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Speaker Issue/ Mod. (Polarity)


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#1 subsonicPH

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Posted 23 January 2013 - 08:17 AM

I got my Pipo M8 a few days ago . At the store, the 1st tablet the store brought out was reserved for me. i noticed the speaker output was so low even at max volume and the rear shell was shakey so i asked for a another one. the next M8 they gave me had the same low speaker output. i noticed that there was no low frequency or mid bass output and the sound was not at the center , rather in a surround sound effect. I knew that one of the speaker was connected in reverse polarity which produced cancellation of the mid bass range of both speakers. I disassembled it at home to see that the wiring of the speakers was ok in color and position but I switched the polarity of one speaker. after that i got the right polarity which improved the sound output and correcting it to a stereo configuration.

To those who are experiencing a unbalanced sound or when the sound is not at the center of the two speaker, try blocking one of the speaker ports with your hand, if the sound output becomes more thick or has more bass, then the polarity of one speaker is wrong/inverted

I dont know if this is an assembly error or if Pipo did this on purpose to enhance its 3D sound effect or surround but among 3 m8 tabs i listened to at the store had the same output and out of polarity speakers.

Simple solution, just reverse the polarity or connection of one speaker to the board. then test if the sound is better.

btw it was a heart attack disassembling a tablet =@


Edited by subsonicPH, 06 February 2013 - 12:11 AM.


#2 carlsberg

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Posted 05 February 2013 - 08:31 AM

hello , i have the same problem ..
How did you disassamble the tablet ?
fixed it already .

Edited by carlsberg, 05 February 2013 - 10:53 AM.


#3 subsonicPH

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Posted 06 February 2013 - 12:09 AM

hello , i have the same problem ..
How did you disassamble the tablet ?
fixed it already .

so you opened and fixed the speaker issue?

#4 carlsberg

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Posted 06 February 2013 - 01:10 AM

so you opened and fixed the speaker issue?

Yes , i found on xda forum some pics about how to open it .
Changed + and - all good now .

#5 BamaPanda

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Posted 10 February 2013 - 06:15 PM

Yes , i found on xda forum some pics about how to open it .
Changed + and - all good now .


I looked but did not find. Do you have a link for the XDA opening of the device?

Thanks.

#6 carlsberg

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Posted 11 February 2013 - 11:35 AM

I looked but did not find. Do you have a link for the XDA opening of the device?

Thanks.

It doesnt show exactly how to open it , jus some pics of the opened device .
To open , on the backside lower corner with a nail go under the lid then use a credit card to unhook all the small hooks .
You need to be a bit carefull but it works . I am planning to install an 10.000 mha battery in it soon :rolleyes:
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#7 BamaPanda

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Posted 11 February 2013 - 12:05 PM

It doesnt show exactly how to open it , jus some pics of the opened device .
To open , on the backside lower corner with a nail go under the lid then use a credit card to unhook all the small hooks .
You need to be a bit carefull but it works . I am planning to install an 10.000 mha battery in it soon :rolleyes:


That is quite ambitious. Posted Image

You will have to take pictures and report back with your progress.

Curious: Have you experienced the digitizer problem that others have seen when charging?

Thanks

Edited by BamaPanda, 11 February 2013 - 12:05 PM.


#8 carlsberg

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Posted 11 February 2013 - 12:28 PM

That is quite ambitious. Posted Image

You will have to take pictures and report back with your progress.

Curious: Have you experienced the digitizer problem that others have seen when charging?

Thanks

Hey ,

I installed an firmware from the pipo BBS , rooted and some other things .
Seems to work okay , sometimes the screen seems to be to sensitive when charching or not dont mather .
About the battery , i have to open up the device and measure the place i have for the battery .

#9 carlsberg

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Posted 14 February 2013 - 12:28 AM

That is quite ambitious. Posted Image

You will have to take pictures and report back with your progress.

Curious: Have you experienced the digitizer problem that others have seen when charging?

Thanks

Hi , found a link to xda XDA

#10 ch-vox

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Posted 21 February 2013 - 03:07 AM

Hi,

I also post my pictures on Slatedroid too so that you can disassemble your M8.
Regards


- take your tablet from the rear side in one of the two round corners
- insert a nail in the round corner and pull off the corner
- then a thin plastic card, unlock each hook one by one along the edges

you'll find the mainboard, the batteries (that are approximately 2 or 3 mm thick), the connectors that are very roughly soldered, the logic board of the screen...

sorry for those poor pictures :

Posted Image

Posted Image

#11 Glenn2

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Posted 06 April 2013 - 06:26 PM

I wonder if all M8 are like this?

I just got one today and it is - or was - as I just reversed the polarity of the left speaker and the sound is absolutely fine now.

This is not for the faint-hearted and I should point out that I am used to performing micro-surgery on things like this.
I would advise against anyone doing it unless they are very confident (or can afford to kill the tablet).

To do it properly you'd have to completely remove the main logic board so you can remove and re-attach one of the speakers which are front facing so not accessible just by taking the back off. This would involve disconnecting the tiniest of connectors.

I didn't fancy doing that, so after removing the six screws that hold the board in, I just lifted it away at the top, enough to be able to prise one of the speakers out of its mounting with a small screwdriver. With the speaker hanging out to the side on its blue and red wires I cut them about half way, soldered them together again crossed over, insulated them and re-fitted the speaker. Very tricky indeed as the wires are so thin. Instead of trying to strip the ends of the wires to rejoin them, I just burned the insulation off the cut ends with my iron.

One other thing to be careful of is that the buttons for home, esc and power are not attached to the case, so when you move the board away from them they are likely to drop behind the board. In hindsight I would have put tape along the outside edge to grip the buttons in place during the operation.

I doubt very much if Pipo would fix it via firmware, because any change that reversed the polarity of one of the audio channels would fix the speaker sound but completely ruin the headphone sound. If they could make it user selectable or detect when headphones were attached then perhaps that would be a different matter. I hope not anyway as I would have to reverse my wires again!

Such an easy thing to change during factory assembly too. Maybe they are OK now and mine rolled off the assembly line before anybody noticed.

I also have the much-reported crazy digitizer problem when charging. This is just AC leakage from the switch-mode power supply that gets into the tablet and then flows out to earth through you when you touch it. You can feel it as a tingle if you stroke the back of the tablet too. It's quite common on touch-screen devices. It's a combination of a noisy PSU and an intolerance of noisy PSUs by the tablet.

I have a multi-voltage linear PSU, i.e., based on a normal-sized transformer and a linear (not switching) regulator. That causes no such problems.

A suitable one from e#b#a#y would be the 9V/2.1A one for the Sinclair Spectrum +2 home computer. You'd have to take it apart and swap the lead from the Pipo one.

Another solution is to open the Pipo one and connect a wire at the DC ground at the output that exits the PSU. You would then connect this to mains earth at the socket. I tried this too. I wedged the other end of this wire in with the metal earth pin of a plug in an adjacent mains socket. This earths the tablet so no AC current flows through you when you touch the screen. The touch screen was again fine when I tried this. You'll also notice the tingling sensation has gone if you stroke the back panel. This method however could cause some issues (hum loops) when connecting the tablet to another earthed device such as a desktop PC with an earthed metal chassis, as your Pipo PSU is no longer floating but also earthed. A good quality PSU replacement (i.e., another SMPS as that is all you can get these days) may also cure it, but you'd have no way of knowing until you bought it. I don't have another 9V one to try.

Apart from that, very nice tablet!

Edited by Glenn2, 06 April 2013 - 06:27 PM.