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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

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 ?

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

Regarding the removal of the two attenuator boards/assemblies, is the best way to get at the nuts holding them to the front panel with a small spanner? I'm having a little difficulty getting them free.

On Aug 15, 2018, at 7:35 PM, Tom Miller <tmiller11147@... <mailto:tmiller11147@...>> wrote:

Look for a tantalum with a small hole in it.

It turns out that C965 (Board A9), a tantalum bypass capacitor on the +15 rail had gone bad; removing brought the +15 rail resistance to ground back to where it should be. Most of the capacitors look to be in pretty good condition; I have not come across any bulges, deformities, leaked electrolyte or burn marks on any of them, even the larger axial lead supply capacitors.

I powered it on, and checked the supply voltages at the test points; all were within specification, although I haven't checked the ripple on each yet. I haven't checked any of the high voltage test points yet, as I'm currently lacking the equipment to do so safely.

A couple minutes into testing the powered on scope (I couldn't find the test point for +105/160), some other component let go, with a loud pop, accompanied by a whistling sound and small quantity of smoke. So, the hunt is on for the culprit. I have removed boards A3, A7 and A8 so far, and have found no obviously failed components on any of them. I thought at first that something on A7 (timing board) failed, given the location where the smoke seemed to come from, but that doesn't seem to be the case. Is there any component in the recess along with the CRT known to fail in such a way?

Interestingly, after the component failure, all the supply voltages were still within specification.

Regarding the removal of the two attenuator boards/assemblies, is the best way to get at the nuts holding them to the front panel with a small spanner? I'm having a little difficulty getting them free.

Thanks,

John

A hot chassis can also be caused by RF filter capacitors connected from each side of the line

chassis. I would be much more suspicious of these if they exist in the 453 than of the

shield in the power transformer.