IcePower module

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Hi to all my fans,  

just completed repairs on one of these:    

http://www.sound-power.ru/files/doc/ICEpower125ASX2_datasheet.pdf

Found it fitted inside a mini-size bass instrument amplifier, which the own
er had just purchased over the net and failed on him at first power up.  

Smelling a rat, I checked the AC switch on the rear panel first - blow me d
own, it was set to 120VAC and we live in a 240V country.  

Reset the switch, then it drew zero AC current - no surprise.  

Replaced the blown 5AT fuse in the IcePower module and then the PSU began h
iccupping - drawing an amp or two very briefly then shutting off every few  
seconds.    

IME feeding double AC supply voltage to a unit with a SMPS is almost always
 fatal, sure the AC fuse blows but semis in the HV part of the circuit fail
 in a fraction of a second. But these must be OK this time because the PSU  
was hiccupping - ie working but sensing an overload so shutting down.  

Soon enough, multimeter testing showed two small power mosfets on the outpu
t side of the SMPS tranny were shorted while two others seemed OK. But what
 the heck are mosfets doing there ?  

Well, it's the fist time I have come across seen a *synchronous rectifier*  
in such an unit. IcePower had certainly gone all out to reduce losses and h
eat in this module by using a synchronous bridge.  

The particular TO-252 fets here are made by ON, number FDD86110 rated at 10
0V and 8mohms on resistance.  

Removing the duds cleared all shorts and after fitting some new ones ( deli
vered to me by Element14, from their Singapore warehouse ) I gingerly Varia
ced the unit up from zero.  

No hiccupping this time and it began to run normally - after which it passe
d all my usual bench testing, no problems.  

FYI:  

AC current draw was 120mA at idle, 2.4A at full power (340W rms/4ohms)  
  
No PFC and inrush surges were about 25A for a few milliseconds.  

There was a residual sine wave signal on the audio output of about 1V at 50
0kHz - no biggie except it makes THD testing a right PITA.  

I find it odd the way the SMPS failed, just two mosfets in the secondary re
ctifier, nothing else. For a brief time, the DC supply to the switching fet
s must have been nearly double voltage.  

Seems the two rectifier fets failed SHORT instantly and protected the rest  
of the circuitry - remember the power supply is NOT regulated, just a squar
e wave inverter running at 100kHz.  

I also feel that supplying an expensive amplifier to a buyer living in a 24
0V country with the AC inlet set to 120V and giving NO warning is criminal.
 BTW the amp was fitted with a regular IEC inlet which most of the world us
es for 240VAC.  

Any comments?  



...  Phil  



  













Re: IcePower module
On Thursday, September 19, 2019 at 11:52:31 PM UTC-4, Mr. Charm & Warmth wr
ote:
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**There's internet in hell?


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 down, it was set to 120VAC and we live in a 240V country.  
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240V country with the AC inlet set to 120V and giving NO warning is crimina
l.  


**  I've found that when an item fails, the customer will flip every switch
 in a vain attempt to "repair" the failure.  Even though the amp failed on  
first use, we don't actually know where the switch was set when the custome
r obtained the amp.  There's an even (or better) chance the customer flippe
d it after the amp failed.
  

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**Good repair.

  


Re: IcePower module
John Dope wrote:

----------------

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** Small mistake, the internet IS hell.  


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me down, it was set to 120VAC and we live in a 240V country.  
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a 240V country with the AC inlet set to 120V and giving NO warning is crimi
nal.  
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ch in a vain attempt to "repair" the failure.  Even though the amp failed o
n first use, we don't actually know where the switch was set when the custo
mer obtained the amp.  There's an even (or better) chance the customer flip
ped it after the amp failed.
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** Errr  - nope.  

The particular "switch" is tiny - looks like a round, 20mm panel fuse holde
r with sub mm white print saying 120/240  - PLUS requires screw driver to o
perate.  

Every knowable fact points at the supplier being in the USA and sending the
 buyer here a "cardboard box" with a local model inside.  

The chance the amp arrived in the buyer's hand with a faulty low voltage mo
sfet in the synchronous rectifier cct AND no other fault is miniscule.

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** I was careful, observant and a tad lucky.  

Replacing the 2 DPAK mosfets mounted flat on the PCB was a new job to me -  
everything I had read suggested it required solder paste & liquid flux that
 I did not have.

In the end, I used 1.2mm Savbit 60/40 wire solder, a Hakko FX-888 iron set  
to 330 C and acted damn quick.
  


.....  Phil  




Re: IcePower module
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Once I had a defective PSU in a Dell desktop PC, made a case at the local
Dell phone number, got sent a PSU from a European parts center, and it
was set to 120V.   BANGGG!!  (OF COURSE I did not check that!  All newly
delivered Dell PCs come with the switch correctly set for our region!
and there was no "please be advised that you need to check the setting"
note packed with it either...)

Called them again, got sent another PSU, again set to 120V.  Of course
this time I switched it before plugging it in.

I think this is crazy.  When you manufacture PSUs and have to have a
default setting, then at least SET IT TO 240V!!!
When the local line is 120V then at least it will not fail, and when
it does not work you can still change the setting.

Re: IcePower module
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It may seem like this PSU is fancy, but in a really modern PSU there is
no 120/240 switch and the PSU automatically works between 80 and 250V AC.

Re: IcePower module
Rob wrote:
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** Yep  - most of those kind of SMPSs are know as "PFC corrected" .

 The incoming AC is rectified and converted to 400V DC by a switching converter that tracks the incoming AC voltage. Makes the current wave follow the voltage wave ( both sine) so the "power factor" is close to unity.  

 Has advantages in terms of how many units can be run of the same power circuit and is often mandated in regulations for lighting and computer products.  

But not for domestic or entertainment audio.  


..... Phil  



Re: IcePower module
On Friday, 20 September 2019 14:31:05 UTC+1, Phil Allison  wrote:
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PFC is mandated for domestic goods above 20w here.  
PFC correction & the ability to run at 120 & 240 without changing a switch are of course 2 separate things.


NT

Re: IcePower module
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Before the PFC solution there were SMPS that used the standard
rectifier/doubler setup with a TRIAC in place of the jumper that
normally selects 120V/240V operation.

Re: IcePower module
Rob wrote:
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** Yeah - the cct starts off in the 240V position and jumps down to the 120V setting if the output voltage is much too low.  

Think makers called it "auto-select" or something like that.  

Few examples were ever made so I suspect their were some issue with it like when the AC supply was dodgy - ie brown outs and such like.  

It's safer to have the setting locked to the AC voltage where you live - and not have it jump to voltage doubling cos of a short term voltage drop.  

The PFC solution normally works brilliantly, long as the AC supply impedance is reasonably low. If there are hundreds of metres of 15amp cable between the load and the supply - all bets are off.  

Then, if the AC voltage drops, the load draws more current causing the voltage to drop more - and well you get the idea.


....  Phil  







Re: IcePower module
On Saturday, 21 September 2019 12:53:01 UTC+1, Phil Allison  wrote:
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on.  
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20V setting if the output voltage is much too low.  
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ke when the AC supply was dodgy - ie brown outs and such like.  
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and not have it jump to voltage doubling cos of a short term voltage drop.
  
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nce is reasonably low. If there are hundreds of metres of 15amp cable betwe
en the load and the supply - all bets are off.  
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ltage to drop more - and well you get the idea.
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Safest is to simply design the psu to output the correct voltage with eithe
r 240 or 120 in. It's not a big problem to design an smpsu to cope with tha
t from the get go, so there's no need for any bolt-ons to try to get round  
an inadequate working range. And that's exactly what most do.


NT

Re: IcePower module
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That's what I thought but being in a 120 volt country never had to deal with it.  

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That makes perfect sense in a 240 country.  

Here, it can't really hurt itself.  

There are some high power amps here that need 240. They just can't run on 120. Those don't switch down.  

Anyway yes, you are definitely better off with a switch.  


Re: IcePower module
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The typical PFC circuit is a boost regulator placed between the rectifier
and the reservoir cap. In this way, the reservoir cap can charge during
the entire AC cycle instead of only during the peaks, improving the power
factor. But this also has the effect that the PWM circuit will see the
same input voltage regardless of the line voltage. So, wide input range
often comes along with PFC.

-- Adam

Re: IcePower module
Adam wrote:
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** Most PFC circuits have damn near sine wave current draw, so the PF is around 0.9 to 0.95. However, with the vast majority of domestic, electronic appliances this is of no advantage to the user or the supply system.
  
Only lighting and computers are required to have good PFs in places like Europe and the US while the main reason for that is cos it allows twice as many of these to run from the same AC supply, compared to non PFC versions.  

Many buildings have hundreds of light fittings installed and large numbers of mains powered PCs for workers - and that is where it matters!  

FYI: domestic fridges, microwave ovens plus most washers and clothes driers have long had near sine wave current draw and so good power factors.  

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 ** Correct.


.....  Phil  




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