[sdiy] Siel OR400 Transformer needed

Tom Wiltshire tom at electricdruid.net
Fri Jul 26 19:47:23 CEST 2013


Well, that doesn't look *too* awful. That schematic you posted shows +/-6V and +/-12V supplies.

You've got +5.9 and -6, so that's probably the +/-6V supply, and it looks like it's working. The other voltages aren't so good. +9.5 is a bit low for +12V, and -10.3 is not -12V either, so those aren't so hot. If you didn't have the main synth boards connected when it went bang, you're lucky, 'cos you unlikely to have damaged irreplaceable. Power supplies are just power supplies, and anything that gives the right voltage at the right amperage will do.

If you're happy poking around in mains powered equipment ( and I can see why you might not be after your recent experiences) you should test the AC output from the secondary of the transformer (NOT the primary). It's AC, so don't test it with a DC meter (my usual error - forgetting to switch the multimeter to AC).

If the secondary voltage there is ok, probably the regulators are dead, or possibly there's something shorting/ed and dragging the output down. If the secondary voltage is not ok, then you definitely need a new transformer, and once you've replaced that you can repeat your test and find out if you got lucky and that's all that's wrong.

Good luck, and be careful.

Regards,
Tom



On 26 Jul 2013, at 17:54, M Maeghan Skala <synth.diy at pulsewidthmod.com> wrote:

> So I decided to test the poet supply once more so I connected everything back up and did some readings … out's for each of the IC"s are as follows:
> 
> IC1:		-10.3
> IC2:		9.5
> IC3:		-6
> IC4:		5.9
> 
> Just to make sure I tested at the Ribbon cable out:
> 
> 5.9
> 0
> -6
> 9.5
> 0
> -10.3
> 
> So the synth is giving a constant noise, it's also modulating it's pitch. When I hit the keyboard, it does nothing. I guess when the power supply short circuited … it arced over to other components. This is a really really sad day for me. I can't afford to send it off to get to get fixed. It's all over most of tracks :(
> 
> I don't know what to do.
> 
> I purchased the schematics from music parts.com … :( I don't know what the hell I'm doing.
> 
> 
> 
> 
> 
> On Jul 26, 2013, at 6:16 AM, Steve Lenham <steve at bendentech.co.uk> wrote:
> 
>> On 26/07/2013 10:39, M Maeghan Skala wrote:
>> 
>>> So, I"m looking for a 30VA transformer, center tapped … which has two
>>> secondaries rated at 15VAC.
>>> 
>>> Please correct me if I am wrong.
>> 
>> That's about right.
>> 
>> To be absolutely clear, a transformer will only be described as centre-tapped if it has three secondary pins (two ends and one centre tap). It may also be described as, say, 15-0-15 or 30VCT.
>> 
>> Here in Europe at least, pretty much all transformers now seem to be made with two separate secondaries, i.e. four secondary pins. These are not strictly centre-tapped. They can be wired centre-tapped as I described, but can also be used in other configurations which is why the modern parts are made that way. They may be described as 2 x 0-15 or 2 x 15V.
>> 
>> BTW, it is OK to use a higher VA-rated transformer if it is easier to source and will physically fit.
>> 
>> HTH,
>> 
>> Steve L.
>> 
>> 
>> 
>> 
>> 
>> 
> 
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