Technics 615 recondition

Giaime · 19th March 2005, 02:11 PM

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?

Giaime · 20th March 2005, 10:29 AM

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.

pinkmouse · 20th March 2005, 10:59 AM

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.

Giaime · 20th March 2005, 12:02 PM

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?

Carondimonio · 20th March 2005, 01:52 PM

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

Giaime · 20th March 2005, 02:02 PM

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?

Netlist · 20th March 2005, 02:55 PM

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

Giaime · 20th March 2005, 03:32 PM

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?

Netlist · 20th March 2005, 03:41 PM

Don’t 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

Giaime · 20th March 2005, 06:37 PM

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

19th March 2005, 02:11 PM	#1
Giaime diyAudio Member Join Date: Oct 2004	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?

20th March 2005, 10:59 AM	#3
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	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. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

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20th March 2005, 10:29 AM	#2
Giaime diyAudio Member Join Date: Oct 2004	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.

20th March 2005, 12:02 PM	#4
Giaime diyAudio Member Join Date: Oct 2004	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?

20th March 2005, 01:52 PM	#5
Carondimonio diyAudio Member Join Date: Jun 2004 Location: Bern	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

20th March 2005, 02:02 PM	#6
Giaime diyAudio Member Join Date: Oct 2004	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?

20th March 2005, 02:55 PM	#7
Netlist diyAudio Moderator Join Date: Jan 2003	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

20th March 2005, 03:32 PM	#8
Giaime diyAudio Member Join Date: Oct 2004	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?

20th March 2005, 03:41 PM	#9
Netlist diyAudio Moderator Join Date: Jan 2003	Don’t 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

20th March 2005, 06:37 PM	#10
Giaime diyAudio Member Join Date: Oct 2004	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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