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Old 20th March 2005, 11:59 AM   #11
Giaime is offline Giaime  Italy
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What is azimuth? And how I can demagnetize the head? Should I replace it or try these things?
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Old 20th March 2005, 02:00 PM   #12
Giaime is offline Giaime  Italy
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Aaaarghhhh! Ten minutes ago I plugged the tape deck into my amp and stroke "play"... I've got a very high oscillation sound, not dependent of my amp (because it does the same when the deck is unplugged) and the VU meters on the deck go on the max. What can cause a tape deck to oscillate if some hours ago it didn't?
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Old 20th March 2005, 02:35 PM   #13
anatech is offline anatech  Canada
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Hi Giaime,
The record play switch has dirty contacts. This may be a long switch or a relay. If it's a relay, cleaning it will be temporary, don't replace it until everything else is working properly.
Do not correct the azimuth (head angle, 0 = perpenticular to the side of the tape) unless you know for sure there is no path worn in the head. Use your fingernail and pull it from bact to front. Any ridge indicates wear.
Check the capstan bearing for wear and relubricate now. The oils are not effective at this time and the bearing will wear quickly if you use it now.
If the deck has ferrite heads, visible wear occurs slowly, but the actual head gap "chips" wide and HF response goes down.
-Chris
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Old 20th March 2005, 02:53 PM   #14
Giaime is offline Giaime  Italy
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Thanks! Cleaning the switch didn't help, and I don't know if it's linked to a relay, there are 2 black rectangular things on the board that seem to be relays, but they don't make that relay "click" when I push play. And I noticed that when the RCA cable to my amp is connected, the oscillation waits a moment before starting, and with the cable disconnected it starts to oscillate immediatly when I push play.

I won't correct the azimuth because I can't find an adjust screw, and yes, the head seems to have many scratches now that I removed the screws that holds it in place. They are vertical scrathces (I mean not parallel to the tape). It's the worn head that's causing oscillation and it needs replacing or it is something else?
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Old 20th March 2005, 03:52 PM   #15
anatech is offline anatech  Canada
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Hi Giaime,
The relay would engage when you go into record mode. Why not try that a few times to see if it clears up?
I have only seen an open head cause the playback amp go into oscillation. Bad contacts add resistance to that connection, so the playback amp oscillates for the same reason.
The azimuth screw is one withthe coil spring under it. Damage is done, put a tape in after reassembling the head. Screw the post side down, not overtight and put some nail polish on it. Make the head roughly parallel to the transport. The first tape is an old one you don't want. Play it and adjust the spring side for max highs. Once that is done, use some better tapes and adjust the same screw for max highs. Use the normal setting if the highs are hard to hear. Put some nail polish on that screw when done.
Leave the deck for a few hours before doing anything else so your adjustment doesn't drift.
-Chris
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Old 20th March 2005, 04:11 PM   #16
Giaime is offline Giaime  Italy
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Thanks! I will try that... btw sometimes the left channels make some noise, sometimes it just cuts out... the contacts seems to be good, I think I will have to change the head... How much does it cost one? What brand should I look for?
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Old 20th March 2005, 04:21 PM   #17
shusha is offline shusha  Croatia
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I've had the same problem with oscillations. They were fixed, but can't tell you how. It was 15 years ago. Somebody repaired it for me. As I recall when I pressed play, VU meters jumped to some +3dB and sound of osc. was very high. I remember that I was pushing play/stop few times and osc. were gone.

Azimuth? Record a sine tone of 1kHz to the tape using recorder you can trust. Connect DVM to the output and measure output voltage while changing the azimuth. Try to get same voltage (the higher the better) on both outputs.

If you have an access to the scope try to get them in the phase. Anatech already explained you the way of adjusting azimuth.
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Old 20th March 2005, 04:59 PM   #18
anatech is offline anatech  Canada
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Hi Tomislav,
All tape decks record off azimuth, some can be corrected like three head Nakamichi and some three head Teac / Tascam (122MKII). The only tape deck I trust are azimuth test tapes from people like Nak and Teac.
Your osc. problem was the same thing. Very common with earlier machines until they went with solid state switching.

-Chris
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Old 20th March 2005, 06:30 PM   #19
Giaime is offline Giaime  Italy
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Well, the oscillation problem is fixed (don't know how I did it), but the head misses any adjustation screw. There isn't a screw with a coil under it: the head is fixed by 2 screws on a plastic thing that moves when I hit play. No adjust at all.

Anyway I tried to replace the head with one I found in my junk bin with little results. I don't know how I wired it, I just copyied the original wiring of the previous head (there are four wires: 2 red and white. There are four contacts on the head: red on the lower ones and white on the upper. Is that correct? I even found an head with 6 contacts. How can I wire it?). The sound now is more open, but I believe I missed something because there's big hiss and the sound appears to be mono (the VU now are moving toghether, before they didn't). I suppose I have to buy a new head (or you could just tell me how to wire the 6 contacts one that appears to be bigger and higher quality.)


Edit: that bigger head has 8 (!) contacts. Four per side. Two on one side are joined toghether with a solder blob. The others are linked to a switch that I believe is doing some sort of phase select. I've draw something to explain:
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Old 20th March 2005, 07:06 PM   #20
anatech is offline anatech  Canada
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Giaime,
For now put the original head back in it. Please.

There are different materials used in heads and each has different compensation, for record too. You can't properly switch them around. Then there are autoreverse heads with four gaps, bonded heads with a separate rec head bonded to a play head. Then there are the horrible "flippy heads" used in newer cheap autoreverse machines. These spin on a gear. Azimuth correction is accomplished with a screw in the housing.

Just a friendly suggestion to get things working before playing with more difficult stuff.

-Chris
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