Hi everyone,
I recently got a Yamaha KX-300 on a whim, thought I might get back into cassettes just for a change of pace.
The unit I got came with a very strange issue though. It emanates this low frequency "mmmmmmmm" humming noise during playback. This noise is mechanical in nature and is only present during playback, not rewind or fast forward. I have not tried recording yet.
Any idea where I might start troubleshooting?
Any suggestions would be greatly appreciated!
Cheers
I recently got a Yamaha KX-300 on a whim, thought I might get back into cassettes just for a change of pace.
The unit I got came with a very strange issue though. It emanates this low frequency "mmmmmmmm" humming noise during playback. This noise is mechanical in nature and is only present during playback, not rewind or fast forward. I have not tried recording yet.
Any idea where I might start troubleshooting?
Any suggestions would be greatly appreciated!
Cheers
Possible motor noise.
FF and RW usually use a different motor or at least the playback head is not powered on to pick up the noise.
Check the suppressor capacitor is connected and working.
FF and RW usually use a different motor or at least the playback head is not powered on to pick up the noise.
Check the suppressor capacitor is connected and working.
Clean the heads and tape transport (roller & capstan). The physical tape can interact with dirt and cause quite a bit of noise.
Rewind the whole tape, and then try playing it.
The FF / RW wheels have a slipping clutch mechanism... that could make noise as well.
See if you can tape the hum (ha!), and then post it here... record it on your phone.
Rewind the whole tape, and then try playing it.
The FF / RW wheels have a slipping clutch mechanism... that could make noise as well.
See if you can tape the hum (ha!), and then post it here... record it on your phone.
Will check. Thanks for the pointer.
I took a stab at it. When played back on my phone I have to turn volume to max to get the volume level right.
Cleaning the heads, capstan etc is always a good idea.
The hum can be the induced magnet field of an amp or other device with a big transformer below or on top of the tape deck. That's very easy to check, lift the TD up and if it's reduced or disappears, you found the culprit.
The hum can be the induced magnet field of an amp or other device with a big transformer below or on top of the tape deck. That's very easy to check, lift the TD up and if it's reduced or disappears, you found the culprit.
The magnetic coupling causes that... the playhead is "active" during play, and there's the source of the magnetic field somewhere... so the head picks it up. Common problem.
There are 2 sources of the magnetic field in a tape deck:
1. Check the motor - it should have a few turns of mu-metal blocker sheet, wrapped around it (motor), to block the magnetic field from the motor.
2. The mains transformer can also cause it... if someone was playing with it...maybe turned the transformer around for 90 deg... or similar.
The recording's good!
I think a few photos of the motor and the transformer will be helpful...well-lit, in-focus.
NOTE: that hum might be within specs... You could add more mu-metal tape turns around the motor, though. That should kill it.
Đây là sự gây nhiễu phát sinh từ motor gây ra... . Vòng kim loại nhiễu của động cơ có vẻ có vấn đề, vậy bạn xem xét kỹ năng đó nhé...
Thanks! You reminded me, I read somewhere that activating the recording circuit will demagnetise the heads. I tried that and problem solved! 🙂
I also pulled the mechanism out and put it back again. Can't see anything wrong physically, but maybe it wasn't screwed down properly before?
It's my first time getting inside a tape deck actually. I'll probably tear it down some more and fix the mechanical counter while I'm at it.
Attachments
Good to hear you solved it. What was the definitive fix/issue?
I've worked on countless Yamaha decks and love their relative internal simplicity. Almost as though they were desgined to be serviceable!
An easy thing to miss when buttoning everything back up is to re-attach the ground wire to the chassis. I don't think a ground wire is included on the KX300 though is there?
In any case, if there is a ground-wire present on any deck I always clean the terminal and connector as a matter of course to ensure a good ground and prevent any hum.
😉
The current 'refurb stack'
I've worked on countless Yamaha decks and love their relative internal simplicity. Almost as though they were desgined to be serviceable!
An easy thing to miss when buttoning everything back up is to re-attach the ground wire to the chassis. I don't think a ground wire is included on the KX300 though is there?
In any case, if there is a ground-wire present on any deck I always clean the terminal and connector as a matter of course to ensure a good ground and prevent any hum.
😉
The current 'refurb stack'
You may have dirty switches / switch contacts. They get exercised when you toggle play<-> record. This is valid only if your model has mechanical "glide" switches... but probably not... your tapedeck does play-record switching electronically... I think.
A low current bias signal runs through the head during recording... I do not believe this could de-magnetise the head... maybe..?? Anyway, the mp3 recording you posted tells me that placing the tapedeck in rec could not have fixed that problem.
Yeah... good contact between metal parts is essential.
Check videos on how to clean the transport mechanism... the pinch roller and capstan are very dirty.
I use EI transformer with the section I highlighted in red removed, which will "open" the magnetic field to de-magnetise everything metal... works brilliantly (this will cause a lot of current draw through the transformer because the magnetic force is now dissipated wide and far). But, for 2-3 minutes it will do a job exemplary. You will also need a source of AC voltage to feed it to the transformer. I trust that you will match the AC supply voltage with the appropriate transformer and will keep an eye on the magnetic force dissipation. Check videos online to see the correct (actual) de-magnetising procedure...
I'd rotate the mains transformer for 90deg... but that's nitpicking...
... you could also wrap the mu-metal sheet around the "run" motor (used during the play/rec function). That will also reduce magnetic field leakage from the motor a lot..
The above will keep you busy for a while... it's a hobby.. I find it very useful in my daily life... it works better than meditation !! It worked really well for me for almost 4 decades.
Good luck and keep us posted on your progress. Nice quality photos, by the way...
TRANSLATION
This is a noise generated from the motor causing... . The motor's metal ring noise seems to be a problem, so please consider that skill...
Please check your translation software and post in English.
That's a very impressive stack! Where did you even find so many machines needing TLC haha.
I'm not sure what the definitive issue was. I took the mechanism out and screwed it back in, then I ran the record button with no cassette for around 30 seconds. This combination made the noise go away but I have no idea why.
Maybe it's the act of screwing it back down that solved the issue then? Could have been some sort of vibrational noise that I was hearing perhaps? Reading my original post I see I did not make one thing explicitly clear. I said the hum was mechanical because it came from the deck and not my speakers.
I gave the roller and capstan a quick swab of 90% isopropyl alcohol, then wiped it with a wet cloth followed by a dry cloth. Hopefully that'll get rid of any buildup.
Ah I think you misunderstood. What I meant was the recording of the hum 'when played back on my phone' needed to be at almost max volume to match the real hum.
Well, now you clarified that it was a mechanical 'hum' and not an electrical/signal-path hum it's now sort of obvious.
The lower-end KX decks have noisy mechs and don't have much in the way of mechanical damping. There's also a lot of free space inside most Yamaha cassette deck cases between the top and bottom inside surfaces of the case for vibrations to rattle and resonate around.
For some customer decks I have placed a sheet of noise-dampening material on the ceiling (inside) of the top case cover.
It helps mitigate some of the internal noise of decks with large internal voids quite a bit.
This was for a KX670 which, even though it has a relatively quiet mech was transformed with the noise absorption material.
The lower-end KX decks have noisy mechs and don't have much in the way of mechanical damping. There's also a lot of free space inside most Yamaha cassette deck cases between the top and bottom inside surfaces of the case for vibrations to rattle and resonate around.
For some customer decks I have placed a sheet of noise-dampening material on the ceiling (inside) of the top case cover.
It helps mitigate some of the internal noise of decks with large internal voids quite a bit.
This was for a KX670 which, even though it has a relatively quiet mech was transformed with the noise absorption material.
That is exactly what can be done to alleviate mechanical/chassis noises. Just about any chassis will ring like a bell when undamped. This also means that the chassis will easily transmit unwanted noise.
Unfortunately this proved to be true.
After playing quiet for 4 or 5 tapes I noticed the hum again. Having played about a dozen more since then, the hum seems to come and go. By that I mean the volume seems to fluctuate. Sometimes it's loud and I can easily hear it over background noise during quite sections between songs. Sometimes it's quiet and just blend into the background.
I'm still not sure where the sound is coming from. Might be the motor or it might be the transformer. Might also be the case resonating, but I've tried taking the top case of and that doesn't seem to affect the hum much (when it's present). Very strange.
By the way, does anyone know a good 3rd replacement for Yamaha part number CB 65 04 00? It's the counter belt used in the KX-300 and the K-340 cassette decks.
I would look for a generic drive belt (or square section gasket-ring) with necessary dimensions.