Which pins would I put on the voltage meter?

Pin-5 should be negative, pin-4 should be positive, pin-1 is zero. 

So with the meter's black lead to pin-5 and red lead to pin-1 you will get 1/2 the story: is it 9VDC or to 15-20VDC? 

Black lead to pin-1 and red lead to pin-4 should show the same result.

If you check pin-4+ to pin-5- you will see the "full swing" which could be anything from 18V (2x9) to something like 30-40VDC (2x15-20).

Now you're probably more confused. 

Jimmy J

I am super curious to know too!  I own 2 of the Fernandes "Alembic copy" instruments (bass and guitar), but neither one of them still had the original PS-5.  I've measured the voltages on my Alembic DS-5s, but it seems likely that the PS-5 should have at least a slightly lower voltage due to the IC opamps they used in the instruments - as gtrguy pointed out.  But truth is, they can handle almost as much voltage as the opamps Alembic uses (quite a bit more than +/-9V), so I'd love to know what voltage Fernandes actually designed the PS-5 for.
Thanks Jimmy for the guidance!

Pretty sure Fernandes is +- 9 volts. Fernandes Alembic copies can work with an Alembic power supply, but I think it puts extra stress on the chips.

A while back I bought an older DS-5 that was factory wired for 220v.  The seller had assumed that just putting an adapter on the plug would make it work fine in the US (which of course would actually have it proving half of the intended output).  He said he had been using it with a Fernandes with no problems at that level (~8-10v?).

Yes, most voltages BELOW the instrument's maximum limit will work fine, but it will limit the headroom - i.e. how much volume it will output before it starts distorting.

And even though running a 220V DS-5 on 120V power seems like it may be a problem, remember that tons of active basses and guitars only use one 9V battery (e.g. Stingray basses), and I don't think I've ever heard of anyone complaining that their Stingray doesn't put out enough volume!  By comparison, I measured my Alembic DS-5 power supply at 42.1V, more than 8x as much voltage.  So even if this is running at something like ~23V, that should still be PLENTY of headroom / volume.

15.1v was the reading on my meter

Is that the "full swing" or only half?   Pin-4(+) to ground(-) ... or pin-4(+) to pin5(-)?  I'm gonna guess it's trying to be +/-15VDC for a 30V swing.  And that's good power for running an Alembic as long as it's smooth and well regulated juice.  Still wild to see that external transformer.  All gear has a story...

Thanks for the report.
Jimmy J

Quote from: JimmyJ on December 14, 2024, 11:00:58 AM
Is that the "full swing" or only half?   Pin-4(+) to ground(-) ... or pin-4(+) to pin5(-)?  I'm gonna guess it's trying to be +/-15VDC for a 30V swing.  And that's good power for running an Alembic as long as it's smooth and well regulated juice.  Still wild to see that external transformer.  All gear has a story...

Thanks for the report.
Jimmy J

That's pin one and five. Anything else is really above my pay grade.

Alright!  Pin-1 is ground and pin-5 is the negative voltage, -15VDC in this case.  So now we know that it's a +/- 15VDC power supply which should be nicely compatible with our Series instruments.  Good work on the testing!

Jimmy J

come to poppa 🗿

Sold.
Thank you all for the help with this unit.

Great to know!  Thanks Dan, and Jimmy!  Cheers

ok so here's hopefully the end of this little adventure.  this showed up at CastleBeenDown yesterday after i got home from rehearsal.  took it out to the shop, opened it up, checked the mains wiring and verified the socket pinout and voltages per an alembic DS-5 schmatic.  other than putting an inside strain relief on hte power cord i really didn't have to do anything else to it.  i'll probably install a better power cord down the road i dunno.
since this was supposidly a working unit before i got it, i could've probably saved myself the shop time and just swapped it out with my current DS-5.  however, i take nothing for granted with used equipment, especially if i'm gonna hook it up to the ebony amazon.  fired it up, it's dead quiet just like its mate.  it's got a ground lift switch, i put it in the grounded position.  shouldn't have to deal with that unless ya got a gound loop issue anyways which i don't.
i haven't decided which one stays home and which one goes with the road rig yet.  here they are  side-by-side.  there's not really many ways to do +/- 15 volts.
looks like the ebony amazon is gonna leave the woodshed with me next week and go up infront of a live band in full stereo goodness.  not really sure if it's ever been played live, we're gonna make some eyes bug out whilst saturating ears with an SII strung with fresh rotos played at high volume in full stereo.  gonna be a blast, methinks

Awesome, Tim!