[sdiy] Help ID a diode

Barry Klein barryklein at cox.net
Sun May 8 04:27:30 CEST 2016


Measure the Vdrop across each.

Sent from my iPhone

> On May 7, 2016, at 6:12 PM, MTG <grant at musictechnologiesgroup.com> wrote:
> 
> I have 2 diodes in a logic circuit that I am trying to ID. Their purpose (my best guess) I will explain below. They are in series so I assume they are the same.  They are both the orange glass type and look like a 1N4148 or a 1N914, but the numbering is off.
> 
> The first one has a stylized "F" and the numbers "25".
> 
> The second has what looks like "T1" or maybe "TI" and then "525" as far as I can tell.
> 
> The circuit is a 4011 logic circuit, part of the battery backup logic.  The 4011 is powered by a diode combination of 5v or the 3v coin cell, whichever is larger.  Other diodes, not these ones.
> 
> My attempt at deciphering...These diodes and 1/4 of the gate package are intended to disable a CE* signal when 5v goes away. I will attempt ascii draw:
> 
> 
>                                 |-----\
> "5v"----|>|---|>|----+-----------|      \
>                     |           | NAND  >0----RAM_CE*
>                     <    CE ----|      /
>                 10k <           |--- -/
>                     <
>                     |
>                    Gnd
> 
> This is some home-brewed memory expansion (not mine) and it has issues where some of the bytes change after a while (possibly during power-cycling).  I don't know that this is the culprit but it's pretty odd by what I have seen around synths. I swapped out the RAM and it still occurs.
> 
> Do you suppose these are schottky??  The number 25 or 525 means nothing to me in diode land.
> 
> I may have to come up with some other solution, but I wanted to try swapping these out first.
> 
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