Square Pixel Modification Kit

[sigma7]

To better support Macintosh software under MacWorks, Apple developed a modification kit for the Lisa that changed the screen dimensions from 720 x 364 rectangular pixels to 608 x 432 square pixels.

The kit includes Rev "3A" ROMs for the CPU board, a non-serialized video PROM for the CPU board, and a transformer that connects between the video board and the yoke of the CRT.

Prior to MacWorks Plus and MacWorks Plus II, the screen modification kit was supported only by a variant of MacWorks XL 3.0 that was hard coded to the 608 x 432 screen.

(Is there a square pixel version of LisaTest as well?)

MW+/II are aware of the two screen variations and so work with whichever is installed.

Earlier environments are hard-coded for the 720 x 364 screen dimension.

[sigma7]

Information about the Screen Modification Kit Transformer

Note that the crt + video circuitry are dangerous and potentially lethal. Use this information at your own risk.

Materials:

(1)  FERRITE CORE P 630NH N48 2PCS (1 set)
EPCOS - TDK Electronics B65671T0630A048
- Digi-Key 495-5164-ND $10.46

(1)  BOBBIN COIL FORMER P 26 X 16   
EPCOS - TDK Electronics B65672B0000T001
- DigiKey 495-5166 $0.74

(1)  3 Position Rectangular Connector - Plug Housing 0.200" (5.08mm)
TE Connectivity AMP Connectors - MATE-N-LOK - 1-480303-0
- DigiKey A1429-ND $0.68

(1)  3 Position Rectangular Connector - Receptacle Housing 0.200" (5.08mm)
TE Connectivity AMP Connectors - MATE-N-LOK - 1-480305-0
- DigiKey A1400-ND $0.65

(2)  Pin Contact - Tin 18-24 AWG Crimp
TE Connectivity AMP Connectors - MATE-N-LOK - 60618-1
- DigiKey A1422-ND $0.37

(2)  Socket Contact - Tin 18-24 AWG Crimp
TE Connectivity AMP Connectors - MATE-N-LOK - 60617-1
- DigiKey A1423-ND $0.42

(~ 10 feet / 3m)  22 AWG Magnet Wire
SparkFun Electronics PRT-11363 (kit includes 22, 26, 30 AWG, only 22 AWG is needed)
- Digi-Key 1568-1088-ND $16.94
.. or ..
Belden Inc. 8051 (254' / 77m)
- DigiKey BEL1979-ND  $82.94
.. or ..
- Jameco 22MAG (129' / 40m) $8.95

Miscellaneous

Nylon bolt and nut to hold halves of pot core together. Soft washers (eg. o-rings) may help to limit the clamping force as the ferrite is easily broken. Can use tape or some kind of clamp instead (eg. EPCOS - TDK Electronics B65675B0005X000 DigiKey 495-5167-ND $7.95) The transformer gets warm in use, so don't use hot glue

~ 16" / 40 cm of stranded insulated hookup wire 18-22 AWG (cut into 4 pieces) to connect magnet wire of transformer windings to mate-n-lok contacts

~ 2" / 5 cm of insulating tubing (cut into 2 or 3 pieces) to protect the insulation of the 22AWG magnet wire where it exits the pot core

Tape (to hold windings in place)

Tape or heatshrink to cover connections between stranded wire and magnet wire

Enclosure eg. something like a PVC plumbing cap (or just wrap it in tape, but the ferrite is fragile and brittle so best protected from knocks, and the solid magnet wire should not have any flex/strain load on it).


Wiring:

41 turns + 9 turns (making a step-up autotransformer with one tap)

Socket contacts in plug housing are connected with pin 1 to the beginning (of 41 turns) and pin 3 to the tap (at 41 and 9 turns) This connects to P2 on the video board.

Pin contacts in receptacle housing are connected with pin 1 to the beginning (of 41 turns) and pin 3 to the end (of 9 turns). This connects to the cable to the yoke (formerly connected to P2).

[sigma7]

The 3A ROMs will operate correctly without the screen modification kit transformer installed.

However there is likely to be an issue with the video displayed, as the horizontal width control may not have enough range to fill the screen, and the horizontal phase (position) control may not have sufficient range to prevent the left edge of the image wrapping back on itself.

pic to follow

[sigma7]

If the 3A ROMs are installed without the corresponding video PROM, the video will appear scrambled.

pic to follow

[bmwcyclist]

Sorry about reviving this old thread but it seemed to be the correct topic.

If I have a "Mac XL" Lisa 2/10 with new ROMs and screen kit do I understand correctly that I can't use the older LISA OS/APPs?

[jamesdenton]

Sorry about reviving this old thread but it seemed to be the correct topic.

If I have a "Mac XL" Lisa 2/10 with new ROMs and screen kit do I understand correctly that I can't use the older LISA OS/APPs?

That is correct. If you have the 3A ROMs and corresponding video rom, as well as the screen modification kit, you cannot use LisaOS, UniPlus, Xenix, etc. You'd need to remove the screen kit and revert the ROMs to H or below and procure a video ROM. Not an especially expensive endeavor, just requires some digging (or burning).