green power supply

[dissonantstring]

hello everyone,
i wonder if anyone can help me. i'm having some issues with my green pre PS. checked the voltages on the output and i'm getting my +15V, 0V -15V, but my +48V PP output is only +13.47V.
voltage on the input leg of the LM317 is something like 71V, but the output leg is only 13.47V. any ideas? any help would be appreciated.
thank you.
-grant

 

[matta]

Hey Grant,

Double check your resistor values around that LM317 reg, they set the voltage and you may have the wrong value. Also you could have have a damaged reg, but check the resistors first.

Matt

 

[dissonantstring]

thank you matt!!
actually, before i could check for a response i went back and checked the schem and found that i mistakingly put in a 2K2 resistor instead of the 8K2 resistor off the LM317 regulating the 48V. replaced it and thankfully all my voltages are now o.k. and none of my caps or Vreg were fried.
i love this place. even if i wasn't able to figure it out i knew one of you fine gents would have led me in the right direction (just as matt's suggestion was spot on!)
cheers,
grant

 

[bluezplaya]

I have been trying to figure out this damn PSU for a couple of days now. I just replaced 2 1000uf 16v caps with 1000uf 35v caps after seeing that the paint had melted off of the side of one of them and finding a voltage layout of the PSU. It shows 21.5v passing through the caps so I replaced with the 35v. When I turned the power on with the new caps, it exploded like Old Faithful geyser in Yellowstone Park. White smoke was steaming out of the top. Can anyone give me any ideas??

Adam
:sam:

 

[matta]

Hey Adam,

Did you check the cap was in the correct way? I think all the lytic caps face the same way. Also check for shorts on the board possibly from de and re soldering.

There really is no explanation I can think of why they should blow up since all you did was replace them with a higer V rated cap.

Matt

 

[bluezplaya]

I'm such a FOOL!!!!!! I realized that all the lytic caps were backwards!!! I think I was fooled into thinking that the markings on the side of the caps represented "positive" instead of "negative". And the caps were reversed on my 2 boards as well. It apparently worked for some time because I was getting audio from both pre's, including using phantom. But that was with some hum.

I am going to swap out the caps to their right orientation and hopefully that will fix something. I wonder if any other components might be damaged?

Adam
:sam:

 

[sunyata]

Hi,
I have built my PSU with an old 30VA/230V transformer I saved from an old project. Everything installed in an old metal box I had. So I saved some money. When everything is up and running I will buy a new nice looking casing.
I calculated the primary side fuse value: I = P/U = 30/230 = 0.130A
Somebody told me to use a 500mA fuse (slow) to compensate for the initial startup current. Is this the right way to do it?
I thought of installing an internal fuse on the secondary side to take care of the individual channels. (only one so far.) How many mA would that be?

best regards

Sunyata

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[W DeMarco]

Hey Folks

Im tryin to finish up a new EQ3d using the Green supply.  I was getting a low voltage using the standard silkscreened values for my adjustment resistor on the 317 and 337, I think its a 2k2 as printed.  When I used an online calc to get the correct value for my 18 volt output I get around a 3k, 2948 exactly.  So I dropped in a 3k and it was still very low.  Right now I have a 3k9 in there and shes "putting out" around 17.25 V.  I figure thats about good enough.  I might try something else to get it dead on 18.  QUESTION.  Why am I getting a difference here from the CALCulator.  I have 20 volts AC coming into the psu.  Above the 1.5V extra pre regulator.  I also noticed that changing 1 of the resistors and leaving the other adj resistor alone produced some stange output voltages. 

Are the two regulators interacting?  In other words are the two regs affecting the voltage differently than if I were to have a psu with a single rail?

Im also wonderingif this value will also change when I connect the PSU to the load?

 

[peterc]

Wayne

What DC voltage are you getting out of the rectifier?

It is god to have at least 3v extra for each rail, so about +21v & -21v after the rectifier would make the regs happy.

Peter

 

[W DeMarco]

Thanks for the reply Peter.  It seems I ordered a pretty bad choice for my transformer.  I got an amveco TE62043-ND which offers 2*15 volt a full load.  Luckily I have a 62075 sitting to wait for another 1176 build.  It offers 2*22 loaded.  Live and learn.  Ill pop her in and hopefully Ill have the eq3d up and running in the hour ]

 

[W DeMarco]

OK even with the tranx upgrade Im gettin 18 volts after the rectifier.  OMG I want to use this baby.  I guess Ill need to order a bigger transx than I have.

Or Im thinkin wire the 2*15 secondaries  in series?

 

[W DeMarco]

I put the 2*15 In series and have trimmed out to 18.2 volts with a (2)2k7 resistors.  With load and all!  I hope thats close enough.

 

[Dr nEon]

Hey guys!

I'm about to stuff my first green psu board, to use for powering 2x S800 eqs .

I'm using a 18-0-18 transformer , to give me +/-18vdc.

Can I go ahead and stuff the resistor values shown on the pcb&bom (220r and 2k2's) .....or will I have to change these resistor values for working at 18v?

Thanks in advance

nEon

 

[peterc]

Changing the 2k2's to 2k9 will give you 17.7v.

But are you sure you want to run them that hot? Their max voltage is +-18v & there is not much to be gained from the extra 3v of supply voltage.

Peter

 

[Dr nEon]

Hey Peter!

Thanks for the reply...ok, great to know I can sub those resistors for the correct voltage.

I'm going for 18volts ,only because that's what it says on the s800 schematic , and I have an 18-0-18 to hand, but if you think that it is safer to work at 15v , I can get a nu tx...

Peter, one other question , if I may, ..... What would be the best way to add a 'power on' led to the V6a psu board?

Cheers

nEon

 

[Dr nEon]

What would be the best way to add a 'power on' led to the V6a psu board?

Has anyone done this?

I'm wondering if its as simple as hanging a led off the regulated positive rail to ground via an appropriate sized resistor...

Or would pre-reg be better..... or would adding a led to one side of the bipolar supply upset the +/- balance ( for want of a better word)...??

any thoughts anyone?

cheers

nEon.

 

[chathura]

Hey Guys,

I'm having some issues with the PSU.Every thing seems to be fine except for the voltages around LM337 comes up as 22v. I have changed the reg. but the problem remains the same. Anything else I should check..? Bypass diode..?(i'm going to replace that and see..)

thanx.

-Chat

 

[juanjovincenzo]

Hi Guys!
I get this toroid power  transform for my two green preamps: Triad Magnetis TRANSFORMER, POWER TOROID, 50VA, 115/230VAC, 30VCT @ 1.67A, 15V @ 3.34A  http://www.alliedelec.com/search/productdetail.aspx?SKU=9670204
I will put together with a green V4 PSU (that I maked).
My questiona are:

1._Is to much current 50AV for two green and one PSU V4?? or is OK for two greens or four??

2._This may damage the psu and green´s circuits??

The problem was that only transformer that I can buy here!!

yes, are  beginner questions sorry!

regards
Juanjo

 

[peterc]

Hi Juanjo

This transformer will be fine for up to 8 pres. So 2 or 4 will be no problem.

Regards
Peter

 

[juanjovincenzo]

Thanks Peter!

I´m constructing two Greens (I transfered the layout and made the PBCs V14) but with this transformer maybe I will try to "built" a couple more.


Regards and really Happy New Year!

Mucha Suerte! y Chao

Juanjo