-----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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