Hello everyone. New in here. Audio equipment enthusiast (repairs and diy builds for own use).
I currently work on a very old and obscure Italian tape echo effect + mixer + preamp combo unit.
The tape echo circuits are powered separately from the mixer+pre amp circuits.
The tape echo circuits supply exists and works ok. It provides different values, for different circuits, for the same “use” (effect) on the same rail. But because of its current demand it can’t share its power rail.

The mixer-preamp circuit demands around 8Vdc and less than 500ma (found out after simple experimentation). But there is no appropriate rail (that’s a different story that doesn’t matter for our purposes) in the device to provide that power amount.

Can I use a separate linear supply of 8vdc in the same chassis along with the existing tape echo dc supply?
Should I connect the secondary 0v together as a common? The tape echo one goes to earth.
Is it a safe to connect the 230Vac primaries in parallel (i guess they would need different fuses) before hitting the mains switch? Or is it better to keep the separated and just use and external multi plug with switch?

Thanks in advance

 

Welcome to AAC!

Yes, you can connect the 230 VAC primaries in parallel after the input fuse.
Before connecting the 0V circuits together, check that the two circuits to be powered already share a common 0V rail. This should be the case for audio circuits. If so, it would be safe to connect the two PSU 0V rails.

 

Welcome to AAC!

Yes, you can connect the 230 VAC primaries in parallel after the input fuse.
Before connecting the 0V circuits together, check that the two circuits to be powered already share a common 0V rail. This should be the case for audio circuits. If so, it would be safe to connect the two PSU 0V rails.

Thanks for the reply MrChips.
They do share a 0v. So the secondaries 0v connection is clear.
On the other hand the main fuse for the primaries is common and the parallel connections starts after that. Regardless of power supply size and power consumption. Do I understand correctly?

 

Also I have to add that the hot and neutral of the mains go to the mains switch (dpst) and from there (switch ON position) one (mains) cable goes to one of the mains fuse pins.
But the other goes to a voltage selector switch-pot (which is like an old voltage regulation thing that can reduce input voltage by a maximum 20Vac). I’ve left it to maximum since I don’t want any reduction.
From that switch-pot the other (mains) cable goes to the other mains fuse pin .
Is it ok if I do my parallel connection on the fuse holder pins? Since it’s ac I don’t think what goes where. Is it ok?

 

Sorry. Sorry. Correction of my previous post. Serious mistake what I suggested about fuse holder.

I correct the post.

I have to add that the hot and neutral of the mains go to the mains switch (dpst) and from there (switch ON position) one (mains) cable goes to one of the mains fuse pins.

But the other goes to a voltage selector switch-pot (which is like an old voltage regulation thing, that can reduce input voltage by a maximum 20Vac). I’ve left it to the maximum position since I don’t want any voltage reduction.

From that switch-pot a cable goes to the other mains fuse pin .
So apparently the pot switch is where the two mains cables hide after the fuse and I could make a parallel connection.

But a) it’s no so obvious and easy to make the connection and b)since that switch-pot is variable, it can accidentally damage things.

Do you think I could do a parallel connection on the on-offmains switch (on position side) with another different mains fuse?

Maybe leave it separate and just use common multi plug with switch? Easier and safer.

 

You can get wire splice connectors that allow you to tap into a cable without having to undo the cable.

 

You can get wire splice connectors that allow you to tap into a cable without having to undo the cable.

View attachment 352726

Very neat looking. Thanks for the advice.