Genrad aka Quadtech 1689 1692 1659 Digibridge

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Unofficial supplements to the Service Manual

Fix your Digibridge or back up your EPROMs so you can keep it running forever! EPROMs and PALs have often been known to fail after a few decades. Feel free to share this info or to post it on your own web site.

1659 1692 1689 Digibridge - Newer models with the sloped display bezel and square power button.

Below is the internal logic diagram for the PAL's on the Digibridge Motherboard and Optional High Speed Interface board. The chips are simply used for Address Decoding and GPIB Address Compare so the security fuse is not actually being used. These chips can go bad after 20 or 30 years, so I recommend that you read yours out on a programmer and make yourself a backup of the jedec file to CDROM.

Circuit Diagram aka Schematic reverse engineered from fuse jedec file

ICs U11 and U40 on the Digibridge Motherboard are 256x8 PROMs which are used for sinewave generation. Genrad part number of the programmed part was 5627-0002 00/A as can be seen from the sticker on the chip, and the checksum is 8000. The device can be read on a programmer as Texas Instruments TPB28L22, National Semiconductor 74S471, Monolithic Memories Inc 6309, or Signetics 82S135, which are all equivalent.

The EPROM on the Digibridge Motherboard is a 27256 and you will have a different one depending on the exact model of Digibridge you have.
1659 Digibridge: Part number is 1659-2800 00/B and checksum is 52ED1D for version 1.10
1692 Digibridge: Part number is 1692-2800 and checksum is 52661D for version 2.01
1689 Digibridge: I don't know, PLEASE email me your info if you can. I only have custom version 9.30

The high speed coprocessor U5 on the optional Interface Board is a T.I. TMS320E15JDL EPROM-DSP with checksum 314F5 for version 1.3


1659 1689 Digibridge - Older models with the vertical display bezel and round power button.

The two 256x8 PROMs are used for sinewave generation. Genrad part number of the programmed part was 5627-0002 00/A as can be seen from the sticker on the chip, and the checksum is 8000. The device can be read on a programmer as Texas Instruments TPB28L22, National Semiconductor 74S471, Monolithic Memories Inc 6309, or Signetics 82S135, which are all equivalent.

The EPROMs on the Digibridge Motherboard are 2764s and you will have different ones depending on the exact model of Digibridge you have.
1659 Digibridge: I don't know, PLEASE email me your info if you can
1689 Digibridge: I don't know, PLEASE email me your info if you can


Safety, accuracy and completeness of information provided herein is not guaranteed,
so be inspired by it but do not use it as a basis for experimentation or other actions.

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