Solid State Music S-100 , VB3 vs VB3A

Introduction

This Web page discusses the difference between the SSM VB3 and VB3A board models. So far I found only a few. This page Last update Mar 15 2024. This document copyright Herbert R. Johnson 2024, content authored by others have their copyrights.

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Differences between the SSM VB3 and VB3A

Examining each board: upper left corner near U6 U7. The VB3 has a 4-dip switch S1 and 4 10K resistors R1-R4. On the VB3A switch S1 and those four resistors, are replaced, with IC U55 SN75452 and 2 jumpers and RP4 a 2.7K SIP resistor.

Examine this photo of the area for each board, for details. Also review the VB3 and VB3A schematics and detailes below. VB3 and VB3A manual PDF's are available, ask.

VB3 Schematic and board has two DIP 4-switches, S1 and S2.
VB3 schematic S2 operates U7 with RP1 pullup.
VB3 Schematic S1, shows R1-R4, as U6 with incoming horizontal and vertical sync signals.
VB3 schematic shows U10 and R8 R9 pullups, drive Horiz and Vert signals out.

VB3A board has only one 4-dip switch S2, not far from U7 and RP1. same position on VB3.
VB3A Schematic shows a SW2 4-DIP with RP1 pullups to U7.
VB3A schematic shows U55 as dual NAND which uses RP4 to drive Horiz and Vert signals out.
VB3A scheamtic shows RP4 and two jumper-pairs, upon U6 incoming horizontal and vertical sync signals.

Herb Johnson
New Jersey, USA

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