| Newsgroups |
gmane.music.equipment.yamaha-dx |
| Message-ID |
<[email protected]> |
1. When in standby mode, the RAMs need *very* little current to
maintain their data. (That's the reason why the battery can last
many years.) The RAM holds data down to around 2V of backup. It's
entirely possible that the 10uF capacitor can maintain that for a
while after the DX7 is powered off. In fact, that seems to imply
that the capacitor is fine, IMO.
2. The diode is probably a small signal part like a 1N4148 or 1N914A.
They have < 25nA of reverse leakage at the voltages used here, and
at the tiny currents we are talking about, the voltage drop is only
going to be 0.3-0.4V.
Regards,
-BW
Bruce Wahler
Ashby Solutions.com™
[email protected]
http://music.ashbysolutions.com
http://halfmoon-switch.com
http://ashboys.com
978.597.7008
On 9/4/2018 6:51 AM, geoff baltan [email protected] [YamahaDX] wrote:
> This is very helpful - so thank you, everyone for the input.
> A few questions:
> 1. The device doesn't immediately lose its memory at power-off, it
> usually takes about 8 hours. If the diode were simply open or closed,
> would it still partially-work?
> 2. Is there a list of appropriate replacements for the diode and
> tantalum capacitor?
>
>
>
> On Tue, Sep 4, 2018 at 1:39 AM, [email protected]
> <mailto:[email protected]> [YamahaDX]
> <[email protected] <mailto:[email protected]>> wrote:
>
> Daniel,
>
> What pnetops said, and yes, open circuit means no connection, like
> a simple switch that's off / open. Closed circuit means like a
> closed switch (on), allowing current to pass both ways.
>
> The diode is meant to only allow current from the battery to the
> RAM when there is no external power supply providing 5V, and
> ideally no current at all the other way, though there might be a
> few microamps.
>
> A healthy diode conducts best when the voltage at the anode is
> about 0.6V higher than the voltage at the cathode - for a silicon
> one, or about 0.3V for a germanium diode.... it varies, depending
> on the material and type of diode, but it's generally in about
> that range.
>
> A dead diode either doesn't conduct at all, or conducts like a
> small value resistor, with little or no difference in direction.
>
> Since the batteries were soldered in, a lot of these synths still
> have the original ones because it's not trivial to change one, but
> a lot of those original batteries still work, after all these years.
>
> - Andy
>
>
>