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Hey Ondrej,

In your shoes I'd start by measuring the -1.25 and the +1.36 reference
voltages with a DMM or the like. If they're spot on, you'll be wasting your
time looking for trace damage, and you may complicate the diagnosis and fix
by adding new failures when replacing components. I'm not saying you
shouldn't do it, just that you should start by conclusively diagnosing the
problem FIRST.

Siggi

On Fri, Jun 5, 2020 at 4:17 PM Ondrej Pavelka <info@...

wrote:

Excellent idea, I have plenty experience dealing with corroded tracks

and I

am equipped to fix it. I have microscope, chemical tracers to make the
leaks glow under UV and other means of fixing this. Let me get on with it
do a proper check under the microscope and get back to you.


On Fri, 5 Jun 2020, 22:03 Siggi, <siggi@...> wrote:

On Fri, Jun 5, 2020 at 3:55 PM Ondrej Pavelka <

info@...

wrote:

P.S. I found 3 leaky surface mount electrolytic caps on the board I

think

it's referred to as a A board? I will change those to prevent further
corrosion spread but what are they in charge of ? Could these be the

reason

for the troubles?

Yes, this is quite likely the problem. Your 2445B (the -B is very
important, there are important differences between the 2445 and the

2445B).

The 2445B is a drive-by-wire scope, in that the A5 board generates a
multitude of voltages with a DAC. These voltages in turn control

various

parts of the scope.
What tends to happen is that the leaking capacitors wreck the
components and PCB traces that are involved with creating the DAC's
reference current. The quick and easy way to assess the state of the

DAC

is

to measure the -1.25 and +1.36 reference voltages on the A5 board. On

some

versions of the board, these are broken out to test points, but if not
you'll have to hunt around for suitable test points to assess them.
If those are off, then that's a sure indication that your DAC reference
current network is bad.

Do you have the service manual ? It talks about the boot process and where
things get stopped.

I was lucky enough not to lose my NVRAM contents before I was able to recap
and capture the nvram contents.

As I remember it, failing the RAM test (which includes the NVRAM) stops
things very early in the blinky-light POST cycle.

The section of the service manual is kind of oblique, IMO, but once you get
how they are trying to say things it gets better.

My scope had the GPIB option, and it failed a little while after my recap,
so I just removed it, since I know I would never use it. If you have any
options, I suggest trying to boot without them.

On Fri, Jun 5, 2020 at 2:55 PM <trogg58@...> wrote:

Hi all, another hopeful newbie on here, I found this site whilst looking
for some clues to attempt repair a 2465. I have managed to get it almost
back to life but now stuck, I wonder if anyone would be kind enough to
point me in the right direction.
Here is some background info, I have had the scope for about 12 years,

but

not really had chance to use it, the magic smoke came out about 10 years
ago when I switched it on, it got put on the shelf due to lack of time

and

left there. Now I have some time on my hands (due to being furloughed) I
decided to dig it out and try and repair it.
After opening it up I spotted that C1018 had popped and C1016 didn’t look
good so replaced both. C1020, C1052 and C1020 also had seen better days

so

swapped them too, looking at all the other caps no obvious leaks or

bulges

so reassembled and switched on, the CRT just about came to life and then
the smoke came out again. This time it was C1130, so I decided to re-cap

as

advised on this forum.
I have replaced all the usual electrolytics on both PSU boards, with a

mix

of Nichicon and Panasonics, and the Rifa caps, rebuilt and hey presto

all

the voltages are well within tolerance, ripple all good too, but ….. the
post test gets as far as lighting all the front panel led’s and they stay
on, CRT comes up with a static bizarre display showing four groups of

1111

across the top and bottom a central vertical line of dots, a horizontal
central line of four groups of 4 dots then a top right to bottom left
diagonal of four groups of 4 dots, (picture posted under 2465 strange
display) only focus and readout intensity controls on the front panel
work., pressing the Delta T or V have no effect.
I do believe that I am the first person to effect any repairs to this
scope as all screws are present and there are no signs of any “after
manufacture” soldering of tampering, so its hands up I think I have done

it

in myself.
Anyone have any ideas where to go first?
Thanks in advance…
John Carter

--
Andy

Looking at the datasheets these devices appear the be the same, am I missing
something, or was it just a case of the MCM68766 superseding the MCM68764?

On Fri, Jun 5, 2020 at 3:55 PM Ondrej Pavelka <info@...

wrote:

P.S. I found 3 leaky surface mount electrolytic caps on the board I think
it's referred to as a A board? I will change those to prevent further
corrosion spread but what are they in charge of ? Could these be the

reason

for the troubles?

Yes, this is quite likely the problem. Your 2445B (the -B is very
important, there are important differences between the 2445 and the 2445B).
The 2445B is a drive-by-wire scope, in that the A5 board generates a
multitude of voltages with a DAC. These voltages in turn control various
parts of the scope.
What tends to happen is that the leaking capacitors wreck the
components and PCB traces that are involved with creating the DAC's
reference current. The quick and easy way to assess the state of the DAC is
to measure the -1.25 and +1.36 reference voltages on the A5 board. On some
versions of the board, these are broken out to test points, but if not
you'll have to hunt around for suitable test points to assess them.
If those are off, then that's a sure indication that your DAC reference
current network is bad.

Hi all, another hopeful newbie on here, I found this site whilst looking
for some clues to attempt repair a 2465. I have managed to get it almost
back to life but now stuck, I wonder if anyone would be kind enough to
point me in the right direction.
Here is some background info, I have had the scope for about 12 years, but
not really had chance to use it, the magic smoke came out about 10 years
ago when I switched it on, it got put on the shelf due to lack of time and
left there. Now I have some time on my hands (due to being furloughed) I
decided to dig it out and try and repair it.
After opening it up I spotted that C1018 had popped and C1016 didn’t look
good so replaced both. C1020, C1052 and C1020 also had seen better days so
swapped them too, looking at all the other caps no obvious leaks or bulges
so reassembled and switched on, the CRT just about came to life and then
the smoke came out again. This time it was C1130, so I decided to re-cap as
advised on this forum.
I have replaced all the usual electrolytics on both PSU boards, with a mix
of Nichicon and Panasonics, and the Rifa caps, rebuilt and hey presto all
the voltages are well within tolerance, ripple all good too, but ….. the
post test gets as far as lighting all the front panel led’s and they stay
on, CRT comes up with a static bizarre display showing four groups of 1111
across the top and bottom a central vertical line of dots, a horizontal
central line of four groups of 4 dots then a top right to bottom left
diagonal of four groups of 4 dots, (picture posted under 2465 strange
display) only focus and readout intensity controls on the front panel
work., pressing the Delta T or V have no effect.
I do believe that I am the first person to effect any repairs to this
scope as all screws are present and there are no signs of any “after
manufacture” soldering of tampering, so its hands up I think I have done it
in myself.
Anyone have any ideas where to go first?
Thanks in advance…
John Carter