Author Topic: Leaky Power comb on Super Chromonica 270  (Read 2140 times)

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Offline Elaphe

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Leaky Power comb on Super Chromonica 270
« on: March 13, 2021, 04:50:20 PM »
Hello everyone,

This is my first topic.

I bought a Power comb from Brendan Power for my 270 because it was really hard to play, requiring a lot of air and leaking most of it.

Following advice from Brendan’s videos I applied Vaseline to the slide assembly but it made very little difference, so I went ahead and got one of his combs. I bought the sanded and finished version because I have no gear at home to do a lot by myself.

When it arrived I went ahead and assembled it following the recommended instructions. I am very experienced in customising my diatonic harmonicas, so it was fairly easy.

The original comb was not great: I attached a photo of it. It wasn't helping with air tightness!

To my surprise, when the harmonica was back together, it was even worse! Horrible to play. Trying to play lightly only one reed produced a sound, the 7th hole blow G. The rest was breeze through the harp. To say that I was disappointed is an understatement.

I decided to proceed to gasket the harp like I was doing with my leaky diatonics: Micropore tape!

I gasketed the comb both sides and the slide assembly on the comb side and mouthpiece side (not the back of mouthpiece itself, the tape just won't stick to it enough to not move while cutting out excess), and after some laborious work to get all the excess tape cut out I reassembled the 270, putting some vaseline back onto both sides of the slide itself. I also did some very light embossing on all reeds, after checking the gapping.

Only one word: wow. That is so much better it's amazing! The sound is back to what it should be on a 270, it plays lightly and has a consistent response throughout.

I know that someone said that Micropore might be unhygienic, but it's easy to peel off and re-gasket every once in a while!

Anyone had a similar issue with so much leaking with a sanded custom comb?

Offline BeauKim

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Re: Leaky Power comb on Super Chromonica 270
« Reply #1 on: March 13, 2021, 11:49:53 PM »
Hi Elaphe,

I know you say that you have experience customizing diatonics.  Does that include doing screw conversions?  The reason I ask is if your drilling isn't smooth or your drill bits are worn you could've warped the reed plates.  Also you would know that you have to check for burrs that can impede on airtightness.  The original reed plates were probably slightly warped anyway from the factory, but you could check the flatness.  It's also best to make sure the inner windsavers aren't making contact with the chamber walls.   

Did you sand the front of the mouthpiece and reed plates after you assembled it?  I'd also double check the flatness of the comb even though it was sanded before. 

Offline Elaphe

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Re: Leaky Power comb on Super Chromonica 270
« Reply #2 on: March 14, 2021, 11:45:18 AM »
Hi BeauKim,

thanks a lot for the response!
Yes, I have experience re-driling/doing screw conversions, I was even changing reeds for a period: the drill bits were brand new, I de-burred the holes, and verified the reed plates for the fit in front on the comb - it was flush.
I haven't checked the flatness of the comb, I assumed that Brendan Power might know what he's doing!  ;)
The inner wind savers seem to be ok.

I definitely didn't check for reed plate flatness, but looking through the comb without the mouthpiece assembly on and shining a light from the back I couldn't see any gapping anywhere.

The sanding after assembly is something I hadn't even considered.

I see that chromatic harmonica customisation is much more complex on the macro level, the diatonic is difficult on a much more detailed level:
the instrument construction on the diatonic is disarmingly simple, and getting it airtight is a breeze (pun intended). But setting up the reeds for overblowing is a real skill.
The chromatic might need a less specific work on the reeds (embossing and gapping certainly) but not necessarily fine tuning the arcing of specific reeds. The real skill seems to be in the air tightness at the mouthpiece level. I have to learn a lot here!

Thanks again! I will be playing the instrument as it is now, which is pretty good, and when necessary I will take the mouthpiece off again and sand the front of the comb/reedplates. If I did it now the Micropore tape would get damaged and I would have to redo it, which was not that much fun!

Offline Jimmy Halfnote

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Re: Leaky Power comb on Super Chromonica 270
« Reply #3 on: March 14, 2021, 05:39:33 PM »
 The top-plate of the mouthpiece assy' has four flanges which often need to be filed down a tad so as to prevent slide leakage , also the slide should be smoothed and as mentioned already the reed-plates must be flush with the comb for mating to the MP assy' , if the edge of reed-plates are sitting a bit proud of the comb when attached then leakage is a certainty, regardless of the comb face itself being dead level before attaching reed-plates....... good luck.
                                                   jh.

Offline Elaphe

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Re: Leaky Power comb on Super Chromonica 270
« Reply #4 on: March 15, 2021, 08:37:33 AM »
Thanks a lot for the extra information!
I will definitely look into these details of the mouthpiece assembly.
I’m sure it will make a difference.

Cheers!

Offline BeauKim

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Re: Leaky Power comb on Super Chromonica 270
« Reply #5 on: May 04, 2021, 03:30:06 PM »
Hi Elaphe,
Have you been able to improve this? 

Offline Elaphe

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Re: Leaky Power comb on Super Chromonica 270
« Reply #6 on: May 06, 2021, 05:11:53 PM »
Hi Elaphe,
Have you been able to improve this?

Hello BeauKim,

I haven't been able to improve it much so I sent it to John Cook in London to have a look.
He said that I had done a decent job in sealing it but the reed plates and reeds are just plainly bad.
It is a 23 years old harmonica but it was never used. Apparently in those times bad copies weren't that uncommon.
It had not been used because I always found it to be unduly hard to play but had no chromatic experience.
At the end it's not worth spending the time and money on that harmonica...I might just but some replacement reed plates and get on with it!

Piro39

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Re: Leaky Power comb on Super Chromonica 270
« Reply #7 on: May 06, 2021, 05:39:27 PM »
Elaphe, I don't know if you know this, you can get pre-made gaskets for most model harmonicas instead of using micropore tape from dee's gaskets. I don't have his url handy but easily found, I think he is on Ebay and is a member of this group. Also sometimes harmonicas will leak from distorted reed plates caused by over tightening of reed plate screws.

Offline Elaphe

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Re: Leaky Power comb on Super Chromonica 270
« Reply #8 on: May 08, 2021, 06:48:32 AM »
Thanks a lot for your advice Piro39,

I saw that Brendan Power produces some (is he still doing so?) but I haven’t seen other options. I’d be very happy to see those! I’ll look into it.

I am very aware of the screw overtightening issue from my diatonic harmonica customisation experience, which is considerable. But thanks for pointing that out!

Flavio