Tag Archives | Logic


BCD Decoder Schematic

The other posts show the bits and logic schematics for relay implementation of typical gate level logic. This is the main schematic of the BCD decoder. It does have a bug in that the circuit that controls all of the output relays (EN’) will not work. Due to not thinking about other relay’s giving the […]

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Working Relay BCD Decoder

  Been a while since I posted on this subject. I have had the PCB fabricated and assembled one BCD controller. It tool a long time to solder in all the parts, but eventually it got built. After some initial testing of the PCB I found that I had messed up ONE circuit, the one […]

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logic friday screen shot

BCD Decoder Logic

7 Segment decoder full truth table. Note that RBI’ segment decoders are exactly the same except in the A=B=C=D=0 condition Here is my original truth table for the encoder. It features 7 segmenmt decoding of a BCD input from 0-9. It also features Ripple Blanking input and output much like the standard TTL Decoders of […]

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Relay AND Logic

Relay Logic Diagrams

Here is the start of the 7 Segment BCD decoder logic. The idea is to make a generic board that can decode BCD data and display like a LED Digit might. This is similar to the 7447 (or many variants). This post will show the general Relay based logic that I will be using. AND, […]

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EZ260 Tube Amplifiers and Tube Projects