All things Green Pre

[peterc]

I think it will work with -21v but it's not good for audio, that's fer sure.

2 things:

Check the diode across the in/out of the LM337 is put in with the correct polarity.

The 337 could be broken & passing the input voltage straight through to the output. Replace if needed.

Peter

 

[matta]

Hey Adam,

What Pete said, and which I mentioned in an e-mail. The other to check is your resistors like I said. The output voltage of the regs are set by a resistor pair, even a few ohms as I mentioned can make difference, so mistaking a 130R instead on an 120R will increase the voltage from -15V to -18V.

I suspect that you may have broken your Reg though if neither of the above suggestions work for you.

There are not alot of components on each rail so it should be easy to troubleshoot.

I have bombarded Matta with a bunch of questions (in which I am grateful) and I don't want to bug him too much

No worries, if I can answer I will.

Hope that helps.

Matt

 

[bluezplaya]

I think it will work with -21v but it's not good for audio, that's fer sure.

It definitely works! Just want to make it right!

Check the diode across the in/out of the LM337 is put in with the correct polarity.

Good to go, there. I am using the older board where diodes are opposite each other.

The output voltage of the regs are set by a resistor pair, even a few ohms as I mentioned can make difference, so mistaking a 130R instead on an 120R will increase the voltage from -15V to -18V.

All good there as well :wink:

The 337 could be broken & passing the input voltage straight through to the output. Replace if needed.

I suspect that you may have broken your Reg though if neither of the above suggestions work for you.

That's probably the solution. I'll get another 337. I just replaced the 48v 317. It must be a "Voltage Regulator strike" this week.

Also, my LED's are not working. :? New LM339's?!

Thanks tremendously for all the help!!

Adam
:sam:

 

[bluezplaya]

Just got my 337 voltage regulator in from Mouser, along with my 5532 opamp, dropped them in. I'm getting 15.2 and -14.8 on the rails, and both Green pre's working superbly!! :grin:

Thank you Matt and Peter (Hey, weren't those the names of some Saints?)

I'm ready for two more of these babies. However, my LED's aren't working? Do you think it's a bad LM339?


Adam
:sam:

 

[peterc]

317's & 337's can be very sensitive to... well virtually anything. I blew up a couple by not having a cap on the outputs.

Check the 074 to see that the signal is being recitfied. Measure on the DC scale & see if the DC voltage goes up n down as the amplitude changes.

Make sure this is getting to the 339.

Peter

 

[matta]

Hey Adam,

Glad you got them up and running :thumb:

I'd try pop in a new LM339 and recheck em, just buy one new and and test it out and if it works in one, most prob same issue with the second one.

Enjoy your new pres, they sound great!

Cheers

Matt

 

[Luke]

hey, I've been having a lot of touble with this PSU board..(I am using the one from peterc's site, with diodes facing diff directions)

I get a fluctuating +17 - +30V on the +15

Steady -20 on -15

steady +35 on the +48

just replaced the LM317 on the +15, didn't do anything...


Any Ideas? I was thinking of replacing the diodes on the two rails. Seems like its got to be something in there, don't think its a resistor issue, i've checked them like a hundred times, but who knows. Probably blew the Reg again with that high of voltage coming out of it, going to get some more.

One thing is that on your document it shows 21V DC on the big cap before the reg, so it should never get up over that right? that makes be think maybe the input caps are bad?

thanks for the help

Edit:spelling

 

[peterc]

First the +- 15v:

Pull out the regs, make sure the voltages are correct & steady with just the rectifier & smoothing caps.

Put in one reg with no bypass diode. Make sure it works.

Then the next.

Then put in the bypass diodes, the correct way. I'm pretty sure your neg supply problem is either a bad reg or a wrongly soldered bypass diode.

Phantom:

Put in 2 diodes & caps, check the voltage. If too low, put in another diode & cap. Keep going until the voltage is high enough to regulate down to 48.

Peter

 

[Luke]

hmm, wierd results...

I took out the diodes and regs and measured voltages

I am getting 33.5V out of the rectifier when you show 21.5V...I checked my wires in from the transformer and they are showing 24VAC, which makes me think they gave me the wrong transformer or I screwed something up with it...

heres my tranfo:

http://rocky.digikey.com/WebLib/Amveco-Talema/Web%20Data/62000%20Series%20Low%20Profile%20Miniature%20Transformers.pdf

I got the 62083 at the bottom, seems like this should be putting out 15VAC...or I guess 17VAC with no load like it says in the data sheet, but 24 seems way too high.

Primaries:
I have red,yellow going to nuetral, black and purple to Hot
Secondaries:
blue & green to 15VAC on board, Red & brown to chassis ground then to 0V on board.

Now for the even wierder part, I tested my input voltage and it is 165 VAC, there is no way the wiring in this place is that far off (US 120 VAC wiring), seems like my DMM might just plain suck!

I also checked the phantom and it is 90V coming into the reg, seems plenty high enough(maybe too high?), this is with 3 diodes/caps.

A little worried with all these high voltage measurements, my input electros are 35V and its getting very close to that, 90V is getting close to the 100V electros I have in phantom...

Any ideas? thanks

 

[peterc]

Secondaries:
blue & green to 15VAC on board,

I assume these are not joined together, but go to the separate 15v AC inputs on the PSU? :grin:

How's the battery in your meter? Even if it is new, try another. Sometimes they sit on the shelf for ages & they only have a 9 month shelf life.

Peter

 

[Luke]

I assume these are not joined together, but go to the separate 15v AC inputs on the PSU?

No, I haven't screwed up quite that bad...

Replaced the DMM battery, now I am getting sane values for AC volts, like 120 in and 18VAC on the Tranfo otuputs...

The rectified voltage into the regs is 24.5, this is a little higher than your doc says, but then again my transformer is at 18VAC right now, i guess that could be due to not having any load? Maybe bad rectifier?

the positive rail still jumps around, from like 15V - 23 V, i don't know what could cause the voltage to move like that, I am going to get some more regs, but this was a newer one...

neg rail is doing bouncing a little, staying around -19.8V

phantom is coming into the reg at 70V, which I believe is good, but output ting 26V, so I am guessing blown reg?

this is all without those diodes on the rails...

next time I will definitely build the PSU, hook up tranfo in pieces like you suggest, but this is my first rack project so, live and learn...

 

[matta]

Hey Luke,

Can you shoot a details pic of the PSU as it is now, so I can see the components clearly and I'll take a look at it for you, just to triple check your component layout?

If you can't host it, e-mail it to me matt(@)matt-allison(.)com (Remove the brackets)

Cheers

Matt

 

[Luke]

thanks for the help matt, got the psu working...

the only thing is I have some quite noticeable hum, noise floor is at -48 db. Any thoughts on what a newbie might do wrong when racking these up to cause this, I moved it away from the psu and still am getting it.

Grounding seems the most obvious.

I have the sleeve of trs in to star gnd and trs out to gnd, my center tap of my tranny is also going to gnd.

there was no hum when I had it hooked up to my bench supply so I am pretty sure it has something to do with psu/grounding/ tranfo issues.

thanks

EDIT: Got it working, didn't have every ground going to the star, made a big difference

 

[Luke]

I think this has been covered before but I couldn't find it again,

to leave output trim off just short the pins closest to switches

to leave out phase switch just connect pcb holes next to edge of board with middle.


is this correct?

 

[peterc]

Check your ripple on the + & - rails, using AC volts on your meter, This could be the hum source.

The pad connections sound fine.

Regards
Peter

 

[kato]

Would this transformer work for power for 2 channels of green?

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=122-605

I still haven't found mention of this part in N.America. (still wading through the meta...)

Thanks for any advice, Kato

 

[peterc]

Would this transformer work for power for 2 channels of green?

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=122-605

Looks good to me. Will work for up to 8 channels.....

Peter

 

[peterc]

Here are some tips on getting the phase of the mains transformer right, for those units that have multiple primary & secondary windings.

Remember, if windings are out of phase, they will cancel the voltage. If you use mains voltage, & the windings are out of phase, the transformers will get HOT & eventually self-destruct.

http://www.groupdiy.com/index.php?topic=10005&sid=3e9f662c414603fbad28d70bf780ea77

What I do when wiring a mains transformer, is to solder the connections as per the datasheet & before applying mains power, I hook up my signal generator to the mains transformer.

If you put 1v (at about 60Hz) onto the primary, set your voltmeter to AC volts & measure across the primary. There should be no drop across the primary windings. If the level drops acroos the primaries, they are out of phase, swap one of the windings.

Measure the voltage on the secondaries. Each secondary should read about 130-140mV . Across both secodaries should give you double, about 270mV or so.

Once I am happy with this, I connect the transformer to the mains. I have made up a mains cable with a fuse holder & 100mA fuse inline, so if there are any shorts in my transformer, the fuse will blow rather than the transformer or the house circuit breaker.

Do not connect anything to the transformer secondaries yet.

I switch on for a few seconds, & switch off. Smell for anything odd, smoke for e.g. Check the fuse. If everything is OK, switch on again, measure the voltages on the transformer secondaries, should be a little more than 15v, around 16v with no load (PSU) connected. Be aware of any excessive heat anywhere, hot resistors or diodes, etc.

All OK? Now connect the PSU circuit to the secondaries. Switch on, switch off, smell again. Once happy, switch on again & measure to check the voltages on the outputs of the PSU.

Then connect the project to the PSU, & go through the same process again. Checking the rail voltages is the first thing to do. If your +15v or -15v (one or the other, or both) are not reading correctly, there is a problem.

Just call me Mr Cautious Wink

 

[strahl]

I just finished my first DIY ever, a four channel green pre with a lot of help from my best friend. Everything works as its meant to I think =) All thats left now is to polish it a little and get some labels for the switches.

Check out some pictures here if you want to: http://www.thecloud.se/green/

I also got to get myself a drillpress since working that frontplate on freehand didn't work that well as you can see :grin: But you can tell its a DIY :wink:

 

[peterc]

Well done Dennis, looks quite good for hand drilling!

Peter