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On 16 August 2018 at 22:02 Fabio Trevisan <fabio.tr3visan@...> wrote:


Hello John,
As a general rule of thumb, a thorough check of the Low Voltage power supplies, both for voltage on spec and ripple are both important and yet, an easy check.
Not just because problems at the power supplies may cause, at times, unpredictable problems that are hard to make sense of (even odd ones such as everything working BUT syncing), but also because finding an off-spec power supply that has not yet caused a serious damage, can save you from watching the inevitable magic smoke, and the need for a much more complicated repair.
Having made sure the power supplies are healthy, the next step (in your case, where the scope seems to be working to a great extent) is to get acquainted with the operation of your scope, to be sure that the position of the controls are all correct for the operation that you're attempting and for the signals you're applied.

More specific to the symptom you mentioned, here are the basics...
1. Exercise all selector levers, push-buttons and pots a dozen or more times... to make sure that you cleared any false contact that may be present, due to oxidation of contacts, or dried lubricant crud.
2. Make sure Horizontal Display mode ganged push buttons is set to A sweep (button "A Lock Knobs" pressed),
3. That the A and B Time/Div dials are locked (that both the clear dial skirt and the gray knob are aligned and moving together) and a suitable sweep speed is selected.
4. Trigger mode ganged push buttons is set to AUTO (button AUTO pressed).
5. That the A Trigger level pot is set to middle range.
6. Vertical signal level has some healthy 4 or 5 graticules in height (and that you use only one channel (for now)
7. A trigger coupling lever is set to AC
8. A trigger source lever is set to NORM.

From this starting point, if it doesn't sync right away, then there must be some issue at play... and it will become a matter of narrowing it down, by fiddling with the controls, one at a time, in a combinatory fashion... For instance:
A. From the starting point above, try to move (slowly) the A trigger level pot, from CCW to CW. If no avail, put if back to center.
B. Try to change the Source lever, from NORM, to the specific channel where you have your vertical signal fed to (CH1 or CH2), and repeat sweeping the A trig level from full CCW to CW.
C. If still no avail, change the Triggering coupling from AC, to HF REJ, to LF REJ and DC... for each possible coupling, try the steps A and B above.
D. If neither work, use a BNC "tee" and a coax cable, and try to feed the same vertical signal to the A EXT input, in combination with changing the the Source lever to "EXT" or "EXT÷10". At this step, try playing with all combinations of the Coupling lever while sweeping the A trigger level pot from CCW to CW.
E. If neither work, then you can still try to feed a vertical signal from the AC mains (or the output of an AC transformer), select an appropriate sweep speed and change the Source lever to "LINE". While at this step, exercise again the Trigger coupling lever and the A trig level potentiometer...

As an extra resource of information, while at each of the lettered steps above, you can try to press the trig view switch.
Under normal conditions, on a working oscilloscope... while pressing the TRIG VIEW push button, you should see on the screen (instead of your Vertical signal), a "fac simile" of the triggering signal that is coming out from the A trigger amplifier, past all the coupling, source and level controls....It should **normally** display much larger on the screen than your original vertical signal is showing.
While you press the TRIG VIEW button, rotating the A TRIG Level potentiometer should make the signal cross the screen from top to bottom (while turning the A trig level from CCW to CW).
If you see the trigger signal while pressing the TRIG VIEW button, and if it reacts to the A trig level control, and the scope still doesn't sync, then you have a problem on the triggering circuitry past the triggering pre-amplifiers.
If you don't see the trigger signal while pressing the TRIG VIEW button, or it stays stuck at either the top or the bottom of the screen, then you have a problem on the trigger input circuitry or the trigger pre-amplifier.

Hope this helps you move further...

Rgrds,

Fabio

On Thu, Aug 16, 2018 at 05:38 PM, <john@...> wrote:

Greetings All, I recently purchased a 465 on Ebay UK, having now cleaned it up
it's looking good, It seems to be working with a good sine wave on both
channels from the calibrator, but the only way I can trigger the waveform is
by very careful adjustment on the TIME/DIV control and the little red Knob in
the center, I don't have a Trigger light ( the lamp in OK) so I presume that I
have a Trigger fault. I have checked all the voltages and all are in spec.
Although I am fine when repairing Ham Transceivers I know nothing about
Scopes.
Can any kind expert give me some suggestions as to what to test first ??
Thanking you in advance
John
mi0dfg

On 17 August 2018 at 00:18 Harvey White <madyn@...> wrote:


On Thu, 16 Aug 2018 10:18:01 -0700, you wrote:

Greetings All, I recently purchased a 465 on Ebay UK, having now cleaned it up it's looking good, It seems to be working with a good sine wave on both channels from the calibrator, but the only way I can trigger the waveform is by very careful adjustment on the TIME/DIV control and the little red Knob in the center, I don't have a Trigger light ( the lamp in OK) so I presume that I have a Trigger fault. I have checked all the voltages and all are in spec.
Although I am fine when repairing Ham Transceivers I know nothing about Scopes.

Triggers are derived from the appropriate channel, or externally.
They're processed, and that signal is used to trigger the sweep.

AUTO triggers the sweep at a fixed rate in the absence of a trigger.
If it works on auto, then the sweep should be able to be triggered.

That you can trigger, but only at a specific spot, suggests that the
trigger amplitude is *really* small somewhere.

This is a case where you'd love to have a scope to test the scope.

I'd get the manual, then look at where the signal comes from the
vertical amplifier (there's a switch in there). Start tracing the
signal from the vertical amplifier through the trigger circuits,
observing voltages and voltage limits on controls.

If everything is OK, and you get the right signals, then check the
input to the sweep generator, that might be bad.

Harvey

Can any kind expert give me some suggestions as to what to test first ??
Thanking you in advance
John
mi0dfg

On Thu, 16 Aug 2018 06:05:57 +0200, you wrote:

Hello Folks,


Thanks for all thoses interestings comments.

As Ive reconnected the ground, and turned power ON : no differential
main shut down occur, even when my finger

played with chassis parts. I also mesured voltage between ground and
chassis : close to zero -- few mV-..

The idea to use the same wall socket to avoid ground loop is fine.

Question : sometime when troubleshooting radios, I use a ground lead
between scope and radio to avoid using probe's aligator clip.

What do you think about ? can I introduce false mesurements ?

Yes and no. The ground lead for the probe, when properly attached,
minimizes ringing on the signal. The long lead from chassis to
chassis will not. For low frequency signals (especially sine waves),
you're not likely to see much of a difference. Go play digital, and
you will. The length of the probe's ground lead and where it is
placed also have an effect, especially if you've got a different
ground potential (by millivolts) across a PC board or a chassis.

Harvey

Regards

Alain




Le 15.08.2018 à 20:40, Richard Knoppow a écrit?:

??? A hot chassis can also be caused by RF filter capacitors connected
from each side of the line to the chassis. I would be much more
suspicious of these if they exist in the 453 than of the electrostatic
shield in the power transformer. If there are such caps in the 453
lift them to see if the voltage on the chassis disappears. You might
want to replace them. There are special capacitors for this service
which fail open so they don't connect the line directly to the chassis.
??? The voltage on the chassis will depend on the amount of
capacitance and the impedance of the measuring device.
??? You can always generate a long argument by discussing the
differences between lightening protection grounds, power line safety
grounds and grounds to eliminate common impedances in AF and RF circuits.

On 8/15/2018 1:52 AM, Craig Sawyers wrote:

That would be typical if the chassis is ungrounded. Capacitance
between the primary and shield (which
is connected to the chassis) in the mains transformer will cause
this. First thing to do is connect
the ground in the mains plug - the previous user did a dangerous
thing by disconnecting the ground.

There may be other problems to solve, of course - but make the scope
safe first.

Craig

Hi Tom,

Thanks for the documents, I added them to my 2215A paperwork and checked my scope for these mod's.

I am in Spain, but based on the SN (204xxx) my 2215A was manufactured in the UK, so it's probably always been in a 220V environment.
I got the impression these mod's were based on the early US build SN's, depending on scope model. (01xxxx - ), and not for the (later?) manufactured UK (2xxxxx) and Dutch (7xxxxx) SN's?
I checked my scope for these mod's, and some were already standard in the schematic of the 2215A, but funny enough there seem to be many iterations around of the PS design, some mod's are to be done only to 2235's, and some only to 2215 but not to 2215A, etc.

What I did do was:

Replaced the Schaffner line filter to be on the safe side;
Replaced the two (already micro cracked) 2n2 RIFA capacitors in the extra line EMI filter build to the back of the scope;
Kept the capacitor C900, it looks as if that one was replaced before;
Kept the power supply mod's as they are now.

Pictures of the removed components are here: /g/TekScopes/album?id=64919&p=pcreated,,,20,1,0,0

Thanks again for the input,

Leo

Greetings All, I recently purchased a 465 on Ebay UK, having now cleaned it up
it's looking good, It seems to be working with a good sine wave on both
channels from the calibrator, but the only way I can trigger the waveform is
by very careful adjustment on the TIME/DIV control and the little red Knob in
the center, I don't have a Trigger light ( the lamp in OK) so I presume that I
have a Trigger fault. I have checked all the voltages and all are in spec.
Although I am fine when repairing Ham Transceivers I know nothing about
Scopes.
Can any kind expert give me some suggestions as to what to test first ??
Thanking you in advance
John
mi0dfg

Hello Kerry,
I don't own a TG501 so I don't really qualify as an expert, but I downloaded
the service manual from the Tekwiki (here: )
and, by just looking at the block diagram, it doesn't seem a simple tweak
(e.g., the turn of a trimpot) to change the time marks of 20ns to 25, the 10ns
to 12.5 and 5n to 6.25.
Still, it's technically possible that only the 20n and faster ranges are off,
since all the slower ranges are derived by direct division of the 1MHz
reference clock, while the faster ranges, rely on a 100MHz clock internally
generated by PLLing the 1MHz reference clock, which is divided by 100 (in
successive divisions, ÷5, ÷2, ÷5 and ÷2) and phase compared to the
reference 1MHz clock.
If the error is exact (i.e. if the 20ns is turned into exact 25ns) a good
theory could be that something wrong with the 1st stage of dividing by 5
(U310A, U310B and U315A) is making it divide by 4 instead.
This would make the PLL to generate an 80MHz frequency, instead of 100MHz.
First hypothesis that came to my mind was that a decade divider IC could have
been replaced by a binary divider... But not applicable in this case, as the
÷5 is obtained by a discrete combination of 3 ECL flip-flops.
My second hypothesis is that, maybe a false contact, (a bad IC socket comes to
mind) is interrupting some signal in this ÷5 logic, causing it to misbehave
and divide by 4.
In face of the known issues that some Texas sockets used by Tektronix on the
equipment of this vintage, it's worth to give it a check.
See this link () for more
information on the dreadful Texas IC socket.

If, however, the error is not exact... than it may just be that the PLL is
failing to generate the 100MHz clock.
In this case, it can be easily diagnosed (even with an uncalibrated scope), by
just displaying simultaneously (on 2 channels), the 1MHz reference clock, at
the same time with any of the clocks generated from the - supposed - 100MHz
clock.
If you trigger in one and the other roll on the screen, or vice-versa, than
it's the PLL that it's not locking.

Hope this helps,

Rgrds,

Fabio




On Thu, Aug 16, 2018 at 01:14 PM, <kburns@...> wrote:

Hello

I'm a newcomer to this group who has fairly recently acquired a SG503,

PG506

and TG501 in a TM5003 module. All of these units are working fine, apart
from the TG501 which shows some odd outputs on the 20ns, 10ns and 5ns
markers. The timing seems to be correct on the slower markers (50ns and
below), but the 20ns, 10ns and 5ns show as 25ns, 12.5ns and 6.25ns
respectively. The 2ns is correct (can't check the 1ns, given the bandwidth

of

my old Tek 2465A). I've checked the markers on a second scope as well.

The

TG501 is a later model (Bo51xxx).

My first thought was that there must be a fault with the 20ns, 10ns and 5ns
outputs - possibly in the dividers - but then wondered if perhaps the
generator had been deliberately modified at some point to give the 25ns,
12.5ns and 6.25ns values. I'm not sure if this mod would be possible with
the TG501? I've had a good look at the manual, but before I start delving
any further I wanted to be sure it is a fault. I have checked the power
supply voltages and ripple and the 1 Mhz oscillator - these are all good.

Any advice on this issue from the experts here would be appreciated.

Thank you

Kerry

On Thu, Aug 16, 2018 at 03:43 PM, tom jobe wrote:

Hi Leo,
Thanks for the progress report, It's good to see that your 2215A repairs
so far have gone well!
In studying your photos, it looks like you have one of those dreaded
"Schaffner" brand AC inlet filters (where the AC cord plugs into the
back of the scope).
If that is what you have, they have a poor reliability record when used
on 240 AC line voltage, if you also have that too.
I'm in a 120 volt AC part of the world and I started changing them after
having just one scary "Schaffner" failure.
The Tekscopes message archive should have some "Schaffner" discussions
from the past, and a Google search on the term 'Schaffner filter
failure' will get you more information too.
You might also consider changing the few X and Y caps in the 2215A,
especially C904 which is under the AC inlet filter and behind the main
power switch.
C904 is much easier to change while you have the AC inlet filter removed.
The original X and Y capacitors have difficulty with 240 volt mains, so
you might want to get the highest rated replacements you can find.
tom jobe...

On 8/16/2018 4:19 AM, satbeginner wrote:

Hi all,

just a final message: it's all done!

Today I received the 12V 60mm brushless fan that was a perfect fit.
I used the half wave rectifier circuit I was able to place the components

for on the board, the fan is running nicely without real noise on 9V.

I mean, you can hear it, but only just.
There are plenty perforations all around the casing to let cool air in, so I

choose to have it blowing out, so it is sucking the warm air from the inside
of the scope and remove it from the scope.

(Like in my 2465's)

One extra thing I found: When I put all the covers back and ran the scope

for a while, I found that the one screw on the right hand side is actually
quite important.

This creates a thermal connection between where the internal heatsink is and

the outside blue cabinet, so that way the scope's casing helps in cooling the
scope too.

Again, pictures are here:

/g/TekScopes/album?id=64919&p=pcreated,,,20,1,0,0

Un saludo,

Leo

Hi Tom,

As it turns out, it is not yet solved... ;-)

Yes, I opened the scope again, and yes, it's a Schaffner line-filter.
I put a picture of it in the album: /g/TekScopes/album?id=64919

Is this one of the "explosive" types?? If so, I'll will replace it.
Although this scope spend his whole life in The Netherlands,, so maybe it OK?

Further down the line there is this black, plastic box that contains another line-filter.
In there are two 2n2 RIFA capacitors (similar as in the 2465 PS), they already look "cracked", so I will replace them too.

To be continued,

Leo