Research Machines RM380z: Difference between revisions

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|SN7402N /  
|SN7402N /  
|[https://www.digikey.com/en/products/detail/texas-instruments/SN7402N/1575110 DigiKey] [https://www.mouser.com/ProductDetail/Texas-Instruments/SN7402N?qs=sGAEpiMZZMv4BkFy%252BbL2aNCWEGkeux7iMUt0bB7ijAo%3D Mouser]
|[https://www.digikey.com/en/products/detail/texas-instruments/SN7402N/1575110 DigiKey] [https://www.mouser.com/ProductDetail/Texas-Instruments/SN7402N?qs=sGAEpiMZZMv4BkFy%252BbL2aNCWEGkeux7iMUt0bB7ijAo%3D Mouser]
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=== VDU ===
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=== CPU/32K RAM Card ===
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=== Floppy Drive Controller and Serial Card ===
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If ''parts are not available or different selection is preferred, you can use the values in the [[#Original_Parts|Original Parts]] section to perform a parametric search.''
If ''parts are not available or different selection is preferred, you can use the values in the [[#Original_Parts|Original Parts]] section to perform a parametric search.''

Revision as of 02:02, 30 May 2024

Research Machines RM 380Z
Preliminary Information
Release Year Introduced 1977 Discontinued 1985
Mounting Technology Sockets, DIP, through hole and screw mount
Capacitor Types Aluminum Electrolytic and Tantalum
Destructive Entry No
Hardware Specifications
CPU Zilog Z80A 4 Mhz
Memory Capacity Up to 64K with 56K accessible.
Memory Type 8116 which is the Fujitsu labelled version of the 4116.
Storage Early systems were single density single-sided 5¼-inch disks with a capacity of up to 72 KB later systems were up to 360K.
Graphics 40x24 or 80x24 text mode with a High-resolution graphics adapter available.
Display Interface SO239 composite
Power Requirements
Input Voltage 240V AC 50Hz
Power Connector IEC 13

Known Issues

The power supply was blowing fuses and was outputting low voltage.

The bridge rectifiers were also getting very hot after a few seconds.

This unit also exhibited no signal on the video output and no life on the bus, this was due to all the corrosion this specimen was subjected to. This specimen is also missing a floppy drive as that one was very corroded and the bearings were seized that is why the photo has a large hole in the front left.

Causes

  • The large filter capacitors were bad.
  • The tantalums on the cards were bad.
  • Sockets and ICs were corroded

Solutions

  • Tried reforming the large filters however this was unsuccessful so these were replaced.
  • Replace the tantalums which lowered the current draw to what was expected cooling the rectifies down to normal operating conditions..
  • Replaced the sockets and replaced the ICs on the VDU which cured the video output however the machine still doesn't run..

Disassembly Notes

Simple disassembly is easy with two screws on the back of the lid to gain access to the cards however the power supply requires disordering cables and removing the whole case off the base.

Removal of the floppy drives in the vertical configuration is also complicated as they require the removal of the front panel and all the cards. This can be quite difficult especially if the nuts and bolts are corroded like mine, the tight space doesn't help as it can be difficult to get pliers and/ or spanners into the right place.

When the lid is removed the cards and backplane are easily seen and the power supply is on the right underneath the CPU serial monitor board. the floppy drive mounts are on the left for vertical mount BASF 6106s. The serial number tag should be visible on the case above the PSU which this one is hand written SN 691

Original Parts

Disk drives

The early RM 380s use BASF 6106 floppy drives which are 2/3 height SSSD 5 1/4. The drives are Shugart interface compatible. Later on IBM PC full Hight drives were chosen and the mounts were changed from a vertical to horizontal. These are easy to replace as they are more common. The early BASF drives can badly corrode depending on storage conditions so be wary of this as 2/3 height floppy drives are not as common.

  • This is the top view of the floppy drive which is a BASF 6106 single sided 2/3 Hight floppy drive. These drives use the original shugart interface.

    This is the top view of the floppy drive which is a BASF 6106 single sided 2/3 Hight floppy drive. These drives use the original shugart interface.

  • This is the bottom view of the floppy drive which shows how bad the corrosion is.

    This is the bottom view of the floppy drive which shows how bad the corrosion is.

  • The connector position of the BASF 6106 head should be on the top row of pins. This is possibly because the PCB is compatible between the 6106 and 6108 which is double sided though this still needs conformation.

    The connector position of the BASF 6106 head should be on the top row of pins. This is possibly because the PCB is compatible between the 6106 and 6108 which is double sided though this still needs conformation.

  • The PCB top view is pretty complicated though this may be because it supports the double sided 6108 drive too.

    The PCB top view is pretty complicated though this may be because it supports the double sided 6108 drive too.

  • Bottom view of the drive PCB

    Bottom view of the drive PCB

  • The back view of this drive shows that it is serial number 8251 and looks to have been made in the late 70s

    The back view of this drive shows that it is serial number 8251 and looks to have been made in the late 70s

Keyboard

The keyboard is just standard parallel ASCII foam and foil unit external to the unit via a 15 pin cable. The foam pads in mine are still in good shape but are the same size as most replacement pads making replacement easy. My unit was made by alphametric in the UK.

Keylock

The keylock is a old off the shelf part from RS however the keys are unique to each machine so check to see if you have the keys. This is because the switch controls the power input and also lock function of the front. This one was also seized so was soaked in WD40 to unstick it and allow it to rotate freely.

Cards

The cards are pretty easy to service however the early RM380s use Texas Instruments chips which are know for getting corroded legs. The early ones also use cheap sockets which can corrode. For mine to be a reliable machine large scale replacements of chips and sockets was the only way as the IC legs were breaking in the sockets. Below are the first party Research machines cards in this case as originally configured via the original label inside.

  • RM380z 80 and 40 column VDU. This card is text only and produces a composite video output

    RM380z 80 and 40 column VDU. This card is text only and produces a composite video output

  • RM380z CPU and 32K ram card

    RM380z CPU and 32K ram card

  • Rm380z 32K add on ram card which is a CPU card minus most of the parts.

    Rm380z 32K add on ram card which is a CPU card minus most of the parts.

  • RM380z floppy disk controller and serial controller. This card is the early FDC which is for SSSD disks.

    RM380z floppy disk controller and serial controller. This card is the early FDC which is for SSSD disks.

  • RM380z serial controller which is a FDC minus the FDC parts.

    RM380z serial controller which is a FDC minus the FDC parts.

  • RM380z bus terminator card

    RM380z bus terminator card

The following are more first part Research machines cards which aren't in this machine at the moment for one reason or another.

  • RM380Z IEEE-488 controller this is missing the cable for the back panel.

    RM380Z IEEE-488 controller this is missing the cable for the back panel.

  • RM380z prototyping card with bus interface circuitry already included and wire wrap sockets on the back.

    RM380z prototyping card with bus interface circuitry already included and wire wrap sockets on the back.


Power supply

Early supplies use the types below. Later revisions use different types.

Capacitor Specifications and Footprint Information
RefDes Qty Capacitance Voltage Mount Diameter/Size Height Lead Spacing Temp Type Brand Series
C1 3 470uf 63v Axial 13mm 31mm +85c Aluminium electrolytic Solar
C8 1 22000uf 25v Screw mount radial 50mm 90mm 25mm +85c Aluminium electrolytic Mallory CGS223U025V3C
C12 1 15000uf 40v Screw mount radial 50mm 115mm 25mm +85c Aluminium electrolytic Mallory CGS153U040V4C

Floppy Drive

Intergrated Circuits
RefDes Qty Model Number/Part Number Brand (if applicable) Explanation Datasheet
1 MC3470P Motorola Floppy Disk Read Amp MC3470
1 SN74221N Texas Instruments Dual Monostable Multivibrator with Schmitt-Trigger Input SN74LS221
3 SN7474N Texas Instruments Dual D-Type Positive-Edge-Triggered Flip-Flop SN7474
1 7407N Signetics Hex Buffer with Open-Collector High-Voltage Output SN7407
1 LM339N Texas Instruments Quad Comparator LM339
3 SN7404N Texas Instruments Hex Inverter SN7404
2 SN7438N Texas Instruments Quad 2-Input Positive-NAND Buffer with Open-Collector Output SN7438
1 SAA1027 Dale (Now Vishey Dale) Stepper Motor Driver SAA1027
1 LDP1401-151G
1 SN7432N Texas Instruments Quad 2-Input Positive-OR Gate SN7432
1 DM7402N Quad 2-Input NOR Gate DM7402
1 N9602N Signetics

VDU

Intergrated Circuits
RefDes Qty Model Number/Part Number Brand (if applicable) Explanation Datasheet
BV 1 SN7407N Texas Instruments
CW, GW 2 HM6116P-3 Hitachi
DW, ER 2 SN74LS273N Texas Instruments
CV, AS 2 SN74LS374N Texas Instruments
DV, EV 2 SN74LS245N Texas Instruments
FV, GU 2 SN74LS393N Texas Instruments
GV 1 SN74LS166N Texas Instruments
AT, ET, CS 3 SN74LS399N Texas Instruments
BU, ? 2 M5L2114LP-2 Mitsubishi
DU 1 SN74LS173AN Texas Instruments
EU, FU, FR 3 TBP24S10N Texas Instruments
BT, AR, GR 3 SN74LS157N Texas Instruments
CT 1 SN74LS257AN Texas Instruments
DT 1 SN74LS175N Texas Instruments
FT 1 SN74LS390N Texas Instruments
GT, CR 2 SN74LS377N Texas Instruments
BS 1 SN74LS155N Texas Instruments
DS 1 SN74LS04N Texas Instruments
ES 1 SN74LS283N Motorola
FS 1 SN74LS00N Texas Instruments
GS 1 SN74LS32N Texas Instruments
AQ 1 SN74LS244N Texas Instruments
BR 1 SN74LS373N Motorola
DR, EQ 2 SN74LS240N Texas Instruments
CQ 1 SN74LS27N Texas Instruments
DQ, EP 2 SN74LS02N Motorola
FQ 1 SN74LS132N Texas Instruments
GQ 1 SN74LS09N Texas Instruments
BP 1 SN74LS76AN Texas Instruments
CP, DP 2 SN74221N Texas Instruments
FP 1 SN74LS266N Texas Instruments
GP 1 SN74LS168N Motorola
The CPU/32K RAM card marked with the RefDes in the table
The CPU/32K RAM card marked with the RefDes in the table

CPU/32K RAM Card

Intergrated Circuits
RefDes Qty Model Number/Part Number Brand (if applicable) Explanation Datasheet
1, 2, 13, 42, 44 5 SN74LS244N Texas Instruments
5, 6 2 SN74LS241N Texas Instruments
7 1 CD4069UBE RCA
8, 9 2 SN74LS74AN Texas Instruments
10 1 SN7400N Texas Instruments
11 1 SN74LS01N Texas Instruments
12 1 899-1-R4.7K Beckman
14 1 TBP24(The rest is unreadable) Texas Instruments
15 1 TBP18S030N Texas Instruments
16, 18 2 2716JL-45 Texas Instruments
17 1 2716JL Texas Instruments
19, 20 2 SN7432N Texas Instruments
21 1 SN74LS04N Texas Instruments
22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37 16 MBB116H
39, 40 2 SN74LS157N Texas Instruments
41 1 SN74LS374N Texas Instruments
43 1 SN74LS90N Texas Instruments
Research Machines RM380z Floppy Drive and Serial Controller with marked numbers according to the RefDes in the table
Research Machines RM380z Floppy Drive and Serial Controller with marked numbers according to the RefDes in the table

Floppy Drive Controller and Serial Card

Intergrated Circuits
RefDes Qty Model Number/Part Number Brand (if applicable) Explanation Datasheet
1, 2, 14 3 SN74LS244N Texas Instruments
3 1 SN74LS245N Texas Instruments
4, 8 2 SN74LS32N Texas Instruments
5 1 SN74LS21N Texas Instruments
6 1 74LS138N Signetics
7 1 SN74LS02N Texas Instruments
9, 12 2 SN7438N Texas Instruments
11 1 MK3A82N Mostek
13 1 SN7416N Texas Instruments
15 1 SN75188N Texas Instruments
16 1 SN74LS273N Texas Instruments
17 1 SN74LS157N Texas Instruments
20 1 FD1771-AD1 Western Digital
21 1 SN74LS193N Texas Instruments
23 1 N74LS42B
24 1 SN74LS123N Texas Instruments
25 1 INS825IN National Semiconductor
26 1 SN74LS74AN Texas Instruments
28 1 SN74LS00N Texas Instruments

Replacement Parts

Power supply

Capacitors
RefDes Qty Compatible Part Number Order Links
C1 3 598-477TTA063M DigiKey Mouser
C8 1 661-36DA223F025BA2A 36DA223F025BA2A Chemi-Con | Mouser United Kingdom
C12 1 647-LNT1H153MSE DigiKey Mouser

Notes

C12 replacement is smaller in diameter to the original however is the same specifications.

It is recommended to add a crowbar to the PSU as the stock supply holds no protection on the early machines.

Floppy Drive

Integrated Circuits
RefDes Original Part Number Qty Compatible Part Number Order Links
MC3470P 1 DigiKey Mouser LCSC
SN74221N 1 SN74221N / DigiKey Mouser
SN7474N 3 DigiKey Mouser LCSC
7407N 1 SN7407N DigiKey Mouser LCSC
LM339N 1 LM339N DigiKey Mouser LCSC
SN7404N 3 SN7404N / DigiKey Mouser LCSC
SN7438N 2 SN7438N / DigiKey Mouser
LDP1401-151G 1 DigiKey Mouser LCSC
SN7432N 1 SN7432N DigiKey Mouser
DM7402N 1 SN7402N / DigiKey Mouser

VDU

Integrated Circuits
RefDes Original Part Number Qty Compatible Part Number Order Links
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC

CPU/32K RAM Card

Integrated Circuits
RefDes Original Part Number Qty Compatible Part Number Order Links
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC

Floppy Drive Controller and Serial Card

Integrated Circuits
RefDes Original Part Number Qty Compatible Part Number Order Links
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC
DigiKey Mouser LCSC

If parts are not available or different selection is preferred, you can use the values in the Original Parts section to perform a parametric search.

History

The Research machines 380Z is a British Z80 based microcomputer made in oxford England from 1977 to 1985. This machine found a popular use case in schools before the BBC micro was released and could be used in conjunction with Research Machines 480Zs to form a network with a 380Z running as a file sever over the proprietary RM 800kbps network. A kit version of the 380Z is believed to have been made called the 280Z however this cannot be confirmed. The RM380 can use multiple operating systems with COS (cassette operating system) been the default OS in ROM, the versions of COS changed over the lifespan adding and removing functionality. The main revisions known are.

  • COS 2.2 –
  • COS 2.3 – cassette-only and 40×24 video card support
  • COS 3.0 – floppy disk support for external 8 inch drives.
  • COS 3.4C - cassette only version of 3.4
  • COS 3.4 – main COS version supporting single density 5.25 disks and the 40×24 video card.
  • COS 4.0 – 80×24 VDU text display with no cassette support due to the VDU80/02 not having the cassette interface.
  • COS 4.2 – double density disk drives (380Z-D). This version is very rare due to the limited run of it.


The RM 380 could also run CP/M in both the 32K and 56K configurations. The two known versions of CP/M used on the 380 were CP/M 1.4 and later on it was CP/M 2.2. MP/M version 2 was used on 380s which formed the file server on a network of 480s using CP/NET

Related Links

References

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