Date   
Re: Tektronix 2215, pulsing/chirping noise, no trace.

Samuel Rey
 

I have seen that replacement, but I’m holding on, I’ll try to fix mine
before I buy it.

El El mié, 10 jul 2019 a las 18:10, Bob Albert via Groups.Io <bob91343=
yahoo.com@groups.io> escribió:

Good advice! One thing you didn't suggest was to replace the entire
board. I see that someone in Europe has a board for sale at a reasonable
price on ebay.
I was lucky that replacing the power FET solved my problem with that same
model oscilloscope.
And there is no 'green power LED' that I can see on mine. In fact, they
saved money by leaving it out.
Since the repair, mine has worked flawlessly; it's been a month or more
now.
It's not my favorite 'scope. The controls aren't very user friendly for
me, and the panel legends are hard to read. It has a few functions that
baffle me in terms of daily use. The delaying sweep especially is a bit
arcane. But considering how much I paid for it, I have no complaints. (I
won it in a raffle at a swap meet and I see why someone put it on the
table.)
Bob
On Wednesday, July 10, 2019, 07:13:33 AM PDT, <tekscopegroup@...>
wrote:

I doubt that you have a problem at the output of the pre-regulator that
is causing the problem and it shutting down due to an abnormal condition on
the load side. As you pointed out the scope works fine with an external +43
volts being fed into the secondary power supply. So that would point
towards a faulty component that is not allowing the prereg to start up. In
my experience repairing this section in a 2213A some years ago was that it
is absolutely necessary to check everything in that stage specially
transistors and diodes, even if in-circuit measurements do not point at the
part being faulty before you even apply power at all. You need to pull
every single transistor, diode, etc in the preregulator and test it, and
all the lower value and/or higher power resistors as well for open circuit.
Of course it goes without saying also check the power input components,
like the 75uF cap and the associated rectifier, etc. Double check the
Mosfet and driver transistor. Even if it was fine last time you checked,
you need to double check everything in one batch before ever applying
power. Check the regulator IC as well, I seem to remember it was a TL494
that sometimes just quits. Pull it out and place a socket then put in a new
one. The socket will also allow for easier future testing & replacement.
You might also have a faulty T906 switching transformer, which will be
difficult to verify, so leave that possibility aside for last when you are
sure everything else is ok and the preregulator is still not working. As a
matter of fact my scope happened to have a bad T948 switching transformer,
and the only ay to make sure it was the problem was to replace it. But I
digress as this particular trasformer is located downstream from the
preregulator circuit.

Unfortunately dealing with a switching power supply you will usually be
able to follow a trail until you hit the fault because it works in a closed
loop where everything either needs to be right, or all (or most) will be
wrong. You will have to test every active component and make sure it is not
open or shorted, leaky, etc. The fact that the fault happened while you
where using the scope would suggest that it is not related to some
component slowly going out of tolerance, but rather of something popping,
usually at start up which is the (very short) time interval of highest
stress for a switching regulator until after a few milliseconds when things
quickly settle down.

This prereg stage, as with usually most other switching power supplies is
very temperamental and will absolutely not work unless all is good, and
will also tend to blow freshly replaced components during the intermediary
"let me check if that was all that was bad" situation, and then you might
be quickly sent back to square one (or even further back) with one or more
of the higher power parts blown and/or smoking.

Again good luck with the hunt, and don't be discouraged. You will soon be
rewarded with that green power LED on the front panel coming back on a
fully working scope. And please don't even consider using some sort of
permanent external power supply as a hack to operate the scope instead of
fixing the problem.





Re: 7A26 Ch 1 gain low

Jim Ford
 

Hi, Colin.I will be home in a couple of days and will check my 7A26's then.  Let me see if I can replicate your issue.Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: "Colin Herbert via Groups.Io" <colingherbert=blueyonder.co.uk@groups.io> Date: 7/11/19 4:02 AM (GMT-07:00) To: TekScopes@groups.io Subject: Re: [TekScopes] 7A26 Ch 1 gain low Doesn't anyone have any comments?Colin.-----Original Message-----From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Colin Herbert via Groups.IoSent: 09 July 2019 13:20To: TekScopes@...: [TekScopes] 7A26 Ch 1 gain lowI have a 7A26 dual trace vertical amplifier with a Ch 1 gain problem. When trying to set the gain, I cannot set it correctly, as the GAIN adjust goes to fully clockwise but the trace on the CRT is a mm or so low. This is with the VOLTS/DIV at 10mV and a 20mV square wave from my PG506. The VOLTS/DIV VAR control won't go beyond this either. Ch 2 works fine, with about one small division of excess available using both the GAIN adjust and the VOLTS/DIV VAR. Anyone have any ideas?TIA, Colin.

Re: Tektronix 2215, pulsing/chirping noise, no trace.

tekscopegroup@...
 

Most switching power supplies need a load on the output to be able to operate normally, so just as a reference by testing the pre-reg section with its output disconnected is most probably not a valid test. The full wave rectifier that you mention deals only with the mains AC input to convert it to DC for the operation of the switcher which then generates the +43V, so I doubt that the problem is there as it would rather blow the main fuse or would simply do nothing. But in any case have you checked the voltage across the (big) 75uF input capacitor? If for any reason that voltage is low or has a lot of ripple because that cap has aged and/or dried out I would think this might prevent the pre-reg from starting. On the output of the pre-reg there is only one rectifier diode that if I remember correctly is labeled CR907. Check that one as well, it might be leaky or open/shorted, and if in need of replacement has to be a high-speed fast recovery rectifier diode.

Re: 7A26 Ch 1 gain low

 

On Tue, Jul 9, 2019 at 02:19 PM, Colin Herbert wrote:


Ch 2 works fine, with about one small division of excess available using both
the GAIN adjust and the VOLTS/DIV VAR.
I think that's not enough, meaning that overall gain for *both* channels isn't enough. Usually, there's at least half a major division headroom.
Did you try the other vertical slot of the mainframe?
Do you know the mainframe is ok? Do you have another plugin to check the mainframe?

If the mainframe is new to you, a previous owner may have adjusted mainframe vertical sensitivity incorrectly.

Raymond

Re: 7603 Intensity control assembly 311-1404-00

 

On Thu, Jul 11, 2019 at 01:43 PM, NigelP wrote:


does anyone know if the "switch" actually does anything???
Turn the readout intensity knob (the small one) fully CCW, into the detent. The position is marked "OFF" on the front. It turns the readout display off...
The OFF position avoids the time-multiplexing artifacts in the trace that are visible with certain timebase settings. These are caused by the beam alternating between trace and readout display. The multiplexing is active even with Readout intensity at its lowest. Only OFF stops it.

Raymond

Re: 7A26 Ch 1 gain low

Colin Herbert
 

Hi,
Yes, it does occur at other volts/div settings. I was quoting what I did to quantify the low gain in some way. The frequency was the "standard amplitude" 1kHz square-wave from my PG506.

As it happens, I have two 7A26 plug-ins (I like them) and swapping them around between the two vertical bays of my 7623A mainframe shows that the problem lies with the 7A26, not the mainframe or one of the bays. The "good" 7A26 shows an excess gain of about one half of a major division on both channels.

I was thinking, from a cursory inspection, that the ICs were soldered in, but I think this may not be the case on closer viewing. From what I can see of the markings on the ICs, the first three numbers differ, but then the next group of six numbers are "0078 10" followed by another group of two numbers and a letter. My service manual lists three types of ICs, the earlier ones were "SEL" for "selected" I am guessing. The later ones were designated 155-0078-10 and aren't "SEL". The 155-0078-10" are available on eBay. I might just buy a couple.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David C. Partridge
Sent: 11 July 2019 11:47
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7A26 Ch 1 gain low

OK I'll make some guesses.

1. Have you checked that the output level from the attenuators is correct (same both channels)?

2. Does the problem occur at other volts/div settings?

3. What frequency signal are you testing with? Is the problem also present at DC?

4. You may be reduced to comparing signal levels on each channel through the various amplifier stage until you find one with low output. If you find one initially suspect any surrounding gain setting components, but equally could try swapping the ICs between channels.

HtH
David

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Colin Herbert via Groups.Io
Sent: 11 July 2019 11:03
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7A26 Ch 1 gain low

Doesn't anyone have any comments?

Colin.
-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Colin Herbert via Groups.Io
Sent: 09 July 2019 13:20
To: TekScopes@groups.io
Subject: [TekScopes] 7A26 Ch 1 gain low

I have a 7A26 dual trace vertical amplifier with a Ch 1 gain problem. When trying to set the gain, I cannot set it correctly, as the GAIN adjust goes to fully clockwise but the trace on the CRT is a mm or so low. This is with the VOLTS/DIV at 10mV and a 20mV square wave from my PG506. The VOLTS/DIV VAR control won't go beyond this either. Ch 2 works fine, with about one small division of excess available using both the GAIN adjust and the VOLTS/DIV VAR. Anyone have any ideas?
TIA, Colin.

Tektronix 2430A occasionally fails some tests

user920
 

Hello, I recently bought this oscilloscope as partially working, the owner said it worked fine but once it failed some tests (PA and TRIGS). At home, no errors appear and the scope seems to be working. While I was trying some signals using an android app for function generation, the signal disappeared from the screen. I proceeded to make the self diag and there were two fails (CCD and PA, all relative to gains). Here are the pictures: https://imgur.com/a/DNgRcPG
After I restarted the scope, however, there were no errors and I continued to test the scope without trouble. I am not sure what the problem can be, if there is any. Do you have any ideas of what I can check? Thank you

Re: 7603 Intensity control assembly 311-1404-00 + Tek parts

 

It turns out we actually HAVE 3 *NEW* 311-1404 concentric pot/switch assembles
at Sphere, I'm just behind in posting the many Tek parts we bought from service centers.

please email me off list (walter2@...) if you need one.

Also, I have a box full of new  small Tek mechanical parts and display bezels (all rectangular).
ther eis zero chance I will have the time to photograph and post all of them on line,
so is there anybody that can use them? covers numbers from 1xx to 3xx.  happy to swap them for nixie tubes or 3015F minitrons, etc.

Also, anybody traveling up here in western Canada, please stop by and rummage through our two outside storage buildings.  lots of free goodies to be had, as I am still trying to make more space.

all the best,
walter & susan

Walter Shawlee 2
Sphere Research Corp. 3394 Sunnyside Rd.
West Kelowna, BC, V1Z 2V4 CANADA
Phone: +1 (250-769-1834 -:- http://www.sphere.bc.ca
+We're all in one boat, no matter how it looks to you. (WS2)
+All you need is love. (John Lennon)
+But, that doesn't mean other things don't come in handy. (WS2)
+Nature is trying very hard to make us succeed, but nature does not depend on us.
We are not the only experiment. (R. Buckminster Fuller)

Re: 577 step amplifier

DW
 

https://groups.io/g/TekScopes/album?id=86536&p=Created,,,20,2,0,0

I replaced all 3 MC1456N with MC1456P, when I switch collector supply polarity the dot on the screen aligns to the corners more correctly. Step generator noise has noticeably decreased but is still present under high horizontal and vertical sensitivity.

I fixed the problem but not completely. I need to observe why I am getting a few mV peak to peak noise spikes on the 12V rails for the MC1456 when the step generator is on. Perhaps I have a partially failed IC somewhere in the step generator circuit being supplied with +12 -12 V

Re: 7A26 Ch 1 gain low

Leon Robinson
 

I havent messed with a 7A26 in some time but I think that there is a gain adjustment between the channel switch and the output that is set too low.



Sent from K5JLR

-------- Original message --------
From: "Colin Herbert via Groups.Io" <colingherbert=blueyonder.co.uk@groups.io>
Date: 07/11/2019 10:44 AM (GMT-06:00)
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7A26 Ch 1 gain low

Hi,
Yes, it does occur at other volts/div settings. I was quoting what I did to quantify the low gain in some way. The frequency was the "standard amplitude" 1kHz square-wave from my PG506.

As it happens, I have two 7A26 plug-ins (I like them) and swapping them around between the two vertical bays of my 7623A mainframe shows that the problem lies with the 7A26, not the mainframe or one of the bays. The "good" 7A26 shows an excess gain of about one half of a major division on both channels.

I was thinking, from a cursory inspection, that the ICs were soldered in, but I think this may not be the case on closer viewing. From what I can see of the markings on the ICs, the first three numbers differ, but then the next group of six numbers are "0078 10" followed by another group of two numbers and a letter. My service manual lists three types of ICs, the earlier ones were "SEL" for "selected" I am guessing. The later ones were designated 155-0078-10 and aren't "SEL". The 155-0078-10" are available on eBay. I might just buy a couple.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David C. Partridge
Sent: 11 July 2019 11:47
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7A26 Ch 1 gain low

OK I'll make some guesses.

1. Have you checked that the output level from the attenuators is correct (same both channels)?

2. Does the problem occur at other volts/div settings?

3. What frequency signal are you testing with?  Is the problem also present at DC?

4. You may be reduced to comparing signal levels on each channel through the various amplifier stage until you find one with low output.  If you find one initially suspect any surrounding gain setting components, but equally could try swapping the ICs between channels.

HtH
David

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Colin Herbert via Groups.Io
Sent: 11 July 2019 11:03
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7A26 Ch 1 gain low

Doesn't anyone have any comments?

Colin.
-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Colin Herbert via Groups.Io
Sent: 09 July 2019 13:20
To: TekScopes@groups.io
Subject: [TekScopes] 7A26 Ch 1 gain low

I have a 7A26 dual trace vertical amplifier with a Ch 1 gain problem. When trying to set the gain, I cannot set it correctly, as the GAIN adjust goes to fully clockwise but the trace on the CRT is a mm or so low. This is with the VOLTS/DIV at 10mV and a 20mV square wave from my PG506. The VOLTS/DIV VAR control won't go beyond this either. Ch 2 works fine, with about one small division of excess available using both the GAIN adjust and the VOLTS/DIV VAR. Anyone have any ideas?
TIA, Colin.

TM500 and TM5000 Prototyping Boards for Sale

 

I have some TM500/TM5000 prototyping boards for sale.



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Re: Tektronix 2430A occasionally fails some tests

user920
 

So I was testing it, and found out that, if I run the self test, the scope doesn't glitch as long as I keep it on. If I turn it on, after some minutes it starts to have those gain problems, but as soon as I run the tests (after the warm up) all is good and I can use the oscilloscope as normal. Is it possible that the battery is failing and causing this problem? Are self-cal values stored in the nvram? I really hope it's not a ccd fault...

Re: 577 step amplifier

Mlynch001
 

DW,

Don't know if this is relevant or not, but have you replaced any caps in the power supply, display circuit or the step generator? I have a 576 which had noisy signals and found almost all the electrolytic caps, especially the tantalum caps to be very leaky.

--
Michael Lynch
Dardanelle, AR

Re: 577 step amplifier

DW
 

I have not but that is a good thought.

Re: 577 step amplifier

Mlynch001
 

My 576 was built mid to late1980's and had a handful of bad axial tantalum caps scattered throughout the machine. I replaced them all as well as the power supply filter caps. Time consuming, but since all but one or 2 caps showed drifted capacitance, high ESR or high leakage, it was way past time to do this job.

--
Michael Lynch
Dardanelle, AR

Re: 577 step amplifier

DW
 

With replacing electrolytics and tantalums as you have, know of any good brands and ones to stay away from? As for the disk capacitors I have heard they rarely fail is that correct?

Thanks

Re: 577 step amplifier

Mlynch001
 

DW,

I rarely see ceramic or similar type caps fail. Electrolytic caps are the weak link in this old gear. For replacements I choose Nichicon, Panasonic, Vishay-Sprague or IC. Always use name brand caps. I don’t have a single brand that I stick to, but anything made in Japan or USA is my first choice. Try to use high temp and low ESR caps whenever possible. I avoid Chinese made caps at all costs. I try to find caps that will fit nicely into the space previously occupied by the bad cap. One nice thing is that many caps have become smaller in package, so finding one to fit is not such a big problem.
--
Michael Lynch
Dardanelle, AR

Re: 577 step amplifier

DW
 

Thanks

Re: Tektronix 2430A occasionally fails some tests

Miguel Work
 

CCD KAPUT :(

-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de user920
Enviado el: jueves, 11 de julio de 2019 10:54
Para: TekScopes@groups.io
Asunto: [TekScopes] Tektronix 2430A occasionally fails some tests

Hello, I recently bought this oscilloscope as partially working, the owner said it worked fine but once it failed some tests (PA and TRIGS). At home, no errors appear and the scope seems to be working. While I was trying some signals using an android app for function generation, the signal disappeared from the screen. I proceeded to make the self diag and there were two fails (CCD and PA, all relative to gains). Here are the pictures: https://imgur.com/a/DNgRcPG After I restarted the scope, however, there were no errors and I continued to test the scope without trouble. I am not sure what the problem can be, if there is any. Do you have any ideas of what I can check? Thank you

Re: 7A26 Ch 1 gain low

Colin Herbert
 

I have looked at the Service Manual and cannot find anything about a gain adjustment between the channel switch and the output. However, on looking closer at the problematic 7A26, I think that the problem is not only with Ch 1, as the Variable gain control on Ch 2 doesn't give as much gain increase over the calibrated setting as do both channels on my "good" 7A26. It is about one half of a major division on the "good" 7A26.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Leon Robinson
Sent: 11 July 2019 19:03
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7A26 Ch 1 gain low

I havent messed with a 7A26 in some time but I think that there is a gain adjustment between the channel switch and the output that is set too low.



Sent from K5JLR

-------- Original message --------
From: "Colin Herbert via Groups.Io" <colingherbert=blueyonder.co.uk@groups.io>
Date: 07/11/2019 10:44 AM (GMT-06:00)
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7A26 Ch 1 gain low

Hi,
Yes, it does occur at other volts/div settings. I was quoting what I did to quantify the low gain in some way. The frequency was the "standard amplitude" 1kHz square-wave from my PG506.

As it happens, I have two 7A26 plug-ins (I like them) and swapping them around between the two vertical bays of my 7623A mainframe shows that the problem lies with the 7A26, not the mainframe or one of the bays. The "good" 7A26 shows an excess gain of about one half of a major division on both channels.

I was thinking, from a cursory inspection, that the ICs were soldered in, but I think this may not be the case on closer viewing. From what I can see of the markings on the ICs, the first three numbers differ, but then the next group of six numbers are "0078 10" followed by another group of two numbers and a letter. My service manual lists three types of ICs, the earlier ones were "SEL" for "selected" I am guessing. The later ones were designated 155-0078-10 and aren't "SEL". The 155-0078-10" are available on eBay. I might just buy a couple.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David C. Partridge
Sent: 11 July 2019 11:47
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7A26 Ch 1 gain low

OK I'll make some guesses.

1. Have you checked that the output level from the attenuators is correct (same both channels)?

2. Does the problem occur at other volts/div settings?

3. What frequency signal are you testing with? Is the problem also present at DC?

4. You may be reduced to comparing signal levels on each channel through the various amplifier stage until you find one with low output. If you find one initially suspect any surrounding gain setting components, but equally could try swapping the ICs between channels.

HtH
David

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Colin Herbert via Groups.Io
Sent: 11 July 2019 11:03
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7A26 Ch 1 gain low

Doesn't anyone have any comments?

Colin.
-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Colin Herbert via Groups.Io
Sent: 09 July 2019 13:20
To: TekScopes@groups.io
Subject: [TekScopes] 7A26 Ch 1 gain low

I have a 7A26 dual trace vertical amplifier with a Ch 1 gain problem. When trying to set the gain, I cannot set it correctly, as the GAIN adjust goes to fully clockwise but the trace on the CRT is a mm or so low. This is with the VOLTS/DIV at 10mV and a 20mV square wave from my PG506. The VOLTS/DIV VAR control won't go beyond this either. Ch 2 works fine, with about one small division of excess available using both the GAIN adjust and the VOLTS/DIV VAR. Anyone have any ideas?
TIA, Colin.