Re: Triggering problem with TDS6604


RICHARD W. MURRAY
 

Jim

I spend way to many hours hours checking out the trigger components until I noticed the main line going into the trigger IC
appeared to be quite thin so I checked the trace and found it was open. Your board is likely different
but the location of the problem was in the front center of the motherboard about 1.5" in from the front
of the board.

Regards

Richard

-----Original Message-----
From: Jim Potter
Sent: Monday, December 31, 2018 4:51 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Triggering problem with TDS6604

Thanks for the response, Richard. I will look at the board carefully to make sure it's not something that simple. I'm leaning toward thinking it's the trigger chips. I just found out that the TDS694C uses the same chip, and I have two 694Cs that are potential donors. However, replacing the chips is difficult enough that I need to eliminate simpler possibilities first.

Jim

On December 31, 2018 2:34:24 PM MST, "RICHARD W. MURRAY" <inertial@...> wrote:
Jim

This may not help but I had the same problem with a TDS640. The problem
was
a trace on the
board which was to thin and failed. Worth a look.

Regards

Richard

-----Original Message-----
From: Jim Potter
Sent: Wednesday, December 26, 2018 10:58 PM
To: TekScopes@groups.io
Subject: [TekScopes] Triggering problem with TDS6604

I recently acquired a Tektronix TDS6504, which is apparently a
non-entity.
The software says it is a TDS 6604. It seems to work fine except for a
triggering problem which renders it useless.

If I put a 4 GHz sine wave signal in on one channel, for example
channel 3,
and set up automatic triggering with the triggering selecting another
channel, say channel 2, with no signal I see an unsynchronized waveform

displayed. The display is set for interpolated time and the sample rate
is
20 GHz/sample. The trigger status reads READY. If I switch the trigger
source to the channel with a signal the trigger status light TRIG'D is
lit
as though it's being triggered, but the display is frozen. If I restore
the
trigger source to the empty channel, the TRIG'D light stays lit.
However, if
I remove the signal automatic triggering resumes, and when I put the
signal
back to the channel that is not being used for a trigger, I see the
unsynchronized waveform again.

So the issue is that when I apply a signal to a channel and set the
trigger
input to that channel, the scope appears to be triggering, but the
display
is frozen to whatever was previously display

Another phenomenon is if I mess around too much trying to see if I can
get a
display the controls lock up and I get a message about a long operation

taking place.

A further note is that the scope passes all the internal tests.

For a while I thought maybe it was waiting for a B trigger, but that is

turned off, and if it was waiting the TRIG'D and READY lights would
both be
lit according to the manual.

It seems to be such a simple problem, but I haven't found any
workaround to
get the scope functioning normally. Since it isn't a production scope
maybe
there is something weird going on, but I don't have a clue what it
could
be.

Any insight about what to try or to look for would be greatly
appreciated.

Thanks,

Jim





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