6 HAM - Head Assembly Module

HIB - Head Interface Board

For a layout of this board, please refer to original Haystack drawings 4712A005--4712A008. A copy of the board artwork is also provided in the documentation binder.

This is a four-layer board and it cannot be thicker than 1.0mm because it needs to fit in a slot in head assembly mechanics. (In principle only one inner layer is required, but two layers were provided due to manufacturability reasons.) The board is populated with SMD components on both sides. The inner layers are continuous ground planes and they are connected to the copper track pattern via four plated-through holes located near the headstack connector J1. This custom-specified AMP connector plugs directly into the headstack; two boards are required per one head.

Wiring---long Brimflyx

A 40-way standard IDC female socket is wired to the HIB matching the track numbers present in drawings 4712A005--4712A008 and the schematics of WRM.

24~cm long cuts of Brimflyx Ultra Flexible wire is used, green for ground and white for write signals. The pairs are twisted and the wire ends are soldered onto board pads and on bottom of the wire slot in the IDC connector.

Strip about 1mm of insulation, carefully insert the stripped stranded copper wires into the bottom of the wire slot, and bend the wires 90 degrees to align them in behind of contact posts. Warm up the contact post with soldering iron tip and introduce solder wire at the bottom of the post.

1. Do not strip too much of insulation, as this can easily cause shorts between adjacent posts!
2. Do not pre-tin the wires! If you do, they will not fit into the slots.
3. Ensure that the wires stay in the bottom of the slots! Otherwise when you install the cover piece it will cut the wires.
4. Remember to check that no short circuits were introduced during soldering!

As a standard IDC connector does not provide good stress relief for individual wires, the wires are secured with epoxy adhesive to the IDC base. Do not let epoxy flow into the female contacts of the connector!

HIB - Head Interface Board

The septum divider is manufactured using 3/16" (4.7625~mm; 5.0~mm can be used as well) aluminium according to its mechanical drawing which is available in the section ``HAM'' of the documentation binder. (The original Haystack drawing ``54330M017'' is included, too.) The original inch-based measurements have been converted to metric except for the mounting holes/threadings of the divider: they are UNC 2-56.

Two HRMs (with four HPBs) are fitted to the SDP using four M2x25mm screws. The boards are spaced by twelve 4.75mm high (outer diameter 4mm) aluminium spacers. This stack of boards is separated from the SDP with four 1.75mm high spacers.

The SDP is mounted in head assembly mechanics by using three UNC 2-56 screws (length about 10~mm each), two from the front of the recorder and one from the underside of the assembly block.

The so-called ``open form interface'' clamp ring is mounted using two M2x8mm screws onto the SDP. A shield cover is slided into grooves in SDP and secured in place with a M3x6mm screw and lock spacer into clamp ring. Mechanical drawings of the clamp ring and the shield cover are available at the end of ``HAM'' section in documentation binder.

The CPM acts both as a strain relief for delicate cabling coming from HAM and it also allows for easier dismantling of HAM, because the long runs of HAM--WRM/RDM interconnection cables are permanently mounted to the CPM. Mechanical drawings of the CPP are available at the end of ``HAM'' section in documentation binder.

CPP - Aluminium connector plate

This plate is fabricated with 3.0~mm aluminium according to the drilling plan included in the documentation binder section ``HAM.''

The plate is treated with Alodine~1200 yellow chromate conversion process to fight oxidation and then silkscreened with the pattern provided in the section ``HAM'' of the documentation binder.

Fixings

Spacer pillars (4 per CPM).

Fabricated using 7mm hexagonal brass rod, total length 46mm, spacing length 40mm. At recorder end, make UNF 10-32 threading at 6mm length. At the other end, drill a 15mm deep centered hole, diameter suitable for tapping for a M4x10mm screw. These spacing pillars are mounted on the backside of recorder front plate.

CPP is mounted on these pillars with four M4x10mm DIN912 hex screws (with M4 spacers).

M5x20mm DIN912 hex grounding screw (2 pcs).

These screws are mounted at the center of CPP with two M5 nuts and two M5 spacers each. These are intended for HAM grounding braid lugs. (WRMHAM and RDMHAM cables are grounded at screws mounted in NIM module box rear plates.)

12 M3x8mm DIN912 hex fixing screws.

These screws are used to mount six panel-mountable IDC male connectors of the cables WRMHAM and RDMHAM to the CPP.

Cable WRMHAM (4 per CPM)

Each of these cables provides signals for even or odd tracks of one headstack. The signals originate at WRM write outputs. A reference description of these cables can be found in a Haystack drawing located in the ``HAM'' section of the documentation binder. Each of the cables is assembled using:

1. 40-way panel-mountable IDC male connector.
2. 40-way IDC female socket.
3. Two runs of 150~cm each of 20-way color-coded twisted-pair ribbon cable.
4. Copper braid (Raychem RAY-90-10.0), terminated in a AMP Faston-style lug (DVR5-5: TERMINAL, RING YELL 5MM) at WRM end only.
5. Nylon braid (Terigaine Braided Sleeving VOG 12-18 Grey).
6. Adhesive-lined heat shrink tubing (Raychem CGAT-24/8-0).

Do not forget to add the braids and heat shrink tubings before crimping both ends of the cable with IDC connectors. Use about 50--70~mm of heat shrink tubing for both ends and shrink it only after crimping the connectors.

It is important that the WRMHAM cables are not grounded at the CPP end! This grounding style may provoke the read circuitry to oscillate uncontrollably, thus rendering the read signal unusable.

Cable RDMHAM (2 per CPM)

These cables provide reproduce signals from read/write head preamplifiers to the RDM read inputs. A reference description of these cables can be found in a Haystack drawing located in the ``HAM'' section of the documentation binder. Each of the cables is assembled using:

1. 50-way panel-mountable IDC male connector.
2. 50-way IDC female socket.
3. Two runs of 150~cm each of 26-way color-coded twisted-pair ribbon cable (actually, only 22 ways are used, two pairs i.e. red-brown and orange-brown are dissected away from both cable runs, leaving centermost six pins of the connector unused) .
4. Copper braid (Raychem RAY-90-10.0), terminated in a AMP Faston-style lug (DVR5-5: TERMINAL, RING YELL 5MM) at RDM end only.
5. Nylon braid (Terigaine Braided Sleeving VOG 12-18 Grey).
6. Adhesive-lined heat shrink tubing (Raychem CGAT-24/8-0).

The same instructions apply to RDMHAM as well as to WRMHAM.