ReCap on a Monitor Audio RSW-12 Sub

[Agent24]

Re: ReCap on a Monitor Audio RSW-12 Sub

Out of interest, how hot was your soldering iron that you used to get the old capacitors off of the board?

What you should be asking is how powerful. A small iron turned up really high will not work, it will just burn things. You also need to add fresh solder when desoldering, to aid in maximum heat transfer. Your iron needs to be clean. Preheating the board with a hot air tool or a hairdryer can help, if your iron isn't powerful.

It is a dual-layer (at least) board going by the photos, so that will make it harder.

I assume you are having problems trying to repair one of these yourself. Post what your soldering iron is etc

[Nutcasey]

Re: ReCap on a Monitor Audio RSW-12 Sub

I see so would something like this do it?

https://www.amazon.co.uk/INTEY-Solde...ing+iron&psc=1

I'm a bit new to this!

Thanks

[Nutcasey]

Re: ReCap on a Monitor Audio RSW-12 Sub

What I currently have is this from Maplins:

https://www.maplin.co.uk/p/maplin-40...iron-kit-n72hy

[kaboom]

Re: ReCap on a Monitor Audio RSW-12 Sub

Oh no, one of those ~900 Fahrenheit/~500 Cel. setscrew-tip land killers.
This is what leads to disgust and discouragement to newcomers.

Tips that oxidize and are poorly coupled to the heater. Which get stupid hot, then rapidly cool when placed against a PCB.
The extreme thermal cycling is practically guaranteed to rip off traces/pads.


A better tool will give a far better result, with less trouble.
If it's double sided, you really need something temperature controlled (closed-loop, NOT a variable "power control") with a high-mass tip.

[bmor]

Re: ReCap on a Monitor Audio RSW-12 Sub

I'm recapping my RSW12 as well and as Mikay's photos pointed out, the heat sink mating surface connection is poor. Not enough paste and questionable contact over the whole surface. I estimate the paste coverage to be 25% at best on mine and there's a strip of black insulator material (seen in his photo) that probably prevents complete mating of the two surfaces. Seems to be a problem with these subs that I'll be correcting when re-assembling.

[Agent24]

Re: ReCap on a Monitor Audio RSW-12 Sub

I'm not sure what the "black insulator material" you speak of is, but removing it may do more harm than good, if it's electrically insulating one part of the circuit from the other. Be careful...

[bmor]

Re: ReCap on a Monitor Audio RSW-12 Sub

Thanks for the warning, good advice. It's a stick on foam strip on the edge of the board where it attaches to the backplate. I'd just remove it in the area of the heatsink attachment so it's not interfering with the connection, which it is now.

[Agent24]

Re: ReCap on a Monitor Audio RSW-12 Sub

That looks like a multilayer board, and depending on how it was laid out and/or manufactured, there's a possibility of live copper being exposed on the board edges. They may have added that tape to avoid potential short circuits. Or maybe it's just to stop vibration- who knows.

It might be better to put a thin piece of aluminium or copper shim, or a thick thermal pad on the heatsink to extend it, rather than removing that insulating tape.

[bmor]

Re: ReCap on a Monitor Audio RSW-12 Sub

Good point, that whole edge does mount up against the metal back plate. I like your idea of extending the connection face, I'll probably try that. Thanks!

[R_J]

Re: ReCap on a Monitor Audio RSW-12 Sub

That black tape is likely there to prevent vibration. So the board does'nt vibrate against the heatsink

[bmor]

Re: ReCap on a Monitor Audio RSW-12 Sub

I guess I'll leave as much of the tape as I can in place while making sure the heatsink connection is 100%. On another topic, I'm replacing all the caps. Is there any advantage to increasing the size of the two 4700uf in the picture to a higher rating?

[bmor]

Re: ReCap on a Monitor Audio RSW-12 Sub

Sorry, last post didn't have the photo.

[Agent24]

Re: ReCap on a Monitor Audio RSW-12 Sub

As mentioned earlier in the thread, increasing the capacity may improve power somewhat. How much, or if it's even noticeable will depend on the rest of the design. If you like the performance as is, don't bother, you'll be spending extra money for nothing. If you want to experiment, go ahead...

Note that higher capacity power supply capacitors will cause a larger inrush current at power on. This added stress may or may not be a problem.

[bmor]

Re: ReCap on a Monitor Audio RSW-12 Sub

I'll just keep them the same size, seemed to work well. Thanks for the help!

[charlesgage]

Re: ReCap on a Monitor Audio RSW-12 Sub

Sorry to drag up a thread, but I am replacing my caps right now and nobody mentioned the 47uf 25v cap that is the last orange one towards the back of the board in BMOR's pic... I am a capacitor noob and only ordered the listed caps. Can i use any of them in it's place? Unfortunately that cap is measuring 4.4 ESR

Maybe the 100uf 25v panasonic cap? I have an extra...

[sam_sam_sam]

Re: ReCap on a Monitor Audio RSW-12 Sub

Sorry to drag up a thread, but I am replacing my caps right now and nobody mentioned the 47uf 25v cap that is the last orange one towards the back of the board in BMOR's pic... I am a capacitor noob and only ordered the listed caps. Can i use any of them in it's place? Unfortunately that cap is measuring 4.4 ESR

Maybe the 100uf 25v panasonic cap? I have an extra...

The 47uf@25volt cap will a value of 4.4 ESR is very high

I would recommend replacing it with a 47uf@50volt one

[charlesgage]

Re: ReCap on a Monitor Audio RSW-12 Sub

The 47uf@25volt cap will a value of 4.4 ESR is very high

I would recommend replacing it with a 47uf@50volt one

Ok, so I cannot get away with 100uf? I will have to order one more cap!

The only thing I will say is that I have a cheapie ESR meter. I read a bunch of reviews and the reviewers said it was great for part identification but that it was only good for ESR "directionally". It is supposedly within .1-.5 on ESR readings depending on the cap size. I am seeing readings on most caps I have removed at the "just passable" level but 3 of the caps have shown very high ESR, so I do think it is directionally correct.

My only trepidation on this meter is that I bought a set of Nichicon Caps alongside the Panasonic to try both. The nichicon's are at the "worst case, but should still work" ESR levels while the panasonics are all super low which is good. Maybe capacitors still have a broad difference in ESR? Both were supposed to be good brands.

This is a similar model to the one I have:
https://www.ebay.com/itm/LCR-T4-Mega...8AAOSwjjBcvWHt