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Old 23rd May 2008, 10:35 PM   #1
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Default UCD180ST broken?

I have a problem with a hypex UCD180ST module. it produces very distorted music and i have no idea why.

My brother is building an amp based on this module, and today he fired it up for the first time. At first it worked fine, but after he did some fidling it sudenly sounded really really awfull.

Unfortunatly i was away at that time, so i have no idea what happend. He is more a mechanic than an electric person so he couldn't tell me.

I measured the rails and they are good, +41 and -41
He drives the amp with a philips go mp3 player conected to the positive input. The negative input is left open (i know it should be shorted to ground, but after trying that didn't solve anything)
I've checked the module, no obvious burnt/cracked parts or tracks.

You have to turn the volume of the mp3 player up (80%) to hear anything. What you hear almost sounds like extreme class B crosover distortion, its really hard to identify the music.

Does anyone know what this could be, or maybe someone has some suggestions on how to troubleshoot or find the problem? Are there things i can measure or check?
I was thinking maybe the regulators for the frontstage? But on this ucd180ST version they are smd mounted below the circuitboard, and i can't find a layout/explanation were the regulators are located on this ST module (found only HG )

Thanks in advance!
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Old 24th May 2008, 05:07 AM   #2
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Go to our webshop, www.hypexshop.com login, go to 'RMA REPORTS' click on 'Click here to report a new RMA'.

There you can explain everything, print a shipping label and return the amplifier.

We do not disclose any schematic or board layout for repairing by third parties.

Regards,

Jan-Peter
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Old 24th May 2008, 07:40 AM   #3
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Thanks for the reply

I thought about requesting a RMA but perhaps someone on this forum has had a similar experience so i've posted my problem here first. Would be stupid to send the amp back if there's nothing wrong with it and its just a wrong connection or something else very simple.

I noticed a potmeter on the board, what is it for i was wondering?
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Old 24th May 2008, 08:33 AM   #4
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Perhaps here is the problem.....;

Quote:
My brother is building an amp based on this module, and today he fired it up for the first time. At first it worked fine, but after he did some fidling it sudenly sounded really really awfull.
Jan-Peter
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Old 24th May 2008, 11:36 AM   #5
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I didn't realy mean fidling with the UCD but changing stuff like source/speaker/wire-placement. There is not much you can do with the UCD module then connect and let it play. Because it played before and i know the UCD was connected right (i've checked ) i got the feeling that it might be something else.
It sounds almost like a voltage rail is missing, or some serious crossover distortion. I'll try to get a scope to check it out. At first i thought maybe one of the two(?) voltage regulators for the buffer might be malfunctioning. For the HG modules there is some info on the hypex website were the regulators are located. (for regulator bypassing/upgrading)
Can't find any info on the ST modules however. They're not even on the product list?? What is the main difference between a normal HG module (withoug HRxx reg.) and a ST module?

I do think RMA is the best option if there is something wrong with the module, but i would like to know for sure that it IS the module that is causing this.
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Old 24th May 2008, 02:46 PM   #6
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I found an old scope and tested the amp with a 1khz test signal. It seems the ucd only amplifies the positive part of the input signal (as if there is a diode in series with the signal)
The rails are ok, even with a load (lightbulb) they stay at 40.5Volts with virtual no ripple.

Any thoughts on what is going on or how this could have happened?

Will send the ucd back for RMA hope it's an easy fix.
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Old 24th May 2008, 04:05 PM   #7
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Hello,

If I had to hazard a guess, I'd surmise your brother fiddled with one of the pots that he should not have fiddled with, specifically the one that effects dead time and idle current.

If that's the case I'd recommend you send it back for retuning, before real damage happens.
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Old 24th May 2008, 08:13 PM   #8
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Hi,

Sorry I guess our posts crossed and I can't edit the above one now, please disregard.

Did you check the power rails of the input op amp with a volt meter? You should get + and - 12Vdc at the power pins, then you'll know if it's the regulators or not.

RMA still seems like your best option though, but at least that would tell you if it was the regulators as you suspected. You don't really need to know anthing about them to test if they're outputting the correct voltage or not.

You may have caught the early portion of the old bathtub curve, it's bound to happen to someone eventually. At any rate Hypex will fix you up.
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Old 24th May 2008, 08:13 PM   #9
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Hello again,

Something else just came to mind. Since your brother was trying different ways of connecting it before this happened, I wonder if he was soldering the connections directly, or modifying the interconnect/connector?

Perhaps it would be worth testing the cable in case heat from soldering caused an internal short, or there's a solder bridge, also inspect the module in case he formed a solder bridge there.

Sorry if you checked all of that already, but it would suck to send it back if that's all it is.
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Old 27th May 2008, 08:40 PM   #10
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Thanks for your help so far

Most of the connections (at amplifier side anyway) are by isolated connectors that are clamped on the cable. So no chance of a solderbridge there. I measured the incoming voltages on the hypex pcb and they were ok. (rail voltages).

The Hypex pcb never get close to any solder-iron, and i checked it for failty/burned components. I did check it for solder-bridges like you said just to be sure, but nothing (would have been strange if there would have been one)

Good idea to measure the voltage on the opamp pins. I didn't know what voltage they should be. This realy helps.

The RMA is allready requested and the package is ready to be posted so hopefully hypex can find and fix the real problem.
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