Date   

Re: X-Y mode for Tektronix 2465A

ballen4705
 

Hi Mark,

Thanks very much for the manual page. This page describes exactly what we are doing.

The reason we grounded first one input and then the other input was to force the trace motion to be purely horizontal or vertical. In fact we achieved purely vertical motion with CH1 grounded but did not get purely horizonal motion with CH2 grounded. Instead we got diagonal motion. Do you agree that this is not what should happen?

Cheers,
Bruce

On 22 Mar 2016, at 09:08, Mark Huffstutter <mhuffstutter@...> wrote:

Bruce,
If You don't have a copy I've attached the page from the 2465B manual that
speaks to XY operation. This works on My 2465.

If You are comparing channels 1 and 2, only CH2 should be selected in
Vertical Mode. You should not ground any inputs, that is Your comparison signal.

Mark


At 12:33 AM 3/22/2016, you wrote:


Gary, thanks for the suggestion. Yesterday we tried all possible combinations of turning off CH1 and CH2. Also setting the input of CH2 to GND. But we'll double check, just to be sure. Any other ideas? Cheers, Bruce



<2465B XY.pdf>


Re: Timebase and CRT Issues on Tektronix Type 545A

 

On 21 Mar 2016 16:49:36 -0700, you wrote:

@David,

Never mind, I had never seen bumble bee capacitors before I Googled them. They are all over the place. I'll have to look into buying a jumbo set of capacitors, it looks like. Is there a preferred replacement? Electrolytic, ceramic, polyester, etc?
I forget exactly who but the bumble bee capacitors came from one
particular manufacturer (Sprague?) of oil and paper capacitors and
earned the name just because of their looks. All paper and oil
capacitors suffer from the same problems though. I have had to
replace a few myself.

Polyester film would be the natural and superior replacement. Ceramic
capacitors could be suitable in some applications.

The ripple in A seems to go away after the unit running for around 15 minutes.

I think somebody earlier mentioned a tube tester. I do not have one personally. Could a dead tube render Timebase A inoperable? Is there a visual check that can be done on tubes to find out if they are dead? The trouble with Timebase A is that is harder to work with than Timebase B, which just swings out. The tube part of the Timebase A circuit is upside down, making it harder to see the tubes.

Alex Brinister
You will not be able to visually find bad tubes unless the failure is
an open heater.

Someone more familiar with the 545A will have better troubleshooting
suggestions. I have not used mine in a while.


Re: Timebase and CRT Issues on Tektronix Type 545A

Albert Otten
 

Alex, for the A time base you can check the Sawtooth Output at the front panel. That signal is picked off in an earlier stage, before the (switches to the) horizontal amplifier. This could distinguish a saw tooth problem from a horizontal amplifier problem. For the B time base this would require internal measurements; not difficult but you have to know at which points a measurement would not disturb circuit operation ("low ohmic" points).
Of course dead tubes can/will disturb proper circuit operation. But so can an intermittent slider of an adjustment pot. It makes no sense to check tubes in the wild, without the tube being suspect already.

Albert


Re: X-Y mode for Tektronix 2465A

Mark Huffstutter
 

Bruce,
If You don't have a copy I've attached
the page from the 2465B manual that
speaks to XY operation. This works on My 2465.

If You are comparing channels 1 and 2, only CH2 should be selected in
Vertical Mode. You should not ground any inputs,
that is Your comparison signal.

Mark


At 12:33 AM 3/22/2016, you wrote:


Gary, thanks for the suggestion. Yesterday we
tried all possible combinations of turning off
CH1 and CH2. Also setting the input of CH2 to
GND. But we'll double check, just to be sure. Any other ideas? Cheers, Bruce

[Non-text portions of this message have been removed]


[Non-text portions of this message have been removed]


Re: X-Y mode for Tektronix 2465A

ballen4705
 

Gary, thanks for the suggestion. Yesterday we tried all possible combinations of turning off CH1 and CH2. Also setting the input of CH2 to GND. But we'll double check, just to be sure. Any other ideas? Cheers, Bruce


Re: 475a, no trace

 

Don't forget to check the op-amps in the LV PS. Often, they are seated in bad sockets (TI) or their contacts have deteriorated with time. Reseating often helps in such cases.
I've seen dead ones as well. Since they're very cheap, you might choose to just replace them.
If you don't have any replacement available, you could swap/interchange U1418, U1454 and U1464, since they all are the same type.
+ 50 V is up, so U1418 should be OK. You may lose + 50 V if you swap in a defective chip in its position. Might be a good check for the others.
It's likely that you'd still be able to identify a bad chip in the absence of known-good r(new) replacements. Remember though that + 50 V needs to be up for any of the others to work.

Obviously, it's far preferable to just get a few new chips and put them in. Would cost you less than 1 USD for 3 pcs.

Raymond


Re: 7A22 Differential Amplifier Calibration

 

On Mon, 21 Mar 2016 18:54:14 -0000, you wrote:

If the neutralization is that far off then I do not think you can get
into any more trouble; something is broken or misadjusted or your
measurement was bad. The neutralization adjustments alter the
response of the two sides of the differential amplifier independently
but this is masked by the 1 MHz bandwidth limit which is trimmed by
C425 shown in the middle of schematic 2. I think they should be
adjusted for maximum *matching* bandwidth with clean response using
either input.
I am attaching two photos which hopefully show the traces that I see. A 50mV
1KHz square-wave from a PG506 is connected to the +ve input of the 7A22 with
DC coupling in both cases. The photo “Input+ve_Input –ve GND” is what shows
when the –ve input coupling switch is at “GND”. It seems like pretty good
square-wave to me. The photo Input+ve_Input-ve DC” is what appears when the
–ve coupling switch is set to “DC”. A rounding of the upper leading corner
can be seen. According to the Service Manual, the aberration should not
exceed ±1%. Is this so in my case and how can one estimate or measure that
anyway? If the 50mV 1KHz square wave is connected to the –ve input, there
is no perceptible change when the +ve input coupling is changed between
“GND” and “DC”.

I haven’t adjusted C241 at all. It has occurred to me that some insect may
have crawled into the zone where C241 and C141 are located and died close to
C241, changing the capacitance just enough…..

Colin.
I broke out my 7A22 and ran some tests to duplicate what you did. I
used a function generator instead of PG506 but verified that it is
fast and clean enough. This is actually the same function generator
that I modified to do oscilloscope vertical deflection calibration.

I found no interaction between the + and - inputs under any conditions
which is not surprising because there is not suppose to be any. Both
inputs produced identical displays no matter what coupling was used
for the other input.

I need to think about this and study the schematics but I am not
convinced that your problem is with the neutralization adjustments.
What I think might be happening is AC coupling between the + and -
inputs. When one input is left floating, then the fast edge at the
other couples through and subtracts from the displayed waveform so the
slow edge is created by the recovery of the unconnected input.


Re: new member here

Paul Charron
 

maybe i will take a break from year end and try a few things


Those funny 311-0603-00 pots

snapdiode
 

I thought the white part is made of Delrin, but so far it has shrugged off every glue and solvent I threw at it.
MEK, dichloromethane, hot glue, cyanoacrylate, plastic bonder epoxy, nothing affects or sticks to it.


How can I be sure the material is Delrin, and not say, Nylon?


Re: new member here

Paul Charron
 

thanks for your latest suggestion...... i was just thinking about that........ and yes year end first accountant for income tax second and a business trip north third and maybe after......... ;) ...... meanwhile i just purchassed a 7854 to complement my 7104 and my 10 other scopes .....Paul


Re: new member here

 

On 21 Mar 2016 16:41:56 -0700, you wrote:

Test 41 fail is described as "INS,SO, and EOA flip-flops" circuit in the time base card that has no IC in sockets they are all soldered on the pc board, i just got this module hours ago and the self test pointed at this description in the manual..... so first things first what is a INS,SO and EOA ????...... i didn't have time to study schematics as i am presently working on my year end and will be tied to this choir for at least a week but a good short-cut to the problem from someone familiar with this issue is my first approach and would be welcomed.....re-seating ic's was a good idea that i tried and successfully repaired a 7a42 with thia aproach a few months ago......
so does this ring a bell ?????
I am not an expert on the 7D20 so I just outlined the easy steps that
I would start with which do not require an extender.

Another thing worth trying is cleaning and reseating various card and
cable connectors.

On Tue, 22 Mar 2016 00:18:51 +0000 (UTC), you wrote:

well i have one and the plug in plugs in 3 slots...... it looks like it's a major job.....Paul

I guess it will have to wait a few weeks
That will leave plenty of time to study the manual.

From the description Dennis gives, it should be possible to narrow the
problem down enough to try replacing just a couple of ICs and look for
problems in a specific area.

Page 2-62 discusses self test 41 and what hardware is involved. I
would print out some schematics to mark up and follow the signal paths
to see what might cause the problem.


Re: 475a, no trace

ArtekManuals
 

On 3/21/2016 8:01 PM, 'G. Widmayer' satoperator@... [TekScopes] wrote:
Need some guidance on troubleshooting my 475a purchased at Dayton a few
years ago and has never worked. Dials light up but no trace or using
the "beam finder" has no success.
Pulled the unit out of the case today and started checking power supply
levels at the TP. Results:
+110 is ok+50v is ok-15 v is 0+15 v is 0-8 v is +.7+5 v is ok
Can someone push me in the right direction for the next step as I'm not
seeing anything on the schematic that is common to the plus/minus 15
volts and minus 8 volts. That said I've never tried to troubleshoot a
scope before, I mostly rebuilt 1930's and 1940's radios.
Gary Widmaye
Gary

All three supplies depend on +50V but that is OK

The -8V supply and the -15V do use +15V to power U1464A & 1464B ( pin 8 of U1464)

So the +15Volt supply is the place to start


Dave



--
Dave
Manuals@...
www.ArtekManuals.com


Re: new member here

Paul Charron
 

I guess it will have to wait a few weeks


Re: new member here

Paul Charron
 

well i have one and the plug in plugs in 3 slots...... it looks like it's a major job.....Paul


Re: new member here

 

Hi,
Tektronix manuals are famous for many things. Especially important in your
case would be to read the Theory of Operation section. This should clearly
explain what the "INS,SO, and EOA flip-flops" are. It will also give you an
idea of where to look.
But if I remember correctly the 7D20 is built like a computer with separate
boards talking to a common bus. If that is the case you will need a way to
extend the plugin outside the scope and then you will need a circuit card
extender to get to the individual chips in question. That will require
equipment (extender plugins and extender cards) you almost certainly do not
have..


Dennis Tillman W7PF

-----Original Message-----
Sent: Monday, March 21, 2016 4:42 PM
Subject: Re: [TekScopes] Re: new member here

Test 41 fail is described as "INS,SO, and EOA flip-flops" circuit in the
time base card that has no IC in sockets they are all soldered on the pc
board, i just got this module hours ago and the self test pointed at this
description in the manual..... so first things first what is a INS,SO and
EOA ????...... i didn't have time to study schematics as i am presently
working on my year end and will be tied to this choir for at least a week
but a good short-cut to the problem from someone familiar with this issue is
my first approach and would be welcomed.....re-seating ic's was a good idea
that i tried and successfully repaired a 7a42 with thia aproach a few months
ago......
so does this ring a bell ?????
------------------------------------
Posted by: docteurpapaul@...
------------------------------------


Re: new member here

Paul Charron
 

please excuse my clumsiness with Yahoo.......I am not familliar with-it


Re: 475a, no trace

Tom Jobe <tomjobe@...>
 

Hi Gary,
While you are waiting for replies from the more knowledgeable members,
with the scope unplugged and turned off, check the resistance to ground
of the low voltage supplies at those same test points where you checked
the voltages at.
Shorted tantalum capacitors are a common problem on the 4xx
oscilloscopes. They may show up as a dead short, but If that doesn't
look too bad, check the output of the full wave bridges for those
voltage supplies, they often fail when they get old.
tom jobe...




On 3/21/2016 5:01 PM, 'G. Widmayer' satoperator@... [TekScopes] wrote:

Need some guidance on troubleshooting my 475a purchased at Dayton a
few years ago and has never worked. Dials light up but no trace or
using the "beam finder" has no success.
Pulled the unit out of the case today and started checking power
supply levels at the TP. Results:
+110 is ok+50v is ok-15 v is 0+15 v is 0-8 v is +.7+5 v is ok
Can someone push me in the right direction for the next step as I'm
not seeing anything on the schematic that is common to the plus/minus
15 volts and minus 8 volts. That said I've never tried to
troubleshoot a scope before, I mostly rebuilt 1930's and 1940's radios.
Gary Widmayer

[Non-text portions of this message have been removed]


[Non-text portions of this message have been removed]


475a, no trace

G. Widmayer <satoperator@...>
 

Need some guidance on troubleshooting my 475a purchased at Dayton a few years ago and has never worked.  Dials light up but no trace or using the "beam finder" has no success.
Pulled the unit out of the case today and started checking power supply levels at the TP.  Results:
+110 is ok+50v is ok-15 v is 0+15 v is 0-8 v is +.7+5 v is ok
Can someone push me in the right direction for the next step as I'm not seeing anything on the schematic that is common to the plus/minus 15 volts and minus 8 volts.  That said I've never tried to troubleshoot a scope before, I mostly rebuilt 1930's and 1940's radios.
Gary Widmayer


[Non-text portions of this message have been removed]


Re: 2445a power supply repair

 

On 21 Mar 2016 04:00:34 -0700, you wrote:

Hello,

I've got a 2445a, which was burned by the previous owner (he was debugging the mains power supply without an isolation transformer). After repairs, where I've changed the channel #1 hybrid, TL072, TL074 and MC1458, now it seems, that the scope can be calibrated.
Before starting the calibration, I've checked the voltages on the power supply connector. All are nominal for exception of the analog +5 and -5 volts, which read well before the minimum.
I've got 4.78 and -4.76 volts. Voltages don't drift. Ripple is within the spec. The scope traces are stable before and after the warmup.
I looked at the PSU schematics and +5VA/-5VA are sourced via the linear regulators from the rectifier/filter. Could it be that the C1115 and C1114 caps have "dried out"? I don't see any leaks. Checked the capacitance, seems ok. Don't have a possibility to check the ESR.
It is very odd that +5VA and -5VA are both off by the same amount
while none of the other voltages are. A single bad capacitor should
not be able to cause this problem and all of the supply voltage rely
on the same +10 volt reference.

What are the voltages for +5V UNREG and -5V UNREG?

If both C1114 and C1115 are bad, then the UNREG voltages into the
regulators could be low enough to cause matching low output voltages.

Can I substitute a different capacitors instead of 250uFx20V?
Can I use for example, 330uFx25V?
Yes, the values are not critical.

Do I have to use the "low ESR" caps, or I can buy the standard "heavy duty" caps?
C1114 and C1115 should be low ESR to keep the ripple from the
switching power supply down but "heavy duty" capacitors should at
least work. They might not last as long.

Thank you!
If you have not already pulled or replaced C1114 and C1115, measure
+5V UNREG and -5V UNREG with the old capacitors still installed. Then
when you replace them, measure +5V UNREG and -5V UNREG for comparison.

Do you have a working oscilloscope that you can use to measure the
high frequency ripple on +5V UNREG and -5V UNREG?


Re: Timebase and CRT Issues on Tektronix Type 545A

Alex Brinister
 

@David,

Never mind, I had never seen bumble bee capacitors before I Googled them. They are all over the place. I'll have to look into buying a jumbo set of capacitors, it looks like. Is there a preferred replacement? Electrolytic, ceramic, polyester, etc?


The ripple in A seems to go away after the unit running for around 15 minutes.


I think somebody earlier mentioned a tube tester. I do not have one personally. Could a dead tube render Timebase A inoperable? Is there a visual check that can be done on tubes to find out if they are dead? The trouble with Timebase A is that is harder to work with than Timebase B, which just swings out. The tube part of the Timebase A circuit is upside down, making it harder to see the tubes.


Alex Brinister