XTZ W10.16 subwoofer repair

[mtah]

Update: No success yet

So far I've replaced:
C1/C2(SW)
C5/C6/C122/C123(ASW)
C17/C18/C23(GSW)

The only capacitor of the ones I replaced that was seemingly broken/in bad shape(according to my multimeter capacitance test) was C18.

I measured the output of the subwoofer and got these values:


120mV AC @ 50hz
15mV DC

Should mention that mains in my country is 50hz.

Also, I'm just guessing now, but one thing that could've caused something to break is that I've never had the subwoofer in standby mode or turned it off, so it has been connected to mains for long periods of time.

So, where do I go from here, any ideas?



Side note: There are a four poly caps on the SW that seems to be missing from the schematic(or atleast not explicitly drawn), see attached link.
I also checked the bridge rectifier IC and it seems to be in good condition. Could it be a transformer issue?

[mtah]

I just made a big discovery that I'm really beating myself up over having missed before.

R20 (10k ohm), and possibly D8 as well seems to have gotten really hot, take a look at the uploaded image right here:

https://imgur.com/a/nKn3bzL

In circuit measurement of the two components dosnt show any faults though.

You guys recon I just order and replace these two parts or should I look to replace anything connected to those as well?

[g1]

Has that resistor already been replaced before? I can't see how you could get that much browning/burning under the 10K without the resistor itself browning a little bit, but it looks brand new condition.

[mtah]

Has that resistor already been replaced before? I can't see how you could get that much browning/burning under the 10K without the resistor itself browning a little bit, but it looks brand new condition.

Nope, never been touched, atleast not by me and I bought it brand new.

Could it be the just the solder flux thats brown?

[g1]

Nope, never been touched, atleast not by me and I bought it brand new.

Could it be the just the solder flux thats brown?

It could be. The picture does not show very clearly for me. Do they measure ok?

IC1 (UPC1237) is a protection circuit. Find out if it is putting amp in protect mode. Datasheet attached.

[mtah]

It could be. The picture does not show very clearly for me. Do they measure ok?

IC1 (UPC1237) is a protection circuit. Find out if it is putting amp in protect mode. Datasheet attached.

Thank you!

I've only measured them in circuit but they seem to give the right results. 9.9k on the resistor and 0.5V from the diode and an open circuit if I reverse the probes.

I'm had a quick look at the datasheet and I'm not sure I fully understand how to find out if it puts the amp in protection mode. I guess it amounts to finding the relays it controls and see if they're open circuit or not? I will have a look at it again tomorrow, its getting late here.

[g1]

If the relay is not closing due to protection, there may be DC offset at the amp output that you can not measure at the speaker side of the relay.