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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 7th May 2020, 9:46 am   #1
G4CMY_Tony
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Default Pioneer CT-740 Playback Noise

I am puzzled by the noise that this cassette deck produces on playback.

It sounds like static discharges that you might hear on a vinyl record.

The file I have attached contains a .WAV file demonstrating the noise coming through the audio output when play is pressed with no cassette in the drive. When a cassette is played the noise is superimposed on the audio from the cassette.

When anything is recorded onto a cassette and the cassette is played back on another machine the noise is not present so it only occurs on playback.

I have played a different cassette deck through the same audio channel on the amplifier and the noise does not occur.

If anyone has any ideas what might be causing this I would be very grateful to hear them.
Attached Files
File Type: zip Playback Noise.zip (880.0 KB, 47 views)
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Last edited by G4CMY_Tony; 7th May 2020 at 9:49 am. Reason: Additional information
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Old 7th May 2020, 11:35 am   #2
TIMTAPE
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Default Re: Pioneer CT-740 Playback Noise

A little unusual.

I'm not saying this is what it is but I had a similar clicking sound with a Sony cassette recorder, also only on playback. This Sony deck had a moulded plastic chassis for the mechanism. In the end it was a static buildup from the capstan shaft, occasionally discharging to deck ground. The solution I came up with was a piece of wire grounding the capstan shaft.
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Old 7th May 2020, 11:41 am   #3
DMcMahon
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Default Re: Pioneer CT-740 Playback Noise

Yes does sound like static possibly. If you select Pause when playing does the noise stop, i.e. is the noise only present when tape moving ?
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Old 7th May 2020, 12:09 pm   #4
G4CMY_Tony
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Default Re: Pioneer CT-740 Playback Noise

Thank you both for your input.

Yes it does stop when the pause button is pressed.

I'll have a go at grounding the capstan shaft.

Many thanks.
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Old 8th May 2020, 11:48 am   #5
G4CMY_Tony
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Default Re: Pioneer CT-740 Playback Noise

Just an update.

I tried grounding the capstan shaft and it made no difference, even though it was a prime candidate - It rotates through a brass bush which is supported in plastic casting and the flywheel rotates against a nylon block thrust bearing.

I did, however manage to track down the problem it was cured by grounding the casing of the record/playback head. That was screwed to a plastic moulding too.

Problem solved and, having replaced the drive belts, I can now start digitising my old cassettes which is what I bought it for anyway.

Thanks once again for your help.
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Old 8th May 2020, 12:47 pm   #6
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Default Re: Pioneer CT-740 Playback Noise

Well done, it's nice when there's a simple cure.

I wonder whether there was an official mod? Or was it wrongly repaired in the past?
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Old 8th May 2020, 1:03 pm   #7
G4CMY_Tony
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Default Re: Pioneer CT-740 Playback Noise

Well everything looks to be untouched and in accordance with the service manual that I have dated April 1983 (which matches well with the dates on various components) so I don't think it has been repaired in the past. However, it does seem odd that an issue like this was allowed to go out.

I know very little about Pioneer equipment (although I know a bit more now )

No doubt someone on this learned forum will have some knowledge.
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Old 8th May 2020, 1:21 pm   #8
TIMTAPE
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Default Re: Pioneer CT-740 Playback Noise

Quote:
Originally Posted by G4CMY_Tony View Post
...I did, however manage to track down the problem it was cured by grounding the casing of the record/playback head. That was screwed to a plastic moulding too...
Well done. I should have also mentioned the other vital components in the tape path such as the head. With the Sony, the R/P head was mounted onto the plastic chassis but the designers had already grounded it by a dedicated cable.

Pioneer used a plastic chassis on a number of their mechanisms including the the CT-F series.
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