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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 24th Apr 2021, 6:20 pm   #1
tocatech
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Default Sony TC-K15. Soft volume when recording to tape.

Hi guys,

I recently picked up a Sony TC-K15. when i tested it the playback was good. I had an Eric Clapton live cassette album and it sounded good. I did give the head a clean with isopropyl. But I'm having trouble recording. When I try to record the FM radio or if I hook up my electric guitar; the sound quality is so soft. Before recording I can set my recording levels and I can see from my VU meters that the recording level is healthy; even if I turn the recording level higher it's still so soft. I've tried different batches of tapes as well. is there possibly something I'm missing or is it something like head alignment or adjusting the recording level with pod on the board. It's just strange because the playback is so good.
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Old 24th Apr 2021, 7:56 pm   #2
TIMTAPE
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Default Re: Sony TC-K15. Soft volume when recording to tape.

Recording and playback use different circuitry. A tape machine can record well but play badly, or vice versa. or record and play badly.

The tape deck needs to be matched to the tape used, especially in recording. There are usually Types 1, 2 and 4. Most cassettes are Type 1 or maybe 2. Assuming you have a Type 1 tape, switch the deck to Type 1.
If the cassette you use gives poor results, try another. Some cheaper cassettes especially in earlier days performed poorly. TDK or Maxell C60's or C90's were generally very good.

Switch the Dolby off in both record and play and see what the result is.

Make sure the small felt pad behind the cassette tape is intact. It pushes the tape against the tape head. Without it, the sound will probably be inconsistent and muffled.

Make sure the central tape head is really clean. To see if the head is properly clean you may need powerful magnification like a lupe or strong reading glasses.

These are old machines and yours may need a good service. Tape machines always required regular servicing and occasional parts replacement and alignment. It appears the K15 used a standard record/play head. These wore down with use. The head wear often reduced record performance more than in play.

Last edited by TIMTAPE; 24th Apr 2021 at 8:07 pm.
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Old 28th Apr 2021, 10:55 pm   #3
John_BS
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Default Re: Sony TC-K15. Soft volume when recording to tape.

There are many switch contacts which change over between Record and Play modes. At least one pair is unique to the record signal fed to the heads, independant of the VU meters. So, try contact cleaner on the long S 303/ 304 switches and switch many times from play to record to clean the contacts.

Other than that, if you know this machine hasn't been tampered with, it may be a similar problem with the tape type switch S302 (same procedure). If someone has been in a had a tweak, they could have upset the preset recording level pots RV151 /251, but this seems unlikely. Those pots could take the level down to zero if maladjusted, but leave the VU's unaffected. Manual from HiFi Engine

John
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Old 29th Apr 2021, 10:17 am   #4
knobtwiddler
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Default Re: Sony TC-K15. Soft volume when recording to tape.

If Tim and John's advice doesn't cure it, then you might want to check that the bias oscillator is putting out the right level and frequency. A faulty oscillator can result in a 'dull' and quiet recording.
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Old 29th Apr 2021, 11:04 am   #5
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Default Re: Sony TC-K15. Soft volume when recording to tape.

Quote:
Originally Posted by knobtwiddler View Post
If Tim and John's advice doesn't cure it, then you might want to check that the bias oscillator is putting out the right level and frequency. A faulty oscillator can result in a 'dull' and quiet recording.
I think at this stage that's the first thing I'd check. But you'll need an oscilloscope or high-impedance voltmeter.

Mike
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Old 29th Apr 2021, 1:54 pm   #6
John_BS
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Default Re: Sony TC-K15. Soft volume when recording to tape.

Quote:
Originally Posted by knobtwiddler View Post
If Tim and John's advice doesn't cure it, then you might want to check that the bias oscillator is putting out the right level and frequency. A faulty oscillator can result in a 'dull' and quiet recording.

That's a really good point. More likely than correlated switch problems on both channels.

John
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