Defects with a PCW

One of the nice things about the PCW (or PcW for that matter) that it hardly ever breaks down. There are only two weak points in the design. First of all the matrix printer, which will wear out after 10 years of use. This is only natural and there is nothing else to do than to purchase a Centronics parallel interface and a standard printer. Or to print using a PC. An instrument maker just might be able to fix the pins of the dot matrix printer but this would be extremely expensive and the maximum of 270 dpi, produced by the printer, is outdated anyway. Contact the HCC for more information about suitable printers. Another defect, common to the daisy wheel printers, is a broken hammer armature. You can (still) find replacements for this part.

The second category is due to wear as well. Especially the rubber drive belt in the 3" disc drive is vulnerable to wear and climate. This problem can easily be identified: the PCW will no longer start and the light green display remains (the 'curtain' with the familiar black lines is not displayed) and the PCW will sound three beeps after a while (not in all cases, though). The remedy is simple and cheap: a new belt 68-72 mm long, 3 mm wide. Just to be sure, take the old one with you to an electronics store (one with a reasonable range of spares: Handyman, for instance). It will set you back a maximum of 5 Euro as it is a standard belt which is also used in video records. You may also try eBay as they are offered there quite often too. Then it is time to replace the belt: switch of the power, remove the back of the PCW (6 screws), the drive cables (one power and one data) and remove the metal casing containing the drive (another 4, long, screws).

The number of screws to be removed from the metal casing of the 3" disc drive depends on the type of drive used: 3 or 4 screws. The PCB on the bottom of the drive can also be fixed to the metal frame with 2 or 3 screws, depending on the model used. The model also determines what kind of disc-in detection system is used: mechanical or electronical.
The more modern EME-155 (single sided, 40 tracks) and EME-231 (double sided, 80 tracks) models have an electronic detection system using LED-light: a sensor determines whether there is a disc in the drive or not. The elder EME-156 (single sided, 40 tracks) and EME-232 (identical to the 231 but configured as drive A and mounted in the PCW 9512) models have a mechanical pin that is pushed away when a disc is inserted in the drive. You have to be very careful with this (tiny) pin when disassembling the drive: it can fall out and get lost so very easily... See the picture for the location of the pin. The last photograph on this page shows the location of the model number of a disc drive: to the left on the rear on the inner frame of the drive. Basically, you will see it when it is already too late: I advise you therefore to keep the drive with the PCB upwards, at least until you know which type of drive you are dealing with! Otherwise you will loose the disc in/out detection pin for sure...

The trick the replace a drive belt is fairly easy: remove the PCB from the frame of the drive and lift the PCB tilting movement over de vertical shaft of the disc drive (see the left part of the photograph: the PCB has been moved backwards and lifted over the shaft here). The red LED-light of the drive (on the right part of the picture, dangling from the PCB, just below the right upper corner) can slide out the frame and the PCB can then be lifted a short distance.

The distance that you can lift the PCB depends on the type of disc drive and varies from 5 to 10 centimetres. Do not apply brute force to the PCB if it does not lift (further)! You can (in my opinion) better spend some more time in twiddling with a pair of tweezers, in order to remove the old belt and place a new one, than remove and afterwards reconnect the various connectors that lead to the PCW!

Do check whether the belt will not run off the shaft and drive wheel and re-assemble the Joyce only partially: you had better test the drive before mounting the metal casing in the plastic housing and the plastic housing itself. Connect the two drive cables (power and data cables) and held the disc drive simply in your hand or place it on a stable and flat surface. If all works you can assemble the remaining parts as well. The method described works for both the A-drive and the B-drive but, when you have to overhaul both drives you have to start with drive A because that (normally) is the drive used to boot the PCW with. You cannot start or test a PCW with a malfunctioning drive A so you have to begin with drive A!

The last category of possible defects relates to power problems: the PCW's are underpowered in the literal and figurative sense. The single power supply is not only a bit short in capacity but it has to supply no less than three voltages (5, 12 and 24 volts). You may notice circumstances where the display on the monitor starts to act up when the disc-drive is running or the printer working. Do note that this will always happen when you produce a graphics screen print using [EXTRA]+[PTR]: that is normal behaviour as this process takes up much power (there is a lot of black involved and all needles are being fired by the printer). Only when the screen flickers under normal operations and turning the contrast of the monitor down (using the wheel on the right bottom side on the front of the PCW monitor) does not help, you would have to consider repair or replacement. We lack the knowledge to repair a power supply, believe that repairs can become too expensive quickly and, as we have plenty of spare parts, always recommend replacement with used spare parts.