<div dir="ltr"><span style="font-size:12.8px">Schottky diodes would erode the voltage margin. The two diode drops are intended to ensure the gate negates chip select before the RAM's voltage has dropped enough to allow spurious writes op's (or any ops) if /CS was true.</span><div><span style="font-size:12.8px"><br></span></div><div><span style="font-size:12.8px">p</span></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Sat, May 7, 2016 at 7:44 PM, MTG <span dir="ltr"><<a href="mailto:grant@musictechnologiesgroup.com" target="_blank">grant@musictechnologiesgroup.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">0.6v approx.<div class="HOEnZb"><div class="h5"><br>
<br>
On 5/7/2016 7:27 PM, Barry Klein wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Measure the Vdrop across each.<br>
<br>
Sent from my iPhone<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
On May 7, 2016, at 6:12 PM, MTG <<a href="mailto:grant@musictechnologiesgroup.com" target="_blank">grant@musictechnologiesgroup.com</a>> wrote:<br>
<br>
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.<br>
<br>
The first one has a stylized "F" and the numbers "25".<br>
<br>
The second has what looks like "T1" or maybe "TI" and then "525" as far as I can tell.<br>
<br>
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.<br>
<br>
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:<br>
<br>
<br>
|-----\<br>
"5v"----|>|---|>|----+-----------| \<br>
| | NAND >0----RAM_CE*<br>
< CE ----| /<br>
10k < |--- -/<br>
<<br>
|<br>
Gnd<br>
<br>
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.<br>
<br>
Do you suppose these are schottky?? The number 25 or 525 means nothing to me in diode land.<br>
<br>
I may have to come up with some other solution, but I wanted to try swapping these out first.<br>
<br>
_______________________________________________<br>
Synth-diy mailing list<br>
<a href="mailto:Synth-diy@dropmix.xs4all.nl" target="_blank">Synth-diy@dropmix.xs4all.nl</a><br>
<a href="http://dropmix.xs4all.nl/mailman/listinfo/synth-diy" rel="noreferrer" target="_blank">http://dropmix.xs4all.nl/mailman/listinfo/synth-diy</a><br>
</blockquote>
<br>
<br>
</blockquote>
<br>
_______________________________________________<br>
Synth-diy mailing list<br>
<a href="mailto:Synth-diy@dropmix.xs4all.nl" target="_blank">Synth-diy@dropmix.xs4all.nl</a><br>
<a href="http://dropmix.xs4all.nl/mailman/listinfo/synth-diy" rel="noreferrer" target="_blank">http://dropmix.xs4all.nl/mailman/listinfo/synth-diy</a><br>
</div></div></blockquote></div><br></div>