[sdiy] mine transformer question....

[Magnus Danielson]

From: "Dj" <mte at softhome.net>
Subject: Re: [sdiy] mine transformer question....
Date: Sun, 31 Aug 2003 02:03:28 +0200

> List,

Dj,

> i'm just starting in diy-electronics, at this time i never would change a power-suply, since i'm a beginner,
> i just wanted to know if that is possible, i'm trying to figure out the service-manual, but still a long way to go, i'v ordered some books, i hope this list can help on mine journey even when it is modifying/servicing a commercial synth. 

Well, welcome you are... ask questions (including the "silly" ones) and pick up
from the answers and other threads. Dig in the (huge) archive - it has alot of
accumulated knowledge by now.

> Apparently i have some questions, but don't know if it fits here so it may skipped..., here they are:
> - what is a tempco?

A "tempco" is the synth-builders lingo for a Temperature Compensating resistor.
It is a resistor which resistance changes with something like +3300 ppm/C in
order to compensate for another temperature dependence, namely that found in
the exponential response of a transitor (actually a NP-junction to be correct).
In synths will a exponential converter be used to convert the 1 V/Oct style of
voltages into linear current to drive the oscillator, filter or whatever.
The tempco thus helps to keep this more frequency stable in relation to
temperature than you would do with a normal resistor.

> - Does a synth only run on AC or also DC, what is that excactly in synth terms?

The actual synth electronics runs from a DC supply, but since AC is what pops
out of the wall, we always have a AC/DC converter which delivers the necessary
DC-levels and also makes them stable (idealy). In short it's just power.

Cheers,
Magnus