Faulty ICEpower 50ASX2 - Page 1
Forum section: electronics / repair

author: almamater
author_rank: Regular Contributor
timestamp: June 24, 2021, 02:55:09 pm
content: Hello everyone.I have an audio amplifier (which doesn't work) and I'd like to get it working because it's good stuff (Fender Rumble 150 Bass Amplifier Head)It just doesn't turn on. From what I can see the power supply (ICEpower 50ASX2) doesn't have any active output... but it's something more complex than the ones I've been trying to repair and learn, this one has more componentsIf anyone can give me some help.I found some information available for this power supply:Esquema do AmplificadorManual da FonteDatasheet da FonteBut I can't find the schematic of the entire circuit\componentsI've been doing some measurements and unfortunately the fuses (which are about 3) are all fine, the 2 giant capacitors (primary side) have a voltage of ~150V eachOn the secondary side, I don't have any voltage, even on the Enable Pin that should be +5V (according to the manual) has 0V.There is one component that is an NTC 5.0 and has a resistance of ~5R, which makes me believe that it's fine too.I don't know however if this is normal:There are 2 components at the bottom, and next to the larger transformer (on the primary side), which on one side have voltage but not on the other, it's a capacitor and a black component (looks like a diode, it says "EB 11"), the voltages in this part are like this:is supposed to have on one side of the capacitor, and that diode, voltage but not on the other side?Testing the "diode EB 11" in the normal way (with the multimeter in the diode mode) has 0.445 and in the reverse it has 2.950 (but it could be because it is in the circuit, I haven't tested it outside).All the elect. capacitors from the board, i measured them (with the multimeter in the capacitor mode) and the values, even being in the circuit (I didn't remove them), seems to be ok, and they seem to be of good brand and quality..There are 2 large transistors next to the larger transformer (primary side), are they responsible for activating the voltages?

author: Manul
author_rank: Super Contributor
timestamp: June 24, 2021, 03:47:12 pm
content: So the controller seems to beSG2525SG3525. Does it have power? What about voltage on this capacitor?

author: almamater
author_rank: Regular Contributor
timestamp: June 24, 2021, 04:06:19 pm
content: Thanks for the reply.The Pin Vi (15) of the SG3525 is connected to the capacitor C300 the voltage oscillates between 0 and 1.3v..(The Vc (13) pin have the same voltage.. 0 and 1.3v..)

author: Manul
author_rank: Super Contributor
timestamp: June 24, 2021, 04:28:43 pm
content: I guess I misread part number from picture, it is SG3525. But these ICs are very similar, so it does not matter. As far as I understand, it should get power on pin 15, without it nothing can start. So that supply might have problem or it could be that IC tries to start and shorts the supply. I would try to remove all power, wait until capacitors discharge and try to reverse engineer how pin 15 is powered.

author: almamater
author_rank: Regular Contributor
timestamp: June 24, 2021, 05:37:52 pm
content: From what I see pin 15 is connected to a circuit that has a PNP Transistor (BCP53):I'll try to check if this PNP is working ..P.S.:The PNP has continuity between The Collector and the Emitter.Base and Emitter has ~15v input. But Collector Output is only ~1.3VShould i remove this transistor ant test it out of circuit?

author: Manul
author_rank: Super Contributor
timestamp: June 24, 2021, 07:08:43 pm
content: Quote from: almamater on June 24, 2021, 05:37:52 pmIf both base and emitter is at 15V, so it means there is 0V between them? Is this what you mean? Then it should be off. What exactly you mean by saying that there is continuity?It can be hard to follow such PSU without schematic. Scope with differential probe is very useful. For example, here in this case we don't know if this PNP is off all the time or pulsed on with short pulses.

author: almamater
author_rank: Regular Contributor
timestamp: June 24, 2021, 07:58:41 pm
content: Sorry, by "continuity" i mean that i test it with the multimeter (postitive meter lead to the COLLECTOR (C) and the negative meter lead to the EMITTER (E)) supposedly there shouldn't be conductivity..And yes, he has ~15v at Base and Emissor Pins...

author: Manul
author_rank: Super Contributor
timestamp: June 24, 2021, 08:23:39 pm
content: According to datasheet there are three protection circuits which may stop the PSU from running. Overcurrent protection would keep PSU trying to restart (cycling). It is good to keep in mind, because it might be related. It also has low mains voltage detection. If it thinks voltage is too low, it might not start.I wonder if you short PNP base and emitter (to guarantee it is off) does it still have 1.3V on collector? If no, then probably it means that it is actually trying to start in quick cycles and 1.3V is what your multimeter sees as average. Then the suspicion would move to overcurrent protection turning it off very rapidly after it starts. Do you by any chance hear something? Like clicking, buzzing, something like that? Or is it perfectly silent?

author: Audiorepair
author_rank: Frequent Contributor
timestamp: June 24, 2021, 09:52:39 pm
content: Check C300 isn't faulty.Unless you have at least a constant 8v on pin15 the IC will not run.Usually on power up this is supplied by a string of resistors connected to the rectified mains HT.Once the IC starts, the supply via the mains HT through the high value resistors is not enough to keep up with the extra current draw, and the IC is then supplied via the now working power supply.Is the PNP transistor actually acting as a diode, which takes over from the resistor string from HT once the power supply is running?It doesn't make sense that you are measuring very low voltages (1.3v) on pin 15 yet the IC is still attempting to start.

author: almamater
author_rank: Regular Contributor
timestamp: June 25, 2021, 12:08:37 am
content: Hello and thanks.The power supply is perfectly silent, no clicking or buzzing noises..I made a little video:http://youtu.be/VXpCVsWPq4M

author: Manul
author_rank: Super Contributor
timestamp: June 25, 2021, 04:26:11 pm
content: As a further test I suggest to solder a small wire to short base and emitter of BCP53. Does it still have 1.3V on collector?

author: almamater
author_rank: Regular Contributor
timestamp: June 25, 2021, 05:27:37 pm
content: Hello.I connected the Emitter with the Base directly and the collector now has0v, do it means that this PNP transistor is ok?

author: Manul
author_rank: Super Contributor
timestamp: June 25, 2021, 06:12:10 pm
content: I would guess that it is good. This PNP seems to control power to the SG3525. The voltage 1.3V was strange, but after this test we can probably say that it was just cycling on-off, and 1.3V is average (multimeter is not fast enough to show short pulses). When you forced PNP to be off - there is 0V to SG3525. So it can be cycling, which means that PSU senses something worng and goes shutdown - restart (more likely). Or it could be something wrong with the circuit which is driving the base of that PNP (less likely).

author: Manul
author_rank: Super Contributor
timestamp: June 25, 2021, 06:30:01 pm
content: For such repair it would be very useful to have isolation transformer, then you could use scope to look the signals. Or differential probe, but these are quite expensive.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: June 25, 2021, 07:17:01 pm
content: Isolation transformers can be cheap, and invaluable with SMPS.https://www.screwfix.com/p/carroll-meynell-1-5kva-intermittent-isolation-transformer-230v-230v/752HV?tc=NA7&ds_kid=92700055281954493&ds_rl=1249401&gclid=Cj0KCQjw_dWGBhDAARIsAMcYuJxrvBJdl7Q7A0sLYAhGohyYVMQ-l7Pf1wDbsLA-oBjr9VH5PDzTPPEaAnqTEALw_wcB&gclsrc=aw.ds

author: Chris56000
author_rank: Frequent Contributor
timestamp: June 25, 2021, 09:20:06 pm
content: Hi!It's very likely there's a short–circuit across one or more of the power supply rails, most likely due to switching MOSFET failures in the output stages – you'll need to test between the drain (middle or tab) and the source (right–hand leg of TO–220 or surface mount type) – if you do find a MOSFET has gone you also need to examine the inductors in the Output Stage that filter the audio–modulated PWM back into audio – failure of these inductors is usually self–evident as obvious overheating damage!If there is signs of such damage, then you may have to bin the complete module as ICE Power/B & O will NOT support component level repairs on their ICEPower modules if anything like a choke, transformer or specialist IC has been damaged – I think these use a custom A–D pwm driver device if my memory serves me correctly!If you're certain there's no obvious physical damage to flter inductors, feed chokes, etc., that would potentially write the module off, then you might be able to persue it further – begin with the Output MOSFETs, checking them for shorts drain/source, then look at the output rectifier diodes from the power supply transformer in the switch–mode PSU – my experience with this type of unit is that the rectifier diodes are usually OK and the fault is down to short–circuits across the power amplifier supply rails, again down to faulty MOSFETs as mentioned above!Chris Williams

author: almamater
author_rank: Regular Contributor
timestamp: June 26, 2021, 07:16:27 am
content: Hello.So the MOSFETS you mentioned are the TR301 and TR300 (two 9N50C NPN Mosfets)?They has:TR301G ->0vD ->295vS ->0vTR300G ->290vD ->311vS ->290vThe secondary side doesn't has any voltage..

author: Chris56000
author_rank: Frequent Contributor
timestamp: June 26, 2021, 09:40:25 am
content: Hi!TR300 and TR301 are the primary side switching MOSFETs and from the readings you provided they are not short circuited – they are simply not being driven!The MOSFETs I was referring to in my previous note are NOT TR300 and TR301 – I was referring to the output stage PWM class D switching MOSFETs on the right-hand side of the board above the output coils!Chris Williams

author: Manul
author_rank: Super Contributor
timestamp: June 26, 2021, 10:35:23 am
content: The mosfets Chris56000 mentioned are these. You should test them with PSU off, maybe best to use diode mode. Look if they are shorted. Could try to test other things on the output side too. Also output power rails. There are 4 electrolytic capacitors on the output side, check if they are not shorted. 5V rail too.What seems puzzling to me is that the PSU seems to not make any output at all. With the shorted output I would expect at least some 10's of millivolts apearing on the output until overcurrent kicks in. Usually together with some ticking sound from transformer.Quote from: almamater on June 26, 2021, 07:16:27 amGenerally, it is a bit dangerous to probe primary side mosfet gate (G) with multimeter. If the gate driver is in high impedance (for example, not powered), multimeter and lead capacitance could potentially cause false turn on.

author: almamater
author_rank: Regular Contributor
timestamp: June 28, 2021, 02:00:39 pm
content: Oh ok!With multimeter in Diode Mode i´m not sure. The readings are strange.. for all of them.D->S 2.68S-> D 0.52G-> S 1.62S-> G 0.57G->D 1.62D->G 2.82Probably it's better to take them out of the circuit and make the test..

author: Manul
author_rank: Super Contributor
timestamp: June 28, 2021, 06:06:25 pm
content: Quote from: almamater on June 28, 2021, 02:00:39 pmAll 4 of them measure like this? I would say it looks really good. What about output rails? Nothing shorted? Did you measure on the capacitors? What about +5 rail?

author: RayRay
author_rank: Frequent Contributor
timestamp: June 28, 2021, 06:32:39 pm
content: I'd suggest you replace the 35V 470UF capacitors. Visually, I can tell that at least 3 of em are faulty (the top of a healthy capacitor is suppose to be flat, and those look like they're gonna burst!). Since your'e from Finland, I think you'd be best getting em from TMEhttps://www.tme.eu/en/details/uhw1v471mpd/105degc-tht-electrolytic-capacitors/nichicon/Edit: Sorry, didn't notice that that particular one is out of stock (not to mention the minimum quantity!). Get these instead:https://www.tme.eu/en/details/eeufr1h471/tht-low-imped-electrolytic-capacitors/panasonic/

author: Manul
author_rank: Super Contributor
timestamp: June 28, 2021, 07:03:12 pm
content: Quote from: RayRay on June 28, 2021, 06:32:39 pmReally?

author: RayRay
author_rank: Frequent Contributor
timestamp: June 28, 2021, 07:11:04 pm
content: Quote from: Manul on June 28, 2021, 07:03:12 pmFrom a side profile (2nd pic, first post) their top doesn't look good.

author: Manul
author_rank: Super Contributor
timestamp: June 28, 2021, 08:39:32 pm
content: Quote from: RayRay on June 28, 2021, 07:11:04 pmMust be lens distortion.

author: almamater
author_rank: Regular Contributor
timestamp: June 28, 2021, 09:20:26 pm
content: Quote from: Manul on June 28, 2021, 06:06:25 pmHello.The values yes, are more or less the same in the 4.I took off all the 4 Capacitors and the values are fine with Low ESR.I dont see nothing shorted, small caps, resistors..Now, sorry for my question, but where is the +5V Rail?I dont know if im doing something wrong, im testing this Power Supply module disconnected from the rest of the amplifier unit (signal cables), connected only the 220v input, i assumed that outputs P103 or 104 should have some voltage, or even the Enable pin of P102..Thanks for all the patience.

author: Manul
author_rank: Super Contributor
timestamp: June 28, 2021, 09:52:59 pm
content: Quote from: almamater on June 28, 2021, 09:20:26 pmI was not suggesting to remove capacitors, but thats nothing wrong. Now you really know that they are good. I was mentioning capacitors because they help to find power rails. At least for me, when I try to quickly troubleshoot something. If I see 5 electrolytic capacitors, I just quickly measure resistance on them. Some power rails may lack electrolytics and have just ceramics, but those often can also be recognized just by looking. For me it is quickest way, because I can test that no voltages on the board is shorted. If someone gives me failed unknown board I just spend frst 30 seconds doing that.Quote from: almamater on June 28, 2021, 09:20:26 pmI don't know, but it has 5V logic level on enable, right? So I assume that some logic is working from local 5V supply. Maybe also 3.3V. Poke around capacitors near IC's. Just to see if nothing is shorted.Quote from: almamater on June 28, 2021, 09:20:26 pmI do believe, that this board should work on its own.Anyway, somehow I have suspicion from begining, that the problem is something on the primary side. Do you have scope?

author: almamater
author_rank: Regular Contributor
timestamp: June 28, 2021, 09:57:00 pm
content: Yes i have one scope (bought very recently but still learningfrom UNIT-T), i didn't test anything from this board with him because i dont have one Isolated transformer..

author: Manul
author_rank: Super Contributor
timestamp: June 28, 2021, 10:07:09 pm
content: Quote from: almamater on June 28, 2021, 09:57:00 pmYeah, but there are always some creative things to do. Connect ground clip to probe tip (short the probe), and move that wire loop very near transformer in a bit different directions, without connecting electrically. Be sure that 20Mhz BW limit is not set, have probe at 10X and have scope on low millivolts. Do you see any bursts of noise from transformer? You may try this with some working SMPS to see how it works.Idea is: to see if your boards primary side does something, or nothing at all.

author: almamater
author_rank: Regular Contributor
timestamp: June 29, 2021, 10:19:32 am
content: Hi.I made the suggested test with the oscilloscopeFirst i test with a good SMPS (salvaged from one printer i guess) and then i test with this faulty one:The result with the good SMPS:But with the Fender Module SMPS i don't get anything, only when i turn ON the Power Button, but nothing more..:

author: Manul
author_rank: Super Contributor
timestamp: June 29, 2021, 10:49:35 am
content: You probed both transformers, also that one with silver sticker? I saw you had 500mV vertical, did you try lower like 10mV vertical (trigger on auto)? No pulses, no noise? This is what I was thinking, it does not even try to start I guess. There could be something with mains voltage detection and undervoltage lockout or something which prevents starting...By the way, there were a few cases when there was no tools available, I used AM radio to listen for circuit "activity". Noise which is heard (or not heard) can sometimes be a useful insight. AM radio picks up well not only transformer noise, but also some digital signal activity.

author: KevinA
author_rank: Regular Contributor
timestamp: June 29, 2021, 04:39:02 pm
content: B&O do not release any service data these days, all B&O dealers repair products by replacing complete modules (not that any of them would have a technician who could repair something).Even companies who use B&O modules for their sound systems are not given service data - everything is to module level replacement.You can (I believe) still download Karsten Ballhorn's dissertation on class D amplification, which all their modules are based upon, but there are no schematics there.

author: almamater
author_rank: Regular Contributor
timestamp: June 29, 2021, 10:49:47 pm
content: Quote from: Manul on June 29, 2021, 10:49:35 amyes i try again with 50mV and nothing.. and no sound\noise from transformer..It seems very complicated to detect the problem of this module...

author: Manul
author_rank: Super Contributor
timestamp: July 02, 2021, 03:21:17 pm
content: Quote from: almamater on June 29, 2021, 10:49:47 pmDepends with what you compare. Of course it is not the simplest thing in the world. But also it does not look to me, that you spent a lot of time on this problem. You measured that there is nothing at the output side, capacitors are good, rails not shorted, output mosfets good. You also measured that main PWM controller is not powering. And that is pretty much all as far as I understand. Have you traced how the PNP transistor is controlled? Mains undervoltage circuit?A lot of people in this forum would likely troubleshoot such board in one hour or less, but they will not be able to tell exactly how to do it, because there is no exact algorithm, it is just probing, thinking, reverse engineering sections of PCB, finding some datasheets, drawing schematic sketches on a piece of paper and probing again until something is found and the problem understood.Also I will note, that people generally hesitate to offer ideas which might be risky. For example in this case you might consider to force start the SG3525 by bypassing the circuit which controlls 15V. But it is risky, bad things might happen, more damage to the board. So if I suggest this idea and you respond that your SMPS went on fire and now it is totally destroyed, I would feel really bad about it.You might consider such repair as opportunity to learn. It really depends what is your goal. If you want just to save some money, then maybe it is not worth.

author: almamater
author_rank: Regular Contributor
timestamp: July 02, 2021, 05:19:01 pm
content: Thanks for the message.Yes I've already tried to understand how the PNP is being controlled but I haven't drawn any schematics... anyway, the idea of forcing the SG3525 to start up doesn't seem bad idea to me, what better way to supply the 15V to him, removing the PNP from the circuit with a shunt wire?

author: Manul
author_rank: Super Contributor
timestamp: July 02, 2021, 06:17:23 pm
content: Well, yes, you could short emitter and collector to bypass. If you want, do such experiment, buton your own risk. The logic is that it is not powering the SG3525 probably because it thinks that mains voltage is too low or temperature too high. If it will not explode and start running and you will get output voltages, turn it off and try to analyze what exactly is preventing it to run.

author: Vicus
author_rank: Regular Contributor
timestamp: July 05, 2021, 08:03:08 am
content: In my opinion something load too much the output of the pnp. It can be the 3525 or something else. I suggest you to power the 3525 from a external and current limited psu WITHOUT apply main voltage.

author: Vicus
author_rank: Regular Contributor
timestamp: July 05, 2021, 08:08:37 am
content: Someone know what's the purpose of the smaller transformer?

author: almamater
author_rank: Regular Contributor
timestamp: July 07, 2021, 11:12:47 am
content: I tested connecting ~10v directly to the IC 3525 and it seems to work, at least there was no excessive consumption, from the ~300mA that I provided him it only consumed 50mA.And the IC output stays active with a voltage of ~3.8vPossibly I will now make theManulsuggestion to bypass the Transistor..

author: almamater
author_rank: Regular Contributor
timestamp: July 07, 2021, 04:05:17 pm
content: So.. i bypassed the transistor (shorting between emitter-collector) nothing exploded but still no voltage at Enable Pin

author: Manul
author_rank: Super Contributor
timestamp: July 07, 2021, 04:51:57 pm
content: And how about SG3525 supply voltage? Is it normal? How about Vref? Should be 5.1V.

author: almamater
author_rank: Regular Contributor
timestamp: July 07, 2021, 08:59:48 pm
content: Hello.The SGS3525 has:Vref= 1.13v+Vi= 2.52vOutputA= 1.2vLooks like it's not very well...

author: Manul
author_rank: Super Contributor
timestamp: July 09, 2021, 12:25:56 pm
content: Quote from: almamater on July 07, 2021, 08:59:48 pmYou wrote, that applying 10V externally it consumed 50mA. This is quite a lot. I would expect way less. This could mean that SG3525 is bad. Something else could be draining the current, but I thing there are not a lot of devices powered from same supply. You could desolder the SG3525 and try again to apply 10V. What is current consumtion? Also you can trace and measure things interfacing to that IC. Or you could just buy a new SG3525 and try. Not very expensive part.

author: almamater
author_rank: Regular Contributor
timestamp: July 11, 2021, 10:12:00 pm
content: Before buying a new IC, i removed the SG3525 from the circuit and tested again with10vand seems now Ok, a consumption of10mAand5vat Vref.

author: Manul
author_rank: Super Contributor
timestamp: July 21, 2021, 10:07:35 pm
content: Quote from: almamater on July 11, 2021, 10:12:00 pmI would say it is not a conclusive test, you would need to build a full circuit. For example the output stage of SG3525 could be damaged. You should also check what else on the board is powered from same source.

author: almamater
author_rank: Regular Contributor
timestamp: October 14, 2021, 05:02:37 pm
content: I only now managed to test this with anewSGS3525, (I had to buy it online because there wasn't one like the original here).But same result..i assume its to difficult (for me) to find the problem of this module.I appreciate the time you took for this.

author: Dorian
author_rank: Newbie
timestamp: February 13, 2023, 04:02:07 pm
content: I know the topic is old, but maybe someone will need it, there is a general solution and it is very simple. Coil L401 should be temporarily removed and under the white glue are 4 smd resistors, 2x62k and 2x5k. The 5K resistors are always intermittent and should be simply changed, they will work with 5K1 as well. after changing those two resistances, put the coil L401 back as it was and the module is correct and works. That's all and it's checked.

author: almamater
author_rank: Regular Contributor
timestamp: February 14, 2023, 10:18:44 am
content: Ok, Thank you!I'm going to buy these resistors and try it out..

author: kevinj72
author_rank: Newbie
timestamp: September 08, 2023, 12:32:37 am
content: Hey, were you able to try it and did it work?

author: almamater
author_rank: Regular Contributor
timestamp: September 08, 2023, 06:32:58 am
content: Yes i tried it but no luck..