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.
