开云体育

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

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

-----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?

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