Memory Packs

[David G]

Wow, this site has a lot of information on memory expansion packs. I only used the Sinclair 16K pack briefly and my main unit was a Memopak 32. But there is so much to learn from the early wild years of the home computer boom


Great resources:

• Hardware Forum: 16K RAM Pack photos - please add yours

• Extensive list of modules: RAM expansion at timexsinclair.com

• RAM Packs Alternatives?

• ZX 16K RAM Pack – Instructions for use and Test Program

The two most common RAM packs. Or at least the most infamous ...



INDEX

• Cases by Size

• Troubleshooting/Repair

• Sinclair

• ZX-Panda

• Jigsaw/BYG BYTE

• SPECIAL RAMPACK

• ZX80 RAM packs

SEE ALSO

• ZX MEMORY PACKS SURVEY article from 1982
  

[David G]

Starting with the external looks, external memory packs may be categorized by the size of the case

* Square rectangle
* Low-profile wide rectangle
* Short rectangle
* Wide rectangle


Square
* Sinclair ZX 16K RAM
* Timex sinclair 1016 (TS1016)
* and many other lesser-known brands use a similar size


photo by Carlos Pérez Ruiz - Wikimedia Commons


LOW-PROFILE RECTANGULAR
* Memotech Memopak models




SQUAT RECTANGULAR
* SPECIAL RAMPACK




WIDE RECTANGULAR
shorter than the Sinclair module, but much wider
* STL Made in England
* Jigsaw by Gladstone with BYG BYTE PCB

[David G]

Most RAM packs use 4116 or equivalent DRAM chips, which are 16K x 1 bit, so eight are needed. These most-common chips require 12V, +5V and -5V. This was before the 64K chips arrived which only required 5V

The ubiquitous 16K RAM pack, designed -- as with most Sinclair products -- for economical manufacturing, low part cost, and compact packaging. But what about quality?

The Sinclair 16K RAM packs suffer from a number of different faults. This could include broken wires, faulty 4116 DRAM chips, faults with the internal power circuitry, faulty ULA (depending on which version). RAM packs from other manufacturers are typically a bit more reliable, but may still suffer from 4116 DRAM chip faults.

So what to do if your pack is experiencing problems? Or if you are given an old unit that is not functioning, the challenge of restoring it may be worth the effort

Start with Sinclair ZX World:

• How is the onboard RAM deactivated? and the function of RAM chip-select

• Intermittent Memory Errors

• 16K RAM Pack Schematic / Chip Layout

• Repairing Sinclair ZX81 16K RAM Expansion Packs

• How to troubleshoot a Sinclair ZX16K RAM Issue 3

[David G]

The Sinclair packs (including the Timex branded units) were all 16K

* two circuit boards sandwiched in the square case

ISSUE 1 boards looks very much like an Issue 2, but with a few components on the back of the logic board

• sinclair ZX 16K RAM [issue 1]

• sinclair ZX 16K RAM [issue 2]

• sinclair ZX 16K RAM [issue 3 with single PCB]

• Timex sinclair 1016 (TS1016)

The only difference in the Sinclair pack and the Timex-branded version was the logo on the case. The circuit boards inside are the same, which differed by Issue 1, 2 and 3.


photo by Carlos Pérez Ruiz - Wikimedia Commons





These 16K units used the common 4116 DRAM chips. They used a DC/DC inverter circuit to generate 12V and -5V from the 9V power line of the ZX81 expansion connector. 5V also comes from the connector, but needs no conversion

The DC/DC power converter is on the bottom edge of the memory board
(left side of this photo)


ISSUE 1 EX


ISSUE 1981 schematic


[edit: add more photos]

[David G]

The revised Sinclair ZX RAM 16K used different circuit boards on the inside. Reportedly, most TS1016 units were Issue 2

The cases look identical to Issue 1. Minor changes are on the inside

sandwich boards


memory board with eight 4116 chips


logic board


While the Issue 2 board circuit layout appears to be identical to Issue 1, several changes were made

Issue 2 has:

• reverse side has no components
  * all three capacitors on the reverse side moved to front side
  * small diode on reverse side moved to front side and is larger

later Issue 2:

• green solder mask and more modern PCB material

• larger power traces

COMPARE to Issue 1 with 3 capacitors and 1 diode on the reverse side



More photos: 16K RAM Pack Schematic / Chip Layout

schematic: 16K RAM Pack Schematic


Technical article: "Understanding and Upgrading the TS1016 RAM Pack" from Time Designs magazine NOV/DEC 86 VOL. 3 NO. 1 pages 16-19


Troubleshooting: Intermittent Memory Errors

[David G]

SINCLAIR ZX16K RAM ISSUE 3
* single PCB

Issue 3 rationalized the product by replacing the logic board with a custom chip, the Ferranti ULA IH035E




"ULA" is a Ferranti trademark from the early 1970s -- eventually similar chips were eventually made by other semiconductor companies, but were called something else. The generic type is Gate Array. This has since evolved into the Structured ASIC, the CPLD, and on to today's user-programmable FPGA. The ULA was not user programmable, but had to customized before final manufacturing -- a custom semiconductor mask had to be created and used in the creation of the chip at the Ferranti chip fab. Once the design is finished, the ULA is dedicated to the particular application, making it a type of application-specific IC (ASIC).


component side



Schematic

from SQ Syntax Quarterly Summer 1983 Vol. 2, No. 2 page 35


Troubleshooting/Repair
How to troubleshoot a Sinclair ZX16K RAM Issue 3

[David G]

SQUARE CASE

ZX-PANDA by Stonechip Electronics of Surrey, England was another RAM pack in the "square" case format, similarly sized to the Sinclair ZX Pack

* ZX-PANDA 16K Expandable RAM Pack (8116) £25 (1982)
* ZX-PANDA 16K Expansion RAM Module (8116E) £20 (1982)
* Full 32K RAM pack (8132) £40 (1982)

Sync magazine Volume 3 Number 3 page 29

ZX-Panda Expandable 16K RAM Pack. $55.95.
Contoured case fits snugly against the rear of the computer for a sure fit. LED indicates "Power On." Easily expandable to 32K with simple plug-in module that fits inside the existing case, no tools or soldering needed. Allows for inexpensive upgrading at any time.

Andy's Retro Computing Collection documentation and box

MADE IN ENGLAND BY STONECHIP ELECTRONICS


Distributed also by AFDEC of Hampshire, England



memory board with MM5290 DRAM chips


[edit: added links for more information]

[Moggy]

Out of all the ram-packs I've owned over the years I always found the Panda the most reliable and still have my original one purchased over forty years ago, still going strong, on the now rare times I use it, with my ZXpands being my main memory interfaces.

[David G]

WIDE RECTANGLE shape

Jigsaw by Gladstone Electronics, Buffalo, New York. Has an LED power indicator, just to let you know your 81 is still plugged in

sync magazine September/October 1982 Volume 2, Number 5 page 45
* Jigsaw 16K RAM $49.95
* Jigsaw 32K RAM $89.95 "with piggy-back feature" enable use with a 16K pack giving 48K total
* Jigsaw 64K RAM $149.95


JIGSAW



16K single PCB board include 8 DRAM chips plus logic chips and power chips

3/39-004 ISS 2 with "Made in Hong Kong" sticker

other side BYG BYTE RAM PACK 16K

3/39-004 ISS 2 REVERSE

[David G]

Is that the good old "MADE IN ENGLAND" quality

Out of all the ram-packs I've owned over the years I always found the Panda the most reliable and still have my original one purchased over forty years ago, still going strong, on the now rare times I use it, with my ZXpands being my main memory interfaces.