3 WRM - Write Driver Module (2 modules supplied)

Contents of this section

The WRM provides reclocking, amplification, and current driving capability to drive headstacks through HIBs. It accepts logic level signals from the formatter (for WRM~1 and 3 routed via IOM, for WRM~2 and 4 cabled directly from the formatter). The WRM also provides the capability to return the write signals of two tracks in bypass mode to the decoder for checking purposes.

The modules have been tested with the procedure ``testwrm'' presented in section autotest . The test reports can be found in the station-specific section of this documentation binder.

The front panel of a WRM is illustrated in figure wrm.eps .

3.1 WRB - Write Board

This is a standard double-sided PCB with plated-through holes and 35~μm of copper. WRB documentation can be found in the directory ftp://kurp-ftp.hut.fi/pub/mk4/wrm/wrb and printouts of these files are provided in the section ``WRM'' of the documentation binder.

The board is populated according to the parts list provided in a straightforward fashion. There are no jumper blocks nor optional components on this board. Use eight No~4x1/4" self-tapping Supadriv screws to fix the ribbon cable connectors tightly to the WRB.

Wiring

A Weidmüller-Klippon (FEC order numbers ``151-987'' (PCB mount) and ``151-971'' (for cable)) 0.2" pitch connector pair provides power from RWB to WRB. (AMP 0.2" pitch connectors may be substituted, if required.) Strip 6mm at Weidmüller-Klippon end and crimp an end bushel to them. Solder and screw the wires in the following order:

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WRB  -- total wire length incl. stripped ends -- Weidmuller-Klippon
J7-1 -- 70mm orange -- (+V VAR)
J7-2 -- 70mm white  -- (+5V)
J7-4, 5, and/or 6 -- 70mm blue (VHRET)

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Cable WRBRWB (2 needed per one WRB)

These cables route bypass signals from WRB to RWB for selection and returning to the decoder for checking purposes. Cut 65-70mm of standard grey 50-way flat cable. Crimp a 50-pin Thomas&Betts solderable PCB transition header (FEC order number ``223-086'') on one end and a standard 50-way female IDC socket on the other end. Observe pin 1 markings (triangles on connectors and red wire on cable).

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S -- pin 50 ----------- P
t                       C
d                       B
 N   (top view)         T    N = notch
I                       r
D (sockets under)       a (pins under)
C -- pin 1, red wire -- n

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Solder the headers on the underside (solder side) of WRB, again matching the pin 1 to the square pad on PCB.

3.2 RWB - Read Board for WRM

This is a Read Board (RDB) presented in section rdb without amplifiers and equalizers. It provides WRM with the capability to select two tracks in bypass mode, return them to the decoder for analysis, and buffer the signal for WRM front panel BNC connectors.

RWB uses the same PCB layout as RDB. Its documentation can be found in the directory ftp://kurp-ftp.hut.fi/pub/mk4/rdm/rdb and printouts of these files are provided in the section ``RDM'' of the documentation binder.

Populating RWB

Solder GND test point lug to J8.

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Jumper blocks J9 and J10 (top view, component side):
o - cut  - o      (cut = cut track on solder side)
o - wire - o      (wire = solder jumper wire)
o - wire - o
o - cut  - o (pin 1, square)

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U31 LM323T +5V 3A thermal pad (no insulation required), M3x10mm DIN 912 hex screw, lock spacer, nut.

U30, U32 are not populated; thus C2, C3, C4, C6, C9, C10 are not populated.

R1 is not populated, as WRM doesn't feed power to head preamplifiers at HPBs.

U33 TO220 silicone insulation, M3x12mm DIN 912 hex screw, lock spacer, nut.

A suitable heat sink for voltage regulators is ``IMI MARSTON 05DN01000A100'' (108mm x 100mm). Place a 110mm x 102mm piece of 0.25mm thick mylar insulation under the heat sink. A reference drawing of the heat sink is provided in the section ``RDM'' of the documentation binder.

Use two No~4x1/4" self-tapping Supadriv screws to fix the monitor ribbon cable connector tightly.

The equalizator and amplifier sections of RDB are not populated in RWB configuration. Please refer to RDB schematics where the components not required for RWB are indicated.

Wiring

Replace R6 with a shorting jumper wire and continue it to U14 pin 1 (channel A).

Replace R7 with a shorting jumper wire and continue it to U8 pin 3 (channel B). (This is easier to connect thru R7 and R38 solder pads (use pads which are closer to the front panel).)

Connect pins 5, 7, and 10 of U27 together to ground comparator reference levels.

Fasten an AMP 205841-1 CPC square flange receptable for pin contacts to the front plate location J1 with four M3x10mm hex screws (ISO 7380 low-profile), M3 lock spacers, and M3 nuts.

Although it is possible to populate J1 of RWB with either Weidmüller-Klippon or AMP 0.2" pitch connectors, this is not recommended due to decreased reliability. Instead, wire the AMP connector J1 at WRM front panel directly to the RWB as follows:

With small AMP 66506-9 HD-20 pin contacts (red dot) and 20AWG stranded copper wire (from Alpha cable):

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RDM front -- total length incl. contact + color -- RDB
J1-1 -- 30mm red     -- 3.9ohm 25W resistor -- 30mm wire -- J1-1 (+12V)
J1-2 -- 115mm orange -- J1-6 (+V VAR)
J1-3 -- 95mm green   -- J1-2 (-12V)
J1-5 -- 100mm black  -- J1-3 or 4 (RETURN)
J1-7 -- 110mm blue   -- J1-5 (VHRET)

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Two 10mm spacer pillars separate the 3.9ohm power resistor from the PCB. Two M3x6mm screws mount the pillar to the PCB, secured with Loctite 222. The resistor is mounted with two M3x6mm screws and lock spacers.

3.3 NIM/WRM

The enclosure for WRM is a standard 2/12 wide AEC/NIM cassette described in section NIM of this document. A WRM-specific drilling plan and front and rear panel silkscreening drawings are provided in the section ``WRM'' of the documentation binder.

NIM/WRM Fixings

The RWB is mounted in the NIM box with the following accessories. NIM rails have M3 threadings; mounting order is: NIM rail -- spacers -- WRB -- lock spacers -- screws.

• 6 M3x10mm DIN912 hex screws
• 6 M3 lock spacers
• 6 M3 spacers, height 3.0mm

The WRB is mounted in the NIM box with the following accessories.

• 6 M3x6mm DIN912 hex screws
• 12 M3 lock spacers (thickness 1.0mm)
• 6 M3 hexagonal spacer pillars, spacing height 12mm, 5mm of M3 threading

3.4 Cable PWMWRM

3.5 Cable WRMIOMMON

3.6 Cable WRM1IOMSIG1 - 40-way twisted (odd, for WRM 1 only)

3.7 Cable WRM1IOMSIG2 - 40-way twisted (even, for WRM 1 only)

3.8 Cable WRM2IOMSIG1 - 40-way twisted (odd, for WRM 2 only)

3.9 Cable WRM2IOMSIG2 - 40-way twisted (even, for WRM 2 only)

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