The DC is the operating bias voltage for the 536 input stage and
should be ignored, it's the peak to peak signal voltage you need to
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However I think there's a trap. The TU-2 calibrator only applies the
signal to one of the differential inputs to the 536, the other input
is AC grounded. That should be 0.1 volt per division according to
the TU-2 manual. However if you use the signal through the CA
preamplifier. it should enter the 536 as a differential signal, half
at each input point but out of phase so they add. It's the total
signal between the two inputs that's important so I'd expect to see
50 mV per division on each of the inputs, the grids of V304 and V324
(pins 1 and 3 of the interconnecting socket). They should be
identical but of opposite phase, however I'd measure both and add
them together in case the CA isn't exactly balanced. If your test
scope has differential input you could directly measure the input
between the two grids.
Since the error isn't too great if the signals aren't close to what
they should be then let me know and I'll double check but I think
I'm right. It's a pity they don't have waveforms in the manuals.
Anyone familiar with these models with anything to add or thinks
I've made an error, please jump in.
On 01-May-13 11:33 PM, Cliff White wrote:
I've been using the calibrator
from a different scope, which was calibrated a few weeks
ago, so I'm pretty sure it's right. I do have two other
working scopes right now, just none of the same series.
I'll set the interface to the .1 volt/div and see if that
fixes anything. Is the DC voltage it's floating on
supposed to be calibrated as well?
On 05/01/2013 01:43 AM, Don Black wrote:
I've checked bot the CA and 536 manuals and neither
seem to have the usual waveforms that would indicate
the signal level from the plugin to the mainframe.
However in the TU2 test plugin (attached) it indicates
0.1 volt per division. You should be able to measure
this at the mainframe and see if it gives the correct
sensitivity. I suggest looking for more than one
divisions at 0.1 volts per division. You'll need
another scope for this, however any scope will do, you
can check it against the calibrator if necessary.
Incidentally, are you relying on the calibrator signal
for your measurements? It's always possible that's
drifted and may be fooling you. You could measure an
AC signal with a meter, calculate its peak to peak
voltage (V RMS X 2√2) and see how that agrees with
your cal signal.
On 30-Apr-13 12:07 PM, Cliff White wrote:
I just finished repairing a Type CA plugin.
Everything seems to have calibrated just fine,
with the exception of the channel B gain. It won't
go low enough. For example, if I apply a .1 volt
P-P signal, at .05 volts/div, the lowest the gain
will adjust to is about 2.3 divs. It will go
higher, but not any lower. Channel A adjusts
perfectly. All other adjustments on both channels
work fine. Does anyone have any ideas as to how I
can fix this?
Cliff White, W5CNW