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\documentclass{chowto}

\title{Target Raster Maintenance Manual}
\howtotype{expert}
\author{Chen Yan}
\category{beamline}
\date{July 8, 2003}
\begin{document}

\begin{abstract}
A brief description of the electronic configuration of Hall A/C target
raster systems and trouble shooting procedure are summarized for the
use of professional maintenance staffs.
\end{abstract}

\section{Driver Module Identification}

\[
\begin{tabular}{llll}
ID     &Owner     &Frequency (kHz)      &Status\\
       &          &                     &      \\
$\#$1  &Hall C    &24.96                &in operation\\
$\#$2  &Hall C    &25.08                &in operation\\    
       &          &                     &      \\ 
$\#$3  &Hall C    &24.96                &spare \\
$\#$4  &Hall C    &25.08                &spare \\
       &          &                     &      \\
$\#$5  &Hall A    &24.96                &spare \\
$\#$6  &Hall A    &25.08                &spare \\
       &          &                     &      \\   
$\#$7  &Hall A    &24.96                &in operation\\
$\#$8  &Hall A    &25.08                &in operation
\end{tabular}
\]

\section{Description of Front Panel}

\begin{itemize}
\item{AC switch}
\item{AC power indicator (LED)}
\item{Fuse - 120V, 10A}
\item{AC line receptacle with EMI filter}
\item{9 pin D-sub socket, RS232 for EPICS}
\item{9 pin D-sub socket, for Manual controller}
\item{BNC, FR sync TTL output}
\item{BNC, Helicity (MPS) input}
\item{50A Supercon pin receptacles, FR magnet terminals}
\item{BNC, Pearson 411 current monitor output}
\item{BNC, LEM probe output}
\end{itemize}


\section{Module Internal Configuration}


\subsection{H-Bridge}

The diagonal 2 by 2 power switch consists of 8 HEXAFETs (FA57SA50LS).
Two of them are parallel. 4 snubber capacitors (MP88 2.5$\mu$F/800V,
metalized polypropylene film) are connection between the common source 
and common drain of upper and lower HEXAFETs to eliminate spikes.


\subsection{Energy Storage Capacitors}

Two 165$\mu$F 600VDC Capacitors (Unlytic UL30, Electronic Concepts) 
are connected across upper-left common source and upper-right common 
drain. Other two are connected across lower-left common drain and 
lower-right common source. These four capacitors are used to store 
energy pumped from UltraVolt high voltage power supply to keep a 
stable HV level (~ 1$\%$) at 25 kHz raster frequency under full load.


\subsection{H-Bridge Driver}

Two driver boards directly connect upper and lower rows of HEXAFETs. 
Each driver board consists of 4 separated drivers (Max 4429MJA), 
and each driver drives a single HEXAFET. The input stage of driver
is formed by opto-coupler (HCPL7710). A FLOATING 15V voltage generated 
by Polytron SWU0.75-5S DC/DC converter from 5V, powers the drivers.

\subsection{H-Bridge Control Waveform Generator}

An external trigger signal comes from J1 BNC. A Retriggerable one-shot 
74HCT123 has a time constant 0.22 ms. If there is no external trigger
signal during 0.22 ms, the circuit automatically switches to the internal 
crystal oscillator. If a trigger signal comes during 0.22 ms, the 
generator is controlled by external trigger.

From raster frequency input the 74HCT4046A phase-lock loop generates 
8 $f_0$ synchronized signals. Control waveforms are produced by 161
counters and synthesis logic at OUTA and OUTB. A sync signal signal is 
also produced at line driver max4429.


\subsection{HV Power Supply Input/Output Controller}

The circuit receives analog voltage control and current signals from
either PIC/ADIO EPICS interface or manual controller to generate HV
control signal and voltage/current readback signals. The circuit gets
PIC/ADIO and manual controller operating in parallel but only executes 
the larger value setting from them.


\subsection{UltraVolt Switching HV Power Supply}

The UltraVolt 1/2 C24 - P250 switching HV DC/DC converter (250 W, 500V) 
is used to power H-bridge. Its internal voltage reference is + 5 V.    
It needs a previous 24 V DC power supply. The 14 pin Molex connector
gives following control signal connections:

\begin{itemize}
\item{pin $\#$3 - Output current monitoring}
\item{pin $\#$14 - Output voltage monitoring}
\item{pin $\#$4 - Enable/disable control}
\item{pin $\#$6 - Control voltage input}
\item{pin $\#$5 - Ground}
\end{itemize}

The operational status of HV unit is displayed on FR EPICS control screen.
For all 8 modules in normal operation, the average voltage reading and 
corresponding current reading are shown in the following table :

\[
\begin{tabular}{lrrrrrrr}
Voltage in V   & 50 & 100 & 150 & 200 & 250 & 300 & 350\\
Current in mA  & 54 &  82 & 108 & 133 & 160 & 187 & 215\\
\end{tabular}
\]   
  
The readout values on EPICS screen should be consistent with the display of 
manual controller.


\subsection{HV Safety Protection}

A Sumida mercury-wetted Reed relay with a 10W 10 kohm resistor are connected
in series. The two terminals are connected to storage capacitors in parallel.
The Reed relay is open in normal, as power interruption occurs Reed relay
closed and HV discharges through 1 kohm resistor.


\subsection{PIC/Adio Board}

PIC/Adio board is provided by Fast Electronics Group as the interface 
between UltraVolt HV unit and EPICS control. It executes high voltage 
setting, voltage/current readback, logic control display. Parallel to
manual controller, PIC/ADIO board gives EPICS control full information
about the status of the module.


\section{External Auxiliary Electronics}


\subsection{Field Pickup Integrator}

Each target raster magnet is equipped with a pick-up coil at the center 
of magnet winding plane. The field pickup integrator converts the induced 
voltage signals into linear waveform and adjusts the amplitude of linear 
signals to the same amplitude of output of Pearson current probe.


\subsection{Helicity Synchronization Unit}

This optional NIM module unit is designed for the use of G$_{0}$ 
experiment. Hall A has already preserved such capability for future's 
application. The unit receives trigger signal from helicity reverse (MPS).
A phase-lock circuit generates two correlated raster frequency signals. 
It enables the rastered beam starts at the exact same time of MPS. 
Therefore, the instant beam positions are always the same for each MPS.


\subsection{On-line Raster Pattern Display ADC and Trigger Generator}

A Jorgger 4-channel VME ADC has been shared by Hall C and Hall A two 
raster systems. The trigger generator produces 60 Hz synchronization 
signals from one raster frequency as the trigger of ADC. The 2D and 
3D raster pattern display software was written by Chris Slominski. 
By pushing control button on EPICS control screen, users could 
observe raster 2D and 3D pattern on-line.



\subsection{BRM/FSD system}

It has the same function as of BRM/FSD system of old raster system. It
takes analog magnet current signals to compare the calculated current 
amplitude value from beam energy and raster size. Fault warning signal 
will be given as soon as a discrepancy occurs.



\section{In Site Trouble Shooting Procedure}

\subsection{Visual Diagnostics}


\begin{itemize}
\item{Verify the 2D FR pattern on the scope in Hall A/Hall C counting house}
\item{Verify the 2D and 3D on-line pattern display on EPICS screen}
\item{Verify voltage and current readback on front panel of manual controller}
\item{Verify the module status on EPICS control screen}
\end{itemize}

\subsection{Check Cable Connection}

Start from the scope cable in counting house, the signal channel waveform
should be linear (triangular). If a distorted waveform observed, check the
input analog cables. Bad cable connection could cause such distortion.


\subsection{Module Quick Check}

After the two steps previous check, if problem is still existing, ask
for an entry to open the door of lead shielding cave. Use scope to look
at LEM output. In case of either high level offset or asymmetric waveform
observed, determine to replace the module because that indicates the
core part of H-bridge is defect.


\section{Maintenance in Laboratory}
In most case if H-bridge failure was detected by diagnostics, it is
impossible to fix on site because the complicated mechanical structure
inside the power module. The defect module should be taken back to 
laboratory for necessary inspection and repair.


\subsection{Assembly and Disassembly Procedure}

\begin{itemize}
\item{Dismount the rear panel (heatsink) from module by Hexascrew driver
      1/8"}
\item{Dismount the driver boards by using far-screw holes}
\item{Unscrew the copper bus strips over the bridge}
\item{Disconnect the short wire - first the gate, then the source}
\item{Screw the copper bus strips again}
\end{itemize}

\subsection{HV I/O Controller Adjustment}

\subsubsection{Potentiometer Identification}

\begin{itemize}
\item{VR1 - HV output current adjustment}
\item{VR3 - Current display adjustment}
\item{VR2 - HV voltage limit adjustment}
\item{VR4 - Voltage value display adjustment}
\end{itemize}

\subsubsection{Install the Maximum HV Value}

Turn the multi-turn potentiometer on the front panel of manual 
controller to the right end to set the maximum voltage value of HV output.

\subsubsection{Setup high voltage limit}
Adjust VR2 to set the maximum voltage display on manual controller = 360 V

\subsubsection{High Voltage Current adjustment}

\begin{itemize}
\item{Take P$_{2}$ connector away from Molex 4 position 90 degree 
      socket on Control Waveform Generator board in order to switch
      the H-Bridge is off}
\item{Connect 250 ohm 100 W resistor box (consists two parallel 
      500 ohm 50 W resistors) in series with multimeter and switch the
      multimeter to current measurement. Then, connect them to HV 
      power supply output (copper bus strips), the only load of HV 
      unit is the 250 ohm resistor.}
\item{Measure voltage value at pin $\#$8 of J6 of the HV I/O board
      (current monitoring readout) by the second multi-meter. For
      convenience, one can measure the terminal $\#$41 on PIC/ADIO
      board. Adjust VR1 to make the second multi-meter readout being
      the same value with the first meter. 0pin $\#$8 the same value with 
      multi-meter readout.}
\item{Adjust VR3 to make displayed current value of manual 
      controller the same with multi-meter readout.}
\end{itemize}

\subsubsection{Voltage Calibration}
\begin{itemize}
\item{Use multimeter to measure HV directly}
\item{Set multi-turn potentiometer a fixed position, for example 84.5}
\item{Adjust VR2 to set the control voltage the same with multimeter}
\item{Adjust VR4 to set the displayed voltage value on the manual
      controller front panel the same value with multimeter readout.}
\end{itemize}


\subsubsection{LEM Probe Offset Adjustment}

In normal condition, a small DC offset appears on the zero-crossing 
line of H-Bridge output current waveform.  It comes from tiny time
difference of the diagonal shoulders. Adjust delay time by turning 
VR4 (2k ohm potentiometer) on Control Waveform Generator Board to 
minimize the DC offset at LEM output waveform.      
      

\subsection{Individual HEXAFET Inspection}

After disassembly of H-bridge from heatsink, multi-meter can used to
measure the resistance value between the drain and source. Normal
value of resistance should be 1.5 - 2.2 M ohm. Less value indicates
the HEXAFET was damaged.


\subsection{Driver Board Inspection}

Disconnect driver boards from H-Bridge. Keep input cables connected 
with control waveform generator. Use central needle of scope high 
impedance probe connecting output of each driver. The corresponding 
ground crocodile should connect each floating ground terminal.

The driver output should appear good leading edge and fall edge as
well as top flatness. Both rise time and fall time should less than
10 ns at zero load. When driver is connected with capacitive load
such as 10 nF (10,000 pF), both leading and fall edges become much 
slower like 50 ns at $\pm$ 15 V power supply voltage in the same 
amplitude. It is normal. If the slowdown of leading and fall edges
is much larger than this value, it indicates defect of the driver.


\end{document}

% Revision history:
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% Revision 1.2  2005/03/16 15:03:31  saw
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% Revision 1.1  2003/07/08 17:44:53  saw
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