1802 "Membership Card" production history

Last updated Nov 24 2019. Edited by Herb Johnson, (c) Herb Johnson. Contact Herb at www.retrotechnology.com, an email address is on that page.

[rev D CPU]

[rev D assembled]

This is the Web page of production history of the 1802 Membership Card. This page will be referenced by support pages of various versions. "For those just tuning in, the Membership Card is a reproduction of the original Popular Electronics Elf computer, but shrunk to fit in an Altoids tin!" Check with the 1802 Membership Card Home page for mor information. - Herb Johnson.

Reverse Chronology of products, support and development

Notible revisions compared to pre-Rev G Membership Cards

Stacking of ROM and RAM for Rev F and earlier is discussed on this linked Web page. rev G introduced a 300-mill wide RAM under the 600-mill wide ROM.

Also, adding a serial interface to a Rev F or earlier Membership Card, is discussed on this linked Web page. Rev G and forward provide serial interface hardware. Rev I and forward provide a power/serial connector that mates to many TTL/USB adapter "cables".

Rev ? and forward, added a ceramic resonator clock to the CPU board. A ceramic resonator and RAM/ROM can be added (with effort) to various older revision cards, see this Tech Note.

The narrow 300-mil wide RAM chip U8 is under the 600-mil wide RAM/ROM socket. But four address lines to U8 were "scrambled". In Rev K and later they are now unscrambled and in normal order; jumpers support ROM use there.

Some Rev G and earlier kits, may benefit from a change to the CPU /A15 FET circuit, to improve speed of response. See these notes for details. In Rev H the FET was changed to a resistor-biased transistor; in Rev H2 forward it's a pair of N and P channel FETs. Refer to the revision Web pages for details of their operation.

Rev JK2 back to Rev C

"Rev JK2" July 20 2019: Rev K2 CPU and Rev J front-panel are in production. The Rev K and earlier CPUs had a 74HC244 to buffer the INP 4 toggle switches. Lee Hart says: "Replacing the 74HC244 with the 74HC541 eliminates the [brief] high power consumption in the special case of going from CLEAR to LOAD, before you press IN for the first time." see the Rev JK page for details.

"Rev JK" Aug 1 2018: Rev K CPU and Rev J Front-panel are in production. The Rev J had a 4093 CMOS logic gate to operate the 1802 clock, but the gate limited the run frequency. In Rev K, the 1802's oscillator circuit is in use. The now-available gate, now a 74HC00, is used as the A15 logic-inverter, replacing two MOSFETS as the previous inverter. The MOSFETs required a physical change to the EPROM socket, which is now eliminated. In previous revisions four address lines to U8 - the narrow RAM - were "scrambled". In Rev K and later they are now unscrambled and in normal order; jumpers support ROM use there. see the Rev JK page for details.

"rev J" July 1 2017: Rev J CPU and Front-panel are in production. Some small layout changes for the CPU board, a transistor was added to the Front-Panel board for the Q LED, to better show data activity. see the Rev J page for details.

"Rev I" April 2017: Rev I CPU in production. No obvious changes from H2 CPU, silk-screen fix.

"Rev I" Feb 1 2017: Rev I Front Panel in production, now with a power/serial connector, a signifigant change. The H2 CPU was still in distribution. Some problems of use were found. see the Rev I page for details.

"Rev H2" is in distribution as of June 4 2015 as a CPU board, with Rev H front panel. Here's the Rev H and H2 support Web page. The H2 CPU provides front-side jumpers for HI/LO address changes, and some resistor values were changed. The CPU /A15 inverter is now a pair of N and P channel FETs, which almost eliminate the 1mA current of the previous FET or NPN transitor.

"Rev H" is in distribution as of Apr 21 2015. See the Rev H & H2 support Web page. Rev H kit included a FNJ3301 NPN transistor for /A15.

April 2015: Rev H in pre-production distribution as of April 8th. Pre-production Rev H CPU boards, replace a FET with a FJN3301 NPN transistor; add a /CLEAR diode; make slight changes to layout and resistors. No change to the Front Panel card. Refer to the Rev G support page until full Rev H production is established.

Feb 2014: Rev G in production. Here's the Rev G support Web page. Serial and RAM/ROM options added. In Feb 2015, it was discovered that the Q1 FET circuit with 100K pullup, was insufficient to drive /A15 which chip-selects the RAM or ROM at 8000H. An initial "field fix" was to add an external resistor of 5K to "pull up" the rise-time of that signal. In March 2015, it was determined that replacing the FET with a FNJ3301 NPN (resistor biased) transistor plus a change of SIP R5 to 10K, was also a "fix"; Lee Hart offers these parts upon request; Rev G kits after April were distributed with those parts. Details are noted on the Rev G support page.

May 2013: Rev F in production. here's the Rev F support Web page. Layout now allows optional 1.8 MHz ceramic resonator to replace cap C1 in clock circuit. Rev F went out of production in Feb 2014. A ceramic resonator and RAM/ROM can be added (with effort) to older revision cards, see this Tech Note.

Dec 2012 - April 2013: Rev E in production with no design changes, just minor board layout fixes. Here's the Rev D and E Support page.

Added a 2nd pair of holes for the supercapacitor to allow using parts on 0.4" centers instead of the 0.2" centers at present. parts on 0.4" centers are easier to find.

Removed a speck from a trace on the DB25 connector. It did no harm, but removing it increases spacing in one spot.

Aug 2012: Rev D boards in production. Here's the Rev D and E Support page. Lee Hart reported: "A customer reported a couple bugs in rev.D."

1. The board itself has an extra trace between DB25 connector pins 1-2. It doesn't cause a short, but it's close. A little extra solder on pin 1 and it could short. I will be grinding off that extra trace with a Dremel moto-tool on existing stock [sold].

2. Note 4 on the schematic said all toggle switches should be UP to use the DB25 with a PC. Switch S8 should be DOWN. I just fixed the note on the schematic.

3. There are a couple updates needed to the "cheat sheet" for rev.D. DB25 connector J2 pins 18 and 22-25 have changed. [Later Lee reported: "There are jumpers to bring out all 8 bits of the I/O port on the 25-pin D-connector, or to use the D-connector for power and serial I/O."]

June 2012: Rev.D board: Changed R1 back to 1meg. Changed R2 to 5.6k (for wider clock frequency range). Added D12 (so power is available on DB25 connector J2). Added R14 (to use J2 pin 1 for serial input). Added jumpers A/B, Q0, Q1, Q2, and Q2 (to use J2 for general purpose I/O instead of PC parallel I/O). The holes for the toggle switches are smaller than the Rev C card, to accomodate PC mount pins not solder-loop.

Apr 2012: R1 changed from 500k to 1meg (ran out of the 500k pots).

Mar 2012: If you look in the picture in the rev C manual, you'll see that my Membership Card has clear (instead of red) LEDs. Those are blue LEDs. I also changed the 1k series resistor network to 3.3k, as they are *way* too bright [and consume too much power] at 1k. :-)

Feb 2012: Lee Hart constructed a graphic of how the "elves" run the 1802. Lee also constructed some Membership Card operating notes and an 1802 instruction set summary. These can be printed and stored in the Altoid case. Here's the operating guide PDF

Jan 6 2012: Here's a Tech Note about stacking two Rev C CPU boards, to double-up the RAM or ROM and also double the I/O. Rev D now makes that easier to do.

Aug 2011: Rev C kit in production. Changes from Rev B to Rev C are informative. They are listed in the rev C manual, and on the Rev C support Web page. Here's the Rev C schematic .JPG.

Rev B, A, initial design

2011: Some notes and comments about Membership card Rev B upgrades.

2010:Here's a Rev B Tech Note about drilling the Altoids can, the use of pin sockets, and other mechanical issues.

Sept 2010 - July 2011: Rev B kit was available. Here's the Rev B support Web page.

May - Aug 2010: Rev A prototypes distributed and constructed.

2005-2009 development history: See the Membership Card early development page for years of discussion about the 1802 Membership Card design, and the philosophy behind it; up to the first products.

30 years ago, Lee developed an 1802 single board computer called BASYS. Look at the BASYS manual for hardware interface suggestions for the Membership Card.

This page and edited content is copyright Herb Johnson (c) 2019. Contact Herb at www.retrotechnology.com, an email address is available on that page..