True bypass relays + 12v PSU for Dual mono and Stereo project

This project is perfect for a GSSL, W492 EQ, and others…
Possess its own PSU and doesn't use the main power supply.


The PCB:



Here to buy the PCBs:

http://www.groupdiy.com/index.php?topic=44050.0


The links:





For stereo operation:




Link Left bypass and Right bypass, connect one switch on Dual bypass.



For dual mono operation:




Link Dual bypass and connect one switch on Left bypass and one switch on Right bypass.


Connect XLR inputs/outputs and inputs/outputs from the machine board.


It’s also possible to use the 12V to powered  a Leds.


BOM:


1x diode bridge W04G

1x 1000uF 63v cap radial 7.5mm :

http://fr.farnell.com/jsp/search/productdetail.jsp?SKU=9693076

http://search.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=ECA1JHG102

2x 100nF 63v poly 5mm, C1, C2

4x 1N4004 diodes

1x 7812 Reg TO 220

1x heatsink:

http://cgi.ebay.fr/TO-220-Heatsink-Small-Power-Aluminum-Heat-Sink-x-4pcs-/260481603013?pt=Vintage_Electronics_R2&hash=item3ca5e9d5c5&_trksid=p4634.c0.m14.l1262

4x relais RT424012F:

http://fr.farnell.com/jsp/search/productdetail.jsp?SKU=1608374
http://search.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=RT424012F

11 or 12x 2 pins Molex (facultative).

1X switch for stereo mode or 2X switches for dual mono mode, of your choice.

3 boards on their way - thanks Marc.

boards received today - very fast! - nice quality boards - Thank you very much!

Hi,
do you still sell these boards?
thanks

x2 stereo/dual boards paid

is there a limit regarding the PSU input Voltage ?
thanks

It depends on the 7812 regulator which you use.

Check the datasheet of your reg.

I usually connect a 15V transformer with standard 7812 without problems.

hi marc, i received the boards thank you !
the ST L7812 regulator that i have will support a maximum DC voltage of 35 Volts (as mentioned on the data sheet).
the project i want to use this with (dual LA4) uses an 18V bipolar power supply and your board's PSU is meant to be used with a single supply. i was hoping to use the LA4 power supply's output poles to feed the L7812 regulator directly and ignore the rectifier+capacitor section of your board but that's 36VDC its over the limit !!
is there another solution to avoid the cost/congestion of an extra power transformer ? can someone with the knowledge tell me if it is ok to use one half of the mains transformer wich is 2x18V?? 18x1,414=25,50VDC is perfect but would there be an issue power wise if only one half of the transformer has an extra load to it ? would that have an influence on the main PSU board?
what's the best solution ? hope i'm clear with my explanation...

If your transformer have enough VA to powered the main board and the bypass board, you can use the 18v from the alf transformer.
I often do that

   

my power transformer is rated 830mA per secondary (30VA total)
x2 la4 boards =160mA + x2 VU meter LEDs=40mA + x2 Switch light bulbs=40mA, so that's about 590mA still available for your board right ? now i need to know the relay switching current draw and see if all is ok

I don't know exactely the needed current for the bypass board, but i'm sure that 590mA is much more than enough.

ok if someone has an idea of how much the switching consumes it would be great if they could share their knowledge  : i'm sure there's already some info about this on the forum (and i will do a search right now) but this thread is more than appropriate for divulging such information don't you think ? thanks for your help !

??? from datasheet (see 1st post) http://search.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=RT424012F
this type of relais draws about 33.3mA DC current (12VDC / 360R coil resistance). You've got 4 relais, totaling about 133mA.

Your previous power calculation seems a little off. This 30VA is AC. For DC current this is (2x 15VA) / (2x 18VAC) / k-factor 1.6 for fullwave rectifier, giving roundabout 0.52A, not 0.83A.
From your previous post you need 240mA + 133mA for the relais, so transformer rating seems sufficient,
but iI doubt the needed 40mA for the light bulbs. (FI base T5.5 incandescent lamps for maybe EAO switches @12V supply come in 0.6W or 1.2W, drawing either 50mA or 100mA per lamp and your 'light bulbs' implies plural. Thankfully they have a 14mA LED base T5.5 version as well).

Connect the light bulb on the other alf transformer 

yes i made a mistake, i just checked the 2 switches (EAO) and the bulbs in them are 30V/40mA so that's 80mA total,
it should be ok then, i will give it a shot tomorrow.
thank you !

Hey Marc will these work for Stereo / Dual Mono 1176 projects?  I think they will just wanted to confirm.

Hi Dan,

yes, it can work with all Dual mono or Stereo projects 

But you have to provide a low AC tension that could be regulate by the 7812 reg.

Sweet! Glad I saw these. Do you still sell them?

marcfrom said:

But you have to provide a low AC tension that could be regulate by the 7812 reg.

Click to expand...

So can you explain what you mean by this?  My guess is that the PSU for the 1176 is to big and I need to put some resistors in front of the bypass board so I don't blow it up. 

The L7812CV regulator can accept  35 DC voltage maximum input.

This is the datasheet:

http://www.datasheetcatalog.com/datasheets_pdf/L/7/8/1/L7812CV.shtml

You can mesure it on the board, just after the diode bridge.

So if there is more than 35 volts, you must add a resistor, but i think the G1176 use 25 volts.

What is the AC voltage in the secondary of the transformers on your 1176?

So I should be good to wire the boards directly up off of these transformers.

http://hairballaudio.com/shop/product_info.php?products_id=37

Looks like they are 25v.

Thanks