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Old 15th Jul 2013, 10:35 am   #1
Ann23262
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Default Akai X 355 record head coil connections

Hi there, I wonder if someone could please help me offer some guidance. I am currently restoring an old AKAI X355 and I have a problem with connecting a small inductor (coil) to the record head.

As shown in the picture, there are 4 wires (4 yellow dots). I just don’t know how they are connected to brown coil (standing just behind the record head).

If someone has repaired this or has a unit and can check the connections for me, then I will be really grateful.

Kind Regards
Annie
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Old 15th Jul 2013, 6:03 pm   #2
Vicboduk
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Default Re: Akai X 355 record head coil connections

Hi Annie, I don’t know this machine but it looks as if the wires have been accidentally cut.
Initially I think I would try; Red to Red and Brown to Brown. Here is a link to the service manual, unfortunately it’s not in colour and the pictures are difficult to make out. Page 32 shows the wiring to the erase head assembly. You may be able to trace them back to plug P-901.

Vic
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Old 15th Jul 2013, 9:29 pm   #3
Michael Maurice
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Default Re: Akai X 355 record head coil connections

Quote:
Originally Posted by Vicboduk View Post
don’t know this machine but it looks as if the wires have been accidentally cut.
Initially I think I would try; Red to Red and Brown to Brown.

Vic
I dont think so Vic

The coil is part of the bias circuitry, this machine uses crossfield bias.

This is what I would expect: Click image for larger version

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Can you post a picture of the wiring at the back of the erase head?

Can you also post a picture of the wiring to the Bias head?

Michael
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Old 16th Jul 2013, 1:15 pm   #4
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Default Re: Akai X 355 record head coil connections

I bow to your better knowledge Michael - Annie, please ignore my ramblings....

Vic
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Old 19th Jul 2013, 10:19 pm   #5
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Default Re: Akai X 355 record head coil connections

I have one of these machines. Right next to the computer as it happened, so whipping the cover off and getting some shots was no big deal.

There is a red wire and a white wire coming up from below. The red wire connects to the coil, the white to the rear of the erase head. The brown wire links the erase head to the coil, it is connected to the next tap along as you work clockwise on the coil.

The cross field head is not involved in this part of the circuit so leave it be.

It looks like somebody has performed a bit of a hatchet job on yours, judging by your photo! If you still have doubts, put some more pics up. I'll keep my machine accessible just in case!

HTH
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Old 20th Jul 2013, 11:17 am   #6
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Default Re: Akai X 355 record head coil connections

Quote:
Originally Posted by ben View Post
I have one of these machines. Right next to the computer as it happened, so whipping the cover off and getting some shots was no big deal.

There is a red wire and a white wire coming up from below. The red wire connects to the coil, the white to the rear of the erase head. The brown wire links the erase head to the coil, it is connected to the next tap along as you work clockwise on the coil.

The cross field head is not involved in this part of the circuit so leave it be.

It looks like somebody has performed a bit of a hatchet job on yours, judging by your photo! If you still have doubts, put some more pics up. I'll keep my machine accessible just in case!

HTH
Here is the schematic of the head assembly from the service manual which also corresponds to X-355 register 670417. Ultimately one terminal of
the adjustable choke routes to the focus field head. The post appeared in a
few other forums, however without an actual deck, the photo of the other head was requested.
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Old 20th Jul 2013, 3:59 pm   #7
Michael Maurice
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Default Re: Akai X 355 record head coil connections

Quote:
Originally Posted by ben View Post

There is a red wire and a white wire coming up from below. The red wire connects to the coil, the white to the rear of the erase head. The brown wire links the erase head to the coil, it is connected to the next tap along as you work clockwise on the coil.

The cross field head is not involved in this part of the circuit so leave it be.

I think you'll find it is Ben, look at the diagram in the previous post, the wiring from below, ie the plug, goes to the erase head, the coil is in series with the bias head.
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Old 21st Jul 2013, 8:52 pm   #8
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Default Re: Akai X 355 record head coil connections

Could well be, Michael. I only had a quick glance at the head area and am not (yet) very familiar with this part of the machine.

One thing is for sure, on my example the red white and brown wires are connected as I detailed and pictured above. I assume that is their original location!
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Old 21st Jul 2013, 10:40 pm   #9
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Default Re: Akai X 355 record head coil connections

I have always wondered if the Akai cross field bias system erases or degrades
the recording on the alternate direction tracks. They move the erase and bias
head to record mono, but employ only a series connection of the poles ? Has anyone
ever opened a head to see if there is only one coil and two pole pieces?

This curiosity was again awakened wondering why someone would have cut those
wires in the first place.

I had discussed this with Mr. Masaki Gomi, forty years ago, but he told me the
engineers who worked on the tube machines never shared much with the younger
ones.

The only X-Field machine I have now is a 770 Roberts (M8).

Mr. Gomi was the engineer with us for video tape era.
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Old 23rd Jul 2013, 9:32 am   #10
Ann23262
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Default Re: Akai X 355 record head coil connections

Hi All,
I am really grateful for your help and for giving me all these details. It is so wonderful to see people genuinely willing to help. I have now fixed the coil issue but am working on the smoke issue. I ran the unit for about 10 minutes and then a huge amount of smoke started coming out of the top vent. Disconnected everything, checked power supply circuits and all was well. Then I re-connected it all again and started running the machine but after about 10 minutes, I started smelling (something was getting too hot). I immediately switched it off and will now try to investigate this issue. If someone has experienced something similar, then it would be great to get some tips (I am planning to play with it over the weekend as I have recently bought a 4 channel teac a-3340 and am focusing my attention on fixing that (I love those big VU meters!).
Kind Regards
Annie
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Old 23rd Jul 2013, 2:44 pm   #11
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Default Re: Akai X 355 record head coil connections

I had a similar scenario years back. I found the area of the circuit in question by disconnecting the plugs to the solenoids (or did I unplug relays?) one by one.
Turned out to be a stuck solenoid/mech, the one that moves the head up and down, that was dawring too much current and I think it had taken out a rectifier. Sorry, memory is a bit hazy.
I'm sure with some deductive checks you will find the problem, but whatever you do don't run it for more than a few moments at a time to avoid damaging the top transformer (irreplaceable!)
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Old 23rd Jul 2013, 8:44 pm   #12
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Default Re: Akai X 355 record head coil connections

Annie,

Check the motor run capacitors, I had this happen on an Akai 1710 machine.

Michael
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