holland).
I bought this (third hand) from a local Market site.

Ever since I own this scope, it behaves as follows:
It takes quite some time (~10 minutes) before it is fully stabilized (focus, vertical positioning ).
My work room is normally not heated (it is now winter), so might this simply be due to the need of heating up of components?
Or is this a sign of catastophe coming (e.g. in the Power supplies due to e.g bad tantalum capacitors).
Are there known failure prone compoenets, which in your opinion, could be preemtively replaced, before creating a chain reaction, due to failure.

Appreciate your experience with this scope.

Re: TEK: 475 Long stabilization times normal: or Failure dooming.

Brendan
 

On Thu, Feb 7, 2019 at 04:46 AM, Redguuz wrote:


Hi,
I own a TEK 475 scope (Made in Holland).
I bought this (third hand) from a local Market site.

Ever since I own this scope, it behaves as follows:
It takes quite some time (~10 minutes) before it is fully stabilized (focus,
vertical positioning ).
My work room is normally not heated (it is now winter), so might this simply
be due to the need of heating up of components?
Or is this a sign of catastophe coming (e.g. in the Power supplies due to e.g
bad tantalum capacitors).
Are there known failure prone compoenets, which in your opinion, could be
preemtively replaced, before creating a chain reaction, due to failure.

Appreciate your experience with this scope.

It would be a good idea to check the power rails for correct voltage and ripple while its warming up to see if they are out of specification. That will at least give you a starting point.

Re: TEK: 475 Long stabilization times normal: or Failure dooming.

C Smith
 

What is temp of 475 at turn on? I don't think 10min. Is out of norm. Most of my Tek/HP Equipment are never turned off, unless I'm away..
Wouldn't hurt too do some recapping, but personally I probably wouldn't.. my old school rule, "IF IT'S WORKING OK DON'T MESS WITH IT".
I'm sure I will get flack abt that, but just my two and a half cents..
;_)

--
c smith
ka3bnn

Re: Interested in comments on Chinese oscilloscopes

Marvin Moss
 

Hi, I have been using Tek scopes since the mid 50's and I recently bought a Hantek and realized that I made a serious error. My problem is with the granularity of the traces on the digital scopes. No clean nice straight line but a waveform that has hundreds of spots dancing around. It looks like a Tek trace with a bunch of digital noise added to the entire trace. The Hantek works fine but I am unable to get used to the noise(digital) on the trace. I still pull out my Tek rather than look at the "noisy" trace on a digital scope. Beware that you may not like what you see. Marvin, a ham radio operator for 68 years now!

Re: TEK: 475 Long stabilization times normal: or Failure dooming.

John Clark
 

I've had my 475 for about 3 years and it does the same thing. On initial turn on it's bright and then dims a bit after 5-10 minutes. Both traces also take a bit of time to settle in vertically, as well. I think I've been told by the group here before that it's normal. It works quite well and I have no intention of "fixing" it until something actually breaks. I've done a couple of repairs and replaced some failure-prone tantalums before they failed but I'm not recapping it until it actually tells me it needs recapping.

John

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Redguuz <mgrbosma@...>
Sent: Thursday, February 7, 2019 6:46 AM
To: TekScopes@groups.io
Subject: [TekScopes] TEK: 475 Long stabilization times normal: or Failure dooming.

Hi,
I own a TEK 475 scope (Made in Holland).
I bought this (third hand) from a local Market site.

Ever since I own this scope, it behaves as follows:
It takes quite some time (~10 minutes) before it is fully stabilized (focus, vertical positioning ).
My work room is normally not heated (it is now winter), so might this simply be due to the need of heating up of components?
Or is this a sign of catastophe coming (e.g. in the Power supplies due to e.g bad tantalum capacitors).
Are there known failure prone compoenets, which in your opinion, could be preemtively replaced, before creating a chain reaction, due to failure.

Appreciate your experience with this scope.

Re: Interested in comments on Chinese oscilloscopes

Bert Haskins
 

On 2/7/2019 1:23 AM, hardyhansendk via Groups.Io wrote:
Hi
I am using Rigol ds1054z,very satisfied-it can be upgraded free to an ds1014z with all optionds enabled--bw about 140Mhz.Ofcourse its not the same as a tek - but price versus performance are super.
Hardy

-----Oprindelig meddelelse-----
Fra: TekScopes@groups.io [mailto:TekScopes@groups.io] På vegne af John Williams
Sendt: 6. februar 2019 23:53
Til: TekScopes@groups.io
Emne: Re: [TekScopes] Interested in comments on Chinese oscilloscopes

Many thanks to both you and Harvey for your information. I also have a 475A and find it very useful. I took a look at your website and found it very refreshing to look at after my messy shop.

I don’t know that I would actually use a “lunchbox “ scope or not. I would purchase one more to see what some of the new stuff is like. I have looked at some of the sellers feedback and was not impressed by some of what I read. For working on plugins which is what I do mostly now I use the 551 setup, lower to connect the plugin and upper to trace through it. For working on scopes I use the 475 or 2213.

Still these lunchbox scopes interest me and I might just pick one up for fun. They say you can’t have enough love, money, or scopes. So one out of three is not bad, right?
I guess that I have crossed over to the "dark side" also.

I have a Hantek DSO5102P, several of the toy scopes like the DSO150 (hacked), and I will probably a Hantek handheld as soon as I can figure out which one to buy.

I do a lot with the STM32 micros so I just have to have a bunch (toy scopes) of those, all of which  have complete source code.

I am glad that I bought the DSO5102P especially since I may end up with the the full source code for it also and if that happens I'll buy a second one just to hack.

This is all in addition to about a dozen Tek scopes my favorite being my Tek 2232 and 7K models.


Have lots of fun and if any of this gets too far off topic, contact me off list.

-Bert


---
Denne mail er kontrolleret for vira af AVG.
http://www.avg.com


Re: Interested in comments on Chinese oscilloscopes

Adrian
 

I got a Uni-T 2062 (60MHz/1G sample) about 5 years back and thought it quite good value for the money until one input channel died after about 11 months use followed a few weeks later by the second one. Got it from a UK supplier who didn't want to know, was utterly unhelpful, told me that model was now discontinued and so no longer supported but he "could send it back to the factory at your expense to see if they could do anything". Gave up and got a TDS2012 off ebay which is still going strong plus I can talk to it via GPIB not some weird USB interface. I've had similar experience with other Chinese TE, quite nice at first but doesn't last and support is non-existent.

Stick with Tek/HP is now my motto!

Adrian

On 2/6/2019 2:39 AM, John Williams wrote:
Hi. This may be totally off topic and may even upset some of you. I hope not so here goes.

I am wondering if anybody has any experience with the Chinese oscilloscopes such as the Uni-T 2025 family. I am thinking of bringing one in to evaluate and compare to tektronix models of similar specs. I would be grateful if someone had experience with this type of equipment and would comment. If they are junk I would like to know or if they are useful that would be the sort of thing I would like to know. Thanks. John

Beaten by 7834 LV Regulator

 

I've got the inverter running, replacing Q1252 on the C/R board, plus VR1246
(120V Zener), C1243 and C1249. I also had to replace C1354 (100uF 25V) in
the -17V circuit on the Cap/Rectifier board.

I also had to replace a whole slew of parts in the -50V regulator circuit
(most xistors and diodes plus a couple of resistors).

If I try to run the supply with Q1254 installed, then the control IC shuts
the system down as the supplies are out of balance.

Removing Q1254 allows me to get it all running and I see the following
voltages:

Supply Actual
+108V +108V
-50V -50V

+50V +46.9V
-15V -14.58V
+15V +13.8V
+5V +4.275V


All the raw voltages (+/- 17V, +/-54V, +7V) are present and correct.

I've checked the divider resistors (e.g. R1440, R1441 in the +15V supply)
and they all seem correct. The dual xistors (e.g. Q1436 in +15V supply)
seem OK.

I'm really struggling to see where the fault is that's sending those
supplies low.

Cheers
David

Re: Tek 555 K601 contacts chattering and sparking

Matt Russell
 

someone had remove the original power connection to the power supply, so me working the heating and ac business(commercial) I thought the good choice was to install a new #12 SO cord(nice soft extra insulated) with strain relief, and new plug end too.......over done for certian.
I also have a scope mobile that has the original recessed male connection that I will be transplanting soon.

I know I actually have good line voltage I record music so my power is conditioned and has a digital read out on it as far as supply.

Re: Interested in comments on Chinese oscilloscopes

EricJ
 

Does that scope have a variable intensity feature? I've seen a lot of posts like yours in various electronics fora. I believe Dave at EEVBlog even did a video about this. The noise is still there on your CRT scope too, you just don't see it because it's so fast it doesn't show. So this noise could actually be considered kind of a benefit by some. You can kill a lot of it by adjusting persistence and intensity on better scopes. Averaging helps too.--EricSent from my Samsung Galaxy smartphone.

-------- Original message --------From: Marvin Moss <mmoss@...> Date: 2/7/19 7:32 AM (GMT-06:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Interested in comments on Chinese oscilloscopes Hi, I have been using Tek scopes since the mid 50's and I recently bought a Hantek and realized that I made a serious error.  My problem is with the granularity of the traces on the digital scopes.  No clean nice straight line but a waveform that has hundreds of spots dancing around.  It looks like a Tek trace with a bunch of digital noise added to the entire trace.  The Hantek works fine but I am unable to get used to the noise(digital) on the trace.  I still pull out my Tek rather than look at the "noisy" trace on a digital scope.  Beware that you may not like what you see.  Marvin, a ham radio operator for 68 years now!

Chinese "Dupont" connectors, a "how to"

Harvey White
 

You've seen the ads, an entire box for not much money, strips of pins
and sockets, and does wonders. Did I mention cheap?

So you also buy the crimper, because that thing you got at the hamfest
a long while ago was never made for this thing.

Now they are NOT 26 gauge, and you can argue whether or not they
should be replacing Tektronix made harmonica connectors. Well,
sometimes yes, sometimes no.

THEN you start to use the tool.

and throw away the crimped connector

You do that lots. This gets annoying. It's even more annoying that
the BERG connectors (which you may have some strips for, and the crimp
on connectors are not the same size, quite.

So one option is to go buy the female/female ribbon connector cables,
take off the single connector ends, and then plug them into the
plastic headers... That works, but what if you need a longer cable?

First, I'd recommend #26 or above wire. The crimper is supposed to
work with #26 or #28 at that notch.

Note the crimper, it has several detent notches. Since we're dealing
here (other sizes may be similar) with #26/28, that's what works for
this description.

Strip the wire so that about 1/8 inch is bare. You judge this by
putting the wire in a pin so that the bare wire is in the nearest set
of ears to the socket. That's all you need there, you want the larger
(and rear) ears to be crimped over insulation.

Close the crimper to the second notch (two clicks).

Put the pin/socket in so that the end of the connector is more or less
even with the left side of the crimper (it's a right hand tool). Put
it so that the ears are up. Don't allow it to rotate.

Close the crimper one more notch.

At this point, you may need a magnifying glass. Pull the pin through
the crimping tool until it stops. This is the second crimp
(insulation) hitting the narrower part of the tool. It won't go any
further.

Note that the jaws on the right side stop at the front end of the ears
for the bare wire, and don't get close to the actual socket or pin.
This is critical.

Next insert the wire so that the stripped portion aligns with the
first set of ears. You don't want it to go further and into the
actual socket part. Needs to stop short of that.

Squeeze the crimper to crimp the connection the rest of the way.

When pushing it into the connector, make sure that the over insulation
crimp is small enough to fit into the body of the connector. The
crimped part of the connector that connects to the bare wire should be
"up", that is, the little removable tongue ought to be on the same
side. Push in the wire bit by bit with a pair of needlenose (less
problem with smaller wire) until the little tab settles down behind
the connector pin/socket.

That's it. Good connections, no wasted pins, no frustration.

Harvey