Studiomaster Drive 15A repair, help needed to identify components

[Cerbertech]

A local pub that I regularly engineer bands at has an installed rig with Studiomaster PA15 cabinets as the tops, one has stopped working so after dropping it and taking out the amp module there is a clear failure of what look like 2 capacitors on the final output stage / crossover board.

Google has failed me to get any info on the boards at all.

Has anyone come across repairing these and can help identify replacements, only marking is the number 220 on top of the cannister? 

[DrV]

220 in that size of case almost certainly means 22nF but if that's the only marking then you'd also need to specify a suitable voltage and dielectric type. The working voltage needs to be at least the same as the supply rail voltage but ideally around twice that. So if your supply is 40-60V you'd fit a 100V part. Dielectric type would be polyester film. With a cursory search I can't see any cylindrical, radial leaded ones like that but there are plenty of axial lead or rectangular box types available.

Edit: are you sure the caps have failed and that the black goop isn't just the adhesive holding them down? It does seem a different colour from the rest though.

Edited February 14 by DrV

[Cerbertech]

Thanks for the quick response and info.

Am pretty sure these have failed as the black scrapes off easily the pictures were after cleaning up the board a bit.

I am also thinking that they may have had a plastic coating like the others with more markings that has melted.

Trying not to have to drop the second one as its in an awkward place to get access but may have to see if there are other markings.

[sunray]

Can you see any legend beside them?

I think the shape and the 220 markings could just as easily be inductors. What sort of dimensions are they, it's difficult to assess but look big assuming those are the main smoothing capacitors to the left.

Something along these lines? 

https://www.mouser.co.uk/ProductDetail/Murata-Power-Solutions/19R226C?qs=RzyoSnN9rS1rBH8pFy5fSQ%3D%3D

https://www.mouser.co.uk/ProductDetail/Murata-Power-Solutions/18R224C?qs=AG1tZYOK7s7JGHJ5L0KsgQ%3D%3D

Edited February 14 by sunray

[DrV]

6 hours ago, sunray said:

Can you see any legend beside them?

I think the shape and the 220 markings could just as easily be inductors. What sort of dimensions are they, it's difficult to assess but look big assuming those are the main smoothing capacitors to the left.

Something along these lines? 

https://www.mouser.co.uk/ProductDetail/Murata-Power-Solutions/19R226C?qs=RzyoSnN9rS1rBH8pFy5fSQ%3D%3D

https://www.mouser.co.uk/ProductDetail/Murata-Power-Solutions/18R224C?qs=AG1tZYOK7s7JGHJ5L0KsgQ%3D%3D

Silly me - yes, could easily be inductors. More likely in fact.

[sunray]

2 hours ago, DrV said:

Silly me - yes, could easily be inductors. More likely in fact.

I don't know about silly as they appear to be massive.

[KevinE]

these are part of the output filters, they're inductors in the class-d woofer output stage, as already suggested. The dark stuff is the glue that holds them to the board gone a bit dark. Inductors are marked in uH plus multiplier, so 220 is 22uH.

 

rs wurth 22uH ferrite power inductor

Edited February 14 by KevinE
added link

[sunray]

44 minutes ago, KevinE said:

these are part of the output filters, they're inductors in the class-d woofer output stage, as already suggested. The dark stuff is the glue that holds them to the board gone a bit dark. Inductors are marked in uH plus multiplier, so 220 is 22uH.

 

rs wurth 22uH ferrite power inductor

Brilliant, that makes a lot of sense.

[Cerbertech]

Thanks everyone for the help, the black is very crumbly and looks like melted something as it flakes off, can't see any other obvious damage.

As they are cheap enough will order some and replace to see if that resolves the issue.

I knew the hive mind on here would help figure out what they were!

[KevinE]

No harm changing them, but while they're out I would carefully check the PCB tracks. The sort of glue that is used on active speaker pcbs can liberate a corrosive substance over time which can rot the copper.

Make sure you glue the new ones back in, use neutral cure high modulus silicone or similar fixative or they'll be rattling around at the bottom of the cabinet in a few week's time.