AKAI GXC-39D Tape Deck head advice - diyAudio
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Old 24th July 2007, 04:39 AM   #1
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Location: Dona paula, Goa
Default AKAI GXC-39D Tape Deck head advice

I have an AKAI GXC-39D tape deck. One of the channel is not working and this deck is not something u can buy or replace only because of the unbelievable high sound quality of the head.

I had checked the deck some years back and infered that one of the head channel coil is open. While hunting for some other thing I fumbled on the head.

Yesterday, I was making visual inspection of its material out of curiosity and found that the head front face has a step at the joint between recording part and the upper saphire(looks like). The two coils show correctly. The blank upper part has shifted outwards. This protruded portion IMO seems to be preventing the tape contact with the head surface and so the channel does not work.

The head is the heart of this tape deck and sounds detailed then anything. I would compare it in par with a turntable if not better.

The question is How do I reopsition the shifted front face.
Any ideas, pleeeeaaase

Gajanan Phadte
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Old 24th July 2007, 05:32 AM   #2
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Glass and crystal ferrite heads are nice.

I had a similar problem recently with my GXF-90... and spent
several afternoons trying to readjust the head thinking it was a
contact problem. Ended up botching the cosmetics of the deck
with my "mods". In the end... the problem turned out to be the
stupid tape. It was an old TDK medal tape... and for some odd
reason... one track had dropouts. The deck itself was fine.
I never suspected that tapes don't age well.

The old akai stuff sells dirt cheap on ebay. Lots of bargains to be
had.
I never thought that cassette tape sound reproduction was on
par with phono. Even when using metal tape and a compander
the sound was always flat to me.

GOOD phono is hard to beat.
I use a Dual 701 turntable with an AKG P8ES, or AKG P25 MD II
cartridge ... with mostly imported vinyl. The AKG's are well known
for channel separation, that few cartridges can match. It works
for me.
Your mileage may vary.

Edit... the cassette tape itself has a spring clip with two felt pads
that should provide constant contact with the head. You might be
able to take off the front plate that covers the transport... and
maybe use a cotton tipped q-tip to add some pressure for testing.
Good liuck.
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Old 24th July 2007, 06:00 AM   #3
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The shift in the face is about 0.2mm and can be seen by the naked eye. If i move my nail over the front face from bottom to top, it stops. All the tapes play one channel.

Gajanan Phadte
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Old 24th July 2007, 06:46 AM   #4
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Here is the photo.
arrow shows the raised point.

Gajanan Phadte
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Old 24th July 2007, 10:39 AM   #5
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Location: Dona paula, Goa
The damn thing is labeled Vintage and costs 800euros and up.

I read about the deck on the net and its all praise,
hurts more to have it not fixed.

Any help will be highly appreciated.

Even if anybody has a head to dispose I will buy it.

The turntable thing was just an exageration.
Indian music is not produced on vinyl at all.

Gajanan Phadte
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Old 24th July 2007, 11:07 AM   #6
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Hi gmphatde

I too had one of these GXC39D. Weren't they amazing sounding decks. I had various models of the series, GXC38D, GXC40T etc.

There are still plenty of these around, watch eBay. One will come up before long for sure. Now, when it does, this is what I'd do: Ask the seller if they would be kind enough to remove the heads and any other small useful parts (motor, reel tables etc). It will cost a tiny amount of postage and you can have your classic up and running again with spares.

If I see one I'll let you know.

regards
Blake
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Old 24th July 2007, 11:27 AM   #7
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Default Glass, Crystal and ferrite heads have not deep gap


If yours is "eroded" by friction it will need replacement..also contact area was increased and azimuth cannot be adjusted anymore because of the "rail track" you already have to fix the tape between the wearing parts.

Try another head.

In advance you will need a testing tape... with 400 hertz zero db and 10 kilohertz -10db.

This will be the reference to align the level and azimuth during playback and setting of the new head.

than you will need to control your record levels... recording to zero VU and reproduccion will have to be in this same level...if not...increase your recording level to the new head (recording level trimpot)

Do not touch VU meter adjustment... and check, when finish, if signals rigth and left, having zero VU level, if they are the same in level measured into the line out plugs... Ac measurement, 400 hertz into the tape, mode playback and measuring milivolts into the output plugs.... rigth and left must be the same.

Than send a 10 kilohertz signal to the - 10 decibels level and check what happens when you reproduce...do not touch anymore in the playback trimpots rigth and left...do not touch the VU meter trimpots left and rigth..also do not touch the recording levels trimpot rigth and left.

If you have losses.... when reproducing the previously recorded 10 kilohertz sinusoidal tone, recorded previously at - 10 decibels... having losses, for instance....-20 decibels.... than reduce your bias oscilator level...you may have trimmers, padders, variable condensers or resistive trimpots to this adjustment..called Bias channel L and Bias channel R.

This oscilator produces a square wave signal, sometimes sinusoidal, from 40 to 100 Kilohertz, that is used to modulate the audio during the recording and also it is sent to the erase head to erase...cannot record this frequency on tape at this speed...the result is erasure instead of recording..... more common is 60 Kilohertz Bias frequency...adjust level of this bias...check with voltimeter to read a relative voltage.... just a reference when you will increase or decrease bias level...decrease it to increase level into recording 10 kiloherts.

Increasing level will "kill" high frequencies.

Decreasing level will increase High frequencies and depending how much you decrease the bias level, you will have problems with your low end bass.

Normally, those recorders are able to record a flat signal from 30 hertz to 14000 hertz.... some of them, with your Glass and Crystal heads can go to 17000.

Recording 400 hertz at zero VU, having the same level into reproduction (low frequencies, the adjustment is level only).... and recording 10 Kilohertz and having the reproduction at the same level you may understand your deck as good!.

Check, of course, if zero dB level will correspond with the output line level (775 milivolts to zero dB)...and if both channels have the same output level.

Do not try to sand, or to polish your heads...sorry...they will need replacement... measure the resistance....normally 100 ohms...and try another unit with the same resistance to replacement.

Of course, mechanically they will have the need to be equal... glass and cristal use to be long.... a projection in the tip...and cannot be replaced by others...also the distance of the tape deck chassis base, where the head will be fixed must be considered... finishing to adjust the new head, during playback of 10 kilohertz (azimuth adjustment) and 400 hertz (level adjustment), fix the nuts with glue.

Glass and Cristal heads normally do not need magnetic degaussing...sanding, polishing will not result fine.

Be happy.

regards,

Carlos
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Old 25th July 2007, 04:21 AM   #8
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Default So nice of you

Carlos,
Thanks for the detailed explanation.
I have stored the explanation for later reference.

Quote:
If yours is "eroded" by friction it will need replacement..also contact area was increased and azimuth cannot be adjusted anymore because of the "rail track" you already have to fix the tape between the wearing parts.
The surprising and the best part is that the manufacturer never felt the need for azimuth adjustment as the head is guaranted for 17 years and is rock-hard fitted to the chasis,(using nut-bolts IIRC).

Blake wrote
Quote:
There are still plenty of these around, watch eBay. One will come up before long for sure. Now, when it does, this is what I'd do: Ask the seller if they would be kind enough to remove the heads and any other small useful parts (motor, reel tables etc). It will cost a tiny amount of postage and you can have your classic up and running again with spares.

If I see one I'll let you know.
A nice idea, I would have never thought.
Thanks a lot.

Enjoy
Gajanan Phadte
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Old 26th July 2007, 04:32 AM   #9
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Default GXC-46D head for 39D.....

On ebay, USA, an AKAI GXC-46D is available for 25$. It is playing, but no idea about recording as the seller has not mentioned. He is a non-tech mind.
Does anybody know whether this head is the same as in GXC-39D.

Item location is Henderson,Nevada

Time is very short,
Please anybody.........

Gajanan Phadte
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Old 26th July 2007, 05:43 AM   #10
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You might be fairly safe. The 46-D from memory has an AC motor, and I'm sure the 39-D was a DC type but I might be wrong, there could be other differences. I'd just buy it, but I'm impulsive
Blake
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