Topics

2465 trace focus issues


alan.bain@...
 

My trusty 2465 seems to have developed a trace focus issue. With the focus knob fully ccw I get a just about usable trace (but it honestly looks more like a cossor scope I used to own than the sharp crisp trace I expect from a Tek). Any further clockwise is just a green fog.

I've had to replace the odd exploding electrolytic in the scope PSU boards, wondering if it's now time to do a full replacement? I do have a rather elderly HP183 around so do have the option to do some trouble shooting (never liked the HP as much as the Tek from a usability point of view but it does work).

A photo of a trace is here
http://www.the-sot.org/Nft/DSC_3717.JPG

So wondering if anyone is familiar with the issue and has any advice - if that advice is to sort the caps before fault finding then that might indeed make sense.

[Thanks are due to the very helpful person who provided the drawing of the fan collet on the files section - in my first dismantling attempt for capacitor replacement I broke mine, but machining a new one was fairly straightforward]


satbeginner
 

Looks like a 20us interval, so possibly a switcher frequency.

Check all voltages and ripple, my guess would be power supply issues

Have fun,

Leo


Chuck Harris
 

Try replacing the electrolytic capacitor inside of the
CRT's HV compartment. It filters the EHT's oscillator
off of the scope's -15V supply.

Any 2465 should have all of its power supply electrolytic
capacitors changed, with the possible exception of the two
large axial leaded caps in the mains filter.

The 180uf 40V, and 250uf 20V caps are especially likely to
spill their guts all over the power supply's circuit boards.

-Chuck Harris

satbeginner wrote:

Looks like a 20us interval, so possibly a switcher frequency.

Check all voltages and ripple, my guess would be power supply issues

Have fun,

Leo




Tony Fleming
 

Have you tried the CONTRAST adjustment?
Tony

On Mon, Jun 8, 2020 at 12:27 PM <alan.bain@...> wrote:

My trusty 2465 seems to have developed a trace focus issue. With the focus
knob fully ccw I get a just about usable trace (but it honestly looks more
like a cossor scope I used to own than the sharp crisp trace I expect from
a Tek). Any further clockwise is just a green fog.

I've had to replace the odd exploding electrolytic in the scope PSU
boards, wondering if it's now time to do a full replacement? I do have a
rather elderly HP183 around so do have the option to do some trouble
shooting (never liked the HP as much as the Tek from a usability point of
view but it does work).

A photo of a trace is here
http://www.the-sot.org/Nft/DSC_3717.JPG

So wondering if anyone is familiar with the issue and has any advice - if
that advice is to sort the caps before fault finding then that might indeed
make sense.

[Thanks are due to the very helpful person who provided the drawing of the
fan collet on the files section - in my first dismantling attempt for
capacitor replacement I broke mine, but machining a new one was fairly
straightforward]




Chuck Harris
 

Uhmmmm? What CONTRAST adjustment is that?

-Chuck Harris

Tony Fleming wrote:

Have you tried the CONTRAST adjustment?
Tony

On Mon, Jun 8, 2020 at 12:27 PM <alan.bain@...> wrote:

My trusty 2465 seems to have developed a trace focus issue. With the focus
knob fully ccw I get a just about usable trace (but it honestly looks more
like a cossor scope I used to own than the sharp crisp trace I expect from
a Tek). Any further clockwise is just a green fog.


Tony Fleming
 

I have on the left bottom corner, under the CRT, 3 options:
1) INTENSITY
2) FOCUS
3) READOUT INTENSITY
Play with them until you like your display.

I'm sure you know how to do that, but short of opening the scope and .....
that is a quick way for me.

Have a great day!

Tony

On Mon, Jun 8, 2020 at 5:18 PM Chuck Harris <cfharris@...> wrote:

Uhmmmm? What CONTRAST adjustment is that?

-Chuck Harris

Tony Fleming wrote:
Have you tried the CONTRAST adjustment?
Tony

On Mon, Jun 8, 2020 at 12:27 PM <alan.bain@...> wrote:

My trusty 2465 seems to have developed a trace focus issue. With the
focus
knob fully ccw I get a just about usable trace (but it honestly looks
more
like a cossor scope I used to own than the sharp crisp trace I expect
from
a Tek). Any further clockwise is just a green fog.



Chuck Harris
 

You should have Intensity, Focus, Astigmatism, and Readout Intensity.

Readout Intensity is just that, only the readout.

The main intensity only affects the trace.

Focus, and Astigmatism affect all screen displays.

However, I haven't run into a Contrast adjustment.

There is an additional concern that affects the sharpness of the
trace, and that is the 20MHz BW limit. Wide bandwidth allows
for a lot of noise, which shows up on the trace as fuzz.

There are circuit failures, and CRT failures that will stymie even the
most fastidious tweaking of the available adjustments.

-Chuck Harris

Tony Fleming wrote:

I have on the left bottom corner, under the CRT, 3 options:
1) INTENSITY
2) FOCUS
3) READOUT INTENSITY
Play with them until you like your display.

I'm sure you know how to do that, but short of opening the scope and .....
that is a quick way for me.

Have a great day!

Tony

On Mon, Jun 8, 2020 at 5:18 PM Chuck Harris <cfharris@...> wrote:

Uhmmmm? What CONTRAST adjustment is that?

-Chuck Harris

Tony Fleming wrote:
Have you tried the CONTRAST adjustment?
Tony

On Mon, Jun 8, 2020 at 12:27 PM <alan.bain@...> wrote:

My trusty 2465 seems to have developed a trace focus issue. With the
focus
knob fully ccw I get a just about usable trace (but it honestly looks
more
like a cossor scope I used to own than the sharp crisp trace I expect
from
a Tek). Any further clockwise is just a green fog.