TID12-01 TCI board schematic and extra info

sleddog83

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I have been collecting this information for a while. Finally getting around to posting it. I don't think this stuff is stored in the tech section. The picture of the bottom of the circuit board was done when I was reverse-engineering the board. I thought it might be useful for anyone who is doing some troubleshooting. The board works similar to the 12-03 board in that it creates a couple integrator waveforms that it compares for the advance timing. I have changed the resistors at R22/R23 and R14/R51 to correct the advance curve on my board, but the values listed on the schematic were what it came with. Other boards may be different. I suspect they were "fine tuned" at the factory. I also replaced C5. I am not sure what the factory value should be, but I have a 10uF on the board right now. This was an oops on my part. I missed the cap during the reverse-engineering process then subsequently removed and lost it when I was doing some bench testing of the board. The 10 uF seems to work, but if anyone knows what should be in there let me know.
The board I have is my backup board as well as bench test board that I try out different stuff on, so it is a little hacked up. A note of caution with this version of board. The circuit board traces are quite delicate. It doesn't take much heat to rip the traces right off the board. Takes a good soldering iron and a delicate touch.
A couple of other things to note. I have successfully used the ST901A as a substitute for the output transistor(PTR1) on this board. I have been unable to find original replacement transistors for T1 and T2. I have found a substitute KSC1845 that I think will work okay, but haven't tested them on this board yet.
 

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  • 12-01tci-scope-trace.jpg
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  • TID12-01 schematic 1.jpeg
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  • TID12-01 schematic 2.jpeg
    TID12-01 schematic 2.jpeg
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xjwmx

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I popped my spare open to find C5 for you, but it's a different design, that uses about half as many parts...maybe the difference between a -01a and -01b versions, just guessing?

For substitute transistors you might try 2N2222 and TIP120, both should be at Radio Shacks. MJE5742 would be good too, and slightly more robust (note EC and B might be different pins)
 
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sleddog83

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10 uF... good. I guessed correctly.

The abbreviations I used such as T1C, refers to connecting to the collector of transistor T1. Some of those signals go all over the place. It easier just to reference it one place, rather than draw schematic lines all over the place. On the oscilloscope captures, I also refer to the cathode of specific diodes. For example, D3C refers to the cathode of diode D3.

Those transistors you suggested are OK general purpose transistors. But I suspect some of the parameters such as the beta are not the same. I am not an engineer and my training in that theory disappeared many beers ago. My thinking is that the original design with that particular biasing created a mode where the transistors are just barely switched on, just on the edge of saturation. When a negative pulse comes in, the transistors switch off. On an original board, a pulse of -0.7 v will cause the transistor to switch off. It is very sensitive. My first design with the 2n3904 required a pulse of -2 v. I tried different biasing and the sensitivity improved but the pulse shape and delay changed a little. I tried reading up on transistor theory and design, but ended up going with a transistor that closely matches the original. The substitute is KSC1845FTA Testing on the breadboard with this transistor showed it switching at the same levels as the original board.
 

xjwmx

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^Could be. I was assuming it wasn't balanced on a knife edge. Are you going to make one from scratch on a perfboard? That would be fun.
 
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