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TexasDude's avatar

Vintage electronics gurus: would you kindly help me troubleshoot my turntable home audio set up?

Asked by TexasDude (25234points) August 12th, 2011

I recently purchased a Kenwood KD-45 fully automatic turntable from Craigslist and a 70’s HH Scott 320R receiver. (Both were advertised by their sellers as being in perfect working order)

I set everything up and I was listening to records earlier today through cheap headphones with no issues at all. I turned everything off and went about my day. I came back from getting a huge haul of albums from my grandparents a few hours later and got ready to listen to a pristine copy of Meet the Beatles. To my dismay, the volume was very quiet, even when I turned the knob up, and there was a great deal of static, pops, and distortion to the sound. I tried the new LPs I was listening to earlier and they had the same issues. I tried a different set of headphones and had the same problem. Thinking it might be a headphone issue, I went out and bought some Koss over the ear headphones that a few people have recommended to me. I got home and plugged them in, turned everything on (with the Beatles album in again) and the sound was beautiful and clear. Just as the album went to the second track, the volume dropped dramatically and the distortion/crackling sound came back.

I don’t have any speakers, so I can’t really troubleshoot everything, but I’m thinking this may be a headphone jack issue. Can anyone here help me figure it out?

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17 Answers

woodcutter's avatar

If that is an old receiver it may need to have the controls (knobs) turned briskly back and forth to loosen up any corrosion on the contacts. Don’t do this with it on. At low volume if you adjust the knobs and you hear static, its the controls that may loose contact in certain spots. Does the record machine have a ground wire? Really important it’s connected or you will get wicked hum.

YoBob's avatar

Have you checked/cleaned the stylus?

Sometimes a little bit of lint/dust/crud will get stuck in between the two sides of the stylus and will keep it from registering properly. Diskwasher used to make a stylus cleaning kit that consists of a little brush with a mirror on one side to help you look. It is designed to be used with SC-2 stylus cleaning solution.

gasman's avatar

As I understand it, you’re listening through a headphone jack in the Scott receiver, which is connected by cables to the turntable.

If you suspect the problem is the jack, try using a spray can of compressed air to blow out the jack. Try plugging & unplugging the headphones repeatedly, maybe with a little alcohol on the plug, to break up oxidation / tarnish on the metal contacts inside the jack.

Or the problem could be cables between turntable and receiver, which I assume use RCA phono plugs (picture). You can rotate the plugs around the jacks (again to break up tarnish) and tighten each plug’s “collar” by bending the outside metal tabs inward a little. Often a wire will break in the cable itself just outside the strain relief. Try new cables.

Are you able to connect any other audio sources to the receiver without this problem? Then the turntable is faulty. I’d look at the little wires connecting the cartridge, where it attaches underneath the end of the tonearm.

In the end you might need to open something up & be prepared to replace one or more parts.

TexasDude's avatar

@woodcutter the grounding is connected securely. I did the thing with the knobs and it had no effect. I should probably mention that I have tested the AM/FM radio feature on the receiver and it sounds fine. I should also mention that the sound quality improves slightly when I switch to mono as opposed to stereo, if that is relevant.

@YoBob the stylus looks ok to me. Then again, I’m not really sure what to look for?

@gasman it’s probably not the jack, because FM radio sounds fine through headphones and doesn’t have the audio quality issues like when I’m listening to my turntable. I just now put on a record and listened while fiddling with the knobs and jacks. My right side audio goes out when I switch to stereo from mono. The quality is more consistent on mono mode, if that helps.

@everyone, thank you all for helping me out here.

woodcutter's avatar

It still might be the plugs though. The input for the receiver is internal, unless it is a separate tuner. Dumb question- the player is plugged into phono? It might be the cables that come from the turntable. When its playing, again low volume, wiggle the cables to see if it gets louder or clearer. Or the wires from the cartridge, 4 I think sometimes if they are wonky they will play well at one place on the record but as the tonearm gets closer to the end it could affect the connection. Sometimes with my old amp the speaker switch from a to b- to a and b together are scratchy and again zip them back and forth to get the contacts back to rubbing on metal again.
It could be the stereo reverse knob. It would be good to scrounge a set of speakers, even if they are auto and see if the speaker switch is working right.

TexasDude's avatar

@woodcutter soooooo I have my receiver set to mono and everything is fine. As soon as I set it to stereo is when the problems start. I guess I have it figured out now… there is something wrong with stereo on my receiver.

XOIIO's avatar

I’m interested in this but I can’t help, so I’ll jst sit back and watch.

woodcutter's avatar

It’s been so long since I have dared to even look behind my system. It’s a real flustercluck back there. You could be getting one channel only coming through both speakers. If that is the case it could still be the record player. If you have a discman with the RCA adapter cable to 1/8 inch phono plug, you could hook that up to another input to see if it changes. Does the receiver have two phono inputs, ( back in the D J days when there were two spinning?). If so try phono 2.
Something else I thought of. There are 2 kinds of phono cartridges. One is ceramic, and the other is magnetic. One or the other sometimes needed separate pre amp to run? I think the ceramic .

gasman's avatar

The problem is somewhere in the right channel. Switching from stereo to mono clears it up by feeding Left+Right to both ears, masking the problem. It could be a problem in the phono preamp section of the receiver, in the cartridge of the turntable, or (still) in a connector / cable. Hope for the latter.

TexasDude's avatar

@gasman alright, I’ll do a bit more investigating and see what I can figure out. Thank you so much for your help!

Oh, and will this affect speakers when I hook them up? (haven’t bought any yet)

YoBob's avatar

@Fiddle_Playing_Creole_Bastard – Sounds like it could just be a dirty contact in the stereo selector switch.

gasman's avatar

@Fiddle_Playing_Creole_Bastard You said it sounds ok with the radio on, so it’s not the headphone jack or the stereo-mono selector. Switching FM radio from stereo to mono normally reduces noise a little by improving the signal:noise ratio (when I listen to small radios I try to use mono mode if possible). So I think the improvement in sound quality with mono is a “red herring” with radio as the source.

john65pennington's avatar

Wiggle all your wiring and see if you get a better contact. Sounds like a wiring problem.

TexasDude's avatar

@gasman it works fine in mono with records too. I listened to 5 or 6 records last night without any audio problems when it was set to mono. When I switched it to stereo, the audio problems came back.

gasman's avatar

I’d look specifically at the turntable’s right-channel cable & connector & try wiggling the wire (per @john65pennington) when you play a record. I can’t find Kenwood KD 45 online. Check cartridge wires as I mentioned earlier, if possible. The stylus or cartridge itself might be shot. In fact, I’d be careful setting down an unknown stylus on pristine Beatles vinyl.

Also make sure tracking weight and anti-skating are set. If the turntable lacks such controls then it’s fairly low-end, so you might have to replace the cartridge with or without a new tone arm.

We haven’t ruled out pre-amp problems, either. The “phono” inputs generally had an additional stage of amplification (RIAA analog un-compression, etc) that might have failed (bad transistor or diode, e.g.).

My money’s on a mechanical rather than electrical problem but either is plausible. By mechanical I mean a broken cable, bad solder connection somewhere, cracked circuit board, etc.

john65pennington's avatar

I had a set of really good heaphones. My young granddaughter grab one side of the left wires and yanked the sound right out of them.

Loose wiring can play havoc. So can a three year old grand baby.

TexasDude's avatar

@gasman yeah, I’m gonna order a new stylus/cartridge. Thanks for all your help!

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