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Greetings,

 

The above thread is closed, so I’m starting a new one, with the hopes of finding a solution.

My Play 5 gen 1 lost all communication a while ago. There was a very nice videon on YT by Henzelmen, which made me fix the power supply. The unit came back to life, let me update firmware.

But during the update, I noticed a background hiss.

After the upgrade, I can play music, but it is tinny, lacking bass and continues to be noisy and quite low volume from what I do remember this Play:5 delivering in the past.

I did ohm out all the resistors indicated in the picture of the above thread.

 

They all seem ok, except R27833, which according to the marking (30d) should be a 200kOhm, but measures 4.99kOhm…

When I do measure Source-Drain on the MosFET (Q27621), it shows a short circuit. I’m guessing this means the mosfet is busted…

Now, I went on Amazon and on Newark Electronics, looking for APM4307, but it doesn’t show up. And I haven’t found an equivalent either. Can someone point me in the right direction please?

Lastly, if the MosFET is busted, should I be looking for something else to be kaputt too? Cheers

 

cheers

 

Good Evening;

I ordered some APM4307K from AliBaba. Seems the only place to get them. We’ll see, how that goes.

 

In the meantime, I had another look at the Elkos. Sure enough all 5 820uF/35V near the output were bulging, along with a 1mF/25V in the center of the board. I went ahead and replaced them all.

That took care of the hissing sound.

 

Now, measuring the gate of the the MOSFET, it doesn’t seem to move at all, when I mute the unit. Maybe it is totally gone, not just D-S...

Now remains the low bass and the low volume in general…

Any hints?

 

Cheers;

When a transistor shorts, there often some additional damaged components in series with the transistor. Were those capacitors shorted? With regard to that resistor, is anything in parallel with the resistor? Is the value that you measure sensitive to ohmmeter polarity?

Faced with bulging capacitors and a shorted power handling transistor, I will not apply power to a unit until all of these details are fixed. Generally I will also replace any transistors directly connected to the failed unit because they were probably stressed during the failure process and will fail at a later date.

Thanks Buzz;

No, none of the cpacitors were shorted. They all were reading some voltage across…

The MOSFET turns on the power to the amplifier. since it is shorted out, the amp is just on all the time.

I wonder, if a kind soul went trough the trouble of generating a schematic for this unit… since everything is SMD, I have no idea what else is attached to that MOSFET and there are no intelligible markings…

 

Cheers

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