UCD400s shut-off (or clip?) intermittently when the iron is in use at home

jdec

Member
2007-06-27 6:39 pm
Hi,

Hope somebody can help me with this, I'd really appreciate it.

I finished to build my stereo amp with Hypex ucd400s.

Everything seemed to work well for approx. half an hour until my wife started to iron some clothes. The amp started to shut-off (or clip?) intermittently (just to give an idea, about 1 or 2 seconds "off", and then 10 to 20 seconds "on" and so on) while the iron was turned on, like if some sort of protection was activated.

I measured the voltage from the power supply rails when the iron was in duty, and the meter displayed around 60 VDC, which is ok for the ucd400s. (I'm using a 40V secondary transformer, and the AC voltage at home has never surpassed 128 V)

Is this normal with the ucd's? if not, does anybody know what could be causing the issue?

By the way, I saw the following comment in audiogon.com some time ago from someone who owned the Channel Island Audio D-200 (ucd400 based), maybe it's something similar to my issue:

However, the D-200's would clip when an electrical appliance would kick on in my house and I never had that happen with my Bel canto amps.

What do you guys think?

Thanks for any input.
 
What is probably happen is that the iron is causing the line voltage to dip below the point at which the amplifier shuts off.

Irons have pretty powerful elements, I've seen some with up to 1200W. They aren't always on of course, the iron has a thermostat which kicks in when the temperature falls below the set point. The 20 sec interval at which your amp is turning off I'm quite sure corresponds to how often the iron's thermostat kicks in. If you plug a normal incandescent light bulb into the same outlet or circuit as the iron you'll probably see it dim from time to time.

What I'd do is I'd measure the AC mains voltage while the iron is plugged in. See if it drops significantly below 115V when the iron's thermostat kicks in.

Another possibility, though less likely, is that when the iron's thermostat kicks in and out it's creating a surge just big enough to cause the amp's over-voltage protection to kick in.
 

jdec

Member
2007-06-27 6:39 pm
Thanks for your input.

Actually I realized that sadly it happens not only with the iron, but with the TV or a drier too. When any of these electrical appliaces is turned on, the amplifier cuts out for 1 or 2 seconds and then it works normal. Even with the voltage drop when these kick in, the AC line voltage never goes below 115V. So it's very odd what is causing this, maybe it's a normal situation with the UCDs. Everything is connected correctly, I triple checked.

It seems that I'll have to live with that.

If anyone else have any comment about this please go ahead.

Thanks!
 

BWRX

diyAudio Moderator Emeritus
2005-01-17 5:29 am
Pennsylvania
That's a very interesting problem indeed...

It doesn't quite sound like it's power supply related but we could use some more details about your amps. How do you have the "on" connection wired up? Do you have it going directly to the power supply ground or earth ground? Does it go through a switch? It almost sounds like there could be some sort of ground bounce causing the "on" signal to turn the amp off intermittently. Or the other devices in your home are causing line voltage spikes which causes your power supply voltage to increase briefly which trips the over voltage protection. I don't know if the over voltage protection is of the latching type that can only be reset by powering down the amp or if it automatically resets after a set period of time.
 

jdec

Member
2007-06-27 6:39 pm
BWRX said:
That's a very interesting problem indeed...

It doesn't quite sound like it's power supply related but we could use some more details about your amps. How do you have the "on" connection wired up? Do you have it going directly to the power supply ground or earth ground? Does it go through a switch? It almost sounds like there could be some sort of ground bounce causing the "on" signal to turn the amp off intermittently. Or the other devices in your home are causing line voltage spikes which causes your power supply voltage to increase briefly which trips the over voltage protection. I don't know if the over voltage protection is of the latching type that can only be reset by powering down the amp or if it automatically resets after a set period of time.

Sorry for the delay to respond.

The "on" connection goes directly (no switch) to the "on" (input?) on the Hypex HG power supply. This seems to be correct, right?

This issue is becoming pretty annoying. When the amps cut out, one or two strong pops are heard from the speakers at the same time that the blue LEDs on the UCD modules turn off. Then the amp stabilizes (LED's on again) about 2 seconds later, and music sounds good.

Like I said, this happens every time a TV, drier, microwave oven, iron, etc has been just turned on at home, and stabilizes almost immediately (except when the electrical appliance is the iron, which thermostat kicks in intermittently). That is, the intermittent pattern I originally reported happens only with the iron, no with the other appliances.

I have checked the AC voltage with my multimeter when these events occur, and it does never look like the voltage goes below 115V or above 130V (unless it happens quickly enough to not see it displayed on the meter). So if the overvoltage protection is being activated, I don't now why.

What would you suggest me?

Thanks for any input.
 
Hmmm, I have my "on" connected to gnd through a switch. I think if you pull it to gnd it will mute. Try disconnecting the "on" cable (or short it to power supply gnd -don't remember exactly if gnd is mute or unmute) perhaps the delay startup in the hypex ps is acting up... I have a picture here http://picasaweb.google.com/bugandang/Hifi/photo?authkey=xDyo5wY0VJY#5135086473763450354
The control cable goes through a switch and then to the GND terminal of the module... Hope this helps
 
Hi all,
What I did when confronted with similar problems: I bought a UPS via Ebay for about £30, and hooked it up to all my HiFi kit, this included the UCD's I built.
There are a number of advantages:
No dips in the mains that cause problems, excessive noise and spikes to your equipment, plus you get a very stable mains, which will allow you to run the UCD's close to the maximum rail voltage without them cuting out.

I have also observed and heard that the foundation of the music is improved.

Cheers, Arthur