Korg Forums

[voip]

So no one helped you, then?

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[T3owner]

[simianquade]

Yes I would say that I have been assisted in the realms of the unknown. But I must say that towards the end of subject I started to feel disillusioned by the amount of carrots being dangled. I had followed the group with the advice about the purchase of the wrong capacitor leading to the obvious assumption.I had been into various shops and to electrical engineering companies who also couldn't give me the answer for what type it actually was.....That was my question all along. What type is it ? ? ?. Nobody answered that question in reality. I have learn't yes through intervention of other's. The outcome has created a good source for others to view positively unlike many other forums where the person looking for specific information gets bogged down in a sea of nonsense that is time consuming and tedious. At least these post's deal in variety of factual information with a start middle and a true ending.

[T3owner]

[simianquade]

Thanks that is definitely a full reflection concerning actions. I would advise you to continue giving people advice that is factual. May I say that in response to my original question c1 or c3 (the obvious mistake I made) my description was still of the "big pink one"......All biases aside toward any assumption's made the simple question was still there regardless to what level of I.Q you or I posses. Please do not feel negatively about my response or feeling that there was underestimation felt by me against the information you provided. That is not true either.....Thanks again!!

[voip]

People are generally helpful on this forum, and their intentions are genuinely to give good information, giving freely of their own time. I notice the original post has been edited many times (7 times to date), including changing the original capacitor reference from C3 to C1, casting a different light on the question, and making several posters, including T3owner, appear foolish and appearing to miss the point. That is bad manners, I'm afraid, and it would have been far better to admit mistakes were made and correct them in a subsequent posting.

The Korg M1 service manual does not explicitly tie parts, such as C1 and C3 in the schematics, to specific components in the parts list, many of which are now obsolete, or are obscure references, so we have to make educated guesses.

T3 owner is correct in saying that C1 should be an X2 type although some sources of information are not as clear as they could be, so I stand corrected. However, let's put this in perspective. Fitting a Y-type capacitor of the correct voltage rating in the C1 position would probably not have any bad consequences, since capacitors made for these uses are exceedingly reliable, and therefore unlikely to fail. Estimates of actual failure rates are hard to come by, are based on often zero failures, even in large production sample batch test runs at elevated voltage and temperature, and would usually require direct correspondence with the capacitor manufacturer to obtain the estimate for a given capacitor type. Reliability is often given as FIT values (failures in time, or the estimated number of failures in one billion component hours), and might typically be 1 FIT for a polyester film capacitor, equating to a MTBF of ~100000years! Yes, one hundred thousand years!!

I hope this is of some reassurance.

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[T3owner]

[T3owner]

[voip]

I understand, and appreciate your response, which is entirely acceptable to me as the sort of healthy discussion that represents the spirit of the forum :-)

Interestingly, the arrangement of Y capacitors in the M1's KLM-1269 psu, and similarly in the Wavestation, and many other bits of mains powered equipment, acts as an a.c. potential divider for the incoming mains supply. If the keyboard does not have a proper ground, and in the absence of any connections to other equipment, the case of the instrument will "float" at around half mains potential, conducted via C4, C5, C9, and C10 in the KLM-1269. I've just tested this by powering up a Wavestation without the ground wire connected and the case sits at a measured 109V a.c. with respect to ground, so the widely adopted arrangement of these safety components can itself cause what could potentially be a hazard under certain circumstances.

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[T3owner]

[voip]

Agreed on all points, except that a very distinct tingle could be felt whilst moving the back of the hand across the casing of the Wavestation during the "ground off" test.

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[T3owner]

[voip]

The epidermal skin on the back of the hand is generally drier and less conductive than the palmar skin, so current flowing into the back of the hand is likely to occur through smaller, more discrete contact areas, resulting in a higher current density at the contact points, and this could lead to a lower detection threshold.

This is also true of palmar skin. Passing 1mA into the palm of the hand via a metallic object which spreads and lowers the current density, e.g. a coin, will result in no noticeable sensation, whilst passing the same current via the tip of a pin will give a distinct tingling sensation.

There may be another mechanism at play here. Electrostatic attraction of the hairs on the back of the hand to the metal case surface, leading to mechanosensing by the A-beta nerve fibres associated with the hair follicles as the hairs experience successive attraction and release at twice the mains frequency. In support of this, the sensation is stronger when the back of the hand is moving over the case of the non-earthed Wavestation than when it is not moving. However, placing a very thin plastic insulating film over the case markedly reduces the tingle felt. This could be due to the plastic increasing the separation between hairs and case and reducing the electrostatic attractive force between hairs and case, or it could be that the tingle is a bit of both direct conduction between case and skin together with an element of electrostatic attraction.

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[simianquade]

Thanks for all your advice the keyboard now works well. I have another klm 1269 PCB that has also capacitor c11 missing I am looking for a replacement and would like to know what would be the best manufacturing type to reinsert? and what rating would that capacitor be as the other one I own is now inside the keyboard at another location. Thanks