Blown Muse PSU

[WAD62]

Hi there this thread is a continuation from a T-amp discussion in the blank canvas section...

My Muse PSU for my M21 T-amp popped its clogs last night, after relocation...

I've included some photos which I hope will provide some info as to whether it's repairable or not. It would appear that the back of the 'heatsink' (thanks Chris) has blown off. See image 3.

Sorry the images are a bit poor

60W Linear Power supply for T-AMP TA2024 TA2020 DAC

Input:110v or220v

Output:12V 5A

Cheers Will

[Reid Malenfant]

Yes, it's repairable ;) Shouldn't be too difficult to lower the input to the regulator either :)

[WAD62]

Yes, it's repairable ;) Shouldn't be too difficult to lower the input to the regulator either :)

Cheers Mark...It may be if it wasn't in the hands of an unskilled numpty.

What's happened in layman's terms?

[Reid Malenfant]

I can't be 100% sure as i'm not there to take a look at it ;)

Whatever is mounted on the heatsink has obviously expired in a fairly big way. I somehow doubt it'll be a regulator IC as i don't happen to know of any in TO220 packages that'll pass 5Amps continuous. I'd hazard a guess & say it's a series pass transistor which is part of the regulator circuit.

Now it's probably popped due to excessive voltage on the secondary of the transformer, though again it might not be. However the transformer is designed to be run on 220V & most of the UK sees about 240V out of a wall socket & this would produce about 9% greater secondary voltage out of the transformer.

It may not sound like a lot but it means that the regulator (which outputs 12V) may well be having to dissipate up to 50% more power, though this depends on how high the voltage was accross the storage capacitors with a 220V mains feed.

With say a couple of volts overhead (in which to regulate) with a 220V feed that extra 9% secondary voltage would be significant.

Apologies as it's not the most easy thing to explain in a way that most people would understand :doh:

[WAD62]

I can't be 100% sure as i'm not there to take a look at it ;)

Whatever is mounted on the heatsink has obviously expired in a fairly big way. I somehow doubt it'll be a regulator IC as i don't happen to know of any in TO220 packages that'll pass 5Amps continuous. I'd hazard a guess & say it's a series pass transistor which is part of the regulator circuit.

Now it's probably popped due to excessive voltage on the secondary of the transformer, though again it might not be. However the transformer is designed to be run on 220V & most of the UK sees about 240V out of a wall socket & this would produce about 9% greater secondary voltage out of the transformer.

It may not sound like a lot but it means that the regulator (which outputs 12V) may well be having to dissipate up to 50% more power, though this depends on how high the voltage was accross the storage capacitors with a 220V mains feed.

With say a couple of volts overhead (in which to regulate) with a 220V feed that extra 9% secondary voltage would be significant.

Apologies as it's not the most easy thing to explain in a way that most people would understand :doh:

Cheers Mark, I know a couple of fellows who it would make more sense to, it's certainly out of my league, I'll have a word with them and see if it's cost effective, a replacement is only £60

[Reid Malenfant]

Depending on what's blown you could be looking at just a few pounds or less (component value) to fix it ;)

It'll need modifying though to prevent it happening again, there would be a few ways of doing that but all it boils down to is reducing the voltage from the transformer secondary to just about the same level as it'd be if being fed 220V AC.

[Ali Tait]

Yes agreed,not much point in buying another,the same thing will happen again most likely.

[WAD62]

Yes agreed,not much point in buying another,the same thing will happen again most likely.

good point, well made chaps...

I'll get in touch with technical support...

Right time for the Arcade Fire at the worlds worst venue (the NEC)

Cheers...:cool:

[Ali Tait]

Or an alternative would be to use a new one with a variac set to 220v.

[WAD62]

Or an alternative would be to use a new one with a variac set to 220v.

Another numpty question...

The Muse M21 comes with a default laptop style DC adapter;

http://cgi.ebay.co.uk/MUSE-M21-EX-TA2021-T-Amp-Mini-Stereo-Amplifier-25WX2-B-/120567506263?pt=LH_DefaultDomain_0&hash=item1c12622557#ht_4057wt_756

Rated 13.5v 4A (fyi did not work on arrival, or blew as soon as I plugged it in, it's hard to tell)

I then replaced it with a variable voltage/ampage one from Maplins (the only one that could produce 13.5V & 4A), which runs worryingly hot at theses settings, regardless of whether the amp is connected or not.

Hence I bought the upgraded PSU in this thread, however it is rated as 12V and 5A. The amp worked much better with this PSU, in comparison to the Maplins one.

What if anything does this mean, what should be the optimum voltage and ampage be 13.5V & 4A or 12V & 5A ?

And therefore would I be able to find a more appropriate UK alternative?

Cheers for any physics 101 assistance...:scratch:

[Gazjam]

Hope you get an answer to this one Will, the Muse TAmp seems a good 'un especially with the PSU...
If the T-Amp thing does it for me in my system (thanks Jerry!) I might look into the Muse.

Watching this one with interest. :)

[StanleyB]

I then replaced it with a variable voltage/ampage one from Maplins (the only one that could produce 13.5V & 4A), which runs worryingly hot at theses settings, regardless of whether the amp is connected or not.
Any idea what the heat dissipation of a 13.5V 4A power supply would be in terms of Wattage, and how hot that is?

[WAD62]

Any idea what the heat dissipation of a 13.5V 4A power supply would be in terms of Wattage, and how hot that is?

Don't be cruel Stanley, at least give me a multiple choice question :scratch:

At the risk of being stupid I'm not quite sure what you're getting at :(

[WAD62]

Hope you get an answer to this one Will, the Muse TAmp seems a good 'un especially with the PSU...
If the T-Amp thing does it for me in my system (thanks Jerry!) I might look into the Muse.

Watching this one with interest. :)

I think I've now got a bit of a rough strategy, no point in buying a replacement power supply, as you chaps rightly said it could easily go again.

I think the PSU is critical to the Muse's performance, so I'm probably not going to bother with an alternative laptop type power supply, I'm going to see if I can get it repaired locally.

I'm not holding out too much hope of 'customer support' as the reply to my detailed explanation of the PSU woes was as follows...

"if it is burned, not only may be the voltage, the power supply burned or amplifier burned?"

...my hovercraft is indeed full of eels.

Still his English is better than my Cantonese

I'm actually very tempted by the Mini T, as I was going to buy another T Amp as a Christmas gift, particularly after Jerry's comparison between the two (although that was without the PSU on the Muse), it's now being sold with an uprated power supply...
http://cgi.ebay.co.uk/Mini-T-T-Amp-Audio-Amplifier-5A-PSU-TA2020-UK-SELLER-/170565099902?pt=UK_AudioTVElectronics_HomeAudioHiF i_Amplifiers&hash=item27b678e17e#ht_5057wt_977

So the theory is I can run the Mini T in (I've found that they need quite a bit of running in) whilst I source a repair for the Muse PSU. I'll be able to see how good it is for myself for a bit.

There is one point about the Muse M21/Muse PSU combo, it kind of undermines the whole portability and aesthetics of the T-Amp, have a look at the attached picture (a bit blurred I'm afraid). When I bought it I was under the impression that they would be similar in dimensions....:lol:

It's like a jockey on an elephant!!! "this is far away Dougal...and this is close up"

I'll keep you posted...and look forward to your views on the Mini-T

[Gazjam]

Sounds like a plan Will...

The Ebay link looks interesting, couple of points about that.

The one sold looks the same as the one Jerry is loaning me?
http://www.hifiwigwam.com/showthread.php?45670-quot-Mini-T-quot-T-Amp-TA2020-20wpc-and-%A360-UK-delivered.-eBay-bargain!

so thats great.

Also, the Ebay blurb says the amp can be run at 13.8v if desired?
I have the Maplin Variable supply that was recommended for Stan's 7510 Dac, and I noticed the improvement whilst using it.

Will it bring improvement to the T-Amp if I run it at 13.8V?
Interesting...watch this space.

One thing at a time though...be good if Royal Mail is still delivering to up North ...hopefully they have been trying "since the snows of winter covered this land" :)

[WAD62]

Good news all round then...

Mini T ordered, and I've tracked my engineer chum down, he'd been out of circulation after getting his hands caught in a lathe...nasty!!! On the mend now though, we'll see if he can bring the patient back to life

What model of Maplins variable power supply have you got? I was using 'L11BQ' as a stopgap with the muse, but on inspection it doesn't do 13.8, the closest is 13.5, so you must have a different one.

I'm still unsure as to what StanleyB was alluding to with regard to the heat dissipation stuff... help Stan :scratch:

[Gazjam]

just checked, its the same Maplins supply.
my bad, only does 13.5.

ah well...

[WAD62]

just checked, its the same Maplins supply.
my bad, only does 13.5.

ah well...

Interesting, the difference between the maplins supply & the muse PSU was like night and day, presumably the big caps on the PSU help

[Reid Malenfant]

I wouldn't worry about the Maplin supply running hot as you call it ;) As it's a switch mode supply it'll have a small built in load simply because damn near every SMPS needs a minimum load to function correctly.

If the load wasn't there the PSU would attempt to keep the output voltage stable by narrowing the pulses into the main switching transformer & it's quite possible that it woudn't be able to keep the output voltage stable & it'd increase to a possibly dangerous level for any equipment it might be feeding.

When you set the output to 13.5V this load, which will be a power resistor will be dissipating much more than it would with only 5V accross it. It's nothing to worry about ;)

As for modifying the linear PSU that's packed up i suggest you get 4 x 6amp diodes & connect them so you have two in series & the other two also in series but back to back with the first pair. This will result in a 1.2 - 1.4V drop in the transformer output if you connect it in series with the transformer secondary :)

[WAD62]

I wouldn't worry about the Maplin supply running hot as you call it ;) As it's a switch mode supply it'll have a small built in load simply because damn near every SMPS needs a minimum load to function correctly.

If the load wasn't there the PSU would attempt to keep the output voltage stable by narrowing the pulses into the main switching transformer & it's quite possible that it woudn't be able to keep the output voltage stable & it'd increase to a possibly dangerous level for any equipment it might be feeding.

When you set the output to 13.5V this load, which will be a power resistor will be dissipating much more than it would with only 5V accross it. It's nothing to worry about ;)

As for modifying the linear PSU that's packed up i suggest you get 4 x 6amp diodes & connect them so you have two in series & the other two also in series but back to back with the first pair. This will result in a 1.2 - 1.4V drop in the transformer output if you connect it in series with the transformer secondary :)

Cheers Mark, that's reassuring, I was a bit worried about torching the house.

I'll mention your tips to my man, if and when he accepts the task
:cool:

[DSJR]

Blown regulator/line output trannies were commonplace in CRT TV's at one time and on one tellie which regularly failed with a few years of thrashing under its belt (B&O LX2500/2800) usually failed because the key transistor lost its earth and went wild...

I'm sure that once repaired (hope your mate can do it for peanuts as the bits are cheap) and updated so as not to stress this regulator/follower, you'll be fine ;)

[WAD62]

Thanks for all the help guys, very much appreciated...
:cool: