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From: DaveC on 31 Jan 2010 15:16
This scope has the famous "FAIL ++ Acq" error which points to the infamous
failed (and leaking) SMD caps on the acquisition PCB.

I'm moving on to troubleshoot another (unrelated, I think -- and hope) issue.

During the 25 second "on" period, relays click on & off, the monitor goes
through it's boot display (all bright, then dark, then the clock icon), then
the graticule is drawn, which is quickly replaced with the "Tek Running
Autoing" display listing the "FAIL ++ Acq" error.

During the power-up period, the front panel LEDs all turn on for about 25
seconds, then off for 5 seconds, then only the CH 1 LED lights.

The service manual says (in the Front Panel troubleshooting chart):

Do all
of the front panel
LEDs turn on and then
turn off a short
time later?

(Then:)

Does one
front panel LED
turn on and then turn off,
followed by the next LED until
all LEDs have turned
on and then
turned off?

The LEDs do not go through this one-at-a-time sequence. The manual's flow
chart points to a failed CPU PCB if the LEDs don't blink this sequence.

Can someone with a TDS4xx confirm power-on LED behavior?

I'm trying to determine whether, because the LEDs aren't blinking "properly"
and most of the front panel buttons are not working (the buttons bordering
the monitor, plus all the CH input buttons), does this mean a replacement CPU
PCB is in my future, or if it's possibly related to cap failure (ie, other
cap failures beyond the acquisition PCB)?

Has anyone else here have a similar problem (non-functional buttons) in the
past? I'd appreciate hearing your experiences.

Thanks,
Dave

From: mike on 31 Jan 2010 15:19
DaveC wrote:
> This scope has the famous "FAIL ++ Acq" error which points to the infamous
> failed (and leaking) SMD caps on the acquisition PCB.
>
> I'm moving on to troubleshoot another (unrelated, I think -- and hope) issue.
>
> During the 25 second "on" period, relays click on & off, the monitor goes
> through it's boot display (all bright, then dark, then the clock icon), then
> the graticule is drawn, which is quickly replaced with the "Tek Running
> Autoing" display listing the "FAIL ++ Acq" error.
>
> During the power-up period, the front panel LEDs all turn on for about 25
> seconds, then off for 5 seconds, then only the CH 1 LED lights.
>
> The service manual says (in the Front Panel troubleshooting chart):
>
> Do all
> of the front panel
> LEDs turn on and then
> turn off a short
> time later?
>
> (Then:)
>
> Does one
> front panel LED
> turn on and then turn off,
> followed by the next LED until
> all LEDs have turned
> on and then
> turned off?
>
> The LEDs do not go through this one-at-a-time sequence. The manual's flow
> chart points to a failed CPU PCB if the LEDs don't blink this sequence.
>
> Can someone with a TDS4xx confirm power-on LED behavior?
>
> I'm trying to determine whether, because the LEDs aren't blinking "properly"
> and most of the front panel buttons are not working (the buttons bordering
> the monitor, plus all the CH input buttons), does this mean a replacement CPU
> PCB is in my future, or if it's possibly related to cap failure (ie, other
> cap failures beyond the acquisition PCB)?
>
> Has anyone else here have a similar problem (non-functional buttons) in the
> past? I'd appreciate hearing your experiences.
>
> Thanks,
> Dave
>
All my experience is with the 540, but I think you're wasting your time
trying to troubleshoot ANYTHING until you replace ALL, AND I DO MEAN
EVERY SINGLE ONE on every board, the caps and CLEAN
CLEAN CLEAN and CLEAN again the circuit boards.

Sure you didn't miss any newsgroups with your cross post????
From: DaveC on 31 Jan 2010 15:49
> All my experience is with the 540, but I think you're wasting your time
> trying to troubleshoot ANYTHING

OK, I suspected that, but non-functional buttons seemed a symptom not related
to caps issue. But I'll take your advice to heart and do *all* the caps.

> until you replace ALL, AND I DO MEAN
> EVERY SINGLE ONE on every board, the caps and CLEAN
> CLEAN CLEAN and CLEAN again the circuit boards.

Yeah, I plan to do that. Making a complete list right now.

What techniques and chemicals did you use?

Thanks for your reply.
Dave

From: mike on 31 Jan 2010 17:14
DaveC wrote:
>> All my experience is with the 540, but I think you're wasting your time
>> trying to troubleshoot ANYTHING
>
> OK, I suspected that, but non-functional buttons seemed a symptom not related
> to caps issue. But I'll take your advice to heart and do *all* the caps.
>
>> until you replace ALL, AND I DO MEAN
>> EVERY SINGLE ONE on every board, the caps and CLEAN
>> CLEAN CLEAN and CLEAN again the circuit boards.
>
> Yeah, I plan to do that. Making a complete list right now.
>
> What techniques and chemicals did you use?
>
> Thanks for your reply.
> Dave
>
On the subject of technique.
You have significant risk of lifting pads when you remove the old caps.
The solder will be corroded. You need to "tin" each joint to expose
clean solder for heat transfer.
To remove caps, use two soldering irons. One on each end but on opposite
sides.
Gentle pressure provides a twisting motion that rotates
the cap off the pads. This is MUCH less stressful to the pads than
trying to pull upward on the cap.

I'd suggest you NOT try to use a heat gun unless you clean
the boards before removing the caps.
From: DaveC on 1 Feb 2010 04:01
> On the subject of technique.

Mike, Thanks very much for your advice and experience. Not having done more
than a few SMD caps the techniques will be valuable.

Thanks again,
Dave

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