All,
I inherited a old DOD mixer from my dad and I'm trying to revive it. It is missing the power supply and I am having a real hard time locating something that would work. The power requirements on the back say (34 Volt ~ CT 50/60 Hz 1 Amp). It is also a 5 pin DIN connector which contributes to my lack of options here. Any ideas on a replacement? Or will I have to build one?
Any help would be greatly appreciated.
Thanks - Joby
I inherited a old DOD mixer from my dad and I'm trying to revive it. It is missing the power supply and I am having a real hard time locating something that would work. The power requirements on the back say (34 Volt ~ CT 50/60 Hz 1 Amp). It is also a 5 pin DIN connector which contributes to my lack of options here. Any ideas on a replacement? Or will I have to build one?
Any help would be greatly appreciated.
Thanks - Joby
Welcome to diyAudio 🙂
I suspect that what is called for is a 34 volt AC supply with a centre tap (CT) from which can derived a dual or split supply.
So if that assumption is correct, it means a 17-0-17 transformer which would create DC rails of around -/+24 volts (so -24, 0, +24 volts DC).
That would be my best guess without knowing more details, and if so then such a supply would be easy to create. Just a transformer and lead to a 5 pin DIN plug.
If you have circuit details of the mixer (or sometimes even good pictures of the internals) then it might help a bit more.
I suspect that what is called for is a 34 volt AC supply with a centre tap (CT) from which can derived a dual or split supply.
So if that assumption is correct, it means a 17-0-17 transformer which would create DC rails of around -/+24 volts (so -24, 0, +24 volts DC).
That would be my best guess without knowing more details, and if so then such a supply would be easy to create. Just a transformer and lead to a 5 pin DIN plug.
If you have circuit details of the mixer (or sometimes even good pictures of the internals) then it might help a bit more.
I cannot find any information on this mixer, let alone a diagram of any kind. I can take it apart and upload pics this afternoon if that will help. If we assume your assumption is correct, can you please provide an example of a transformer that would work? I am new to power supplies in general and don't understand all of these variables.
So assuming the basic assumption is correct we would also need to hazard a guess at the current rating required. If we take the '1 Amp' at face value then that would mean a 36VA rated device (VA is volts amps and used when specifying transformers).
The good news is that 1A is actually quite a lot when it comes to small signal circuitry and so that could be just a nominal rating, the unit may use considerably less... but that is why we need more detail.
http://cpc.farnell.com/block/fl42-18/transformer-42va-2x-18v/dp/TF01085
or a 30VA toroidal:
http://cpc.farnell.com/multicomp/mcta030-18/transformer-30va-2-x-18v/dp/TF01394
There are literally dozens to choose from in all styles and shapes... but we really need to know more.
The good news is that 1A is actually quite a lot when it comes to small signal circuitry and so that could be just a nominal rating, the unit may use considerably less... but that is why we need more detail.
http://cpc.farnell.com/block/fl42-18/transformer-42va-2x-18v/dp/TF01085
or a 30VA toroidal:
http://cpc.farnell.com/multicomp/mcta030-18/transformer-30va-2-x-18v/dp/TF01394
There are literally dozens to choose from in all styles and shapes... but we really need to know more.
If you post pictures then its best to attach them directly to your posts 🙂
How to attach images to your posts.
How to attach images to your posts.
Ok, understood. Thank you for the quick responses. I will keep digging to find info on the unit and take some gut shots this afternoon for you.
So... this is all really low power circuitry as shown but there must be more boards than just this.
This is all powered from 7815 and 7915 regulators which themselves put a 1 amp maximum limit on the DC current draw.
The transformer needed is definitely a centre tapped type (or one with dual secondary's that allow a centre tap to be configured)
If the regulators are not mounted on heatsinks then we can say for certain that the current draw is going to be around a couple of hundred milliamps at most. That is an important thing for you to check. U1 and U2 at the bottom of the diagram are the regulators. If you can locate them in the unit, are they free standing or are they bolted to a large heatsink ? Or perhaps clip on smaller heatsinks.
We can say for sure that the transformer needs to be at least 15-0-15 volts AC which would give -/+21 volt rails. That allows 6 volts headroom for the regs.
An 18-0-18 transformer would deliver -/+24 volts DC giving 9 volts headroom.
The higher the headroom within reason, the better. The downside is the extra voltage is lost as heat in the regulators and so they run hotter.
This is all powered from 7815 and 7915 regulators which themselves put a 1 amp maximum limit on the DC current draw.
The transformer needed is definitely a centre tapped type (or one with dual secondary's that allow a centre tap to be configured)
If the regulators are not mounted on heatsinks then we can say for certain that the current draw is going to be around a couple of hundred milliamps at most. That is an important thing for you to check. U1 and U2 at the bottom of the diagram are the regulators. If you can locate them in the unit, are they free standing or are they bolted to a large heatsink ? Or perhaps clip on smaller heatsinks.
We can say for sure that the transformer needs to be at least 15-0-15 volts AC which would give -/+21 volt rails. That allows 6 volts headroom for the regs.
An 18-0-18 transformer would deliver -/+24 volts DC giving 9 volts headroom.
The higher the headroom within reason, the better. The downside is the extra voltage is lost as heat in the regulators and so they run hotter.
In case you are wondering, the AC voltage is actually a sine wave and the value quoted is always quoted as the 'RMS' value. The peak of the sine is 1.414 (which is the square root of 2) multiplied by the RMS value.
So 18 volts AC when rectified and smoothed with a capacitor gives 18*1.414 which is approx. 25 volts. The capacitor charges to the peak value.
An 18-0-18 transformer therefore gives 25-0-25 volts DC.
The regulators need at least 3 or volts over there nominal value in order to function. So a 15 volt regulator needs at least an input voltage of around 18 volts DC.
So 18 volts AC when rectified and smoothed with a capacitor gives 18*1.414 which is approx. 25 volts. The capacitor charges to the peak value.
An 18-0-18 transformer therefore gives 25-0-25 volts DC.
The regulators need at least 3 or volts over there nominal value in order to function. So a 15 volt regulator needs at least an input voltage of around 18 volts DC.
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