Hitachi AX-M140 noises

Richot

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My mini hifi (Hitachi AX-M140) has started humming noise through the speakers, most noticable when volume is low via all sources (worse with music bank and tuner). What could cause this?

I have renewed 3 capacitors in the amplifier (2x 220uF, 1x 100uF) which looked dodgy, but no improvement.

Could it be the 2 large 4700uF 50v capacitors in the power supply that are faulty? Visually, they look OK with no bulging or leaking.

Thanks!
 
Well, I've just replaced the 2 power caps and the hum remains. What else could it be?

There is an 8A 800v bridge rectifier, 2x 80v-80w DMOS audio amplifier with mute/st-by and a positive voltage regulator screwed to the heatsink. Could any of these be the culprit?
 
Hi. I had the same problem a couple of weeks ago, except now my system fails to turn on at all, the indicator light on the front doesn't even glow red. Did you ever solve your problem? I am going to try and replace the 3 capacitors on the board 1204D2-11 that you replaced - mine look like they have been leaking, they are not bulging in any way though. The board appears to have got pretty hot in that area looking at it from the underside. So I will update you when I have replaced them.

Incidentally what I did about a year ago was I replaced the volume control with one that had fine increments, it did add a better feel and more accurate volume control and worked well. I hope this has not been the cause.

Please be advised I am a complete novice! So fingers crossed. I have nothing to loose!
 
Hi Josmit,

Funny you should ask...

I finally have given up with it, as there is zero information about repairs on the web. Believe me, i've searched everywhere. Upon contact, even Hitachi themselves washed their hands of it and didn't want to know! Every avenue I come to ends up saying "your better off binning it". I even went and swapped out a bunch of Zener diodes, which I thought were suspect - no joy.

I only took it to the recycling centre just yesterday, which is so frustrating as otherwise it was more or less fully functional (just needed a new DVD lens pickup - easy fix). To add to that, a while ago, i believe there was a seller on fleabay who offered a fix for it (and the AX-M137, which seems to succumb to the same fate) for about £20. When i enquired, it seems the seller is no longer registered anymore. :facepalm:

I've just accepted it wasn't meant to be and got shot of it (i've kept the speakers though as they seem pretty decent for a mini system.).

It was only for the bedroom to replace our even more ancient mini system, so no great loss... :)

Good luck in your pursuit!
 
Hello People

I Came across your discussion today while searching on google for an answer to the very same problem!

My Hitachi AX-M140 also started to hum - I thought it seemed to be the volume control as when I pushed it quite hard the hum would disappear. I opened up the amp and I can see it is quite brown around the 3 capacitors you talk about josmit on the board 1204D2-11. So please keep me updated in the meantime I'll try down at Maplins to see if I can get them there, I think I may also get the volume control as that seemed to be where the problem is - Have you tried to push it inwards with the volume down? Because the hum does disappear on my system , but then comes back again. I will update in a couple of days once I have replaced those parts.
 

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Ok. I replaced the Capacitors (2 x 100uF & 1 x 220uF) No change! (8472 I hope for your sake that was a typo when you said you changed 1 x 100uF & 2 x 220uF as it is actually what I have stated :face palm:)

So now like josmit the whole thing does not turn on it may be with all the prodding etc. BUT what I have found in the DVD component is a blown resistor No. R2054 on board 1204D2-20.PCB (See the images indicated by A. (I believe B, the Capacitor the brown stuff is just glue) My BIG problem is I have no idea what type or part number the Resistor is or was! This is where I am stuck this is a very obvious problem and I am sure will work when repaired! Any suggestions out there? Could you check yours josmit? 8472 Run to the recycling centre and get yours back! I am sure we will all win together here!
 

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Hi. Yes! The same resistor has burnt out like yours StretchL. Have you found out what type it is? There doesn't seem to be any others near by that resemble it. This board has to be something to do with the amp board because the DVD player has the main display for volume etc.

Let's hope someone has some way of telling us what the part number is or at least what to replace it with. It is a great pity that Member 8472 has thrown his out. It would have been a great help as to solving the problem. :lease:
 
hi StretchL,

would it be possible for you to post the voltages on the resistor?
( mark A ) , just curious!:)
 
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Hello Fabricator

That is exactly the information I am after :smashin: The voltage etc of the resistor marked A to enable me to replace it with the correct one. User Josmit is also after the same resistor.
I am going to trust a university student with my board 1204D2-20.PCB he says he can try test other things on there to try identify the resistor. All hope seems to be fading away so he seems like my last effort to solve this problem.

As soon as I find out what the resistor is I will post my findings on here.
 
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hi, StretchL

And i hope to know also the voltage rating of the capacitor mark B above.

If the voltage rating is higher ( basing from the resistor i am asking about ) than those below

then it could be the supply line to the regulator lower left of the board ( basing on the image above ).



1204D2- 20 PCB
 
then the TO-220 transistor might possibly be bad or shorted same with the zener diode connected to it.

(lower left of the image )
 
also the 5 pin TO-220 package leftmost of the capacitor mark B ( part number )

the one mounted on the aluminum heatsink.
 
:thumbsup:
http://diagramas.diagramasde.com/audio/Hyundai H-MS1110.pdf
Okay I've got the same problem, had the hum, moved the cable....smell of electrolyte coming from DVD player part, no power, no light...and today I stumbled across the service manual... Has anybody else been able to get their units working again?

Hi Ianspeed

Yes I do watch this thread from time to time. What you have here - the Service Manual is interesting as I can see the board 1204D2-20.PCB that is in the DVD section of the Hifi which is where we both have the fault. Did you compare your board to my image? The resistor that has blown marked A has blown on Josmit's machine as well as mine. Has yours? I will print of the whole PDF you have kindly provided and have a good read to see if I can find out the voltage etc of the resistor a quick look indicates R2054 only has 47 marked on the board. But I will study the rest of the document and will report back on my findings. Thank-you! I had almost given up all hope. :smashin:
 
Hi StretchL,

Buy LM2576 online from RS Components

After looking at the PCB schematic I did a quick google of the main transistor which I think is the problem...but I gave up electronics when I was twenty..so I'm just having a stab in the dark here. :)
Will check to see if the resistor is blown, have to drag the carcass out of the loft, did go and by a Denon DM38, still think the Hitachi had better sound quality though...
 
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I hope I can help regarding the Hitachi AX-M140 problems.
From experience the humming noise indicates that the 44 pin SMT IC on the printed side of board 1204D2-20.PCB is about to go short circuit (5v supply to ground).
Before this the displays will begin to misbehave with the DVD player perhaps being inoperative or/and several other functions including the unit being permanently powered with the red standby lamp not working.
As a result of the said 44 pin SMT IC finally going short circuit the 5v rail supplying it will fail with a smell of cooking!
Resistor R2054 will have cooked (4.7ohms 0.25watts) this feeds the 3pin regulator IC2004 with its output feeding L2002 (10uH 5%) which in turn feeds the 5volt supply to the 44 pin SMT IC.
With the supply removed the IC can be checked on a multimeter and will likely read between 7ohms and 10ohms.
Obviously it is pointless to re-connect both sides of L2002 until the 44pin IC is replaced but with it removed it is possible to check the 5v rail has been re-instated (I am assuming that the unit will default to standby when the mains supply is connected).
The said IC is a Samsung SP9228AZZ-QZ88, this device controls just about every function for all the units including standby!
I am presently attempting to obtain the SP9228AZZ-QZ88 and furthermore to establish that it has been programmed to work with the AX-M140.
It is also well to check X2002 which is a tiny clock crystal for the SP9228AZZ-QZ88, this is on the on the component side of the board above.
The two connecting leads are very fragile, frequency is 32.768 KHz.
 
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Addennum to my pevious comments, hopefully the image will help.
The 10uH inductor may be damaged and look healthy and fall apart when touched.
This however will release the short circuit situation cooking the 4.7ohm resistor.
I would emphasise that the SP9228AZZ-Q88 must be one that has been programmed to work specifically with the AX-M140.
Hopefully the link will illustrate this clearly.http://www.samsung.com/global/business/semiconductor/file/2011/product/2010/2/23/678294um_s3c9228_rev10.pdf
The ovolt (ground) pin of the SP9228AZZ-Q88 is pin 6.
 

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Hi, Think my amp has gone on a Hitachi Mini Hifi AX-M137 andone got a service manual or know where best to send it for repair ?

Thanks Charles
 
Iv had the same problem with DVD player smoking I turned straight off is there anyone who's confident with this model who wants to attempt to repair I will pay for fix and posted please contact me on
+44 7516 155942

Shane

Thank you
 
Iv had the same problem with DVD player smoking I turned straight off is there anyone who's confident with this model who wants to attempt to repair I will pay for fix and posted please contact me on
+44 7516 155942

Shane

Thank you
Hello Shane

Sorry to hear about your system. I don't know where about you are in the country but I have heard that this company in Swindon Wiltshire has a repair shop that do still repair TV's Hifi's etc. you could give them a try asking for a quote first. Here is the link... Burden Electronics - 160 County Road, Swindon, SN1 2DY
Please keep us posted on your progress as I am still keen in getting my stereo repaired but am short of cash at the moment.
 
Thanks for the reply StretchL
I did contact them but it would be to expensive for me to have the whole stereo sent there i offered to send the 1204d2-20 pcb to them but they wanted the whole stereo,

I have taken the stereo to a local repair shop where they was carrying a repair on but the engineer who stated the job left the company since then shop closed down so iv had a half job done.

I have opened the stereo on borrowed the pcb from a mates stereo and it works fine so I am looking to send the pcb to someone who knows a little about them and who haves the same stereo ? I will pay them for the time
repair.jpg
 
I appreciate that I'm trying to wake this thread from the dead, but I was just wondering if anyone might still have a valid link to a service manual for the AX-M140 system, or the identical Hyundai H-MS1110 mentioned by IanSpeed above. I can't seem to find either on the net, and the link to the 1110 manual is just a server error now.

I bought one of these systems cheap off ebay as spares/repairs. I'm not actually trying to get it working again as-was, but am planning on modding the individual components so I can get the amp, Musicbank and tuner working as standalone separates. I'm hoping to fit the tuner and MB with power supplies and phono sockets, but need the service manual to do this (and find out if it's even practical, given the way the DVD player acted as the main switching centre of the system).
 

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