UcD400 Q & A

[ghemink]

Originally posted by ghemink



I think Jan-Peter has mentioned it somewhere that is was connected to GND via a capacitor. I just checked one of my UcD400 modules 4 you. It is indeed connected to GND via a capacitor (100nF according to my DMM).

Best regards

Gertjan

Does anybody know the value of L1-L6? These L's are there (at least that is my guess) to prevent or reduce the amount of HF noise leaving via the power rails outside the module. Also C16 and C17 are small decoupling caps directly at the + and - supply pins. With the L's they form a second order low pass filter at some frequency which would be interesting to know.

Best regards

Gertjan

[lne937s]

Originally posted by ghemink



This is for sure not good. I advise to check the power supply first without any amps connected to reduce the risk of blowing up more parts than needed. Are you sure both transformers give the same output voltage? Be carefull with the power supply caps, what is their voltage rating? They should not be overloaded too much. If those big guys explode, you have a real mess., be careful.

Good luck

Gertjan

Well, I checked everything and it seems I had a couple bad capacitors. Transformers, rectifiers, etc were within .1 v of each other, but the voltage change happened when I hooked up the caps. At first, there was just a huge difference in voltage. Then, the + rail voltage increased when the amplifier was turned on until it tripped the overvoltage protection. Now I think I have two good caps and am reading 59v+-, but when I hooked up the amps, I get nothing, no led, no sound- nothing. Did I fry something? How could I tell/where should I look to figure it out?

If I ended up killing the amps because I used cheap surplus caps, I am not going to be happy... Somebody please tell me there is an easy fix.

Thanks,
Larry

[ghemink]

Originally posted by lne937s



Well, I checked everything and it seems I had a couple bad capacitors. Transformers, rectifiers, etc were within .1 v of each other, but the voltage change happened when I hooked up the caps. At first, there was just a huge difference in voltage. Then, the + rail voltage increased when the amplifier was turned on until it tripped the overvoltage protection. Now I think I have two good caps and am reading 59v+-, but when I hooked up the amps, I get nothing, no led, no sound- nothing. Did I fry something? How could I tell/where should I look to figure it out?

If I ended up killing the amps because I used cheap surplus caps, I am not going to be happy... Somebody please tell me there is an easy fix.

Thanks,
Larry

Did you connect the /on pin next to the input pins to GND? If you don`t connect that pin to GND, the led will not go on since the amp will be switched off.

Hope this is your easy fix that you are hoping for.

Best regards

Gertjan

[lne937s]

Originally posted by ghemink



Did you connect the /on pin next to the input pins to GND? If you don`t connect that pin to GND, the led will not go on since the amp will be switched off.

Hope this is your easy fix that you are hoping for.

Best regards

Gertjan

I checked the ground connection and it seems fine. Where else can I look? I'm thinking I knocked the voltage protection open and got it stuck. I assume it is some kind of relay- should I try to bypass it to test this assumption and then replace it if that is the case? how would I go about doing that? I obviously would rather replace a relay than an entire unit...

I don't know if this info helps, but when I powered down the amp after I tested to see if I could get the modules to light up, the capacitors discharged as if they had a ~1kohm resistor across them.

I was planning to eventually purchase a couple more units to biamp (I figure the ~1.5kVA worth of transformers will easily handle 4 ucd400s and I was going to buy new caps anyway), but I would really love to get the first two back up- both to save money and to get a chance to listen to them. I recently returned to work after being laid off for a couple months (the joys of advertising), so money is still a little tight. I am learning that cutting corners in some places (cheap caps) can end up costing more in the long run.

Thanks for all the advise so far...

Larry

[heresie]

Hello everybody,

I have just bought 2 ucd400 and 2 transformers of 2x45V (on load, 5% regulation , 46V mesured off load) by basing me on the specifications that adire recommends. is this too much? I am good to return it?
I had not read the beginning of this post which advises 2x38v rather

Or it s not to dangerous to use them because the overvoltage protection may work?

I want to use it for my subwoofer (15Hz-400hz) so i need much power

Thank you very much of your assistance

Best regards,
Avi

[Jan-Peter]

Heresis,

This voltage is quite high I recommend to go for 2 x 42AC. Supose the mains voltage is a little bit higher the amplifier will go very easy in overvoltage protection.

Good luck!

Regards,

Jan-Peter

[heresie]

Thank you Jan peter for the reply ,

So there is no way to reduce the voltage for 2-3v in the same way that the bridge rectifier do?

Or maybe can i modifie the overvoltage protection but then i will lose the garantie and is it dangerous for the ucd400? (if i change it to 66V)

Thank you very much, because that would be complicated to return my 2 transformers

[Jan-Peter]

Heresis,

For bypass the overvoltage protection remove D19 and D20.

Of course you will not have guarantuee more.....

And mount the module not horizontal but vertical, this improves the airflow around the PCB.


Regards,

Jan-Peter

[lne937s]

So I bypassed the overvoltage protection (thanks for the info Jan-Peter) and luckily, that (as far as I can tell) was all I damaged on the modules.

However, when I power them up I had the same problem as before- the positive rail voltage went up while the negative went down. Before, I figured it was just bad caps- but I wanted to check before I went out and bought new ones. What causes this? I'm not an engineer and this is my first project- so I have the feeling I am doing something wrong.

From the rectifiers, I am getting steady 59.5-59.7 volts DC on both rails with no load. The transformers are staying within .1v AC of each other. The positive rail's cap has the rail connected to the terminal labled + on the cap and the ground on the other terminal. On the negative rail, the ground is connected to the + terminal.

Both of the caps are on an alumunum shelf directly above the transformers. Would the proximity to the transformers do this? Unfortunately, the caps are huge (7"high x 3"dia each) and the transformers are huge (6.5"dia by 3.5"high each) and I don't have much room to move them within the 1cubic foot enclosure I built.

I will eventually be buying better caps, but I just want to check to make sure I am doing everything right first.

Thanks,
Larry

[Jan-Peter]

Can you put all +/- inputs to ground?

Because I think you have a problem with DC at the input. When the output of the amp has more as 100mV DC you will pump your power supply. I think this is your problem!

Jan-Peter