Smoked UCD180 module

[ekaerin]

Hi,
I smoked one of my UCD 180s the other day. I forgot to cut a track on the tweeter part
of an XO.
This meant that the poor UCD worked directly into 0.6mH + resistance of speaker cables etc.
I thought theese guys had all kinds of protection. Why use sense resistors if they don't provide protection.

Both FETs are gone like both sense resistors + 2 1k resistors. The FETs
are obsolete probably because they aren't ROHS cmpliant but I can use
the non-iso version.
Is it worth repairing or are the drivestages gone too ?
Anybody have experience with a similar UCD failure. Any input welcome.

/ Mattias

[ekaerin]

One of the E-caps referred to in other posts as snubbing caps blew up.
I think it sayss C36 on the screenprint.

/ Mattias

[BWRX]

Which version modules do you have? I had a similar occurence with a UcD180 module while I was just testing it. I still haven't gotten around to checking all the driver circuitry...

[ekaerin]

it has serial No 0517/0155B141.
Its a great amp otherwise..... My "linear" amp just muted with the same load at moderate level. The UCD blew before even thinking of turning
the volume up. But I'm still thankfull it didn't dump the supply on the woofers.


/ Mattias

[ekaerin]

Today I got my STP14NF12FP FETs to replace the meltdown ones.
The original is obsolete. At least in the ISO-package. And, as I understand it Hypex is now putting in the 120V versions.

I also suspect that some of the drivstages are gone and since I do not
have a clue (no schematic) of how things are done I have to measure
the working channel to see if it is NPN or PNP or FETs in the drivestage.
Then use the bipolar/ FETs of my choice.
As stated previous, the sense resistors some caps and 0603 size resistors were burnt.
BTW. the Sw-FETs were shorted through all terminals !!!

I'll keep you updated / Mattias

[Javin5]

Ekaerin, the way I understand you, your UcD smoked up because of a shortcircuit at the output, is this correct?

Note that the UcD180 is supposed to be shortcircuitproof (see posts 1219 and 1313 in the UcD180 Questions thread). Strange indeed ...

However, the UcD180 is not DC-protected, as far as I know. I believe this can be achieved if you use the Hypex HG-Supply with its protection inputs.You must then connect the UcD-Output to the protection input of the HG-supply.

Ekaerin and BWRX: Did you use it with the HG-supply (just curious)?

[IVX]

I've repaired UcD180 and UcD400, both with smoked mosfets, but only UcD400 had BJT's (zumt) smoked. I've tried irf540z (in the UcD180 ~2 time lower gate res required, and for irf540z(100V!) about 108VDC avalanche voltage, so <50VDC to rail could be applied), php28nq15 ok too, you can try php18nq11, IRFB4212(100V!), fqp13n10(100V!) etc.

PS: For new design, today I'd be happy to choice dual in to220 IR mosfets, or IR directfet mosfets, like B&O in the one of their ICEPower for OEM customer.

[BWRX]

Originally posted by Javin5
Ekaerin and BWRX: Did you use it with the HG-supply (just curious)?

I was not using a Hypex supply. It was a pretty standard setup - 250VA toroid, 25A bridge, and large electrolytics. The transformer had 30VAC secondaries, which equates to about 44VDC per rail. That's close to the recommended max but shouldn't have had any effect on the short circuit protection.

[ekaerin]

Thank you all for the input.

I used a standard supply. I had to take off some secondary turns
on my mains trafo to provide for highest possible line voltage and still have
margin, at no load, for the UCD not to shut down.

(You can see some pics in my post "Finnished my UCD180 amplifier"

And yes there was a short in a crossover network. At the first cap
in the tweeter section of a 24dB LR. So the UCD saw the inductor on its output.
However, as I said before my linear amp could actually play music at moderate level with that XO until it went into protection mode.
Therefore I did not discover the short at first. I just thougt the system was real hard-driven.

regards / Mattias

[ekaerin]

......The repairwork has been down for a while.

The only components left to put in is the gate discharge transistors.

The small SOT323 / SC-70 devices Hypex uses are market t72
and I believe they are ZETEX ZUMT718 devices. Seems like a good
choice for the application so that is what I will put in.
I don't want to depart from the original design since my other channel
is working and I want them to be as equal as possible.

Cheers / Mattias