[sdiy] Help ID a diode

MTG grant at musictechnologiesgroup.com
Sun May 8 04:44:48 CEST 2016


0.6v approx.

On 5/7/2016 7:27 PM, Barry Klein wrote:
> 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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