[sdiy] Elektron

[Mattias Rickardsson]

Sorry to hear about the sleeping Machinedrum...

How dead is it? Does it light up anything?
If it lights up but nothing starts, then it might be time to retire
the big capacitors in the PSU after a long and strenous life.

6VAC is only to be expected at full current draw, so higher voltage is normal.

The digital section uses 4 schottky diodes to full-wave rectify the
AC. Then there is probably a 5 V regulator (LM2904T-5) and a 3.3V
regulator (LM317).

The analog section transforms the 6VAC up to 12VAC and half-wave
rectifies it and regulates to +/- 8V (with a 7808/7908). On the I/O
PCB there is an analog 5V regulation as well (LM317).

If you have disconnected the PSU PCB (which you should probably do
while measuring the PSU) then the regulated digital & analog voltages
are floating with respect to each other, i.e., you need to measure an
analog voltage in reference to an analog ground and vice versa.
Measuring between an analog voltage and digital ground could end up
anywhere.

There is a connector for 3.3V, another for 5V, and a 10-pin connector
with the following voltages:

DGND
DGND
AGND
-8VDC
AGND
5VDC (MIDI)
AGND
+8VDC
AGND
AGND

Another thing to watch out for is if some component pins or some
heatsink has come in contact with the casing - this is not good and
can give similar problems.

Unless you find any clues so far, try measuring the voltage coming IN
to the LM317 (should be 6-8 VDC over for example C8, C21) and OUT from
the transformer (should be around 12 VDC over C15).

Good luck, and happy new drummachine year! :-)

/mr


On 30 December 2013 19:43, Jean Bender <lofideadbeat at gmail.com> wrote:
> Well, i've taken my measure with my multimeter. I switched from AC to
> DC as i know the lm** pinouts. I did that fastly this afternoon as i'm
> working this night and tomorrow. I'll go back to my workshop
> tomorrow..
> I should have taken some pictures or other regulators references..
> I'll send that tomorrow night or on Wednesday.
>
> The strange thing is even if powered, and with my AC current ok at the
> fuse output ( so just before the whole regulation unit), absolutely
> none of the regulator was heating. And they have pretty big power
> dissipation stuff !
>
> It's the first time i don't really understand a power supply, and as i
> don't have any schematics...
>
> Thanks for the help.
>
> 2013/12/30 Byron G. Jacquot <thescum at surfree.com>:
>>>Hi everybody !
>>>I've just bought an Elektron Machinedrum sps 1 ( first generation).
>>>The friend who sold it to me tested it before shipping, and it was
>>>working.
>>>Once i tried to plug it, it never started. I fisrt thought it wa sue
>>>to the external power supply ( it should give a 6v AC out), but no..
>>>except if 7,23v AC out is too bad..
>>>So i opened my sps1. The fuse is ok, the power connector also.. i can
>>>get my ac voltage at the fuse output.
>>>After that.. nothing. There are many regulators, but for most of them
>>>i can't figure how they work. I've just check a lm7808 and a lm317
>>>that don't deliver good voltages..
>>>And visually, no component seems to have burn..
>>
>> There's likely nothing wrong with the AC supply.
>>
>> External transformers are usually rated to deliver the stated Voltage at the stated current.  If you draw less current, the Voltage will be somewhat higher...7.23 seems about right for a 6VAC supply.
>>
>> It's also pretty unusual that all of the voltage regulators would fail at once.  I'd suspect something that's common to all of them.  How are you measuring them?
>>
>> If it was just shipped, perhaps a connector slipped out of place?
>>
>> -Byron Jacquot
>>
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>
>
>
> --
> Jean Bender
>
> Hak Lofi Record
>
> ELECTRON CANON
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