Green Pre PSU layout

[RightOnMusic]

does anyone have the parts layout for the green pre PSU pcb available on ptownkid's site?  I've got 4 channels of green pres stuffed and i've got the psu kit, but no idea what goes where on the board.  i've searched and searched on here but can't find it.  help?

 

[dissonantstring]

hi righton,
which version of the Green Pre PSU is it?  Peter has released several versions with very slight differences.  i have some overlay files i could share if you let me know which version it is.
kind regards,
grant

 

[RightOnMusic]

appears to be v4

 

[dissonantstring]

here's a link to Peter C.'s page for his PSU V.4:
http://1176neve.tripod.com/id26.html
the overlay is on that page.
-grant

 

[Ptownkid]

Send me an e-mail at diypartssupply at rogers dot com. My replies to you got bounced back.

 

[RightOnMusic]

sweet that was exactly what i needed, thanks so much!!

 

[RightOnMusic]

ok...  so i'm an ubernoob.  please please bear with me.  this'll be my first complete finished build....  i've got this torroid, the stuffed psu board (damn right i got my soldering iron out the second you posted that layout) and 4 stuffed green pre boards...  how do i put this all together?  i'm not sure about the torroid and what all these wires coming out of it are for.  there's green brown red and blue on one side and then yellow red black and purple on the other side.  (these all have a yellow wrap close to the transformer).  i'd rather not blow anything up, so a little guidance would be excellent.  like i said, i'm brand spankin' new to all this.  i can paint by numbers real well, but that's about it...

 

[Ptownkid]

brand and model of torroid?

 

[RightOnMusic]

amveco magnetics
62075-P2S02

 

[Harpo]

amveco magnetics
62075-P2S02

http://www.amveco.com/Miniature_Low_Profile_Transformers_2.htm

 

[RightOnMusic]

Thank you.  I'm still not sure I understand what's what.  The PSU board has connection spots for +15v, GND, -15v, +48v and then on the other side 15vAC, 15vAC, 0v.

Which of these connect to the transformer, which of these connect to the preamp boards, what connects to the IEC socket?  I'm sorry to be such a pain in the ass, but I know little to nothing about how this all works.  I'd love for someone to explain to me how this is all working and what it's all doing in addition to just 'connect the red wire to x pad' type directions...  I've done a bunch of searching, but most of the threads seem to already assume one has a base of knowledge that i don't seem to have...  Thanks for your patience everyone!

 

[mitsos]

From the amveco site, I think your toroid has 2 x 22VAC secondaries? That's a bit more than you need for +\- 15VDC operation, but it'll just give you more heat. Phantom is another story, see below. You should put some dissipators on your regulators.  Anyway, you~re in the US, so 115V mains... From the picture Harpo linked to, the right (oops! I meant left) side are the primaries.. you want those in parallel, so join Red to Yellow and Black to Violet. Take Black\Violet to the hot of your IEC socket and Red\yellow to neutral.  Done.  Next, join green and brown and take those to the ground pad on the PSU board. Take Red to one AC pad and Blue to the other.  That should do ya.

WARNING: The 22VAC shouldn't make much difference to the +\- part of the PSU (just create more heat), but WILL make a difference in the phantom part. The phantom part of the PSU works as a voltage tripler (rectifies to triple the AC voltage). For 22VAC, a tripler should give you over 90V unregulated (22VAC x 1.414 x 3 = 93.324VDC), which will destroy your regulator (LM317 can have max 37 volts difference between input\output).  What that means is you'll need to figure out how to make this tripler into a doubler.  I didn't have much luck with mine last time I tried but what I will do after the weekend (I am not writing this so you can be my guinea pig, but rather to get some input from more knowledgeable folks) is rewire that part like so:  put a cap in place of the first diode (negative to the right), a diode in the first cap place (anode to ground), the second diode in its normal place, and finally a cap from where the two diodes join, to ground (negative lead to ground). This looks more like a doubler to me, although there are usually more than one way to skin a cat (who came up with that saying anyway?).

For a visual, see "Rearranging the Doubler Circuit" here: http://www.play-hookey.com/ac_theory/ps_v_multipliers.html

EDIT: I was pretty sleepy last night writing this and kept thinking of it after I wrote... I'm still a bit confused, this looks like a Villard multiplier but every resource I can find has the first diode's anode tied to ground. Anyway, the problem I was having with my green psu is that I was getting 59V at the reg input but 31V out. As I was thinking about this I think the problem MAY have been that, since I used only 2 caps, I should have tied the second to ground instead of to the AC input as in the tripler circuit.  I can't check this now but I think I will try just tying that cap to ground before rearranging the whole circuit....

 

[helterbelter]

here's a link to Peter C.'s page for his PSU V.4:
http://1176neve.tripod.com/id26.html
the overlay is on that page.
-grant

Goddamnit (pardon my language), I wished I had seen that before... I found another one, and so I started with that one. It has some differences but with a bit of tracefollowing I got it stuffed.

But stupid me....

I haven't checked the PSU voltages before turning the green pre on. Little gain, and distorted sound. Started searching on the green PCB for faults. Couldn't find any. Then I remembered that I haven't checked the voltages from the PSU... :-[

One of the 15 volt rails was delivering 25.5 volts.

There's one diode that's reversed on this layout. It took a while before I discovered that. All other diodes are facing the same direction, and the other PSU layout had all diodes facing the same direction as well...

I still haven't fixed the green pre by the way. All opamp voltages are correct, I replaced the BC550's, swapped the opamps (luckily I used sockets !). I have to clean my scope and start using that. I haven't trimmed the cmrr yet either.

 

[RightOnMusic]

would i just be better off getting myself a different transformer?

 

[dissonantstring]

hi righton,
if your transformer is a 22V transformer, definitely better to go with a different transformer like a 15V.
the amount of voltage your regulator will have to dissipate will generate a lot of heat.  regardless, use heatsinks on your regulators for longevity.

i'm sure you'll be able to use the 22V for something else since there are some many other projects here so no real loss.

my first Green Pre build used an 18V-0V-18V (36VCT) transformer and the regulators with a heatsink generated a little too much heat for my comfort so i changed to a 15V-0V-15V (30VCT) transformer.  the regulators will last longer and be happier with a lower 15V transformer.   also, if your pre is going into a 1U chassis make sure the transformer will fit comfortably without touching the top of the case.
-grant

 

[RightOnMusic]

no no i've got four channels so it'll be a 2 unit job.

thanks i will definitely go that route.  is there a way i can test and make sure it's actually 22v?

 

[Harpo]

From your part number you don't have a 22VAC transformer. Yours is 2x 22VAC. You can wire this as a 44V CT (=center tap) by connecting two wires of the above described secondary windings. This 2x 22VAC is a frequently used secondary AC voltage to build a +/-24VDC dual rail supply. With a voltage doubler you can generate the maybe needed supply voltage for a +48VDC phantom supply.
For the green pre you probably better go for a 2x 15V or a 30V CT transformer.

You can measure the secondary voltage of a transformer by connecting the 2 secondary lead ends of a winding to a meter, set for measuring AC voltage. Wire the transformer primaries depending on your AC mains voltage as described above. With primary winding connected to your AC mains, your meter will show the stepped down secondary AC voltage. This will read about 10-20% higher for an unloaded transformer and your AC mains voltage may vary by +/-10%, depending on location, time of day or mood of a generator at an open-air venue. For your unloaded part the amveco datasheet says, this will be 25.7VAC for each secondary winding with a 115/230VAC primary feed. With secondaries wired in series for a center tap in the middle, the voltage difference between the unconnected secondary lead ends will measure 44VAC under full load or 51.4VAC unloaded.

Same as for your preamp case, you also want a fuse between your IEC connector and this transformer. A switch might come handy as well.
 
Be careful with lethal voltages. 

 

[RightOnMusic]

thanks guys!  i pick up on this stuff quickly so i feel like i have a much better idea of what's what here.  thanks again.  best forum in the world.

 

[dissonantstring]

oops!  sorry for the confusion righton.
harpo is definitely right (thanks for catching that harpo - i know you have the knowledge) .

i incorrectly included CT for centertap, but with the incorrect voltages.  sorry about that (my brain farted as i was posting). :-[

but go with a 15V -0V- 15V (30VCT) transformer for less wasted heat.
kind regards,
grant

p.s.  i've edited my previous post to correct transformer designations.

 

[RightOnMusic]

so....

next....

how would i rig this up to power the four channels?  would each terminal on the psu just have 4 wires running out from it, or would i wire 'em up in series?  sorry guys.  never done this before.