TF20 Notes

TF20 disk drive notes ---------------------- Dismantling ------------ Case : Remove the 4 screws from the sides, lift off the top cover, then turn the unit over and remove the base cover Rear panel : Unplug the serial cable from the serial PCB. Undo the 2 screws under the rear of the unit. Slide the rear panel out rearwards, unplug the transformer secondary winding connector from the PSU PCB. Serial PCB : Remove the 4 retaining screws and unplug this PCB from the bus connector on the controller Controller PCB : Unplug the power harness and the internal disk drive cable from the controller PCB.. Remove the 4 retaining screws and the 4 tapped spacers (used to support the serial PCB). Remove the controller board PSU : Unplug the power connectors from the drives. Unplug the power LED connector from the PSU PCB. Unplug the controller board power harness the bracket, then the 2 screws holding the regulator hybrid module to the transformer cover. Remove the PSU PCB and recover the insulating sheet Drives : Unplug and remove the disk drive cable. Remove the 8 screws (4 on top, 4 underneath) that retain the drives and slide the drives out from the front. Remaining chassis parts : Free the power LED cable from the clips on the chassis. Remove the 2 crews under the front of the unit and remove the front panel. Remove the 2 self-tapping screws that retain the power LED PCB to the front panel and remove it. Remove the PSU bracket, the transformer cover and the controller bracket (2 screws each). Rear panel dismantling : Unplug the transformer primary winding connector tabs from the power switch and remove the filter PCB. Remove the fishpaper insulator. Undo the 4 nuts retaining the mains transformer, remove the claw washers and the transformer. Unplug the remaining 2 faston connectors from the rear of the power switch, unscrew the earth wire from the chassis (note claw washer under the solder tag), remove the 2 retaining screws and the mains input connector. Unclip and remove the power switch. Undo the 2 retaining screws for each DIN socket and remove the serial cable harness. When reassembling, the 6 pin DIN socket is the upper one, both DIN sockets are fitted with the keyway towards the centre of the panel. ------------------------------------------ Controller PCB links : J1 : 1 : RAMVdd = 12V (16K RAM) 2 : RAMVdd = 5V (64K RAM) * J2 : 1 : Write Precompensation enabled 2 : Write Precompensation disabled * J3 : 1 : EPROM pin 21 = A11 (2732) 2 : EPROM pin 21 = +5V (2716) * 3 : EPROM pin 18 = A11 J4 : 1 : EPROM pin 18 = CS/ * 2 : EPROM pin 21 = CS/ J5 : 1 : Ready line always active * 2 : Ready line from drive J6 : 1 : 16K RAM addressing 2 : 64K RAM addressing * J7 : 1 : RA< A7 toed high (16K RAM) 2 : RA< A7 lined to address mux (64K RAM) * ------------------------------------------ Serial PCB links : J1 : Clock / 128 (2400 baud) J2 : Clock / 64 (4800 baud) J3 : Clock / 32 (9600 baud) J4 : Clock / 16 (19200 baud) J5 : Clock / 8 (38400 baud) * J6 : Clock / 4 (76800 baud) Exactly one of J1..J6 must be fitted J7 : Open : Enable oscillator round CR2 (4.1953 MHz) * Closed : Enable oscillator round CR1 (not fitted) ------------------------------------------ Controller PCB testpoints : TP1 : RAS/ TP2 : CAS/ TP3 : Rd Data TP4 : VCO control voltage TP5 : VCO output TP6 : DW TP7 : Ground ------------------------------------------ Serial PCB testpoints : TXCA : Baud Clock (*16) to serial chip TXDA : Serial data output to host RXDA : Serial data input from host TXDB : Channel B serial data output (not used) RXDB : Channel B serial data input (not used, pulled high via 10k resistor)