Problem with very slack string tension on 12 string guitar

[tmatmatma]

I have just acquired a very nice old Kimbara 12 string acoustic for a great price. The purchase was from gumtree - upon inspecting the guitar the only obvious issue I could spot was that the all the strings had not been changed by the previous owner for many, many years. I bought the guitar on the spot and replaced all the strings. Unfortunately, on about three of the strings - the high octave E, A and G strings - the tension is way, way too slack. I attempt to tune them up, but the looseness of the string does not allow them to stay in tune and obviously they are simply not comparable to the other high octave strings, which sound feel great.

I am trying to determine the source of the problem. The machine heads do not have screws on them, they are part of an enclosure. I have seen advice elsewhere recommending to tighten these, but obviously this is something I can't do.

I did notice that the circular base of these three machine heads is not entirely flush with the headstock. I have tried removing the strings and pushing the machine heads flat, but they don't appear to be moving much.

From the description given, can anyone offer any advise over what to do in this situation? Would removing all the machine heads and reassembling be advisable? I want to check before I take anything apart.

I have enclosed a picture to try and show how the problem machine heads don't appear to be entirely flat (although I have noticed a couple of strings which are not so slack aren't entirely with flush machine heads either, albeit at less of an angle), though I don't know if I have captured this well. I could possibly take a video if the info I have given here doesn't reveal an obvious answer. Any help would be greatly appreciated!

[mirwa]

The top washers are actually a small press in mushroom shaped cover that surrounds the shaft of the machine head.

They will not affect the tuning or function of the machine heads, if you want them to sit flusher, remove the string clean the hole and press them firmly into place

Steve

[ricklt]

The screws in the gear on the back of the headstock are the screws that need tightened. That should solve your problem.

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[LSemmens]

Good score. As above, the washers, do nothing in regards tuning, and the screws just neded a little tightening.

Are you sure that you set the string in the bridge pins properly?

[tmatmatma]

Originally Posted by LSemmens

Are you sure that you set the string in the bridge pins properly?

I now think this could be the issue. I've ordered new pins in case these old ones are past their best.

[HHP]

Dumb question, but are you sure you are tuning an octave above the primary string? If you can get it to pitch, its not the pins or the machine heads as they would affect both octave and primary.

[runamuck]

You're saying that when brought up to proper pitch the problem strings are slack, correct?

If that's right, the string gauges are wrong.

There may be other issues with the tuners but they're irrelevant to the strings being slack.

[ricklt]

Can you explain how you tuned it. Did you tuned it once and call it good. Not trying to say you don't know what you are doing. Just trying to get a good picture of what's happening. I have to tune mine 3 or 4 times initially, to get it right, and then a couple of times later after the strings stretch. I'm sure you probably know all this, but if you don't, it might explain the problem.

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