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Author Topic: Unusual tuning occurrences  (Read 265 times)

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mselic

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Unusual tuning occurrences
« on: February 14, 2020, 03:41:59 PM »

I’m currently doing some spot-tuning work on a PA, and I’ve noticed something peculiar happening that I can’t explain. Some of the reeds needed to be flattened a fair bit, so I got out my file or scratcher and went to work.  Occasionally I will have gone just a tad too far the other way and then have to file near the tip to raise the pitch again. At this point I will check the tuning once again only to discover that, after just a few strokes of the file at the tip, instead of raising the pitch it has actually resulted in the pitch dropping even further. What could be causing this? No gaps in the wax and the valves are ok. This seems to be happening often on this instrument.
« Last Edit: February 14, 2020, 03:46:00 PM by mselic »
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mselic

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Re: Unusual tuning occurrences
« Reply #1 on: February 14, 2020, 03:45:02 PM »

I’m also discovering that some of the reeds are having a very difficult time maintaining their tuning. All will be well and then I’ll come back the next day only to find them wildly off once again.
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4 stops: Melodie D, Beltuna G, HA114 A
Hohner Erica D/C#

Lester

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Re: Unusual tuning occurrences
« Reply #2 on: February 14, 2020, 04:05:09 PM »

My first long distance diagnosis would be that the wax is shot and the plates are not correctly anchored. I would try popping one of the recalcitrant reeds out and see how easily it is removable

Steve_freereeder

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Re: Unusual tuning occurrences
« Reply #3 on: February 14, 2020, 04:14:13 PM »

I concur with Lester's diagnosis as being the most likely.
It's not always possible to tell if the wax is cracked just by looking at it. Try re-melting some of the wax around a couple of the reeds and see if it stabilises the tuning. If it does, then that is the likely cause of the tuning problems. Strip all the old wax and replace with new.

Other causes of pitch instability which I've come across:
1. Cracked reed block, between the reed chambers and base plate. Clean off all wax and reglue and clamp the reed block.
2. Loose reed tongues (remove reed plate and gently hammer the rivet a few times whilst supporting the other side against an 'anvil' (a hefty hammer head works well)
3. Fractured reed (will eventually fail and will need to be replaced)

The fact that you have several reeds with tuning stability problems probably rules out 2. or 3.
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Theo

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Re: Unusual tuning occurrences
« Reply #4 on: February 14, 2020, 04:17:56 PM »

My thought too.  Old wax loosing its grip.  You can sometimes confirm this by sounding the reed and pressing any hand tool onto the top surface of the reed plate. If the pitch changes noticeably when the pressure is applied or released then it’s time to replace the wax. 
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RogerT

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Re: Unusual tuning occurrences
« Reply #5 on: February 14, 2020, 05:33:16 PM »

What the others said about wax etc.
I assume the reeds are all clean and free from corrosion? Esp down near the rivet under the valve, where you can’t see it without taking the valve off?
Pitch dropping when filing the tip can happen if you are filing crossways/at an angle to the reed, but pushing the file away from the rivet. If the file isn’t super sharp you can sort of push the metal towards the tip without taking it off. So it’s good practice to push the file/cut stroke from the tip towards the rivet. Another reason for weird pitch fluctuations is if the rivet is loose, though hardly so you'd notice. I have a little metal block and sometimes hammering the rivet can solve this kind of issue.
If weird behaviour persists you need to gradually work through each potential cause (wax, valve, rivet, corrosion or dirt, consistency of how you sound the reed during tuning) until you discover what is happening. Do this on a sample of reeds. Also, it is good practice to tune and leave an instrument to settle for 24 hours. I’ve no idea why but it often needs a second tweak. I’ve heard of at least one other tuner that does this.

Steve_freereeder

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Re: Unusual tuning occurrences
« Reply #6 on: February 14, 2020, 06:20:53 PM »

...Also, it is good practice to tune and leave an instrument to settle for 24 hours. I’ve no idea why but it often needs a second tweak. I’ve heard of at least one other tuner that does this.
Yes - I do this too.
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Steve
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mselic

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Re: Unusual tuning occurrences
« Reply #7 on: February 14, 2020, 07:11:37 PM »

The wax is getting old, yes.  I always test the wax first by scratching it with my fingernail to see what kind of state it's in, and I could tell that it could probably do with replacing, however it wasn't so bad that it wasn't holding the reeds anymore (they weren't just popping out)  In this case, the client came in with a full-size piano accordion and wanted a few notes spot-tuned.  I informed her of the condition of the wax, but conceded that it did at least appear to be doing its job *for now*.  Re-waxing an entire piano accordion, which would of course involve re-valving and then re-tuning as well, is a huge job and therefore rather costly.  When clients come in with PAs that seem to be playing fine but just need spot-tuning, I inform them of the state of things inside but don't necessarily advise them to overhaul the whole thing as it's often not worth the expense.  If the reeds are falling out, then I tell them it needs to be done and there's no point tuning anything at all, but if they seem to be holding on then I let them decide based on their preferences/needs...thoughts??

I also wondered if my tuning file, which was at the end of its life, was partly to blame.  I swapped for a new file and the problem seemed to subside.  I always file down towards the rivet, never up.  There were a couple of reed tongues that benefited from having the rivets tightened up.  Perhaps that's a contributing factor?
« Last Edit: February 14, 2020, 07:14:15 PM by mselic »
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RogerT

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Re: Unusual tuning occurrences
« Reply #8 on: February 15, 2020, 06:39:43 AM »

Could be. Which reeds were going off after you tuned them? Concert pitch reeds or tremolo? Or did you set an octave and that went off?

Kimric Smythe

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Re: Unusual tuning occurrences
« Reply #9 on: February 15, 2020, 07:16:38 AM »

I have found that hand made and hand finished reeds on old instruments that have not been played much have a tendency to go sharp.
 My best guess is the very close fit of the reed to the plate can get some bi metal corrosion near the bottom and flexing the reed a bit will cause it to often drop into tune.

I never get this problem on reeds with less precise fits.
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