Xltek EMU128 Headbox User & Service Manual
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3. Point to the first menu on the Channel Test control bar and click Sine or Square.
The Sine wave setting is good for general use. A low-frequency Square wave setting
can reveal problems in the integrator of the DC removal stages on the Analog Board.
4. Adjust the waveform frequency and amplitude on the Channel Test control bar as
required.
The Channel Test signal is applied to the first amplifier stage; therefore, it tests the
amplifiers and ADCs but cannot check the connection to the front panel connector.
Use the Reference to Diagnose the Problem
The Reference channel can be used to narrow a problem down within a particular
amplifier channel. To set the reference channel, choose Edit->Settings->Acquisition
and then point to Reference menu and click External.
•
If a Reference signal is visible on a problem channel, then the output stage is
working.
•
If the channel is noisy or unstable when jumpered to Common on the Breakout Box
and referenced to Common, it is possible that an op-amp is defective.
Keep in mind that the channel numbers on the schematics do not correspond to the
channel numbers on the screen. To determine the affected channel, touch a small wire
to the pins of the 37-pin D connector one at a time, and then trace through the
schematics.
Other Causes
•
A broken solder joint on one of the 80-pin connectors between Analog and Digital
Boards may cause a flat line on a channel.
•
Because the ADCs have four channels each, a problem that affects a multiple of four
channels can be ADC-related (an unlikely failure mode).
Disassembly
1. To gain access to the tabs that retain the side panels (handles), remove the
back-panel screws.
2. To see the hardware that fastens the box to the front panel and chassis, pry the
panels off.
3. If disassembling the boards in the chassis, keep detailed notes of the sequence of
disassembly and what hardware was used. Do not mix up the boards because the
calibration will be invalidated. The top board in a stack is the Relay Matrix, then
Analog PCB, then Digital PCB.
4. Pay attention to the orientation of the Analog Backplane.
If doing a rework on the Analog PCB or the Analog Backplane do not clean with a liquid
or the film capacitors may be degraded.
Adjustments
There are no adjustments. The precision of the components renders this unnecessary.
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