RCF powered speaker repair

[bruce]

Hi all, 

Looking for some advice.

I have a RCF Evox 8 powered speaker here, which has started popping fuses as soon as it's powered on (3.15A mains fuse, in the IEC receptacle).

Have removed the amplifier module - no obvious visible problems.

There are a couple of mosfets (P20NK50Z) at the PSU end of the module which look like they may be blown - haven't tested them out of circuit, but prodding them with a multimeter on diode setting suggests they are s/c.

So, I've got several options:

1. Order up a couple of new mosfets, install them, and try again. They're easy access for soldering.

2. Open up the (other) working speaker, remove the amp module and do some side by side meter tests.

3. Send it off to someone who understands this stuff better than me 😀

I know there are several people on this forum who fall into category 3 - any recommendations?

[DrV]

Definitely 3. There is little to be gained by just replacing bits which have blown without checking e.g. the chip which is driving them and any components in between.

[bruce]

Yeah, I’m not wanting to tinker with switch mode supplies.

any recommendations for good repairers? I’m in central Scotland, but the amp module is small and surprisingly light, so could be shipped anywhere in uk.

[Stuart91]

Hi Bruce, try Ollie and his team at Fretronics. https://www.fretronics.com 

Based in Govan so hopefully reasonably convenient for you. They've done a bunch of repairs for us over the last couple of years. 

[J Pearce]

We had similar with an EV amp module. It worked out cheaper (and quicker!) to swap the module than it would have to pay for diagnosis and repair. 

[chelgrian]

23 hours ago, bruce said:

Hi all, 

Looking for some advice.

I have a RCF Evox 8 powered speaker here, which has started popping fuses as soon as it's powered on (3.15A mains fuse, in the IEC receptacle).

Have removed the amplifier module - no obvious visible problems.

There are a couple of mosfets (P20NK50Z) at the PSU end of the module which look like they may be blown - haven't tested them out of circuit, but prodding them with a multimeter on diode setting suggests they are s/c.

So, I've got several options:

1. Order up a couple of new mosfets, install them, and try again. They're easy access for soldering.

2. Open up the (other) working speaker, remove the amp module and do some side by side meter tests.

3. Send it off to someone who understands this stuff better than me 😀

I know there are several people on this forum who fall into category 3 - any recommendations?

Have you asked RCF uk service at

https://ampman.co.uk

how much repair or replacement is?

[bruce]

21 hours ago, J Pearce said:

We had similar with an EV amp module. It worked out cheaper (and quicker!) to swap the module than it would have to pay for diagnosis and repair. 

Yeah, Ampman have replacement units for sale - the cost of the replacement unit is almost as much as the current second hand value of a full system!

[sunray]

Is it a Switched mode powersupply or transformer.

I've done several repairs in powered speakers where the transformer has failed with shorted turn(s) which WILL instantly Blow the mains fuse, possibly with a significant bang.

 

The simplest way I find to test the transformer is to wire a 500W lamp in series with the transformers primary and disconnect the secondary, this will stop the 3A fuse blowing when powered, there should be almost full mains voltage across the transformer and almost none across the lamp.

[J Pearce]

On 9/23/2024 at 7:44 PM, bruce said:

Yeah, Ampman have replacement units for sale - the cost of the replacement unit is almost as much as the current second hand value of a full system!

How boring. EV's weren't unreasonably priced at £149 each.

[bruce]

Thanks to all who responded with helpful suggestions.

The unit is now working again - thanks to K Edwards Electronics Engineers http://www.k-edwards.co.uk - @KevinE on this forum - who carried out a prompt and effective repair on the PSU section of the amp module.