DEC4/DES/STD160 question

[e093116]

Hello,

I have a DEC4 wallbox hooked to an STD160 which has been working fine for the past 3 months or so.

Recently, the selections made from the DEC are not working properly. As an example, if I select 100 I usually get 120, 144 I get 133 or 134, and 177 I get 111 or 117.  The rest of the DEC works fine (credits, pricing, lamps, volume, etc.).  I think I am having most trouble with the C and D data lines.

The DES on the STD160 works properly. 

I've double checked all of my wiring and haven't found any loose wires or bad connections.

I have a spare DES, if I swap the board from this DES into the DEC DES, the 1-9 keys work properly, but if I push "0", the reset lamp will flash.  If I push the reset button on the left, the reset lamp will clear, but if I push the reset button on the right, the reset light will come on or not reset if it's already on.  Is it possible there is a short in the circuit board between the reset button and zero causing this problem?  I have tried this DES/board in the STD160 previously and had the same problem there as well...

Anyway, with swapping the DES board, it makes me think that the problem lies in the DES and not in my wiring or the black box.  I have cleaned the contacts and boards using the method described in Ron's book.  In Tony's book, it says that selection data pulses the line to -21 volts.  Does anyone know what the minimum threshold is for the signal?  Any other things to check or suggestions would be appreciated. 

Thanks,

Bill

 

[Ron Rich]

Hi Bill,
You are correct--data-line problems--(BTW--the DEC does NOT use the DTP-1, in the phono.) Which board (number) is in your DEC ?
I presume since you mentioned my "book", you have the "MicroLog" TS guide ? If so,and if it is the 2nd edition look at the "quadra-bit" chart in it, also,sounds as if you need to clean/lubricate the DES per that book. Ron Rich

[e093116]

Hi Ron,

Thanks for the reply, I finally had some time to work on this issue some more, and yes I have your second edition book as well as Tony's book on the black & gray boxes. 

I have a second DES from another DEC4 that I recently obtained and it results in the same "problem". If anything I now have a hard failure, which should be easier to find, and I'm starting to suspect the problem lies elsewhere. 

Based on reading in Tony's book, I believe the problem is missing data D line.  There is a table in Tony's book which denotes what selections result when this occurs, and the system behavior is exactly as described in the book.

I'm going to see if I can follow the signal for the D data line with an oscilloscope, starting at the terminal block inside the DEC4, then checking the TB in the juke, then checking the connector at the stereo network box.

Any suggestions on anything else to check?

Thanks,

Bill 

[Ron Rich]

Hi Bill,
Read the DCC service notes in notes in the trouble shooting guide about the 311134 board, and you may avoid scoping it ( the "quadrobit" chart is also there !) --Ron Rich