Thanks Manu ! Voltage behind rectifier bridge is 33.9 Volts without load.
Should be ok for ST Microelectronics regulators with spec: max. 35 Volts input. I had that "ST" regulator in the board for one year before the amp stopped to work. I will put a new one of the same type in as next step.
Regarding power consumption:
Layout is: Transformer 24V AC 8VA => 7809 regulator => uC board with 7805 regulator => Atmel CPU & VFD Display
Atmel Atmega64 specification says consumption between 200 to 400mAmps.
Newhaven VFD M0220MD-202MDAR1-3 consumes 290 to 435 mAmps.
Total: 490 - 835 mAmps *5Volts = 2.5 to 4.2 Watt.
On top of that comes dissipation of the 7809:
( 33Vin - 9Vout) * 490mAmp = 11.8 Watt
( 33Vin - 9Vout ) * 835 mAmp = 20 Watt
Total: 14.3 to 24.2 Watts power draw, clearly exceeding the 8VA per side rating of the transformer.
So, maybe the transformer is the root cause of the problem.
I noticed also in past year the power supply got quite warm when in operation....
I wonder why not many of the other UGS builders in France have same problems....many builds were made according to same BOM / Layout.
What kind of Display and central Transformer do you use in your UGS ?
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I use the so called " as blind as a bat" big blue Christallfontz display
Which is not so power demanding ...
And on the PSU side : 12V relays to avoid the reg problem ...
(the first one was running 24V relays without problems though)
Trafo is 16VA (ERA EI54 or block) from Reichelt if I recall right (I am not at home right now and can't check)
Hope you solved your problem ..
Manu
Hi all!
Does anybody have crystalfontz display (CFAH2002L) they would like to sell?
Thanks
I got mine here for 31,80 EURO: www.lcd-store.de
Pass DIY Addict
Joined 2000
Paid Member
Hope you solved your problem ..
Manu
Tried, tried, but no success yet.
I rebuild completely the Logic/Relais section in power supply.
The Mikroprozessor board is working again...yeah....but the relais boards are not working.
First I checked the Mikroprozessor. This one was ok, it switched it outputs between 0V and 5 Volt.
Then I checked the power supply for the Relais boards. Voltage breaks down from 24 Volt to 2.3 volt.
I inserted a 10 Ohm resistor into the 24V supply line for the Relais boards.
measuring 10Volt across the 10 Ohm resistor !
My math says that the relais boards are consuming too much current (1 Amp)- and voltage from 7824 regulator breaks down. (I have only 1 channel out of two relais boards connected).
I measured coil resistance of all relais . All are around 2.7 to 2.9 kOhm. So no short circuit here....
There are 3 Darlington Array Chips on the Relais board, which switch the relais. I was thinking that maybe those chips have a short circuit. I unsoldered all 3 Darlington Array chips (ULN2003, ULN2803) from one relais board.
I then inserted a brand new ULN2003 DIP16 into the socket of 1 board. This Dip16 socket chip is responsible only for switching 3 relais. I did NOT solder the other two Darlington Array chips to the board which would handle volume and input switching. I then connected the single (one out of two channels) board to Mikroprozessor board and supply.
Same effect:
The single, new ULN2003 chip consumes 1 Amp current (max. that the 7824 delivers) and gets very hot.....was there some smoke... ?
I am lost....what is wrong here ?
Schematic: http://psykok.homelinux.org/diy/preamp_ugs/Atours/Atours.pdf
PDF page 2:
I did connect only one side.
In the end for testing purposes only IC2 soldered (not IC1, IC3).
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Thank you Meldano. It was indeed a short, but not at relay or capacitors.
I meditated over your suggestion - and only possibility left was then that the short was within the darlington array chips itself - even after I replaced it.
What I never expected was the case: GND and Supply lines were reversed !
The Mikroprocessor board has two identical plugs to connect right and left relay board to it. The plugs are identical, but do have different pin layout (e.g. GND and supply pins switched). So one should not really try to connect the right relay board to the left-channel plug
Fixed it, works again !
Got my UGS pre up and running a couple of months ago but now I will finally get it into its enclosure. I have the transformers and CRC filter in a separate enclosure and the regulators in the UGS enclosure. To UGS enclosure gets the unregulated DC for left and right channels and unregulated 9V DC (to be regulated to 5V for the arduino controlling the pre). The question is then; what ground should I connect the UGS enclosure to? 5V digital ground or the UGS analogue ground? The safety earth only goes to the PSU enclosure.
I would give none of the 2 grounds at ugs enclosure, best would be to simply give direct Earth to ugs enclosure (assuming you left audio gnd and aux gnd floating)
Best,
nAr
Assi
Hi nAr,
When building my XONO I remember reading somewhere that the PSU enclosure should be earthed and the preamp enclosure connected to analogue ground of one channel. That is the reason for my question. Of course I can run the earth from the PSU to the UGS and connect it to the enclosure if that is the best solution. Since my wall outlets do not carry safety earth it will still be floating though. But if I move in the future I may have safety earthed outlets.
That is not usage intended by any real world audio product or even diy audio product.
For safety issues AND noise issues, I recommend strongly you upgrade your mains to get proper Earth support. Or, if you can't do it, bring Earth from the main house electricity closet, where it all starts. If you don't have, use a water pipe that brings water and gets into the ground. Diy, but better than nothing !
Best,
nAr
I am well aware that it is not the best situation but unfortunately that is how it is in Sweden in most buildings older than 20 years. I live in a rental apartment which means I can not modify the electrical system. And if I would do it I would have to upgrade all outlets in my living room since, according to the law, it is not allowed to mix earthed and not earthed outlets in the same room. If grounding my audio equipment to a water pipe I have to ground all other equipment within reach of the audio equipment. If not, and I touch a device with an electrical fault which is not earthed and at the same time touch my audio equipment the safety earth will be through me which is not recommended
I think most Swedish people on diyaudio are in the same situation as me. I have not had any noise issues though.
I now found where I read that the PSU enclosure should be safety earthed and the preamp enclosure connected to signal ground. It is in the Pearl II article;
"The best approach is usually to put the power supply in a separate enclosure, and if you do this, then Earth ground the power supply enclosure and run just the three wires to the circuit – plus, minus, and circuit ground, grounding the gain stage chassis to signal ground."
"The best approach is usually to put the power supply in a separate enclosure, and if you do this, then Earth ground the power supply enclosure and run just the three wires to the circuit – plus, minus, and circuit ground, grounding the gain stage chassis to signal ground."
Perfectly right, and also if you look into original schematic you'll see that single PSU runs the 2 channels. And also, Pearl II has lots of gain so is quieter this way maybe. For an UGS gain is considerably lower so you don't need to do this.
On UGS if you built you probably have one supply for each channel. That means you can't tie signal grounds to enclosure, or you make a loop and loose some of the benefits running dual mono supplies.
On UGS supplies ground A is linked to earth through 10R power resistor. If you run PSU in a separate chassis, Earth to enclosure is always good; then you might use the main audio enclosure with 2 ground A floating from the chassis, and Earth linked to that enclosure.
Best,
nAr