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Old 19th March 2005, 03:11 PM   #1
Giaime is offline Giaime  Italy
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Default Technics 615 recondition

Hello! I just recived as a gift from a friend of mine this old tape deck. It dates to about 1977 I think, and it's a beautiful model in minty condition (little used) that I believe shlould be worth the effort to use in my system (I never had a tape deck). Where should I start to make it like new? Changing capacitors, transistors, things like this. And what about the mechanics?
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Old 20th March 2005, 11:29 AM   #2
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Hello again! I tried the tape deck after cleaning it. I cleaned the heads with normal alcool, and the sound I'm getting is very boomy, distorted and with no high-frequency content (it has nothing over 1kHz)... What should I do? The other mechanics are working well, maybe I just have to replace some capacitors (?) to extend the frequency range... I've even turned off dolby NR, but with little results.
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Old 20th March 2005, 11:59 AM   #3
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Is this on prerecorded tapes? If so, then the heads are likely out of alignment.

If it is on tapes you just recorded, then the bias may need tweaking.
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Old 20th March 2005, 01:02 PM   #4
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Yes, this is happening with tapes that I've prerecorded on my JVC mini-hi-fi, and on that they play well. On the Technics they play so bad. How can I adjust the allignment? Others suggested me of tweaking the azimuth (don't know what is) and demagnetize the head. Or just replace it. What shall I do?
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Old 20th March 2005, 02:52 PM   #5
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Ciao Giaime,

to adjust the alignment (or azimuth) of the head, you have to adjust a small screw which is usually placed next to the head itself. This screw helps you adjust the relative skew between head and tape.
To de-magnetise the head, there are some special devices around (TDK was manufacturing a de-magnetiser in the shape of a cassette, you just have to insert it into the deck and press play for a couple of seconds).

Cheers,

Bruno
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Old 20th March 2005, 03:02 PM   #6
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Thanks Bruno! I will try... but now the deck has started to act strangely, there's a big hi-freq oscillation over the signal, and the vu-meters stay on the max all the time... What can cause a tape deck to oscillate when some hours ago it didn't?
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Old 20th March 2005, 03:55 PM   #7
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These old tape decks suffered from bad contacts in the record/play switch. You can check that by pressing the record switch a few times with a cassette inserted and pause switch activated. If the VU-meters go back to normal the switch it is.

/Hugo
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Old 20th March 2005, 04:32 PM   #8
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Ok... don't know how I did it, but now the oscillation is gone... but before I cleaned the switch, the resistance across it was 0.3 ohms, after it measured the same. Anyway, problem solved... What can I do for that big loss of highs? Btw what I hear is wonderful, more "stereo" and involving than my JVC. I think this deck has great possibilities but it doesn't have any hi-end. I'm not using the best cable possible, but I doubt it's this causing the problem...

And what are all those trimpots inside it doing? I can't find a schematic of it...

I see that the outputs are transformer coupled (yes, there are 2 small transformers on the board, about 1 cm tall and 1x1cm. Is this usual in tape recorders?

Do I have to change the many electrolytics I see in the signal path for film caps? Will this improve the situation?
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Old 20th March 2005, 04:41 PM   #9
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Dont start fiddling with the trimpots inside unless you have a detailed manual.
The loss of highs is most probably what Al and Bruno said.
If possible, try recording a 3Khz or so signal on the JVC.
Play it back on the Technics and align the playback head. While doing so, listen with a headphone for best reproduction or measure the output of the deck with a scope and align for highest amplitude.

/Hugo
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Old 20th March 2005, 07:37 PM   #10
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I can't find any manual for that, neither a schematic...

I would do so, but...
1) there isn't any adjust screw; I mean the head is fixed by 2 screws on a piece of plastic that moves when I push play
2) the JVC has the record side broken I can only play with it, it does record but difficultly (a mechanic problem) and it does record only right channel...

Anyway I've changed the head with a new one: see results here (sorry, these two threads are running in parallel on the same subject, that wasn't my fault. Sorry again)

Just got new junk from my friend
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