Fabio R312 (X 2) & Fabio PSU Build - Final Couple of Steps - Please Help Noob !!

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Whoops

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Just for reference CAPI VP312 schematic using the same transformer as yours the EA2622

http://www.capi-gear.com/catalog/images/gallery/VP312/VP312-VPR-Rev-A-schematic.pdf
 

Sun King

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Hello again Whoops,

I hope you are well.  I have now soldered both boards' input transformers correctly (i think).  Here is an image.
mvtf8o.jpg


In addition to this I wondered if you might be able to shed any light on the following?  I have colour marked the areas in question on the following image of the PCB layout.
2ebv2tw.jpg


I have populated the whole board so as to get all the functionality that this design intends (although Harpo pointed out that I should not have put in the IC for U1 because the gar2520 already does that job), but was wondering about the IC that I put in for SERVO.

Exactly what is SERVO OUT used for?

Also, what is UNBAL for?  Is it an unbalanced xlr input connection?

Next question is what is SW_LINE for?

Finally is it recommended to connect a VU meter?  Can you just solder any old VU meter into place on this circuit?  Or do you need a separate daughter board with something like a U237 or LM3914 IC LED bar graph display?

Any help on these is much appreciated as ever.

Cheers

Ben  :)
 

Whoops

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I have now soldered both boards' input transformers correctly (i think).  Here is an image.

Transformer primaries look good, where did you put the 1000pf caps, on the top side of the PCB?

In addition to this I wondered if you might be able to shed any light on the following?  I have colour marked the areas in question on the following image of the PCB layout.

Ben, I never did this Reliquia 312 project, and as I told you it's a really old project.
All your questions and doubts were already answered in the proper thread :
http://groupdiy.com/index.php?topic=246.20

There's really no shortcuts to finish the projects, you have to read the project specific threads otherwise the forum would be full of threads asking the same questions.
When I start a new project what I do , is to open a word document , call it in this case "Reliquia 312 Compilation", and then read the thread, every time there's useful info for me in the thread I copy it to the word doc, I read the thread fast, as I skip the posts that are not usefully to me. You should do the same.
That thread is long, but all your questions will be answered in the first 35 pages probably. And  you will have a much better knowledge after reading it.

I have populated the whole board so as to get all the functionality that this design intends (although Harpo pointed out that I should not have put in the IC for U1 because the gar2520 already does that job), but was wondering about the IC that I put in for SERVO. Exactly what is SERVO OUT used for?

The Output transformer provides a Balanced Output,
the Servo Out provides a Balanced output in case you don't use an output transformer,
you are using an Output transformer so you don't need any components on the servo out part of the pcb, skip it


Also, what is UNBAL for?  Is it an unbalanced xlr input connection

Google "balanced and unbalanced audio connections"
Google "schematic symbol for XLR"
Google "Schematic symbol for TS jack"

Next question is what is SW_LINE for?

You have 2 inputs on the Pre,
Mic input and Line input
Switch to change input from Mic to Line?

Finally is it recommended to connect a VU meter?  Can you just solder any old VU meter into place on this circuit?  Or do you need a separate daughter board with something like a U237 or LM3914 IC LED bar graph display?

Have no idea really,
go here:

http://groupdiy.com/index.php?topic=246.20
 

Sun King

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Hi Whoops,

Sorry I didn't reply sooner.  I was away for a few weeks. Thanks for your last post, it is good advice.

I sussed out which components to remove as i have no need for the SERVO option, or the UNBAL output at this stage.  In fact, in doing so, I felt like i learned more about the circuit/electronics in general.

It was pretty easy to figure out, as the components are labelled accordingly - RS1, CS1 etc for the SERVO part, and RU1, CU1 etc for the UNBAL section.

At this stage, I nearly have the lot mounted in the 1U case, I was just waiting on some drillbits to arrive that I couldn't find in the workshop which i needed.  24mm for the XLR holes on the back as well as 3mm for the LED mounting clips in the front and screw holes for the XLR connectors. 

I'm hoping to finish the case drilling and mounting (and wiring!) this weekend.

One thing I'm not 100% sure on is the ADJ_NEG & ADJ_POS on the PSU circuit.  Am I right in thinking that this is where one fine tunes the + & - voltage so as to get both as close as possible to +18V & -18V to power BOTH the pre-amps?

As I understand it, both pres gar2520s ideally need 18V.  As the newb that i am, i've got it into my head that there will be enough to send 18V to each preamp.  Is this correct do you think?

Regards

Ben
 

Whoops

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I sussed out which components to remove as i have no need for the SERVO option, or the UNBAL output at this stage.  In fact, in doing so, I felt like i learned more about the circuit/electronics in general.

Yes, Thats the spirit of this forum and DIY, we keep learning a lot in each project.
Nice that you removed the unneeded components.

At this stage, I nearly have the lot mounted in the 1U case, I was just waiting on some drillbits to arrive that I couldn't find in the workshop which i needed.  24mm for the XLR holes on the back as well as 3mm for the LED mounting clips in the front and screw holes for the XLR connectors. 

I use a Stepped Drills for the XLR holes,
picture attached to this email.
I make a small center hole, and them use the stepped drill.


I'm hoping to finish the case drilling and mounting (and wiring!) this weekend.

Thats a good Plan, let me know how it goes


One thing I'm not 100% sure on is the ADJ_NEG & ADJ_POS on the PSU circuit.  Am I right in thinking that this is where one fine tunes the + & - voltage so as to get both as close as possible to +18V & -18V to power BOTH the pre-amps?
As I understand it, both pres gar2520s ideally need 18V.  As the newb that i am, i've got it into my head that there will be enough to send 18V to each preamp.  Is this correct do you think?


LM317 and LM337 are regulators that can be adjusted to a desired voltage, they are not like the 7815 or 7915 (+15v and -15v) that are regulators for a fixed voltage in this case 15V, in the case of 7818 or 7918 are fixed for +18V and -18V and so on. So you should adjust the ADJ_NEG & ADJ_POS  Potentiometers for the desired voltage , measure the PSU output without being connect to the Mic Pre and adjust to the value you want. You are setting a rough value this way because theres no load presented.
Then after you connect it to the Mic pres, you can measure again and fine adjust because this way you will have a load and the supply value will have a small drift.


In the capi website it says that the gar2520  "Power supply voltage is bi-polar +/- 12 VDC to +/- 20 VDC" , so 18V will be fine.
I would not go higher than that as it will also run hooter and theres no need for that, no advantages in going higher  and  running cooler is also better.
Actually people as far as I remember were supplying 2520 OPamps with 15V or 16V and thats perfectly fine, it's what API use in the 500 series supply.


You didnt answer my question in the other post:

I have now soldered both boards' input transformers correctly (i think).  Here is an image.

Transformer primaries look good, where did you put the 1000pf caps, on the top side of the PCB?



 

Sun King

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Hi again whoops,

Thanks for your reply. Much appreciated.

I put those caps on the top side of the board.

Do you think this is ok?

Regards

Ben
 

Sun King

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Hi Whoops,

Sorry again, late reply.  Been very busy with lots of different things. 

I've got everything soldered in.  I have hooked up the PSU to the mains and probed with multi meter.

I have +18.1V & - 18.1V (after adjusting the bourns pots).  I have 44.1V (is this enough, was hoping it would be 48V) on the phantom rail, and I have 2.5V on the SW rail (shouldn't this be 5V?).

I have wired up to the preamps and tested with a rode NT2A condenser mic. 

I get nothing!  The only thing I get is a signal from touching/tapping the mic, but does not pick up any live sound (voice, clapping etc).

I have tried both gar2520s in both preamps, same result in both.

When I switch on the phantom, the LED lights up, but if I then enable the the pad and/or polarity switches, they do not all light up (like the power gets drained) and causes the 48V LED to go off.  I have also tried the DI and no sound. 

I haven't hooked the chasssis ground yet, would this stop it from operating properly while testing?

Also, I have used the same solid core copper hook up wire for the mic in and line out connections  (does this matter? Should it be stranded?), making sure pin 2 goes to pin 2 of the XLR connectors, and pin 3 goes to pin 3 of the XLR connectors,

I have cleaned all boards with tooth brush and alcohol and re-checked continuity with multimeter (as I had done the whole time while in the soldering stage).

I'm stuck!  Can you help!?

Regards

Ben
 

Whoops

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Sun King said:
I have +18.1V & - 18.1V (after adjusting the bourns pots).  I have 44.1V (is this enough, was hoping it would be 48V) on the phantom rail, and I have 2.5V on the SW rail (shouldn't this be 5V?).

lower the positive and negative rails from 18V to 16V for now, there is not a lot of improvement in terms of headroom in having them at 18V  but I guess the Opamps will run a bit hot in temperature, dont need that now for testing purposes, put them at 16v and decide in the future if you want higher voltage.

For the Phantom power rail 44V is completely fine, most mics work with a much smaller voltage and I never seen you condenser that didn't work at 44V phantom power supply.
Anyway you should be able to set it to 48V, but leave it at 44V for now.

have you done this?
"Lastly......Harpo mentioned something about leaving out the voltage doubler caps C11 and C12 on the PSU.
Also, Harpo said "better use a TL783 or at least a LM317HT instead of a LM317 for REG48 and for +48VDC out instead of +44VDC out use 220R instead of 240R for R7".  "

What DC voltage do you measure after the Rectification? (after D9 /D10 and D11/D12)

has for SW, if you have an 7812 on the SW rail then you should have 12V DC on that rail ouput

Sun King said:
I have wired up to the preamps and tested with a rode NT2A condenser mic. 

Use a Dynamic Mic for testing purposes at the moment so no phantom power is needed, for now you just want to make it work, like an SM57 or SM58

Anyway with phantom power on, measure DC voltages in input XLR pins, Pin1 to pin2 and pin1 to pin3

Sun King said:
  I have tried both gar2520s in both preamps, same result in both.

Who built the 2520? did you tried the opamps in another working preamp to check if they're fine?

Sun King said:
When I switch on the phantom, the LED lights up, but if I then enable the the pad and/or polarity switches, they do not all light up (like the power gets drained) and causes the 48V LED to go off.  I have also tried the DI and no sound. 

As I told you I never done this project, But if you used relays for switching and those are suppose to receive 12V then if you are supplying them 2.5v it will not work. So you have to sort out the problem in that PSU rail before even plugging a mic in.
Only test again when that rail is fine.

Sun King said:
I haven't hooked the chasssis ground yet, would this stop it from operating properly while testing?

If you already have a case,  yes, connect properly all the signal ground, chassis and Earth connections

Sun King said:
Also, I have used the same solid core copper hook up wire for the mic in and line out connections  (does this matter? Should it be stranded?), making sure pin 2 goes to pin 2 of the XLR connectors, and pin 3 goes to pin 3 of the XLR connectors

use whatever you like, just make sure the connections are made


you should as I advised before do this:~

"Ben, I never did this Reliquia 312 project, and as I told you it's a really old project.
All your questions and doubts were already answered in the proper thread :
http://groupdiy.com/index.php?topic=246.20

There's really no shortcuts to finish the projects, you have to read the project specific threads otherwise the forum would be full of threads asking the same questions.
When I start a new project what I do , is to open a word document , call it in this case "Reliquia 312 Compilation", and then read the thread, every time there's useful info for me in the thread I copy it to the word doc, I read the thread fast, as I skip the posts that are not usefully to me. You should do the same."


For troubleshooting  you should have an audio/signal probe:

http://www.freestompboxes.org/viewtopic.php?f=51&t=6820
 

Sun King

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Hi Whoops,

Thanks for your reply.  So very much appreciated.  :)

I'm actually getting sound through an SM58 now and the DI works too!  This is on the one preamp that i have hooked up so far, and with both gar2520s, it works! 


lower the positive and negative rails from 18V to 16V for now, there is not a lot of improvement in terms of headroom in having them at 18V  but I guess the Opamps will run a bit hot in temperature, dont need that now for testing purposes, put them at 16v and decide in the future if you want higher voltage.

Have done this.  both + & - are exactly 16V.

For the Phantom power rail 44V is completely fine, most mics work with a much smaller voltage and I never seen you condenser that didn't work at 44V phantom power supply.
Anyway you should be able to set it to 48V, but leave it at 44V for now.

OK great.  That'll be fine for now then.

have you done this?
"Lastly......Harpo mentioned something about leaving out the voltage doubler caps C11 and C12 on the PSU.
Also, Harpo said "better use a TL783 or at least a LM317HT instead of a LM317 for REG48 and for +48VDC out instead of +44VDC out use 220R instead of 240R for R7".  "

I haven't removed those caps (as I couldn't see that anybody else had for this build). 

I had a TL783C in there for REG48 as per Harpo's advice, but the leads were bent to the point of snapping, so I just put in an LM317 that I had spare in there for now (since your last message), still getting 44VDC there.

DC voltage I measure after D9/D10 = 49.1VDC and after D11/D12 = 20-23VDC (fluctuates up and down - rises, falls, rises etc)

I had an LM7805C in REG_SW, but have now put an LM7824C which now gives me 21.9VDC on the SW rail.

Anyway with phantom power on, measure DC voltages in input XLR pins, Pin1 to pin2 and pin1 to pin3

I am getting 44VDC when i probe GND to pin 2, and 44VDC when I probe GND to pin 3 (I'm getting a really low reading that fluctuates just above and below 0VDC if I touch pin 1 to pins 2 or 3, but I assuming it's because i've not yet grounded those pins (1) to the common ground yet?)

edit: the Polarity flip & Pad also works.  It sounds good!

I feel ever so close now Whoops! 

Thanks so much for your help. 

I can't tell you how grateful i am! 

It's just the condenser mic that I'm not getting signal on now!!!

regards

Ben
 

Sun King

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Could it just be that without the grounding to PIN 1 of the XLR that it's not working with a condenser mic?
 

Whoops

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Sun King said:
Could it just be that without the grounding to PIN 1 of the XLR that it's not working with a condenser mic?

Yes, because it's not receiving phantom power, there's no ground reference.

All Pin 1 XLR inputs should connect to chassis

Chassis should connect to Earth Pin on Power prong

0V on PSU should connect to 10r (2watt) resistor in parallel with 0.1uf (63v) cap and then to Chassis

0V of  each Mic Pre PCB separately should connect to 0V on PSU


 

Whoops

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Sun King said:
REG48 and for +48VDC out instead of +44VDC out use 220R instead of 240R for R7".  "

DC voltage I measure after D9/D10 = 49.1VDC and after D11/D12 = 20-23VDC (fluctuates up and down - rises, falls, rises etc)

Did you Change R7 for 220R?


I had an LM7805C in REG_SW, but have now put an LM7824C which now gives me 21.9VDC on the SW rail.

out of an 7824 you should have 24V , you are getting lower than that so or the regulator is shot or you are not feeding it the voltage it needs. A 7824 regulator will need at least 25,5v dc at it's input.

One thing I dont understand,
this rail is for the relays right?
what voltage do you need to supply to your relays? 5v,12v or 24v?

isn't 24v too much for the relays?
 

Sun King

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Thanks Whoops,

I will ground/earth everything tomorrow (still gotta drill some case holes, and then want to perform the famous 'star ground' on everything).

I did not swap R7 (yet........)

As far as the relays are concerned, they are the 12V kind.  The voltage I have, I think covers the voltage needed for both preamps if they are running with all 'functions' enabled? (POL & PAD)

I noticed that with one preamp running, that the voltage drops on SW, if i switch on the POL & PAD. I can only imagine, that it needs the rest for the other preamp, if you have both running at the same time (which i will!!)?
 

Whoops

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Sun King said:
I did not swap R7 (yet........)

So how are you hoping to have 48V?
you have the info that for "48V use 220R instead of 240R for R7"


If your relays are 12V types why are you using a 7824?
you want the switch rail to be 12v dont you?
 

Sun King

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I will change that resistor, but i don't have one handy at the moment.

as for the LM7824, it was another thing that Harpo mentioned.  If I recall, it was taking into account the voltage draw that both preamps would need for the relays.  Do you think this is wrong?
 

Whoops

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Sun King said:
I will change that resistor, but i don't have one handy at the moment.

as for the LM7824, it was another thing that Harpo mentioned.  If I recall, it was taking into account the voltage draw that both preamps would need for the relays.  Do you think this is wrong?

Where did Harpo say that?

Please read what I wrote in other posts.

7824 regulates to 24v dc
If the relays are 12v you should use a 7812 regulator  so the rail ouputs 12v dc
 

Sun King

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Hi Whoops,

Sorry, it wasn't Harpo (sorry Harpo) who said that.  It was on one of the BOMs that you linked me to for the PSU (where I was able to obtain the info for the missing resistor values that I didn't have).

It must have been that they were using higher voltage relays than 12V.

What I will do, is replace the LM7824 with the LM7812 for REG_SW, and also I will get another TL783 to put in place of the LM317 that I temporarily have in for REG48.

Also, I will swap the 240R for R7 with a 220R to achieve 48VDC for phantom power.

Many thanks.

ps. The next build I will be doing, will be based on the Access-312 design, as per your advice, as there are less components, and can fit 4 in a 1U case!

Ben
 
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