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Hi Everyone,

I'm definitely a newb to electronics repair, so I wanted to get some advice about my Tektronix 2467b. On startup, the scope errors out with one of two codes: "Test 05 Fail 04" or "Test 05 Fail 42". However, if I run the diagnostics (single time or loop), test 5 passes.

Generally, the scope seems to be behaving itself (nothing obvious).

Any suggestions on where to start or why it is behaving like this?

Thanks!
Stefan

On Fri, Aug 17, 2018 at 04:38 <Sscandizzo@...> wrote:

Hi Everyone,

I'm definitely a newb to electronics repair, so I wanted to get some
advice about my Tektronix 2467b. On startup, the scope errors out with one
of two codes: "Test 05 Fail 04" or "Test 05 Fail 42". However, if I run
the diagnostics (single time or loop), test 5 passes.

Generally, the scope seems to be behaving itself (nothing obvious).

Any suggestions on where to start or why it is behaving like this?

Hey Stefan,

This is typically because of leaking surface mount electrolytic capacitors
on the A5 board. If you consult the archives, you’ll find plenty of
information about this problem. Those capacitors will need replacing and
the PCB cleaned to prevent further damage.
The error occurs because the electrolyte wrecks the resistors (or PCB
tracks) that provide the reference for the DAC, so you’ll have to see about
replacing those and/or repairing the PCB. The A5 board generates two
reference voltages, 1.36V and -1.25V. If you measure those, I bet you’ll
find them off a bit.
Note that at least one of those resistors is a low temperature coefficient
type, which helps with holding calibration and working in spec across the
operating temp range.

The other possibility is that there is something going on with the line
triggering path, but even then you’d want to replace those capacitors
preemptively.

Good luck,
Siggi

Hi Siggi,

Thank you for the explanation. Two followup questions:

1) Why would the scope appear to pass test 05 when I manually run the diagnostics but fail on start-up? This probably doesn't change the solution, just curious.

2) Has anyone created a comprehensive list of the caps necessary for a full overhaul? I'd rather not re-invent the wheel if such information has already been collected.

Best,
Stefan

On Fri, 17 Aug 2018 at 13:01 <Sscandizzo@...> wrote:

1) Why would the scope appear to pass test 05 when I manually run the
diagnostics but fail on start-up? This probably doesn't change the
solution, just curious.

I don't know why this would happen, it's a mystery for you to figure out
:). It might be because I'm pointing you in the wrong direction, and what's
actually happening is e.g. that the trigger hybrid's connections have
oxidized, and you have temperature-dependent intermittence.
You might have a bad U500 trigger hybrid - it happens.
It might also be because the leaked electrolyte changes its characteristics
or evaporates to an extent after conducting for a while.

The 05 tests effectively compare DAC-generated voltages to the line trigger
input by means of the trigger hybrid, so anything involved in that process
might be at fault.
However, the most common failure by far leading to the 05 errors in the
24X5B scopes, is leaking electrolytics.

You can conclusively answer the question of whether your DAC's compromised
by opening the scope up and measuring the +1.36 and -1.25V reference
voltages on the A5 board. This is the board on the right side of the scope,
very easy to get to once the case is off. Even if those are good, you want
to do a close visual inspection of the four SMD caps on that board and
surrounding components.

2) Has anyone created a comprehensive list of the caps necessary for a
full overhaul? I'd rather not re-invent the wheel if such information has
already been collected.

There are only 4 of those SMD capacitors on the A5 board, and I don't think
I've ever heard of SMD caps anywhere else in those scopes.

If you want to e.g. do a full power supply recap, there are recent threads
here that will refer you to spreadsheets that I've never consulted. The
caps in question, however, have nothing to do with the power supply,
they're just bulk decoupling caps for the A5 board.

On ?Friday?, ?August? ?17?, ?2018? ?12?:?01?:?59? ?PM? ?CDT, Sscandizzo@... <Sscandizzo@...> wrote:

>2) Has anyone created a comprehensive list of the caps necessary for a full overhaul?? I'd rather not re-invent the wheel if such information has already been collected.

Best,
Stefan
There are two lists.? An excellent one by?Menahem Yachad using Mouser part numbers is here: /g/TekScopes/files/2465B%20capacitor%20refresh%20list%20%20Updated%20June%202018.xlsx
And a pretty good one by Machineguy59 using Digikey part numbers is here: /g/TekScopes/files/2465B%20capacitor%20refresh%20list%20%20Updated%20June%202018.xlsx

I’ve also seen bad mux chips on the A5 board cause this same error.

Manuel

Hey Stefan,

now that I have some time, let me expand on this a bit. My apologies if I'm
preaching to choir, I don't know your level of expertise - it might save
time if you're willing to divulge this ;). If not we'll typically muddle
through anyhow, given sufficient patience and/or persistence on either end.
I can say if you're new to this and/or electronics repair, you're in for a
treat. These scopes are a joy to work on, and the service manuals are a
work of art.

1. Get the service manual.
There's a link on TekWiki <>. If that
doesn't satisfy, I can recommend the Artek Manuals scans <
>. While I don't own
the 2467B manual, I did buy the 2467 one, and it's an excellent scan.
2. Measure the low voltage (LV) supplies at J119.
Measure voltages and ripple both as described in the service manual.
If you don't have a second scope, you can turn the 2467B on its own
supplies to measure ripple and at least get a good indication.
3. If the supplies are out of spec, that's the first thing you need to
address.
Without correct supplies, there's no reasoning about the rest of the
functionality in the scope. The spreadsheets MachineGuy pointed to are sure
to be a big time saver if you need to do a full power supply recap.
4. Assuming the LV supplies are OK.
This is where it gets fun - you'll have a problem on the A5 board,
and/or in the trigger path, and/or in the line trigger signal. You can
quickly eliminate or implicate the most usual failure in the A5 board with
quick measurement of the +1.36 and/or the -1.25V references, but after that
it gets a little hairier.

The 2467(B) is an awesome scope - my 2467 is always my go-to for general
spelunking, I hope you clear this up in yours.

So, a couple of questions for you:
1. Did this fault develop while the scope was in your possession, or did
you acquire it in this state?
2. Do you have a second scope you can use to diagnose this problem?

Siggi