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On 17 August 2018 at 13:38 Fabio Trevisan <fabio.tr3visan@...> wrote:


Hi John,
No problem about the time... It's a relief for my mind to solve those puzzles.
Some comments further down, just after your answers...
Regards,
Fabio

On Fri, Aug 17, 2018 at 07:16 AM, John Stoole wrote:
Hello Fabio , I decided to contact you direct in case I want to send you any photos of my problems here,
Firstly I want to thank you for the very detailed help you sent me, it must have taken up a lot your your valuable time and it is much appreciated.
I have now completed all the suggestions that you made with no results but here are some of the things that I found
1. A trigger level control has no effect with any of the switch positions
3. Pressing the TRIG VIEW I have a blank screen

Hmmm... Both things above together, may mean that the triggering signal, through the triggering input and pre-amplifier stages may be so much offset in D.C. that the triggering signal coming out of the pre-amplifier into the triggering discriminator (Tunnel Diodes or Tek Custom IC yet to be clarified) is never crossing the 0V (which is a must, for the trig. discriminator to operate).
**Please try this one more thing**
While pressing the Trig View, press also the Beam Finder (you should see the trace either stuck near the top or the bottom of the screen).
While keeping both pressed, move the A Trigger Level, to see if the trace shows any tendency to move towards the center of the screen...
This will give you some hints if the trigger preamplifier is really stuck at some DC level, or if it still reacts to the A trig level pot.

2. If I switch the A COUPLING to DC, then as I step the SOURCE switch from NORM to EXT10 the trigger lamp flashes proving the lamp is OK

This is good! It gives us some indication that the triggering discriminator is working... It's probably detecting the triggering signal crossing 0V, when you're changing selections, which is probably causing some change in the DC levels at the input stages...

4. the TRIG HOLD OFF control works well and helps to lock the waveform when moved

Expected... The Sweep control logic seems to be working, otherwise there wouldn't be a trace whatsoever.

5 Tried 5 v AC into the external trigger but that would not sync the waveform

This indicates that whatever the problem is, it's probably at or after the trigger pre-amplifier input selector (e.g. it sort of rules-out that your problem is at the pick-off circuitry).
In time, the pick-off circuitry are the pieces of circuitry of the Vertical pre-amplifiers that "taps" the vertical signal from Channel 1, Channel 2 or from after the channel Alternating circuit (the NORM pick-off) and routes it to the trigger preamp.
If the problem would be at the pick-off circuitry (only), you would still be able to trigger from an EXT input.

the rest of the scope seems to work very well
I will continue to hunt around the the voltages to see if I can find any serious deviations for the service manual voltages

To further help you from this point on, we will need to know:
A. What kind of Trigger pre-amp board your 465 has. I`m not even sure if this "doubt" applies to the 465, but I used to have a 464 and I know that (for the 464 at least) there were two versions of Trigger boards, one that uses Tunnel Diodes, and another one that uses a Tek custom IC (as the triggering signal discriminator).

Many thanks again for the help
regards
John

-----Original Message-----
From: Miguel Work
Sent: Thursday, August 16, 2018 2:25 AM
Subject: [TekScopes] tektronix 214 option 94

Which is optino 94 for a Tektronix 214?

I have to replace the large power transistor on the A6 inter board the TIP35A
one it was damaged from prior ill handling plus it appears to have been
overheated at sometime as the case is deformed. I found a replacement on
Mouser and have ordered it not expensive so I'm asking if ya'all think it will
work as well as the original? It is a Central made & supplied version and it
is now full plastic case no metal tab it is like the 475 ones. It is rated
25A, 60V 125W don't know what original is as no specs in manual.
Also I have discovered that the A6 board has been updated to the later
B2000000 and on type parts added.
My scope sn#168*** and my board is -09 not listed in either manual?
When i get it together and calibrating I will be here for advise on proper
adjustments.
On the A10 storage board cap C1967 is a blue Sprague 1uf 150v aluminum lytic
not a wet tant, interesting the other two are still wet tants.

Jim

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